{ "dataset": "Purely Peptides Research Library", "file": "compounds", "description": "Published compound records: names, molecule type, identifiers, sequence, formula, terminal and structural modifications, links to classes, mechanisms, related records and references, and the record text.", "version": "2026-10-21", "license": "CC-BY-4.0", "licenseUrl": "https://creativecommons.org/licenses/by/4.0/", "attribution": "Purely Peptides Research Library, https://purelypeptides.org/research/, licensed CC BY 4.0", "notice": "Research reference data about peptide identity, structure and the published literature. It is not product information, makes no claim about any product, and is not medical advice.", "count": 101, "records": [ { "id": "aod-9604", "url": "https://purelypeptides.org/research/compounds/aod-9604/", "displayName": "AOD-9604", "canonicalName": "AOD-9604", "moleculeType": "peptide", "aliases": [ "Tyr-hGH(177-191)" ], "developmentCodes": [ "AOD9604" ], "externalIds": { "cas": "221231-10-3", "pubChemCid": "71300630", "unii": "7UP768IP4M" }, "sequence": { "oneLetter": "YLRIVQCRSVEGSCGF", "threeLetter": [ "Tyr", "Leu", "Arg", "Ile", "Val", "Gln", "Cys", "Arg", "Ser", "Val", "Glu", "Gly", "Ser", "Cys", "Gly", "Phe" ], "notes": "Sixteen residues, using peptide positions 1-16. Two source conflicts remain unresolved. The 1993 native-fragment abstract (PMID 8358331) gives LRIVQCRVSEGSCGF, transposing Val and Ser at canonical mature GH1 positions 184-185 relative to LRIVQCRSVEGSCGF; these correspond to peptide positions 9-10 after the added Tyr. That paper describes the native fragment, not an independently established alternative AOD-9604 sequence. The FDA December 2024 briefing places the added Tyr at the N-terminus in its chemistry description and Figure 4, but its narrative on printed page 24 says C-terminus. The sequence here retains the specified N-terminal Tyr without resolving either conflict.", "rings": [ { "kind": "disulfide", "from": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 14, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "sourceNumbering": "Cys182–Cys189 in mature human growth hormone (GH1) numbering", "referenceId": "pmid-29953237" } ] }, "molecularFormula": "C78H123N23O23S2", "molecularWeightDa": 1815.1, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "Cys7-Cys14 disulfide" ], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-25208511", "pmid-29953237" ], "identityOverview": "AOD-9604 is a synthetic, sixteen-residue human GH1 fragment analog specified with an N-terminal tyrosine, free termini and one intramolecular disulfide. AOD-9604 is used here as a provisional development-code name; an INN or USAN has not been established for this record.", "nomenclatureNotes": "AOD-9604 is specified as the tyrosine-extended human GH1 fragment Tyr-hGH(177-191), using the canonical mature-chain numbering. This is equivalent to replacing Phe176 with Tyr in hGH(176-191); the unqualified name “hGH fragment 176-191” can instead denote the distinct native phenylalanine-starting peptide and is not used here as an interchangeable identity.", "structuralNotes": "The specified free peptide has a Cys7-Cys14 disulfide, a free N-terminal amino group and a free C-terminal carboxyl group. Spengler et al. (PMID 29953237) prepared this sixteen-residue chain, an N-terminal tyrosine followed by the fifteen C-terminal residues of human growth hormone, with a Cys7-Cys14 disulfide and free termini. The last fifteen residues correspond to positions 177-191 of the canonical mature human GH1 chain, with the historical sequence conflict retained in the sequence notes. The formula and identifiers describe the oxidized free peptide without a counterion; they do not describe its acetate species.", "analyticalNotes": "Calculated average molecular mass is 1815.100 Da using CIAAW 2024 abridged atomic weights; calculated neutral monoisotopic mass is 1813.860360 Da using the specified isotope masses. These are distinct conventions. Formula and intact mass cannot distinguish Leu from Ile, D from L configuration, or residue order, including the Ser/Val transposition. Elemental composition alone also does not establish disulfide connectivity. The attached Cox reference documents analytical detection work on the named AOD9604 analyte; the accessible abstract is not used to certify every structural field.", "publishedDate": "2026-09-27", "updatedDate": "2026-10-12", "lastVerifiedDate": "2026-09-27" }, { "id": "semaglutide", "url": "https://purelypeptides.org/research/compounds/semaglutide/", "displayName": "Semaglutide", "canonicalName": "Semaglutide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "NN9535", "NNC 0113-0217" ], "externalIds": { "cas": "910463-68-2", "pubChemCid": "56843331", "unii": "53AXN4NNHX" }, "sequence": { "threeLetter": [ "His", "Aib", "Glu", "Gly", "Thr", "Phe", "Thr", "Ser", "Asp", "Val", "Ser", "Ser", "Tyr", "Leu", "Glu", "Gly", "Gln", "Ala", "Ala", "Lys", "Glu", "Phe", "Ile", "Ala", "Trp", "Leu", "Val", "Arg", "Gly", "Arg", "Gly" ], "notes": "Thirty-one residues in the conventional GLP-1 7-37 numbering this library keeps for every analog built on that scaffold: the first token is His7 and the last is Gly37, so a position number in this entry is the array index plus six, and Lys26 is the twentieth token. NO one-letter string is published here. Position 8 is Aib, 2-aminoisobutyric acid; written as Ala it would name the native residue this analog exists to replace, and any other letter would name a different amino acid again. The IUPHAR/BPS Guide to Pharmacology (ligand 9724, release 2026.3.1) prints Ala at position 8 in its sequence fields while its structure encodes Aib; FDA GSRS also records Aib there. The backbone is also not the whole molecule: the Lys26 side chain is acylated through two AEEA spacers and a gamma-L-glutamyl unit to a C18 dicarboxylic fatty acid. Summing the thirty-one residues with Aib at position 8 and Arg at position 34, removing thirty waters, then adding two AEEA units, one glutamyl unit and octadecanedioic acid less the four waters of the four amide bonds, gives C187H291N45O59 and an average mass of 4113.64 Da, reproducing the recorded formula exactly and the recorded mass to 0.36 Da. Against the machine-verified GLP-1(7-37) entry that backbone differs by exactly CH2 and N2 — the Aib8 and Arg34 substitutions, and nothing else. That arithmetic is the identity check this record rests on; the automated sequence verifier cannot reach it, because Aib and the acyl side chain are both outside its derivation model." }, "molecularFormula": "C187H291N45O59", "molecularWeightDa": 4114, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "Aib substitution at position 8", "Arg substitution at position 34", "Lys26 derivatization with a fatty-diacid-containing side chain" ], "compoundClassIds": [ "glp-1-receptor-peptide-analogs" ], "mechanismIds": [ "glp-1-receptor" ], "relatedCompoundIds": [ "retatrutide", "tirzepatide", "exenatide", "liraglutide", "orforglipron", "glp-1-7-37" ], "referenceIds": [ "pmid-26308095", "pmid-34260945", "pmid-31031702", "pmid-32213703", "pmid-23684623", "pmid-28538729", "pmid-21094903" ], "identityOverview": "Semaglutide is an acylated peptide analog of glucagon-like peptide-1. Its discovery record identifies two amino-acid substitutions and derivatization at Lys26.", "nomenclatureNotes": "PubChem lists NN9535 and NNC 0113-0217 as development identifiers for the semaglutide molecular record. WHO Proposed INN List 101 and Recommended List 63 print position 8 in English as 2-amino-2-propanoic acid, without the methyl that their French and Spanish names include; this record keeps Aib, 2-aminoisobutyric acid.", "structuralNotes": "Built on the GLP-1(7-37) scaffold, retaining its C-terminal glycine. Using native GLP-1 numbering, it carries alpha-aminoisobutyric acid at position 8 in place of alanine, arginine at position 34 in place of lysine, and acylation of the lysine 26 side chain through a gamma-glutamyl unit and two AEEA spacers to a C18 fatty diacid. The position-8 substitution sits at the dipeptidyl peptidase IV cleavage site described on the native GLP-1 entries; resistance to that cleavage is the stated design rationale, not independent causal proof for each substitution. The related GLP-1(7-37) entry identifies the native structural parent. The Aib8 and Arg34 substitutions distinguish the peptide backbone from human GLP-1, while the Lys26-linked side chain is part of the declared molecular identity.", "analyticalNotes": "Identity assessment must account for both the peptide sequence and the Lys26-linked side chain represented in the PubChem molecular record.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-12", "lastVerifiedDate": "2026-08-23" }, { "id": "retatrutide", "url": "https://purelypeptides.org/research/compounds/retatrutide/", "displayName": "Retatrutide", "canonicalName": "Retatrutide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "LY3437943" ], "externalIds": { "cas": "2381089-83-2", "unii": "NOP2Y096GV" }, "sequence": { "notes": "Described in words and attributed, not recorded as a verified structure. WHO Proposed INN List 128 describes retatrutide as a 39-residue peptide with a C-terminal amide. In three-letter symbols, the residue order it gives is Tyr-Aib-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Ile-αMeLeu-Leu-Asp-Lys-Lys-Ala-Gln-Aib-Ala-Phe-Ile-Glu-Tyr-Leu-Leu-Glu-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser, where Aib is 2-aminoisobutyric acid (positions 2 and 20) and αMeLeu is 2-methylleucine (position 13), which the WHO entry specifies as the L form. The lysine at position 17 carries a side chain on its ε-amino group, built outward from one 8-amino-3,6-dioxaoctanoyl unit, one γ-glutamyl unit and eicosanedioic acid attached as a mono-amide. No one-letter string is recorded, because a letter string cannot show the three non-standard residues or the side chain. The same residue order and side-chain construction appear in the sponsor patent WO2019125938A1 and in an independently authored synthesis patent, CN117024528B. The drawing of the position-13 residue in CN117024528B shows the opposite configuration to the one WHO specifies; whether that is a different stereoisomer or a drawing error is not established here." }, "terminalModifications": [ "Free N-terminus", "C-terminal amidation" ], "compoundClassIds": [ "multi-receptor-incretin-analogs" ], "mechanismIds": [ "glp-1-receptor", "gip-receptor", "glucagon-receptor" ], "relatedCompoundIds": [ "semaglutide", "tirzepatide", "gip-1-42", "glp-1-7-36-amide", "glucagon" ], "referenceIds": [ "pmid-35985340", "pmid-37366315", "pmid-37385280", "pmid-38858523", "pmid-23684623", "pmid-28538729", "pmid-21094903", "pmid-28514451", "pmid-29300013" ], "identityOverview": "Retatrutide, development code LY3437943, is a single peptide characterized as an agonist at GCGR, GIPR, and GLP-1R in its discovery record.", "nomenclatureNotes": "Retatrutide is the adopted name used for the development compound LY3437943 in the verified bibliography. It is a proposed International Nonproprietary Name, published in WHO Proposed INN List 128 (WHO Drug Information, Vol. 36, No. 4, 2022). PubChem CID 171934787 encodes a fully stereospecified free-peptide candidate despite its sodium-salt title; its position-13 configuration matches the GSRS systematic definition, but this record’s independent configuration conflict remains unresolved.", "structuralNotes": "Like tirzepatide, retatrutide is built on a GIP scaffold rather than a GLP-1 scaffold, with a different substitution set, lipidation position and spacer. The related GIP(1-42) entry identifies scaffold ancestry; GLP-1(7-36) amide and glucagon are native receptor comparators. Activity at the GLP-1 and glucagon receptors is engineered pharmacology and does not make retatrutide a GLP-1-derived or glucagon-derived peptide. Tirzepatide's modification table does not apply to it. The residue order and the lysine side chain are given in the sequence notes as WHO Proposed INN List 128 describes them; they are attributed statements, and one point of configuration is disputed between sources. The CAS registry number and UNII are recorded from the FDA/NCATS GSRS substance record, which lists both on the retatrutide entry. No PubChem CID is published here: PubChem links several compound records to substance records carrying this name, those records differ from one another in stereochemical detail and in one case in composition, and none has been matched to an independently established structure.", "analyticalNotes": "No molecular formula or molecular mass is recorded as a field, because two public records print different values. WHO Proposed INN List 128 prints C221H342N46O68 for the free peptide; counting the atoms of the structure it describes gives the same formula and an average mass of about 4731.4 Da. The FDA/NCATS GSRS substance record lists an estimated formula of C187H281N43O60 and a calculated mass of 4091.5 Da, which are the values for the 39-residue chain written with standard amino acids and free termini, without the non-standard residues, the C-terminal amide or the lysine side chain. Analytical identity values are not inferred from catalog copy or from structurally related peptides.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-08-23" }, { "id": "kisspeptin-10", "url": "https://purelypeptides.org/research/compounds/kisspeptin-10/", "displayName": "Kisspeptin-10", "canonicalName": "Kisspeptin-10", "moleculeType": "peptide", "aliases": [ "KP-10", "Metastin (45-54)", "Human metastin 45-54" ], "developmentCodes": [], "externalIds": { "cas": "374675-21-5", "pubChemCid": "25240297", "unii": "FS1N52VS3S" }, "sequence": { "oneLetter": "YNWNSFGLRF", "threeLetter": [ "Tyr", "Asn", "Trp", "Asn", "Ser", "Phe", "Gly", "Leu", "Arg", "Phe" ], "notes": "The PubChem molecular record represents the C-terminal phenylalanine as an amide." }, "molecularFormula": "C63H83N17O14", "molecularWeightDa": 1302.4, "terminalModifications": [ "Free N-terminus", "C-terminal amidation" ], "compoundClassIds": [ "kisspeptins" ], "mechanismIds": [ "kisspeptin-receptor" ], "relatedCompoundIds": [ "kisspeptin-14", "gonadorelin" ], "referenceIds": [ "pmid-11385580", "pmid-11457843", "pmid-11387329", "pmid-38978171", "pmid-16731583", "pmid-38935498", "pmid-16339030" ], "identityOverview": "Kisspeptin-10 is the amidated ten-residue C-terminal fragment represented by the human KISS1-derived kisspeptin sequence. Foundational records identify KISS1 peptides as ligands of GPR54, now KISS1R.", "nomenclatureNotes": "KP-10 and metastin (45-54) identify the amidated ten-residue C-terminal fragment of the human KISS1-derived peptide sequence.", "structuralNotes": "The sequence terminates in an RF-amide motif shared by the KISS1-derived peptides described in the foundational receptor record.", "analyticalNotes": "The verified bibliography includes a liquid chromatography high-resolution mass spectrometry record specific to kisspeptin-10 detection.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-08-23" }, { "id": "ghk-cu", "url": "https://purelypeptides.org/research/compounds/ghk-cu/", "displayName": "GHK-Cu", "canonicalName": "Prezatide copper", "moleculeType": "peptide-metal-complex", "aliases": [ "Copper tripeptide-1", "GHK copper", "Cu-GHK" ], "developmentCodes": [], "externalIds": { "cas": "89030-95-5", "pubChemCid": "10111685", "unii": "6BJQ43T1I9" }, "molecularFormula": "C14H22CuN6O4", "molecularWeightDa": 401.91, "compoundClassIds": [ "copper-binding-peptides", "matrikine-derived-peptides" ], "mechanismIds": [ "copper-ion-coordination" ], "relatedCompoundIds": [ "ghk", "pal-ghk" ], "referenceIds": [ "pmid-6291585", "pmid-7340824", "pmid-37624577", "pmid-2244543", "pmid-18644225", "pmid-6303307", "pmid-7514608" ], "identityOverview": "Prezatide copper is the Cu(II) coordination complex of the tripeptide glycyl-L-histidyl-L-lysine. The copper ion is part of the declared molecular identity and distinguishes this record from the free tripeptide.", "nomenclatureNotes": "GHK-Cu is a trade and literature name for the Cu(II) complex of the tripeptide glycyl-L-histidyl-L-lysine. The free tripeptide and the copper complex are distinct molecular records with different formulas, masses, and registry numbers: the free peptide is CAS 49557-75-7 (INN prezatide), and the copper complex is CAS 89030-95-5 (prezatide copper). Material sold under the name GHK-Cu should be identified against the intended species. Public databases do not agree on the complex: searching the name GHK-Cu in PubChem returns several distinct structures at 400.90, 401.91, 402.92, 403.92, 742.3 and 744.3, differing in how many protons the ligand has lost and in peptide-to-copper stoichiometry. The formula and mass recorded here are those the FDA substance registry gives for UNII 6BJQ43T1I9, prezatide copper, under CAS 89030-95-5, and match the CAS index name for that substance, which describes the ligand as lysinato(2-) - a doubly deprotonated ligand giving a neutral Cu(II) complex.", "structuralNotes": "Spectroscopic study of the complex in solution reports a mononuclear 1:1 Cu(II) species at neutral pH, with EPR consistent with two or three equatorial nitrogen donors, one of which is located in the histidyl imidazole ring. The polymeric oxygen-bridged structure determined by X-ray crystallography in the solid state is reported not to persist in solution. Potentiometric and spectrophotometric analysis reports that the epsilon-amino group of the lysine residue contributes to complex stability relative to glycyl-L-histidine and glycyl-L-histidylglycine, and equilibrium dialysis reports that the tripeptide competes with albumin for Cu(II): at equimolar concentrations approximately 42 percent of the Cu(II) was bound to the peptide.", "analyticalNotes": "Because the free tripeptide and the copper complex have different formulas and masses, identity methods must distinguish the two species rather than reporting a single GHK-Cu mass. Copper content is part of the identity of the complex. PubChem CIDs 10111685 and 165429100 share this formula but place the deprotonated nitrogen differently, on the His2 imidazole and on the His2 backbone amide respectively; in both, Gly1 is uncapped and Lys3 is a carboxylate, and the Bossak-Ahmad coordination study identifies the terminal amino nitrogen as a copper donor. Complex formation is reversible: analytical work using GHK-modified nanochannels reports dissociation of the GHK-Cu complex on addition of EDTA.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "tirzepatide", "url": "https://purelypeptides.org/research/compounds/tirzepatide/", "displayName": "Tirzepatide", "canonicalName": "Tirzepatide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "LY3298176" ], "externalIds": { "cas": "2023788-19-2", "pubChemCid": "166567236", "unii": "OYN3CCI6QE" }, "sequence": { "threeLetter": [ "Tyr", "Aib", "Glu", "Gly", "Thr", "Phe", "Thr", "Ser", "Asp", "Tyr", "Ser", "Ile", "Aib", "Leu", "Asp", "Lys", "Ile", "Ala", "Gln", "Lys", "Ala", "Phe", "Val", "Gln", "Trp", "Leu", "Ile", "Ala", "Gly", "Gly", "Pro", "Ser", "Ser", "Gly", "Ala", "Pro", "Pro", "Pro", "Ser" ], "notes": "Thirty-nine residues numbered from the N-terminus; the C-terminal amide on Ser39 is recorded as a terminal group, not as a residue. NO one-letter string is published here: positions 2 and 13 are both Aib, 2-aminoisobutyric acid, and no standard letter names that residue. Residue 1 is Tyr, the GIP N-terminus rather than GLP-1's His. There are two lysines, at 16 and 20, and the acylation site is Lys20. The backbone is not the whole molecule: that Lys20 side chain is acylated through two AEEA spacers and a gamma-L-glutamyl unit to a C20 dicarboxylic fatty acid. Summing the thirty-nine residues with Aib at 2 and 13, removing thirty-eight waters, applying the Ser39 amide, then adding two AEEA units, one glutamyl unit and eicosanedioic acid less the four waters of the four amide bonds, gives C225H348N48O68, reproducing the recorded formula exactly; the derived average mass is 4813.53 Da against a recorded 4813, which is a truncation of that value rather than a rounding of it. Residues 29 to 39 are Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser; that tail is shared with other 39-residue incretin peptides and is not by itself evidence of ancestry, which the structural notes take up. That arithmetic is the identity check this record rests on; the automated sequence verifier cannot reach it, because Aib and the acyl side chain are outside its derivation model." }, "molecularFormula": "C225H348N48O68", "molecularWeightDa": 4813, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Ser39" ], "structuralModifications": [ "Fatty-acid moiety linked to the peptide backbone" ], "compoundClassIds": [ "multi-receptor-incretin-analogs" ], "mechanismIds": [ "gip-receptor", "glp-1-receptor" ], "relatedCompoundIds": [ "semaglutide", "retatrutide", "orforglipron", "gip-1-42", "glp-1-7-36-amide" ], "referenceIds": [ "pmid-30473097", "pmid-32730231", "pmid-23684623", "pmid-32396843", "pmid-35333651", "pmid-28538729", "pmid-21094903" ], "identityOverview": "Tirzepatide is a fatty-acid-modified synthetic peptide characterized in its discovery record as having agonist activity at both the GIP receptor and the GLP-1 receptor.", "nomenclatureNotes": "The discovery record identifies the molecule under the development code LY3298176. GSRS UNII OYN3CCI6QE identifies the specified tirzepatide sequence and modifications and lists CAS 2023788-19-2, although its retrieved codes do not include PubChem CID 166567236.", "structuralNotes": "The scaffold is GIP, not GLP-1. Residue 1 is tyrosine, matching GIP's N-terminal Tyr-Ala rather than GLP-1's His-Ala, and across residues 1-29 it is closer to GIP than to GLP-1. Relative to human GIP it carries alpha-aminoisobutyric acid at positions 2 and 13, and substitutions at positions 7, 14, 18, 20, 21, 24, 27 and 29; the native GIP C-terminal segment is replaced by a shorter engineered tail with a C-terminal amide, and the lysine 20 side chain carries a C20 fatty diacid. The related GIP(1-42) entry identifies scaffold ancestry; GLP-1(7-36) amide is a native receptor comparator. Activity at the GLP-1 receptor is a pharmacological property of the engineered molecule and does not establish GLP-1 ancestry. The discovery record describes tirzepatide as a fatty acid modified peptide with activity at both incretin receptors. Receptor-level characterization reports greater engagement at the GIP receptor than at the GLP-1 receptor, and at the GLP-1 receptor a signaling profile favoring cAMP generation over beta-arrestin recruitment, with weaker GLP-1 receptor internalization than GLP-1 itself.", "analyticalNotes": "Identity assessment must account for both the peptide backbone and the fatty-acid modification represented in the PubChem molecular record. PubChem CID 166567236 is retained because it encodes the specified peptide stereochemistry and gamma-L-glutamyl lipid linker, whereas the other four name-linked CIDs contain stereochemical substitutions or undefined centres. GSRS UNII OYN3CCI6QE matches the sequence and structural modifications but reports C225H347N49O66, conflicting with this record and PubChem CID 166567236 at C225H348N48O68.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-08-23" }, { "id": "tesamorelin", "url": "https://purelypeptides.org/research/compounds/tesamorelin/", "displayName": "Tesamorelin", "canonicalName": "Tesamorelin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "TH9507" ], "externalIds": { "cas": "218949-48-5", "pubChemCid": "16137828", "unii": "MQG94M5EEO" }, "sequence": { "oneLetter": "YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL", "threeLetter": [ "Tyr", "Ala", "Asp", "Ala", "Ile", "Phe", "Thr", "Asn", "Ser", "Tyr", "Arg", "Lys", "Val", "Leu", "Gly", "Gln", "Leu", "Ser", "Ala", "Arg", "Lys", "Leu", "Leu", "Gln", "Asp", "Ile", "Met", "Ser", "Arg", "Gln", "Gln", "Gly", "Glu", "Ser", "Asn", "Gln", "Glu", "Arg", "Gly", "Ala", "Arg", "Ala", "Arg", "Leu" ], "notes": "The full 44-residue human growth hormone-releasing factor sequence, carried with a hexenoyl cap on Tyr1 and a C-terminal amide on Leu44. Sermorelin, also in this library, is the first 29 residues of this same sequence, without the hexenoyl cap and carried as a C-terminal amide at Arg29. The recorded formula and mass are the values this sequence derives with both caps applied; without the hexenoyl the derivation falls 96.13 Da short, which is why the cap is declared rather than described only in prose." }, "molecularFormula": "C221H366N72O67S", "molecularWeightDa": 5135.9, "terminalModifications": [ "N-terminal trans-3-hexenoyl at Tyr1", "C-terminal amide at Leu44" ], "compoundClassIds": [ "ghrh-analogs" ], "mechanismIds": [ "ghrh-receptor" ], "relatedCompoundIds": [ "cjc-1295", "sermorelin" ], "referenceIds": [ "pmid-21283099", "pmid-19243281", "pmid-17086939", "pmid-25358450" ], "identityOverview": "Tesamorelin is a synthetic analog of human growth hormone-releasing factor, characterized in the literature as a GRF analog acting at the GHRH receptor.", "nomenclatureNotes": "Development code TH9507 appears in the PubChem synonym set and in the contemporaneous literature. A second registry number, 804475-66-9, also appears in the PubChem record; 218949-48-5 is carried here as primary.", "structuralNotes": "Tesamorelin is the full 44-residue human GRF sequence carrying two modifications, both now recorded. The FDA label describes the first as \"a hexenoyl moiety, a C6 chain with a double bond at position 3, attached to the tyrosine residue at the N-terminal part\"; the second is a C-terminal amide on Leu44. The single sulfur atom is the methionine at position 27, the only sulfur-containing residue in the sequence and the same residue that sermorelin carries, since sermorelin is this sequence truncated at 29. Neither cap contributes sulfur, so a second sulfur signal in a sample is a finding rather than noise.", "analyticalNotes": "Population pharmacokinetic analysis reports plasma clearance of approximately 1,060 L/h and a volume of distribution of approximately 200 L, characterized by a one-compartment model with first- and zero-order absorption and first-order elimination.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-06", "lastVerifiedDate": "2026-08-23" }, { "id": "bpc-157", "url": "https://purelypeptides.org/research/compounds/bpc-157/", "displayName": "BPC-157", "canonicalName": "BPC-157", "moleculeType": "peptide", "aliases": [ "Bepecin", "BPC 15" ], "developmentCodes": [], "externalIds": { "cas": "137525-51-0", "pubChemCid": "9941957", "unii": "8ED8NXK95P" }, "sequence": { "oneLetter": "GEPPPGKPADDAGLV", "threeLetter": [ "Gly", "Glu", "Pro", "Pro", "Pro", "Gly", "Lys", "Pro", "Ala", "Asp", "Asp", "Ala", "Gly", "Leu", "Val" ], "notes": "Sequence derived from the systematic name in the PubChem molecular record." }, "molecularFormula": "C62H98N16O22", "molecularWeightDa": 1419.5, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "regenerative-peptides" ], "mechanismIds": [ "focal-adhesion-signaling" ], "relatedCompoundIds": [], "referenceIds": [ "pmid-21030672", "pmid-30915550", "pmid-34267654" ], "identityOverview": "BPC-157 is a synthetic fifteen-residue peptide corresponding to a partial sequence of body protection compound, a protein reported to have been isolated from human gastric juice.", "nomenclatureNotes": "BPC-157 is described in the literature as a partial sequence of body protection compound, a protein reported to have been isolated from human gastric juice. PubChem lists Bepecin and BPC 15 as synonyms. It has no approved regulatory status in any jurisdiction.", "structuralNotes": "The peptide contains three consecutive proline residues at positions 3 to 5 and a fourth proline at position 8. It carries no reported terminal modification in the PubChem molecular record.", "analyticalNotes": "The sequence contains no aromatic residues, so UV detection at 280 nm gives no useful chromophore response. Identity confirmation therefore relies on mass and sequence-level methods rather than UV absorbance, and the proline-rich backbone should be accounted for in chromatographic method development.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "ipamorelin", "url": "https://purelypeptides.org/research/compounds/ipamorelin/", "displayName": "Ipamorelin", "canonicalName": "Ipamorelin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "NNC 26-0161" ], "externalIds": { "cas": "170851-70-4", "pubChemCid": "9831659", "unii": "Y9M3S784Z6" }, "sequence": { "threeLetter": [ "Aib", "His", "D-2-Nal", "D-Phe", "Lys" ], "notes": "Pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2. Contains alpha-aminoisobutyric acid, D-2-naphthylalanine, and D-phenylalanine, so a standard one-letter representation does not apply. The sequence is stated identically in the PubChem synonym record and in the original characterization paper." }, "molecularFormula": "C38H49N9O5", "molecularWeightDa": 711.9, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [ "Alpha-aminoisobutyric acid (Aib) at position 1", "D-2-naphthylalanine at position 3", "D-phenylalanine at position 4" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor" ], "relatedCompoundIds": [ "cjc-1295", "ghrp-6", "examorelin", "pralmorelin" ], "referenceIds": [ "pmid-9849822", "pmid-11459660", "pmid-21396419", "pmid-11322507", "pmid-32814772", "pmid-21298258" ], "identityOverview": "Ipamorelin is a synthetic pentapeptide with a C-terminal amide, characterized in its original report as a growth hormone secretagogue acting through a GHRP-like receptor rather than the GHRH receptor.", "nomenclatureNotes": "Identified within a series of compounds lacking the central Ala-Trp dipeptide of growth hormone-releasing peptide-1. PubChem lists NNC 26-0161 as a development identifier.", "structuralNotes": "Pharmacological profiling using GHRP and GHRH antagonists reported that ipamorelin acts via a GHRP-like receptor. The original report describes it as the first GHRP-receptor agonist whose selectivity for growth hormone release resembled that of GHRH, noting that plasma ACTH and cortisol were not raised significantly relative to GHRH stimulation even at doses more than 200-fold above the ED50 for growth hormone release, in contrast to GHRP-6 and GHRP-2. Structure-activity work on related analogs examined lysine mimetics combined with naphthyl- or biphenylalanine substitutions in the core.", "analyticalNotes": "Three of the five residues are non-proteinogenic, and the C-terminus is amidated. Identity methods must resolve the D-configuration residues and the amide, which a sequence-only assay assuming L-amino acids will not distinguish.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "cjc-1295", "url": "https://purelypeptides.org/research/compounds/cjc-1295/", "displayName": "CJC-1295", "canonicalName": "CJC-1295", "moleculeType": "peptide", "aliases": [ "CJC 1295" ], "developmentCodes": [], "externalIds": { "pubChemCid": "56841945" }, "sequence": { "threeLetter": [ "Tyr", "D-Ala", "Asp", "Ala", "Ile", "Phe", "Thr", "Gln", "Ser", "Tyr", "Arg", "Lys", "Val", "Leu", "Ala", "Gln", "Leu", "Ser", "Ala", "Arg", "Lys", "Leu", "Leu", "Gln", "Asp", "Ile", "Leu", "Ser", "Arg" ], "notes": "Twenty-nine residues, the tetrasubstituted hGRF(1-29) analog without the drug affinity complex. Against unmodified GRF(1-29), recorded on the sermorelin entry as YADAIFTNSYRKVLGQLSARKLLQDIMSR, the four changes are D-alanine at position 2, glutamine for asparagine at position 8, alanine for glycine at position 15, and leucine for methionine at position 27. No one-letter string is published here: one-letter symbols denote L residues unless marked, so writing position 2 as A would state the L-alanine of the parent fragment. The D-configuration has the same elemental composition, so the three-letter chain still derives the recorded formula and mass. The substitution at position 27 removes the only sulfur-containing residue of the parent fragment, which is why this record has no sulfur while sermorelin does." }, "molecularFormula": "C152H252N44O42", "molecularWeightDa": 3367.95, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Arg29" ], "compoundClassIds": [ "ghrh-analogs" ], "mechanismIds": [ "ghrh-receptor" ], "relatedCompoundIds": [ "tesamorelin", "ipamorelin", "sermorelin" ], "referenceIds": [ "pmid-15817669", "pmid-16822960", "pmid-16352683" ], "identityOverview": "CJC-1295 designates a tetrasubstituted analog of human growth hormone-releasing factor residues 1 to 29, reported to act at the GRF receptor on the anterior pituitary.", "nomenclatureNotes": "The name CJC-1295 is used in the literature and in commerce for two distinct species. The compound identified in the original report is a tetrasubstituted form of hGRF(1-29) bearing an N-epsilon-3-maleimidopropionamide derivative of lysine at the C-terminus; that maleimido group is the drug affinity complex, and it bioconjugates in vivo to the free thiol at Cys34 of serum albumin. Material sold as CJC-1295 without DAC lacks that linker and does not form the albumin conjugate, and is the species this record describes; it is the CJC-1295 component of the catalog's CJC-1295 / ipamorelin blend, while the catalog's CJC-1295 With DAC listing is the other species. PubChem CID 56841945 encodes the non-DAC 29-mer with D-Ala2 and Arg29-amide (C152H252N44O42; 3367.95 Da), whereas CID 91971820 encodes the DAC species (C165H269N47O46; 3647.2 Da; CAS 446262-90-4; UNII 62RC32V9N7); CID 91976842 omits stereochemistry. PubChem CID 91971820, CAS 446262-90-4 and GSRS UNII 62RC32V9N7 identify the DAC form and are excluded from this non-DAC record. No CAS or UNII is published for the non-DAC species because none could be verified against a primary registry. Identity should be established against the intended species, and a supplier certificate quoting 3647.2 Da is describing the other molecule.", "structuralNotes": "The original report describes synthesis of three maleimido derivatives of hGRF(1-29) and their ex vivo bioconjugation to human serum albumin, with all three conjugates showing enhanced in vitro stability against dipeptidyl peptidase IV; the compound selected from that series is the DAC-bearing form. That report characterises the conjugate, not the peptide described here. What this record shares with it is the tetrasubstituted hGRF(1-29) backbone; the maleimidopropionamide lysine that made the conjugation possible is exactly what the non-DAC species lacks.", "analyticalNotes": "Because the DAC and non-DAC species differ by an appended lysine and its maleimidopropionamide group, mass-based identity methods distinguish them directly and unambiguously: 3367.95 Da against 3647.2 Da, a 279.3 Da gap no instrument would miss. The recorded formula contains no sulfur, because the position-27 methionine of the parent fragment is substituted to leucine; a sulfur signal in a sample of this species is therefore a finding, not noise. A conjugated sample additionally carries albumin, which alters apparent mass by roughly the mass of serum albumin and requires a method that resolves the conjugate rather than the free peptide.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-21", "lastVerifiedDate": "2026-08-23" }, { "id": "mots-c", "url": "https://purelypeptides.org/research/compounds/mots-c/", "displayName": "MOTS-c", "canonicalName": "MOTS-c", "moleculeType": "peptide", "aliases": [ "Mitochondrial open reading frame of the 12S rRNA-c" ], "developmentCodes": [], "externalIds": { "cas": "1627580-64-6", "pubChemCid": "146675088", "unii": "A5CV6JFB78" }, "sequence": { "oneLetter": "MRWQEMGYIFYPRKLR", "threeLetter": [ "Met", "Arg", "Trp", "Gln", "Glu", "Met", "Gly", "Tyr", "Ile", "Phe", "Tyr", "Pro", "Arg", "Lys", "Leu", "Arg" ], "notes": "Sixteen residues, all L, with a free N-terminus and a free C-terminal carboxyl, as encoded by PubChem CID 146675088. Methionine at positions 1 and 6 accounts for the two sulfur atoms. Summing the sixteen residues and removing fifteen waters gives C101H152N28O22S2 and 2174.62 Da, reproducing the recorded formula and mass." }, "molecularFormula": "C101H152N28O22S2", "molecularWeightDa": 2174.6, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [ "ampk-signaling" ], "relatedCompoundIds": [ "humanin", "shlp2", "shlp3", "shlp6" ], "referenceIds": [ "pmid-25738459", "pmid-29983246", "pmid-28974774" ], "identityOverview": "MOTS-c is a sixteen-amino-acid peptide encoded by a short open reading frame within the mitochondrial 12S rRNA, rather than by the nuclear genome.", "nomenclatureNotes": "MOTS-c stands for mitochondrial open reading frame of the 12S rRNA-c. PubChem CID 146675088 is retained for the free peptide H-MRWQEMGYIFYPRKLR-OH; CID 164946842 contains three acetic-acid components, and CID 172641109 contains three trifluoroacetic-acid components despite its acetate title.", "structuralNotes": "The discovery report identifies the encoding short open reading frame within mitochondrial DNA and describes cellular actions inhibiting the folate cycle and its tethered de novo purine biosynthesis, leading to AMPK activation. A subsequent report describes nuclear translocation and regulation of nuclear gene expression following metabolic stress in an AMPK-dependent manner, including interaction with antioxidant-response-element-regulating transcription factors such as NFE2L2/NRF2.", "analyticalNotes": "The two sulfur atoms in the molecular formula correspond to sulfur-containing residues and are relevant to oxidation-related degradation pathways. PubChem CID 146675088 contains no counterion component and reports C101H152N28O22S2 for the free peptide, so a counterion-containing preparation requires a separately specified composition.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "epitalon", "url": "https://purelypeptides.org/research/compounds/epitalon/", "displayName": "Epitalon", "canonicalName": "Epitalon", "moleculeType": "peptide", "aliases": [ "Epithalon", "Epithalone", "AEDG peptide" ], "developmentCodes": [], "externalIds": { "cas": "307297-39-8", "pubChemCid": "219042", "unii": "O65P17785G" }, "sequence": { "oneLetter": "AEDG", "threeLetter": [ "Ala", "Glu", "Asp", "Gly" ], "notes": "Tetrapeptide Ala-Glu-Asp-Gly, stated identically in the PubChem synonym record and in the source literature." }, "molecularFormula": "C14H22N4O9", "molecularWeightDa": 390.35, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-12374906", "pmid-31808038", "pmid-12937682" ], "identityOverview": "Epitalon is a synthetic tetrapeptide, Ala-Glu-Asp-Gly, described in the source literature as a short peptide designed following work on pineal tissue extracts.", "nomenclatureNotes": "Epitalon, Epithalon, and Epithalone all refer to the same tetrapeptide. A second registry number, 64082-79-7, also appears in the PubChem record; 307297-39-8 is carried here as primary. The literature describes the peptide as having been designed following work on a pineal extract preparation named Epithalamin, from which the name derives.", "structuralNotes": "The sequence comprises four proteinogenic residues with no reported terminal modification in the PubChem record. Two of the four side chains are acidic, giving the peptide a low isoelectric point relative to neutral tetrapeptides.", "analyticalNotes": "At 390 Da this is among the smallest peptides in the catalog, and it contains no aromatic residues, so UV detection at 280 nm gives no useful chromophore response. Identity confirmation relies on mass and sequence-level methods.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-08-23" }, { "id": "exenatide", "url": "https://purelypeptides.org/research/compounds/exenatide/", "displayName": "Exenatide", "canonicalName": "Exenatide", "moleculeType": "peptide", "aliases": [ "Exendin-4" ], "developmentCodes": [], "externalIds": { "cas": "141758-74-9", "pubChemCid": "45588096", "unii": "9P1872D4OL" }, "sequence": { "oneLetter": "HGEGTFTSDLSKQMEEEAVRLFIEWLKNGGPSSGAPPPS", "threeLetter": [ "His", "Gly", "Glu", "Gly", "Thr", "Phe", "Thr", "Ser", "Asp", "Leu", "Ser", "Lys", "Gln", "Met", "Glu", "Glu", "Glu", "Ala", "Val", "Arg", "Leu", "Phe", "Ile", "Glu", "Trp", "Leu", "Lys", "Asn", "Gly", "Gly", "Pro", "Ser", "Ser", "Gly", "Ala", "Pro", "Pro", "Pro", "Ser" ], "notes": "Thirty-nine residues, all L, with a free N-terminus and a C-terminal amide on Ser39. The methionine at position 14 is the only sulfur-containing residue and there is no cysteine, which is what the single sulfur atom in the recorded formula corresponds to. Exendin-3 differs at positions 2 and 3 only — Ser2-Asp3 in place of Gly2-Glu3 — so those two positions are the whole of the difference this entry describes. With the Ser39 amide applied, these residues derive the recorded formula and mass, and the automated sequence verifier now checks that on every build rather than leaving it to prose." }, "molecularFormula": "C184H282N50O60S", "molecularWeightDa": 4187, "terminalModifications": [ "Free N-terminus", "C-terminal serine amide" ], "compoundClassIds": [ "glp-1-receptor-peptide-analogs" ], "mechanismIds": [ "glp-1-receptor" ], "relatedCompoundIds": [ "liraglutide", "semaglutide", "orforglipron", "glp-1-7-36-amide", "glp-2" ], "referenceIds": [ "pmid-1313797", "pmid-1574068", "pmid-23684623", "pmid-28538729", "pmid-21094903", "pmid-37528104", "pmid-15386269" ], "identityOverview": "Exenatide is synthetic exendin-4, a 39-residue peptide with an N-terminal histidine and a C-terminal serine amide; the natural peptide was isolated from Heloderma suspectum venom and characterized as a member of the glucagon superfamily. Horváth et al. (PMID 37528104) place the exendins among the gastrointestinal peptides of the glucagon family.", "nomenclatureNotes": "Hudson and Andersen (PMID 15386269) describe exenatide as synthetic exendin-4; Eng et al. (PMID 1313797) isolated exendin-4 from the venom of the lizard Heloderma suspectum. Exendin-3, isolated from Heloderma horridum, differs by two substitutions at positions 2 and 3. Both are members of the glucagon superfamily.", "structuralNotes": "Exenatide is synthetic exendin-4 and shares GLP-1 receptor agonism with the native hormone. Its direct sequence parent is exendin-4, a peptide of non-human origin, not human GLP-1. Shared receptor activity and general architecture do not establish human GLP-1 scaffold ancestry, and no human-GLP-1 substitution table applies to it. The related GLP-1(7-36) amide entry is a native receptor comparator only, not a structural parent. The isolation report describes a 39-amino-acid peptide recovered using a sequencing assay for peptides bearing an amino-terminal histidine. Exendin-4 differs from exendin-3 by two amino acid substitutions, Gly2-Glu3 in place of Ser2-Asp3, and is otherwise identical; the report notes that this difference is sufficient to change the observed bioactivity profile. In dispersed guinea pig pancreatic acini, exendin-4 produced a monophasic increase in cAMP that was progressively inhibited by the antagonist exendin-(9-39) amide, whereas exendin-3 produced a biphasic response and interacted additionally with VIP receptors.", "analyticalNotes": "The single sulfur atom in the molecular formula corresponds to one sulfur-containing residue. The C-terminal amide is part of the declared identity and distinguishes the peptide from a free-acid preparation of the same sequence.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-12", "lastVerifiedDate": "2026-08-23" }, { "id": "liraglutide", "url": "https://purelypeptides.org/research/compounds/liraglutide/", "displayName": "Liraglutide", "canonicalName": "Liraglutide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "NN2211" ], "externalIds": { "cas": "204656-20-2", "pubChemCid": "16134956", "unii": "839I73S42A" }, "sequence": { "oneLetter": "HAEGTFTSDVSSYLEGQAAKEFIAWLVRGRG", "threeLetter": [ "His", "Ala", "Glu", "Gly", "Thr", "Phe", "Thr", "Ser", "Asp", "Val", "Ser", "Ser", "Tyr", "Leu", "Glu", "Gly", "Gln", "Ala", "Ala", "Lys", "Glu", "Phe", "Ile", "Ala", "Trp", "Leu", "Val", "Arg", "Gly", "Arg", "Gly" ], "notes": "Thirty-one main-chain residues numbered 1-31, which are GLP-1 residues 7-37: a GLP-1 position number is the array index plus six. Arg28 is the Lys34Arg substitution. The Lys20 side chain (Lys26 in GLP-1 numbering) carries an N-alpha-palmitoyl-L-glutamyl group joined through the glutamate gamma-carboxyl; that glutamate belongs to the side chain, not the main chain, and the one-letter string cannot show it. PubChem CID 16134956 encodes this structure with a free N-terminus and a free C-terminal carboxyl. Summing the thirty-one residues and removing thirty waters, then adding the glutamyl unit and the palmitoyl group less the two waters of their amide bonds, gives C172H265N43O51 and 3751.26 Da, reproducing the recorded formula." }, "molecularFormula": "C172H265N43O51", "molecularWeightDa": 3751, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "K28R (Lys34Arg in GLP-1 numbering)", "Lys20 side chain N-epsilon-acylated with N-alpha-palmitoyl-L-glutamyl through the glutamate gamma-carboxyl (Lys26 in GLP-1 numbering)" ], "compoundClassIds": [ "glp-1-receptor-peptide-analogs" ], "mechanismIds": [ "glp-1-receptor" ], "relatedCompoundIds": [ "semaglutide", "exenatide", "orforglipron", "glp-1-7-37" ], "referenceIds": [ "pmid-25202980", "pmid-23684623", "pmid-28538729", "pmid-33177239", "pmid-21094903" ], "identityOverview": "Liraglutide is an acylated peptide analog of glucagon-like peptide-1, characterized against the GLP-1 receptor.", "nomenclatureNotes": "PubChem lists NN2211 as a development identifier for the liraglutide molecular record.", "structuralNotes": "Built on the GLP-1(7-37) scaffold by a different strategy from semaglutide. Using native GLP-1 numbering, alanine 8 is retained, lysine 34 becomes arginine, and the lysine 26 side chain carries a C16 palmitoyl group through a single gamma-glutamyl spacer. PubChem CID 16134956 specifies free His1 and Gly31 termini and a Lys20 N-epsilon linkage to the gamma-carboxyl of N-alpha-palmitoyl-L-glutamate, corresponding to His7, Lys26 and Gly37 in GLP-1 numbering. Semaglutide's position-8 substitution and its longer diacid and spacer are not features of liraglutide. The related GLP-1(7-37) entry identifies the native structural parent. Receptor-dependence work using fluorescently labeled liraglutide reported binding within circumventricular organs and uptake into arcuate nucleus neurons expressing proopiomelanocortin and cocaine- and amphetamine-regulated transcript. Binding was not observed in GLP-1 receptor knockout mice, establishing that brain uptake in that model was receptor-dependent.", "analyticalNotes": "Identity assessment must account for both the peptide backbone and the acyl modification represented in the PubChem molecular record, as for other acylated GLP-1 analogs in this library.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "semax", "url": "https://purelypeptides.org/research/compounds/semax/", "displayName": "Semax", "canonicalName": "Semax", "moleculeType": "peptide", "aliases": [ "ACTH(4-7)-Pro-Gly-Pro" ], "developmentCodes": [], "externalIds": { "cas": "80714-61-0", "pubChemCid": "9811102", "unii": "I5FAL2585H" }, "sequence": { "oneLetter": "MEHFPGP", "threeLetter": [ "Met", "Glu", "His", "Phe", "Pro", "Gly", "Pro" ], "notes": "Sequence Met-Glu-His-Phe-Pro-Gly-Pro. Met-Glu-His-Phe is residues 4 to 7 of human ACTH(1-39) (SYSMEHFRWGKPVGKKRRPVKVYPNGAEDESAEAFPLEF); Pro-Gly-Pro is the synthetic C-terminal extension, not an ACTH sequence. The molecular formula and average mass recorded below are the values derived from this sequence." }, "molecularFormula": "C37H51N9O10S", "molecularWeightDa": 813.9, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [ "selank", "n-acetyl-semax-amidate" ], "referenceIds": [ "pmid-31667971", "pmid-16996037" ], "identityOverview": "Semax is a synthetic heptapeptide corresponding to residues 4 to 7 of adrenocorticotropic hormone extended at the C-terminus with the tripeptide Pro-Gly-Pro.", "nomenclatureNotes": "The PubChem record describes Semax as ACTH(4-7) extended with Pro-Gly-Pro. The catalog separately lists N-acetyl semax amidate, which carries an N-terminal acetyl group and a C-terminal amide; that is a distinct molecule with a different formula, mass, and registry number, and it is not covered by this record. Much of the published literature instead describes Semax as an ACTH(4-10) analogue. Both descriptions refer to the same molecule: Semax retains ACTH residues 4 to 7 (Met-Glu-His-Phe) and substitutes Pro-Gly-Pro for residues 8 to 10 (Arg-Trp-Gly). This record uses the ACTH(4-7)-plus-Pro-Gly-Pro form because it states the composition of the molecule rather than the fragment it was designed from.", "structuralNotes": "The design follows a fragment-plus-extension pattern: a short sequence taken from a larger endogenous regulatory peptide, extended with a C-terminal Pro-Gly-Pro tripeptide. Selank, also in this library, was constructed on the same pattern from a different parent fragment.", "analyticalNotes": "The single sulfur atom corresponds to the N-terminal methionine. Vanhee et al. (PMID 31667971) is cited here for formula and mass corroboration only, not as the original source of the Semax name-to-sequence mapping. Table 1 lists the reference standard purchased from Sigma Aldrich, lot 035M4701V, rather than a composition assigned to the seized material. Its C37H51N9O10S formula matches this record. The table reports 813.3480 Da monoisotopic mass; this library retains 813.9 Da average mass. These conventions describe the same composition. The N-acetylated, C-terminally amidated variant has a different composition and must be distinguished in identity analysis.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-10-16" }, { "id": "selank", "url": "https://purelypeptides.org/research/compounds/selank/", "displayName": "Selank", "canonicalName": "Selank", "moleculeType": "peptide", "aliases": [ "Selanc", "Tuftsin-Pro-Gly-Pro", "TP-7" ], "developmentCodes": [ "TP-7" ], "externalIds": { "cas": "129954-34-3", "pubChemCid": "11765600", "unii": "TS9JR8EP1G" }, "sequence": { "oneLetter": "TKPRPGP", "threeLetter": [ "Thr", "Lys", "Pro", "Arg", "Pro", "Gly", "Pro" ], "notes": "Sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, stated in the PubChem synonym record. The first four residues correspond to tuftsin." }, "molecularFormula": "C33H57N11O9", "molecularWeightDa": 751.9, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [ "semax", "n-acetyl-selank-amidate" ], "referenceIds": [ "pmid-31667971", "pmid-26924987" ], "identityOverview": "Selank is a synthetic heptapeptide consisting of the tetrapeptide tuftsin extended at the C-terminus with the tripeptide Pro-Gly-Pro.", "nomenclatureNotes": "Selank is the tetrapeptide tuftsin (Thr-Lys-Pro-Arg) extended at the C-terminus with Pro-Gly-Pro. The catalog separately lists N-acetyl selank amidate, a distinct molecule carrying an N-terminal acetyl group and a C-terminal amide. Registry numbers reported for that modified variant are inconsistent across suppliers and no CAS for it is published here.", "structuralNotes": "Selank follows the same fragment-plus-extension construction as Semax: a short sequence from a larger endogenous parent, extended with a C-terminal Pro-Gly-Pro tripeptide. The parents differ in kind. Semax takes its fragment from ACTH, itself a peptide hormone; tuftsin is a fragment of the Fc region of the immunoglobulin G heavy chain, a protein. The sequence contains three proline residues, two of which are contributed by the extension.", "analyticalNotes": "Vanhee et al. (PMID 31667971) reports TKPRPGP and KTPRPGP as de novo candidates at 1.5 ppm. Arg-C digestion did not separate them; subsequent rLys-C digestion yielded the fragment pair consistent with TKPRPGP. This supports the recorded Selank sequence against that transposition and is not the original source of the Selank name-to-sequence mapping. Table 1 describes custom-synthesized reference standards from Thermo Fisher Scientific, not the seized material. Its C33H57N11O9 formula matches this record. The reported 751.4341 Da is monoisotopic mass; the library retains 751.9 Da average mass. The rLys-C result is specific to the parent peptide and is not transferred to its terminally modified variant.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-10-16" }, { "id": "thymosin-beta-4", "url": "https://purelypeptides.org/research/compounds/thymosin-beta-4/", "displayName": "Thymosin beta-4", "canonicalName": "Timbetasin", "moleculeType": "peptide", "aliases": [ "Thymosin b4", "Tbeta4", "TB4" ], "developmentCodes": [], "externalIds": { "cas": "77591-33-4", "pubChemCid": "16132341", "unii": "2D5MRE3SSY" }, "sequence": { "oneLetter": "SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES", "threeLetter": [ "Ser", "Asp", "Lys", "Pro", "Asp", "Met", "Ala", "Glu", "Ile", "Glu", "Lys", "Phe", "Asp", "Lys", "Ser", "Lys", "Leu", "Lys", "Lys", "Thr", "Glu", "Thr", "Gln", "Glu", "Lys", "Asn", "Pro", "Leu", "Pro", "Ser", "Lys", "Glu", "Thr", "Ile", "Glu", "Gln", "Glu", "Lys", "Gln", "Ala", "Gly", "Glu", "Ser" ], "notes": "Forty-three residues of the mature chain, numbered from Ser1; UniProt P62328 lists the same chain as positions 2-44 because its initiator methionine is removed. Ser1 is N-acetylated and Ser43 carries a free carboxyl, as encoded by PubChem CID 16132341; the one-letter string does not show the acetyl group. Positions 17-23, LKKTETQ, are the fragment described in the TB-500 record. Summing the forty-three residues, removing forty-two waters and adding the acetyl increment C2H2O gives C212H350N56O78S and 4963.51 Da, reproducing the recorded formula." }, "molecularFormula": "C212H350N56O78S", "molecularWeightDa": 4963.5, "terminalModifications": [ "N-terminal acetylation", "Free C-terminal carboxyl" ], "compoundClassIds": [ "thymosin-related-peptides" ], "mechanismIds": [ "actin-sequestration" ], "relatedCompoundIds": [ "ac-sdkp", "tb-500" ], "referenceIds": [ "pmid-17468232", "pmid-11112680", "pmid-20536447", "pmid-17495248", "pmid-26962108", "pmid-15037553", "pmid-23739235" ], "identityOverview": "Thymosin beta-4 is an N-terminally acetylated peptide originally isolated from a thymic tissue fraction and subsequently characterized as a G-actin-sequestering peptide.", "nomenclatureNotes": "Timbetasin is the INN for thymosin beta-4. TB-500 is not this molecule. That name designates a distinct seven-residue fragment, carried separately in PubChem as CID 62707662 with a molecular mass of approximately 889 daltons, against 4963.5 daltons for the full-length peptide described here; the two records also carry different UNII identifiers. Material sold as TB-500 should be identified against the intended species rather than against this record. The PubChem synonym set for this record also includes a carbon-13-labelled internal standard used in mass spectrometry; that labelled compound has a different exact mass and must not be used as an identity reference for unlabelled material.", "structuralNotes": "The peptide was isolated from thymosin fraction 5, a mixture of polypeptides, alongside thymosin alpha-1 and polypeptide beta-1. The source review records that none of the isolated peptides proved to be thymic hormones. G-actin sequestration was identified in 1990. The peptide is reported to be unstructured in isolation and to fold into a stable conformation on binding G-actin. Related beta-thymosins have been isolated and sequenced from several species.", "analyticalNotes": "The single sulfur atom corresponds to one sulfur-containing residue; oxidized forms of the peptide are described separately in the literature and are a relevant degradation consideration. The N-terminal acetyl group is part of the declared identity. Reference material should be confirmed as unlabelled, because the PubChem record groups a carbon-13-labelled standard under the same identifier.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "ghrp-6", "url": "https://purelypeptides.org/research/compounds/ghrp-6/", "displayName": "GHRP-6", "canonicalName": "GHRP-6", "moleculeType": "peptide", "aliases": [ "Hexapeptide-2", "Growth hormone-releasing peptide-6" ], "developmentCodes": [], "externalIds": { "cas": "87616-84-0", "pubChemCid": "9919153", "unii": "4H7N4I6X6A" }, "sequence": { "threeLetter": [ "His", "D-Trp", "Ala", "Trp", "D-Phe", "Lys" ], "notes": "Six residues, His-D-Trp-Ala-Trp-D-Phe-Lys, with a free N-terminus and a C-terminal amide, as encoded by PubChem CID 9919153. No one-letter string is recorded, because it cannot show the D-configuration of Trp2 and Phe5. Summing the six residues, removing five waters and converting the C-terminal carboxyl to an amide gives C46H56N12O6 and 873.03 Da, reproducing the recorded formula." }, "molecularFormula": "C46H56N12O6", "molecularWeightDa": 873, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [ "D-tryptophan at position 2", "D-phenylalanine at position 5" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor" ], "relatedCompoundIds": [ "ipamorelin", "pralmorelin", "examorelin", "octanoyl-ghrelin" ], "referenceIds": [ "pmid-11322507", "pmid-9849822", "pmid-32814772", "pmid-21298258", "pmid-34417468" ], "identityOverview": "GHRP-6 is a synthetic hexapeptide with a C-terminal amide, characterized as an agonist at the growth hormone secretagogue receptor.", "nomenclatureNotes": "GHRP-6 is a hexapeptide with a C-terminal amide. A separate PubChem record for the same formula and mass carries a synonym belonging to GHRP-2, a different peptide; identity should be established against CAS 87616-84-0 rather than by name matching alone.", "structuralNotes": "The growth hormone secretagogue receptor was cloned and characterized as an orphan G-protein-coupled receptor mediating the activity of the growth hormone-releasing peptides. GHRP-6 activated a receptor family member isolated from a pufferfish genomic library on expression in HEK293 cells, and the source review reports that the receptor has been conserved for at least 400 million years, with ghrelin confirmed as its full endogenous agonist. Ipamorelin, also in this library, was identified within a series of compounds lacking the central Ala-Trp dipeptide of GHRP-1, and was reported not to raise ACTH and cortisol at doses where GHRP-6 and GHRP-2 did.", "analyticalNotes": "The molecular formula contains no sulfur. PubChem CID 9919153 encodes D-tryptophan at position 2 and D-phenylalanine at position 5, with a free His1 amino group and a Lys6 amide; a plain one-letter sequence cannot specify those configurations. Because a second PubChem record shares this formula and mass while carrying a different peptide's synonym, mass alone does not establish identity within this compound family; sequence-level confirmation is required.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "sermorelin", "url": "https://purelypeptides.org/research/compounds/sermorelin/", "displayName": "Sermorelin", "canonicalName": "Sermorelin", "moleculeType": "peptide", "aliases": [ "GRF(1-29)", "Sermorelina", "Sermorelinum" ], "developmentCodes": [], "externalIds": { "cas": "86168-78-7", "pubChemCid": "16132413", "unii": "89243S03TE" }, "sequence": { "oneLetter": "YADAIFTNSYRKVLGQLSARKLLQDIMSR", "threeLetter": [ "Tyr", "Ala", "Asp", "Ala", "Ile", "Phe", "Thr", "Asn", "Ser", "Tyr", "Arg", "Lys", "Val", "Leu", "Gly", "Gln", "Leu", "Ser", "Ala", "Arg", "Lys", "Leu", "Leu", "Gln", "Asp", "Ile", "Met", "Ser", "Arg" ], "notes": "The N-terminal 29 residues of human growth hormone-releasing hormone, carried as a C-terminal amide. The recorded molecular formula and mass are the values this sequence derives with that amide applied; without it the derivation gives the free acid and does not match. The IUPHAR/BPS Guide to Pharmacology (ligand 6998, release 2026.3.1) prints a thirty-residue sermorelin sequence ending Gln30; this record keeps the twenty-nine-residue fragment ending in Arg29 amide, matching PubChem CID 16132413." }, "molecularFormula": "C149H246N44O42S", "molecularWeightDa": 3357.9, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Arg29" ], "compoundClassIds": [ "ghrh-analogs" ], "mechanismIds": [ "ghrh-receptor" ], "relatedCompoundIds": [ "cjc-1295", "tesamorelin" ], "referenceIds": [ "pmid-15817669", "pmid-14499707", "pmid-2856874" ], "identityOverview": "Sermorelin is the synthetic peptide corresponding to residues 1 to 29 of human growth hormone-releasing factor, the unmodified parent fragment from which several longer-acting analogs are derived.", "nomenclatureNotes": "Sermorelin corresponds to residues 1 to 29 of human growth hormone-releasing factor, the fragment commonly written GRF(1-29). Two related entries are in this library. CJC-1295 is a tetrasubstituted analog of this fragment; the form bearing an added C-terminal maleimidopropionamide lysine, which enables albumin conjugation, is a separate species from the one the CJC-1295 entry describes. Tesamorelin is not a derivative of the fragment: it is the full 44-residue sequence, of which this fragment is the first 29 residues, carrying an N-terminal hexenoyl group and a C-terminal amide.", "structuralNotes": "Sermorelin is the unmodified GRF(1-29) fragment. The cited report synthesised three maleimido derivatives of hGRF(1-29) and bioconjugated them to human serum albumin; all three showed enhanced in vitro stability against dipeptidyl peptidase IV relative to the unmodified fragment, and were active in a growth hormone secretion assay in cultured rat anterior pituitary cells. That study was designed to identify CJC-1295, not to characterise sermorelin: unmodified hGRF(1-29) appears in it as the comparator against which the conjugates were measured. It is cited here for what it shows about the fragment, not as a characterisation of sermorelin in its own right.", "analyticalNotes": "The single sulfur atom corresponds to the methionine at position 27, the only sulfur-containing residue in the recorded sequence, and is relevant to oxidation-related degradation. Sermorelin and tesamorelin have identical residues at positions 1 to 29, so a comparison that establishes only that shared residue sequence does not show which of the two is present; they differ in chain length, in tesamorelin's N-terminal hexenoyl group and in the position of the C-terminal amide, and mass-based identity methods distinguish them directly. CJC-1295 differs from this sequence at four positions, which are recorded on its entry.", "publishedDate": "2026-09-04", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "ara-290", "url": "https://purelypeptides.org/research/compounds/ara-290/", "displayName": "ARA-290", "canonicalName": "Cibinetide", "moleculeType": "peptide", "aliases": [ "ARA 290", "Cibinetida", "Cibinetidum" ], "developmentCodes": [ "PHBSP" ], "externalIds": { "cas": "1208243-50-8", "pubChemCid": "91810664", "unii": "9W5677JKDA" }, "sequence": { "threeLetter": [ "pGlu", "Glu", "Gln", "Leu", "Glu", "Arg", "Ala", "Leu", "Asn", "Ser", "Ser" ], "notes": "pGlu-Glu-Gln-Leu-Glu-Arg-Ala-Leu-Asn-Ser-Ser, eleven residues corresponding to a surface region of helix B of erythropoietin. No oneLetter string is recorded: position 1 is pyroglutamate, and writing it as Q would denote glutamine, a different residue worth 17.03 Da more. Summing the eleven residues with pyroglutamate at position 1 and adding one water gives C51H84N16O21 and 1257.32 Da, which reproduces the recorded formula exactly and the recorded mass to 0.02 Da. That arithmetic is the identity check this record rests on; the automated sequence verifier cannot reach it, because pyroglutamate is outside its derivation model." }, "molecularFormula": "C51H84N16O21", "molecularWeightDa": 1257.3, "terminalModifications": [ "N-terminal pyroglutamate", "Free C-terminal carboxyl" ], "compoundClassIds": [], "mechanismIds": [ "innate-repair-receptor" ], "relatedCompoundIds": [], "referenceIds": [ "pmid-29026145", "pmid-27634442", "pmid-18676614", "pmid-21873879", "pmid-30127368" ], "identityOverview": "Cibinetide is a synthetic peptide corresponding to a surface region of erythropoietin, characterized in the literature as a selective agonist at a heteromeric receptor complex distinct from the erythropoietin receptor homodimer.", "nomenclatureNotes": "Cibinetide is the INN. The development code PHBSP appears in the PubChem synonym set and abbreviates pyroglutamate helix B surface peptide; the related designation HBSP (helix B surface peptide) is used in the literature for the same structural concept. The peptide corresponds to a surface region of the erythropoietin molecule that is not involved in erythropoietin receptor homodimer binding.", "structuralNotes": "The source literature distinguishes two receptor arrangements: erythropoietin receptor homodimers, which mediate erythroid maturation, and heteromers of the erythropoietin receptor with the beta common receptor (CD131), termed the innate repair receptor. Cibinetide is characterized in that literature as a selective agonist at the latter. Two qualifications belong with that characterization and are stated here rather than left to the reader. The first is that the heteroreceptor is not an established structure. An independent group tested the proposal directly, examining the extracellular regions of the two receptors both in the presence and in the absence of this peptide, and reported that the two do not specifically associate; the same work described the proposed complex as controversial. No biophysical demonstration of a direct association has been published. The second is that the supporting evidence comes substantially from the group that proposed the complex: three of the five papers cited on this record share an author set with the compound's developer, and the paper reporting the contrary result is not among them. This record therefore reports the selectivity as a characterization in the literature, and makes no claim about what follows for erythropoietic activity.", "analyticalNotes": "The molecular formula contains no sulfur, so sulfur-based oxidation pathways do not apply. Identity confirmation relies on mass and sequence-level methods. PubChem CID 91810664 encodes L-pyroglutamate at residue 1 and a free Ser11 carboxyl, with the complete structure giving C51H84N16O21 and a calculated average mass of 1257.32 Da.", "publishedDate": "2026-09-12", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-08-23" }, { "id": "kpv", "url": "https://purelypeptides.org/research/compounds/kpv/", "displayName": "KPV", "canonicalName": "KPV", "moleculeType": "peptide", "aliases": [ "Lys-Pro-Val", "alpha-MSH (11-13)", "MSH (11-13)" ], "developmentCodes": [], "externalIds": { "cas": "67727-97-3", "pubChemCid": "125672", "unii": "7V6LGD8S5R" }, "sequence": { "oneLetter": "KPV", "threeLetter": [ "Lys", "Pro", "Val" ], "notes": "Tripeptide Lys-Pro-Val, corresponding to residues 11 to 13 of alpha-melanocyte-stimulating hormone. The correspondence is stated in the PubChem synonym record and in the source literature. The same three residues occupy positions 11 to 13 of Melanotan I, where Lys11 follows Gly10 and Val13 carries the C-terminal amide; that containment does not fix the termini of isolated KPV." }, "molecularFormula": "C16H30N4O4", "molecularWeightDa": 342.43, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "melanocortin-fragment-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "melanotan-i", "alpha-msh", "cosyntropin" ], "referenceIds": [ "pmid-1788140", "pmid-11268347", "pmid-12750433" ], "identityOverview": "KPV is a synthetic tripeptide, Lys-Pro-Val, corresponding to the C-terminal three residues of alpha-melanocyte-stimulating hormone.", "nomenclatureNotes": "KPV is the C-terminal tripeptide of alpha-melanocyte-stimulating hormone, residues 11 to 13, and is written in the literature as alpha-MSH(11-13). GSRS UNII 7V6LGD8S5R identifies free-terminal L-Lys-L-Pro-L-Val and includes CAS 67727-97-3 and PubChem CID 125672; acetate UNII HX2YJ5Z225 identifies a separate form.", "structuralNotes": "Structure-activity work on acetylated, amidated analogs of the alpha-MSH(11-13) sequence reports that substituting D-amino acids at each position affects activity differently: the L-configuration of the proline at position 12 was required, the L-configuration of the lysine at position 11 was not, and D-valine substitution at position 13 was reported to increase activity approximately fourfold relative to the all-L peptide. The source literature also reports that the tripeptide is associated with inhibition of NF-kappa-B activation through preservation of the inhibitory protein I-kappa-B-alpha.", "analyticalNotes": "At 342 Da this is among the smallest peptides in the library. The sequence contains no aromatic residues and no sulfur, so UV detection at 280 nm gives no useful chromophore response and sulfur-based oxidation pathways do not apply. Because commercially supplied material may be acetylated at the N-terminus and amidated at the C-terminus, identity methods must establish which form is present.", "publishedDate": "2026-09-12", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "pe-22-28", "url": "https://purelypeptides.org/research/compounds/pe-22-28/", "displayName": "PE 22-28", "canonicalName": "PE 22-28", "moleculeType": "peptide", "aliases": [ "PE(22-28)", "Sortilin propeptide (22-28)" ], "developmentCodes": [], "externalIds": { "pubChemCid": "165437303" }, "sequence": { "oneLetter": "GVSWGLR", "threeLetter": [ "Gly", "Val", "Ser", "Trp", "Gly", "Leu", "Arg" ], "notes": "Heptapeptide Gly-Val-Ser-Trp-Gly-Leu-Arg. The PE in the name denotes the sortilin PROPEPTIDE, and 22 to 28 are its residue positions within that propeptide — not within any peptide called PE." }, "molecularFormula": "C35H55N11O9", "molecularWeightDa": 773.9, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [ "spadin" ], "referenceIds": [ "pmid-28955242", "pmid-20405001" ], "identityOverview": "PE 22-28 is a synthetic heptapeptide corresponding to residues 22 to 28 of the sortilin propeptide. It is not a fragment of spexin; see the nomenclature note.", "nomenclatureNotes": "CORRECTION, 2026-09-13. This entry previously described PE 22-28 as residues 22 to 28 of spexin and carried the alias Spexin (22-28). That was wrong, and it is wrong for a reason that can be checked without any source: mature spexin is fourteen residues long, so residues 22 to 28 of it do not exist, and the sequence Gly-Val-Ser-Trp-Gly-Leu-Arg appears nowhere within spexin's sequence Asn-Trp-Thr-Pro-Gln-Ala-Met-Leu-Tyr-Leu-Lys-Gly-Ala-Gln. The PE in PE 22-28 denotes the sortilin propeptide, not a peptide. Gly-Val-Ser-Trp-Gly-Leu-Arg is residues 22 to 28 of that propeptide, and the same seven residues form the C-terminal end of the longer sortilin-propeptide-derived peptide spadin. PE 22-28 has no sequence relationship to spexin at all.", "structuralNotes": "PE 22-28 was designed from degradation products of spadin, which derives from the sortilin propeptide. Patch-clamp experiments in hTREK-1/HEK cells measured TREK-1 inhibition at approximately 0.1 nM, against 40-60 nM for spadin. That source is internally inconsistent about which peptide carries which value: its abstract and results report 0.12 nM for PE 22-28 and 0.10 nM for the Gly22-Ala analog, while its figure legend and discussion transpose the two. No single figure is reproduced here as though the source agreed with itself. This is direct evidence about the heptapeptide in that assay. The related founding spadin study provides propeptide and channel-binding context. The sequence contains one tryptophan, its only aromatic residue.", "analyticalNotes": "The single tryptophan provides a UV chromophore near 280 nm, unlike several other short peptides in this library. PubChem CID 165437303 encodes free-terminal GVSWGLR and includes CAS 1801959-12-5 and acetate wording among synonyms, but its structure contains no acetate and the CAS assignment remains independently unconfirmed. The seven-residue sequence must be established directly: a heptapeptide cannot be confirmed by demonstrating that its residues appear inside a longer peptide, and a response attributed to a related longer peptide is not identity evidence for this one.", "publishedDate": "2026-09-12", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "orforglipron", "url": "https://purelypeptides.org/research/compounds/orforglipron/", "displayName": "Orforglipron", "canonicalName": "Orforglipron", "moleculeType": "small-molecule", "aliases": [], "developmentCodes": [ "LY3502970" ], "externalIds": { "cas": "2212020-52-3", "pubChemCid": "137319706", "unii": "7ZW40D021M" }, "molecularFormula": "C48H48F2N10O5", "molecularWeightDa": 883, "compoundClassIds": [ "nonpeptide-receptor-agonists" ], "mechanismIds": [ "glp-1-receptor" ], "relatedCompoundIds": [ "semaglutide", "liraglutide", "exenatide", "tirzepatide", "glp-1-7-36-amide" ], "referenceIds": [ "pmid-39693407", "pmid-33177239" ], "identityOverview": "Orforglipron is a synthetic nonpeptide molecule characterized as a selective, high-affinity agonist at the human GLP-1 receptor.", "nomenclatureNotes": "Orforglipron is a nonpeptide small molecule, not a peptide. It is documented in this library because it is characterized at the GLP-1 receptor, the same receptor as the peptide analogs semaglutide, liraglutide and exenatide, and because the cited structural work compares nonpeptide and peptide binding at that receptor. The development code LY3502970 appears in the PubChem synonym set and throughout the primary literature; both designations resolve to the same molecular record.", "structuralNotes": "Orforglipron is a nonpeptide agonist of the receptor activated by endogenous GLP-1. Residue substitutions relative to GLP-1 are not applicable, rather than unknown or undetermined: this molecule is not a peptide and has no sequence to align. The related GLP-1(7-36) amide entry is a native receptor comparator only, not a structural parent. Competition binding experiments report orforglipron as a high-affinity ligand of the human GLP-1 receptor with an inhibition constant of approximately 1 nM. Signal transduction assays report low intrinsic activation of downstream effectors and negligible beta-arrestin recruitment. Structural work on the same molecule reports a high-resolution active-state receptor structure in which the nonpeptide agonist occupies a binding pocket in the upper helical bundle that is distinct from the peptide-binding mode, which is the basis for comparing the two ligand classes at a single receptor.", "analyticalNotes": "As a nonpeptide molecule the analytical considerations differ from the peptides in this library: there is no amino acid sequence to confirm, and the two fluorine atoms in the molecular formula are relevant to mass-based identity confirmation.", "publishedDate": "2026-09-12", "updatedDate": "2026-09-15", "lastVerifiedDate": "2026-08-23" }, { "id": "matrixyl", "url": "https://purelypeptides.org/research/compounds/matrixyl/", "displayName": "Matrixyl", "canonicalName": "Palmitoyl pentapeptide-4", "moleculeType": "peptide", "aliases": [ "Pal-KTTKS", "Palmitoyl-KTTKS", "Palmitoyl pentapeptide-3" ], "developmentCodes": [], "externalIds": { "cas": "214047-00-4", "pubChemCid": "9897237", "unii": "KK181SM5JG" }, "sequence": { "oneLetter": "KTTKS", "threeLetter": [ "Lys", "Thr", "Thr", "Lys", "Ser" ], "notes": "The peptide core is KTTKS, five L residues, with a palmitoyl group on the Lys1 alpha-amino group and a free Ser5 carboxyl, as encoded by PubChem CID 9897237. The palmitoyl group is recorded as a terminal modification, not as a residue, so the one-letter string shows the core only. Summing the five residues, removing four waters and adding the palmitoyl increment C16H30O gives C39H75N7O10 and 802.07 Da, reproducing the recorded formula." }, "molecularFormula": "C39H75N7O10", "molecularWeightDa": 802.1, "terminalModifications": [ "N-terminal palmitoylation", "Free C-terminal carboxyl" ], "compoundClassIds": [ "matrikine-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "kttks", "pal-ghk" ], "referenceIds": [ "pmid-21535443", "pmid-8486721", "pmid-25143811", "pmid-19393372", "pmid-23822110" ], "identityOverview": "Palmitoyl pentapeptide-4 is the pentapeptide KTTKS with an N-terminal palmitoyl group, corresponding to a fragment sequence of type I procollagen.", "nomenclatureNotes": "Matrixyl is a trade name for palmitoyl pentapeptide-4, the pentapeptide Lys-Thr-Thr-Lys-Ser (KTTKS) carrying an N-terminal palmitoyl group. The source review notes that KTTKS has become erroneously associated with the term pentapeptide in cosmetic marketing, and that the material has also been designated palmitoyl pentapeptide-3 under earlier INCI naming. Identity should be established against CAS 214047-00-4.", "structuralNotes": "The palmitoyl group is a sixteen-carbon acyl chain attached at the N-terminus, and accounts for a substantial share of the molecular mass relative to the five-residue peptide core. PubChem CID 9897237 places palmitoyl on the Lys1 alpha-amino group and retains a free Ser5 carboxyl, distinguishing this structure from a lysine-side-chain-acylated positional isomer. The source review reports an in vitro basis for action on fibroblasts through stimulation of extracellular matrix synthesis, describing the reported stimulatory effect as specific to collagen types I and III and to fibronectin expression.", "analyticalNotes": "The palmitoyl modification dominates the lipophilicity of the molecule and is part of its declared identity; an unmodified KTTKS preparation is a different substance with a different mass. The sequence contains no aromatic residues, so UV detection at 280 nm gives no useful chromophore response. The source review notes a surprising absence of in vitro skin penetration data in the published literature.", "publishedDate": "2026-09-12", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "dsip", "url": "https://purelypeptides.org/research/compounds/dsip/", "displayName": "DSIP", "canonicalName": "Delta sleep-inducing peptide", "moleculeType": "peptide", "aliases": [ "DSIP", "Delta-sleep-inducing peptide" ], "developmentCodes": [], "externalIds": { "cas": "62568-57-4", "pubChemCid": "68816", "unii": "YN28Z5YZ73" }, "sequence": { "oneLetter": "WAGGDASGE", "threeLetter": [ "Trp", "Ala", "Gly", "Gly", "Asp", "Ala", "Ser", "Gly", "Glu" ], "notes": "Nonapeptide Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, determined by amino acid analysis and sequence determination in the original isolation report." }, "molecularFormula": "C35H48N10O15", "molecularWeightDa": 848.8, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-568769", "pmid-6145137" ], "identityOverview": "DSIP is a synthetic nonapeptide, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, first isolated and sequenced in 1978.", "nomenclatureNotes": "The name records the context in which the peptide was originally isolated and does not describe a verified property of the material. The peptide was isolated from the extracorporeal dialysate of cerebral venous blood in rabbits and named at that time. A molecular weight of 849 is reported in the source literature, consistent with the PubChem record.", "structuralNotes": "The original report describes synthesis of the nonapeptide together with five possible metabolic fragments, two nonapeptide analogues with one and two amino acid exchanges, and a related tripeptide. It records that the aspartyl residue at position 5 must be in the alpha-aspartyl form: the report states that only the pure alpha-aspartyl peptide showed the described activity, in contrast to its beta-Asp isomer.", "analyticalNotes": "The alpha-aspartyl versus beta-aspartyl distinction at position 5 is an identity consideration, not merely a synthesis detail: the two isomers share a molecular formula and mass, so mass spectrometry alone does not distinguish them and a sequence- or separation-based method is required. The single tryptophan residue provides a UV chromophore near 280 nm.", "publishedDate": "2026-09-12", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-08-23" }, { "id": "melanotan-ii", "url": "https://purelypeptides.org/research/compounds/melanotan-ii/", "displayName": "Melanotan II", "canonicalName": "Melanotan II", "moleculeType": "peptide", "aliases": [ "Melanotan-II", "MT-II", "MT-2" ], "developmentCodes": [], "externalIds": { "cas": "121062-08-6", "pubChemCid": "92432", "unii": "UPF5CJ93X7" }, "sequence": { "threeLetter": [ "Nle", "Asp", "His", "D-Phe", "Arg", "Trp", "Lys" ], "notes": "A linear one-letter string cannot describe this molecule and none is published here. The peptide is seven residues, closed into a ring by a lactam bridge between the aspartate side-chain carboxyl and the lysine side-chain amine; the N-terminal norleucine sits OUTSIDE that ring, so the cyclized portion spans six residues. Al-Obeidi et al. (PMID 2555512) describe the lactam as joining Asp5 and Lys10 in alpha-MSH numbering, which are Asp2 and Lys7 of this seven-residue chain. It also carries a D-phenylalanine. Written as a plain seven-residue sequence it would denote a different, linear compound.", "rings": [ { "kind": "side-chain lactam", "from": { "position": 2, "residue": "Asp", "atom": "side-chain carboxyl (Cγ)" }, "to": { "position": 7, "residue": "Lys", "atom": "side-chain ε-amino nitrogen (Nζ)" }, "sourceNumbering": "Asp5–Lys10 in alpha-MSH numbering", "referenceId": "pmid-2555512" } ] }, "molecularFormula": "C50H69N15O9", "molecularWeightDa": 1024.18, "terminalModifications": [ "N-terminal acetylation", "C-terminal amide" ], "structuralModifications": [ "Side-chain to side-chain lactam bridge, Asp to Lys", "Norleucine substitution", "D-phenylalanine substitution" ], "compoundClassIds": [ "cyclic-melanocortin-analogs" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "pt-141", "melanotan-i", "alpha-msh", "shu9119", "setmelanotide" ], "referenceIds": [ "pmid-10447101", "pmid-35188390", "pmid-42340853", "pmid-12750433", "pmid-2555512" ], "identityOverview": "Melanotan II is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone, closed by a lactam bridge between an aspartate and a lysine side chain.", "nomenclatureNotes": "The unqualified word melanotan is not a usable identity field. Melanotan II is this cyclic lactam analog; Melanotan I is afamelanotide, a linear thirteen-residue peptide with a different formula and mass. They are distinct molecules and are never interchangeable as identities — but neither are they unrelated: both are analogs of alpha-melanocyte-stimulating hormone and both belong to the melanocortin family. What differs is the structure.", "structuralNotes": "Structure-activity work on the lactam scaffold reports that replacing the phenylalanine or the tryptophan with alanine abolished measurable activity at human MC3, MC4 and MC5 receptors, while replacing the histidine did not, and that substituting the arginine reduced potency roughly a hundredfold. Retro, enantio and retro-enantio analogs all lost substantial potency, which the source literature attributes primarily to side-chain topology rather than backbone arrangement. Separate work replacing the lactam cyclization with xylene-derived thioether linkers reports that the linker chemistry itself correlates with receptor affinity, indicating the ring is a determinant of the pharmacology rather than a passive constraint.", "analyticalNotes": "The identity question specific to this compound is its relationship to PT-141, which differs only in that the C-terminal amide is a free acid. The calculated neutral monoisotopic masses are 1023.54027 for Melanotan II and 1024.52428 for PT-141, a difference of 0.98402 Da; the average masses are 1024.18 and 1025.17. These are calculated neutral values, not measured mass-to-charge ratios, and an observed ion will differ from them by the charge carriers it picked up. A well-specified measurement separates the two compounds without difficulty. The trap is a measurement that is not well specified, and it has a particular shape here: the first carbon-13 isotope peak of Melanotan II falls at 1024.54363, within 0.0194 Da of PT-141's monoisotopic value. A check that asks only whether a signal appears near 1024.5 is therefore satisfied by either compound, and resolving those two specific peaks needs a resolving power on the order of 53,000 at that mass — a figure that describes the scale of the separation required, not a guarantee of baseline resolution, reliable detection of a minor component, or identification on its own. Practically: a certificate reporting a single rounded mass alongside an HPLC purity figure has not established which of the two is present, and neither has a chromatographic method that was never shown to separate them.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-08-23" }, { "id": "pt-141", "url": "https://purelypeptides.org/research/compounds/pt-141/", "displayName": "PT-141 (Bremelanotide)", "canonicalName": "Bremelanotide", "moleculeType": "peptide", "aliases": [ "Bremelanotide", "PT 141", "PT-141 free base" ], "developmentCodes": [ "PT-141" ], "externalIds": { "cas": "189691-06-3", "pubChemCid": "9941379", "unii": "6Y24O4F92S" }, "sequence": { "threeLetter": [ "Nle", "Asp", "His", "D-Phe", "Arg", "Trp", "Lys" ], "notes": "As with Melanotan II, no linear one-letter string is published here: the peptide is closed by a lactam bridge between the aspartate side-chain carboxyl and the lysine side-chain amine. The single structural difference from Melanotan II is at the C-terminus, which is a free acid rather than an amide. FDA GSRS (UNII 6Y24O4F92S) records the same Asp2-Lys7 side-chain amide; no paper giving both ring positions for the free acid itself is cited here.", "rings": [ { "kind": "side-chain lactam", "from": { "position": 2, "residue": "Asp", "atom": "side-chain carboxyl (Cγ)" }, "to": { "position": 7, "residue": "Lys", "atom": "side-chain ε-amino nitrogen (Nζ)" }, "registrySource": "FDA GSRS UNII 6Y24O4F92S; PubChem CID 9941379" } ] }, "molecularFormula": "C50H68N14O10", "molecularWeightDa": 1025.17, "terminalModifications": [ "N-terminal acetylation", "C-terminal free acid" ], "structuralModifications": [ "Side-chain to side-chain lactam bridge, Asp to Lys", "Norleucine substitution", "D-phenylalanine substitution" ], "compoundClassIds": [ "cyclic-melanocortin-analogs" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "melanotan-ii", "melanotan-i", "alpha-msh", "shu9119", "setmelanotide" ], "referenceIds": [ "pmid-34433901", "pmid-34561620", "pmid-42340853", "pmid-32674774" ], "identityOverview": "PT-141, canonically bremelanotide, is a synthetic cyclic heptapeptide melanocortin receptor agonist, structurally the C-terminal free acid of the Melanotan II lactam scaffold.", "nomenclatureNotes": "Bremelanotide is the canonical substance name; PT-141 is the development code and the name under which the compound is most often supplied. Both denote the same molecule. The compound is structurally the C-terminal free acid of the Melanotan II scaffold — the two share a carbon count and differ by one oxygen for one nitrogen and one hydrogen. Chen et al. (PMID 32674774) describe bremelanotide as deamidated Melanotan II and as a metabolite of Melanotan II.", "structuralNotes": "A cryo-electron microscopy structure of bremelanotide bound to the melanocortin-4 receptor in complex with heterotrimeric Gs protein has been determined, making this one of the few compounds in this library for which an exact-compound receptor-bound structure exists rather than an analog structure. The same work reports structures of the receptor bound to alpha-MSH, to afamelanotide and to a small-molecule ligand, and describes a conserved binding mode across the peptide agonists. Separate work on the activation mechanism of the same receptor used NDP-alpha-MSH and setmelanotide rather than bremelanotide; findings from that work describe the receptor, not this compound.", "analyticalNotes": "See the Melanotan II entry for the full statement of the mass question; it applies symmetrically. The calculated neutral monoisotopic mass of PT-141 is 1024.52428 against 1023.54027 for Melanotan II, and the average masses are 1025.17 and 1024.18 — so the two do not share a rounded mass, and a measurement reported to adequate precision separates them. What does not separate them is a check for a signal near 1024.5, because Melanotan II's first carbon-13 peak sits within 0.0194 Da of PT-141's monoisotopic value. In the direction that matters commercially, material sold as PT-141 is not shown to be PT-141 rather than Melanotan II by a single rounded mass, by retention time on a method never demonstrated to resolve the pair, or by a purity figure. What does establish it is high-resolution mass spectrometry at sufficient resolving power for that specific separation, or a chromatographic method validated to discriminate the amide from the acid against reference material — and in either case the method has to have been chosen with this question in mind.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-08-23" }, { "id": "cagrilintide", "url": "https://purelypeptides.org/research/compounds/cagrilintide/", "displayName": "Cagrilintide", "canonicalName": "Cagrilintide", "moleculeType": "peptide", "aliases": [ "AM833", "AM-833" ], "developmentCodes": [ "NNC0174-0833" ], "externalIds": { "cas": "1415456-99-3", "pubChemCid": "171397054", "unii": "AO43BIF1U8" }, "sequence": { "oneLetter": "KCNTATCATQRLAEFLRHSSNNFGPILPPTNVGSNTP", "notes": "Thirty-seven residues with a Cys2–Cys7 disulfide and a C-terminal amide. The backbone string alone is an incomplete description: the N-terminal lysine carries a gamma-glutamyl linker acylated with a C20 dicarboxylic fatty acid, attached at the alpha-amino group rather than the lysine side chain. A 2026 review by Bousch et al. (PMID 41898461) instead describes the N-terminal lysine as lipidated on its side chain; this record keeps the alpha-amino attachment stated above.", "rings": [ { "kind": "disulfide", "from": { "position": 2, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "registrySource": "FDA GSRS UNII AO43BIF1U8; PubChem CID 171397054" } ] }, "molecularFormula": "C194H312N54O59S2", "molecularWeightDa": 4409.01, "terminalModifications": [ "C-terminal amide", "N-terminal acylation via gamma-glutamyl linker" ], "structuralModifications": [ "Cys2–Cys7 disulfide", "C20 dicarboxylic fatty-acid acylation" ], "compoundClassIds": [ "amylin-and-calcitonin-receptor-agonists" ], "mechanismIds": [ "amylin-and-calcitonin-receptors" ], "relatedCompoundIds": [ "amylin", "pramlintide" ], "referenceIds": [ "pmid-34288673", "pmid-40204768", "pmid-40609154", "pmid-41898461" ], "identityOverview": "Cagrilintide is a long-acting synthetic amylin analog, lipidated and disulfide-cyclized, characterised at the calcitonin receptor and at amylin receptor complexes.", "nomenclatureNotes": "An FDA substance record displays C194H312N54O58S2 against an approximately 4409 Da mass. That oxygen count is inconsistent with both the stated mass and the covalent structure; reconstruction gives O59, matching PubChem. The O58 value is 15.9949 Da lighter and is not a salt or protonation difference. This library records O59 and notes the disagreement rather than silently choosing.", "structuralNotes": "A human amylin analog. Relative to native human amylin it carries glutamate at 14, arginine at 17, prolines at 25, 28 and 29, and proline in place of the C-terminal tyrosine, together with N-terminal lipidation through a gamma-glutamyl spacer to a C20 fatty diacid. The three prolines at 25, 28 and 29 are shared with pramlintide, so cagrilintide is also a lipidated, further-substituted relative of that engineered analog. The existing amylin and pramlintide links describe these structural relationships. The Glu14–Arg17 interaction reported for this peptide is a noncovalent ionic contact, not a lactam bridge. Descriptions that render it as an additional covalent ring describe a different molecule. The only covalent ring is the Cys2–Cys7 disulfide.", "analyticalNotes": "Intact mass cannot distinguish conjugation-site isomers: whether the C20 diacid and gamma-glutamyl linker sit on the N-terminal alpha-amino group or on the Lys1 side chain gives the same formula. Establishing the position requires sequence-resolved tandem MS with coverage across the conjugation site. Disulfide reduction gives a calculated +2.0157 Da change before alkylation, which supports disulfide accounting but does not map connectivity. A matching chromatographic peak or a cAMP response is not identity evidence — related amylin and calcitonin agonists share both.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-12", "lastVerifiedDate": "2026-09-13" }, { "id": "survodutide", "url": "https://purelypeptides.org/research/compounds/survodutide/", "displayName": "Survodutide", "canonicalName": "Survodutide", "moleculeType": "peptide", "aliases": [ "BI 456906", "BI-456906" ], "developmentCodes": [ "BI 456906" ], "externalIds": { "cas": "2805997-46-8", "pubChemCid": "171378821", "unii": "2ALA66NS64" }, "sequence": { "threeLetter": [ "His", "Ac4c", "Gln", "Gly", "Thr", "Phe", "Thr", "Ser", "Asp", "Tyr", "Ser", "Lys", "Tyr", "Leu", "Asp", "Glu", "Arg", "Ala", "Ala", "Lys", "Asp", "Phe", "Ile", "Lys", "Trp", "Leu", "Glu", "Ser", "Ala" ], "notes": "Position 2 is Ac4c, 1-aminocyclobutane-1-carboxylic acid. It is NOT Aib. The two differ by one carbon, 12.0000 Da exactly, and substituting one for the other imports the chemistry of a different peptide. The 29-residue main chain is also not the whole molecule: a gamma-Glu-Gly-Ser-Gly-Ser-Gly-Gly linker is amidated to the Lys24 side chain and carries a C18 dicarboxylic fatty acid." }, "molecularFormula": "C192H289N47O61", "molecularWeightDa": 4231.63, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Ala29" ], "structuralModifications": [ "Ac4c at position 2", "Lys24 side-chain branched linker", "C18 dicarboxylic fatty-acid acylation" ], "compoundClassIds": [ "multi-receptor-incretin-analogs" ], "mechanismIds": [ "glp-1-receptor", "glucagon-receptor" ], "relatedCompoundIds": [ "mazdutide", "glucagon", "glp-1-7-36-amide" ], "referenceIds": [ "pmid-36356832", "pmid-38560764", "pmid-37549266", "pmid-34195230" ], "identityOverview": "Survodutide is a lipidated synthetic peptide agonist at both the GLP-1 receptor and the glucagon receptor, built on a modified glucagon-family backbone with a branched side-chain linker.", "nomenclatureNotes": "A registry representation showing the main chain and the linker as separate sequences does not mean the substance is a mixture of two peptides. Survodutide and mazdutide are both GLP-1/glucagon dual agonists and are not interchangeable: they differ in main-chain sequence, nonstandard residue, conjugation position, linker and lipid. Shared receptor pharmacology is a classification, not chemical equivalence.", "structuralNotes": "The 29-residue main chain is glucagon-derived. Position 2 carries 1-aminocyclobutane-1-carboxylic acid (Ac4c), not the alpha-aminoisobutyric acid found in several other analogs here, with further substitutions along the chain, a C-terminal amide, and a branched linker from the lysine 24 side chain to a C18 fatty diacid. The related glucagon entry identifies scaffold ancestry; GLP-1(7-36) amide is a native receptor comparator. GLP-1 receptor activity is engineered and does not indicate GLP-1 ancestry. Zimmermann et al. (PMID 36356832) describe survodutide as made by introducing modifications into the human glucagon sequence, whereas a review by Cabri et al. (PMID 34195230) calls it an oxyntomodulin analogue; this record follows the design paper. Functional potencies at the two receptors have been reported in a single cAMP assay system containing bovine serum albumin. Those are assay-specific functional values, not equilibrium binding affinities, and protein content in the assay materially affects the apparent profile. The published values should not be restated as an invariant balanced ratio, and a full-versus-partial agonist classification independent of assay conditions is not established.", "analyticalNotes": "Confirmation requires the intact mass, the 29-residue main chain, Ac4c at position 2, conjugation at Lys24, the complete linker, the C18 diacid and the Ala29 amide. Tandem MS coverage is needed on both sides of Lys24; a backbone-only database match does not characterise the branch. A GLP-1R and GCGR cAMP panel confirms a functional profile, not molecular identity, because other dual agonists produce similar responses. For bulk powder, counterion, water and peptide content are separate measurements from chromatographic area purity.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "mazdutide", "url": "https://purelypeptides.org/research/compounds/mazdutide/", "displayName": "Mazdutide", "canonicalName": "Mazdutide", "moleculeType": "peptide", "aliases": [ "IBI362", "IBI-362", "LY3305677", "LY-3305677" ], "developmentCodes": [ "IBI362", "LY3305677" ], "externalIds": { "cas": "2259884-03-0", "pubChemCid": "172871914", "unii": "MB76Z4IBZ5" }, "sequence": { "threeLetter": [ "His", "Aib", "Gln", "Gly", "Thr", "Phe", "Thr", "Ser", "Asp", "Tyr", "Ser", "Lys", "Tyr", "Leu", "Asp", "Glu", "Lys", "Lys", "Ala", "Lys", "Glu", "Phe", "Val", "Glu", "Trp", "Leu", "Leu", "Glu", "Gly", "Gly", "Pro", "Ser", "Ser", "Gly" ], "notes": "Thirty-four residues ending Gly-Gly-Pro-Ser-Ser-Gly with a C-terminal amide. BOTH serines near the C-terminus belong in the sequence; a species missing one would be 87.0320 Da lighter. Position 2 is Aib, 2-aminoisobutyric acid — not Ac4c, which is what survodutide carries. Lys20 is acylated through two AEEA spacers, a gamma-L-glutamyl unit and a C20 dicarboxylic fatty acid." }, "molecularFormula": "C210H322N46O67", "molecularWeightDa": 4563.07, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Gly34" ], "structuralModifications": [ "Aib at position 2", "Lys20 acylation via two AEEA spacers and gamma-Glu", "C20 dicarboxylic fatty-acid acylation" ], "compoundClassIds": [ "multi-receptor-incretin-analogs" ], "mechanismIds": [ "glp-1-receptor", "glucagon-receptor" ], "relatedCompoundIds": [ "survodutide", "oxyntomodulin", "glucagon", "glp-1-7-36-amide" ], "referenceIds": [ "pmid-37549266", "pmid-32682761", "pmid-33933675", "pmid-42628555" ], "identityOverview": "Mazdutide is a lipidated synthetic peptide classified as a GLP-1 and glucagon receptor dual agonist, built on an oxyntomodulin-derived backbone.", "nomenclatureNotes": "The formula recorded here is the WHO-defined structure. PubChem's name-linked record reports C207H317N45O65, which differs by exactly one serine residue — C3H5NO2, 87.0320 Da. That is a difference in covalent peptide composition, not a salt form or a protonation state. PubChem CID 172871914 encodes the specified 34-residue peptide ending GGPSSG-NH2 with Aib2 and the Lys20-linked two-AEEA, gamma-L-glutamyl, C20-diacid modification, whereas CID 167312357 lacks one terminal-region serine. The discrepancy is evidence of a database conflict; it is not evidence about what any particular sample contains. Text extracted from WHO Proposed INN List 126 and Recommended List 88 gives Asp at position 9 in English, French and Spanish, but one indexed copy of List 88 gives Lys in French and Spanish; this record keeps Asp9, which its printed sequence also shows.", "structuralNotes": "Described in its literature as an oxyntomodulin analog. The related oxyntomodulin entry identifies the stated structural parent; no direct derivation from mature glucagon is claimed here. GLP-1(7-36) amide is a native receptor comparator, not a structural parent. Position 2 is alpha-aminoisobutyric acid, not the Ac4c of survodutide, and lipidation uses two AEEA spacers from the lysine 20 side chain. Survodutide and mazdutide share a receptor profile and are not chemically interchangeable. The dual-receptor classification is supported at the target-class level. What is NOT established in the verified source set, and is stated here rather than filled in: a quantitative receptor potency ratio for this compound, matched binding affinities, full-versus-partial agonist classification under defined conditions, and signalling-bias parameters. Every reference in this entry is Class B — none is a mazdutide-bound structure or a mazdutide-specific receptor pharmacology study. Findings from comparator dual agonists describe those comparators. Being oxyntomodulin-derived is not permission to substitute oxyntomodulin's sequence or another dual agonist's data.", "analyticalNotes": "The first identity question is whether a sample matches the WHO-defined composition rather than the mass attached to a name-matched database record. Tandem MS should establish the C-terminal Pro-Ser-Ser-Gly segment and verify both serines independently; a species short one serine is 87.0320 Da lighter, which intact mass can flag but only fragmentation can localise. The remaining features are Aib2, Lys20 conjugation, TWO AEEA spacers, gamma-Glu connectivity, the C20 diacid and the Gly34 amide. A correct intact mass without branch mapping does not exclude a linker-connectivity isomer. GSRS UNII MB76Z4IBZ5 describes the matching sequence and modifications but reports C210H328N46O69 and an estimated 3790.0 Da, conflicting with the structure represented by PubChem CID 172871914. A certificate reporting only HPLC purity and an approximate 4.5 kDa mass does not resolve the database conflict above.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-10-16" }, { "id": "melanotan-i", "url": "https://purelypeptides.org/research/compounds/melanotan-i/", "displayName": "Melanotan I (Afamelanotide)", "canonicalName": "Afamelanotide", "moleculeType": "peptide", "aliases": [ "Melanotan I", "Melanotan-1", "MT-I", "MT-1", "NDP-MSH", "NDP-alpha-MSH" ], "developmentCodes": [ "CUV1647", "MBJ05" ], "externalIds": { "cas": "75921-69-6", "pubChemCid": "16197727", "unii": "QW68W3J66U" }, "sequence": { "threeLetter": [ "Ser", "Tyr", "Ser", "Nle", "Glu", "His", "D-Phe", "Arg", "Trp", "Gly", "Lys", "Pro", "Val" ], "notes": "Thirteen residues, LINEAR — no disulfide and no lactam bridge. Nle is L-norleucine, substituted for the methionine of alpha-MSH; position 7 is D-phenylalanine. N-terminally acetylated and C-terminally amidated." }, "molecularFormula": "C78H111N21O19", "molecularWeightDa": 1646.85, "terminalModifications": [ "N-terminal acetylation", "C-terminal amide" ], "structuralModifications": [ "Met4 to L-norleucine substitution", "L-Phe7 to D-Phe substitution" ], "compoundClassIds": [ "linear-melanocortin-analogs" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "melanotan-ii", "pt-141", "kpv", "alpha-msh" ], "referenceIds": [ "pmid-6777774", "pmid-9287296", "pmid-34453129", "pmid-34433901", "pmid-34561620" ], "identityOverview": "Afamelanotide, widely supplied as Melanotan I, is a linear thirteen-residue analog of alpha-melanocyte-stimulating hormone carrying norleucine and D-phenylalanine substitutions.", "nomenclatureNotes": "Melanotan I and afamelanotide are the same defined peptide. One name is commercial, the other the standardised substance name; they are not two different sequences. The opposite error is equally wrong: shared peptide identity does not make a research vial equivalent to a finished pharmaceutical product, and a product brand name is not an additional peptide. Most importantly, Melanotan I is NOT Melanotan II — this is a linear thirteen-residue analog, that is a cyclic lactam heptapeptide, and they differ in formula and mass. The unqualified word 'melanotan' is not a usable identity field.", "structuralNotes": "An afamelanotide-bound MC1R–Gs complex has been determined, making this an exact-compound receptor structure rather than an analog structure. The compound is not MC1R-exclusive: it also stimulates MC3, MC4 and MC5 receptors in receptor assays, and a receptor-bound NDP-alpha-MSH–MC4R structure demonstrates activity at MC4R directly. A product description reading 'MC1R agonist' must not be restated as absence of activity at the other subtypes. An assay-independent quantitative selectivity ranking across the subtypes is not established.", "analyticalNotes": "Two features are invisible to routine intact mass. D-phenylalanine and L-phenylalanine have identical elemental composition, and norleucine is a constitutional isomer of leucine and isoleucine — also identical. Ordinary peptide fragment masses do not establish D/L configuration either. Confirming this compound requires hydrolysis followed by chiral amino-acid analysis with racemization controls and authentic standards, plus a method that distinguishes norleucine from leucine and isoleucine. N-acetylation and C-terminal amidation need separate confirmation. For acetate material, acetate stoichiometry is not derivable from the peptide ion and must be measured, as must water content; a peptide mass match does not convert chromatographic area purity into peptide content.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "p021", "url": "https://purelypeptides.org/research/compounds/p021/", "displayName": "P021 (P21)", "canonicalName": "P021", "moleculeType": "peptide", "aliases": [ "P21", "P-21", "Peptide 021" ], "developmentCodes": [], "externalIds": { "cas": "1246751-68-7", "pubChemCid": "56599151", "unii": "VV8CZC8PAS" }, "sequence": { "threeLetter": [ "Asp", "Gly", "Gly", "Leu", "Adamantane-carboxamide" ], "notes": "CRITICAL: the shorthand Ac-DGGLAG-NH2 appears in the primary literature, where AG denotes a single adamantane-derived unit — NOT alanine followed by glycine. Parsed as an ordinary six-residue peptide it yields the wrong molecule, formula and mass. The leucine carbonyl is amide-linked to an amino-substituted adamantane cage bearing a carboxamide. The aspartate side-chain carboxyl is free." }, "molecularFormula": "C27H42N6O8", "molecularWeightDa": 578.66, "terminalModifications": [ "N-terminal acetylation", "C-terminal carboxamide" ], "structuralModifications": [ "Adamantane-based C-terminal extension" ], "compoundClassIds": [ "neurotrophic-peptide-mimetics" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-20600002", "pmid-25046994", "pmid-39592934" ], "identityOverview": "P021 is a small acetylated tetrapeptide carrying an adamantane-derived C-terminal extension, designed as a CNTF-derived peptide mimetic.", "nomenclatureNotes": "P021 is the preferred research designation; P21 is the common commercial spelling. The primary literature identifies it as a peptide mimetic derived from ciliary neurotrophic factor, CNTF. It is not described there as a chemically identified fragment isolated from Cerebrolysin, and that provenance claim should not be repeated.", "structuralNotes": "Reported effects are at the pathway level: LIF-related signalling, and changes in BDNF expression with associated GSK3beta signalling in experimental models. No direct molecular binding target, binding affinity, receptor-subtype selectivity or receptor-level agonist classification is established. P021 should not be described as a direct TrkB agonist or a direct GSK3beta inhibitor on the strength of downstream measurements. The proposed BDNF increase is also not uniformly reproduced: an independent study reports that chronic exposure failed to raise BDNF under its conditions. That result is part of the record for this compound, not an omission.", "analyticalNotes": "For a molecule this size the useful identity package is LC–high-resolution MS with 1D and 2D NMR, supported by fragmentation and amino-acid analysis. NMR matters specifically because 'contains an adamantane group' does not establish the registered connectivity, and a mass-compatible connectivity isomer — including an Asp/isoAsp rearrangement — would not be excluded by an intact-mass match. Asp and Leu configuration need a chiral method. A BDNF-expression assay is not a chemical identity test and is a poor acceptance criterion given the conflicting reports above.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "pralmorelin", "url": "https://purelypeptides.org/research/compounds/pralmorelin/", "displayName": "Pralmorelin (GHRP-2)", "canonicalName": "Pralmorelin", "moleculeType": "peptide", "aliases": [ "GHRP-2", "Growth hormone-releasing peptide-2" ], "developmentCodes": [ "KP-102" ], "externalIds": { "cas": "158861-67-7", "pubChemCid": "6918245", "unii": "E6S6E1F19M" }, "sequence": { "threeLetter": [ "D-Ala", "D-2-Nal", "Ala", "Trp", "D-Phe", "Lys" ], "notes": "No one-letter string is published here. Position 2 is 3-(naphthalen-2-yl)-D-alanine, a single nonstandard residue; written as ordinary letters it would denote different amino acids. Three of six residues are D-configured and the stereochemistry is identity-defining, not annotation." }, "molecularFormula": "C45H55N9O6", "molecularWeightDa": 817.99, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Lys6" ], "structuralModifications": [ "D-2-naphthylalanine at position 2", "D-Ala1", "D-Phe5" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor", "cd36-scavenger-receptor" ], "relatedCompoundIds": [ "examorelin", "ghrp-6", "ipamorelin" ], "referenceIds": [ "pmid-14763922", "pmid-15176951", "pmid-21298258", "pmid-9285939" ], "identityOverview": "Pralmorelin is a synthetic hexapeptide growth hormone secretagogue acting at the ghrelin receptor, containing three D-configured residues and a naphthylalanine substitution.", "nomenclatureNotes": "GHRP-2 is not GHRP-6; they are different hexapeptides. Arvat et al. (PMID 9285939) describe GHRP-2 as a synthetic super-analog of GHRP-6, although the chain printed in their abstract omits Ala3; the six-residue chain recorded here matches PubChem CID 6918245. And GHRP does not denote a GHRH-receptor ligand — the similar names refer to GH secretion, not a shared receptor. A generic 'Nal' field loses both the 2-naphthyl substitution and the D configuration, either of which changes the molecule.", "structuralNotes": "Pituitary work distinguishes its direct action from GHRH-mediated responses, and it appears in CD36 binding competition experiments alongside hexarelin. The CD36 observation is a binding result in the systems tested; it does not establish that every pralmorelin response is CD36-mediated.", "analyticalNotes": "An intact-mass match distinguishes neither D from L residues nor 1-naphthyl from 2-naphthyl positional isomers — both are identical in elemental composition. Those require chiral amino-acid analysis with authentic standards, or NMR. A growth-hormone secretion assay cannot establish which GHRP is present; the comparative LC-MS work is the reference that actually separates them.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "examorelin", "url": "https://purelypeptides.org/research/compounds/examorelin/", "displayName": "Examorelin (Hexarelin)", "canonicalName": "Examorelin", "moleculeType": "peptide", "aliases": [ "Hexarelin" ], "developmentCodes": [ "EP-23905", "MF-6003" ], "externalIds": { "cas": "140703-51-1", "pubChemCid": "6918297", "unii": "09QF37C617" }, "sequence": { "threeLetter": [ "His", "2-Me-D-Trp", "Ala", "Trp", "D-Phe", "Lys" ], "notes": "Position 2 carries a methyl group at INDOLE POSITION 2 of D-tryptophan. It is not an N-methyl and not an alpha-methyl substitution; those are different molecules with the same formula. No one-letter string is published here." }, "molecularFormula": "C47H58N12O6", "molecularWeightDa": 887.06, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Lys6" ], "structuralModifications": [ "2-methyl-D-tryptophan at position 2", "D-Phe5" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor", "cd36-scavenger-receptor" ], "relatedCompoundIds": [ "pralmorelin", "ghrp-6", "ipamorelin" ], "referenceIds": [ "pmid-11988484", "pmid-15176951", "pmid-21298258" ], "identityOverview": "Examorelin, widely supplied as hexarelin, is a synthetic hexapeptide growth hormone secretagogue carrying a 2-methylated D-tryptophan.", "nomenclatureNotes": "Examorelin and hexarelin are one substance under two names, not two entries. Its relationship to GHRP-6 is a single methyl group — a net CH2, 14.0157 Da — but 'methylated GHRP-6' is insufficient identity information unless the methyl position is retained.", "structuralNotes": "This is the compound that refutes the assumption that synthetic secretagogues are interchangeable or GHSR-exclusive. Beyond ghrelin-receptor agonism, exact-compound work identifies CD36 as a binding target, maps the binding site to a defined fragment of the CD36 sequence, and reports that a cardiovascular response to hexarelin is absent in CD36-null animals. CD36 is a scavenger receptor, not a GHSR subtype. The relative contribution of the two targets belongs to the preparation tested, not to the compound in general.", "analyticalNotes": "The mass difference from GHRP-6 is readily measurable, but equal-mass methyl positional isomers and D/L variants are not resolved by mass alone; establishing the indole-2 position needs NMR or an authenticated orthogonal comparison. A positive GHSR assay is unusually weak evidence here, because the compounds it would distinguish this from were selected for sharing that activity.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "octanoyl-ghrelin", "url": "https://purelypeptides.org/research/compounds/octanoyl-ghrelin/", "displayName": "Human Octanoyl-Ghrelin", "canonicalName": "Ghrelin (human, octanoylated)", "moleculeType": "peptide", "aliases": [ "Lenomorelin", "Human acyl-ghrelin", "Acyl-ghrelin" ], "developmentCodes": [], "externalIds": { "cas": "258279-04-8", "pubChemCid": "91668172", "unii": "UXG268Q86R" }, "sequence": { "oneLetter": "GSSFLSPEHQRVQQRKESKKPPAKLQPR", "notes": "Twenty-eight residues, all L. The backbone string is NOT a complete identity: the Ser3 side-chain hydroxyl is esterified with n-octanoic acid, and that ester is required for canonical receptor activation. A registry synonym for this substance omits a lysine while a correctly specified 28-residue synonym sits alongside it — do not regard every registry synonym as equally authoritative." }, "molecularFormula": "C149H249N47O42", "molecularWeightDa": 3370.92, "terminalModifications": [ "Free Gly1 amino terminus", "Free Arg28 carboxyl terminus" ], "structuralModifications": [ "Ser3 O-n-octanoylation" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor" ], "relatedCompoundIds": [ "ghrp-6", "macimorelin", "anamorelin" ], "referenceIds": [ "pmid-11745115", "pmid-10604470", "pmid-34417468", "pmid-39128804" ], "identityOverview": "Human octanoyl-ghrelin is the endogenous 28-residue acylated peptide ligand of the ghrelin receptor, carrying an n-octanoyl ester on serine 3.", "nomenclatureNotes": "'Ghrelin' alone is not a resolved chemical identity. Species, chain length, acylated versus desacyl, and the acyl chain itself must all be specified. Desacyl-ghrelin is a different substance, not the same one differently formulated.", "structuralNotes": "Cryo-EM structures of the ghrelin receptor bound to ghrelin and to the synthetic secretagogue GHRP-6 reveal a distinct pocket accommodating the octanoyl group, which positions the peptide for receptor activation rather than serving only as a half-life extension. The strong requirement for acylation in canonical activation should not be restated as desacyl-ghrelin having no biological activity of any kind; that broader claim is not established by these receptor experiments.", "analyticalNotes": "Identity work must preserve and measure the Ser3 ester, not merely confirm a ghrelin backbone. Loss of the octanoyl changes the neutral composition by C8H14O, 126.1045 Da; monitoring that product reveals deacylation but does not establish that the original ester was on Ser3. An immunoassay recognising a retained epitope settles neither acylation nor chain length.", "publishedDate": "2026-09-13", "lastVerifiedDate": "2026-09-13" }, { "id": "macimorelin", "url": "https://purelypeptides.org/research/compounds/macimorelin/", "displayName": "Macimorelin", "canonicalName": "Macimorelin", "moleculeType": "peptidomimetic", "aliases": [], "developmentCodes": [ "AEZS-130", "JMV 1843", "EP-1572" ], "externalIds": { "cas": "381231-18-1", "pubChemCid": "9804938", "unii": "8680B21W73" }, "sequence": { "notes": "No conventional amino-acid sequence string exists for this molecule and none is published here. It is a gem-diamino peptidomimetic: an Aib-derived unit and a D-Trp-derived unit connected to an R-configured, indole-containing gem-diamino terminus bearing an N-formyl group. A terminal 'CHO' abbreviation is a formamide arrangement, not a free peptide aldehyde." }, "molecularFormula": "C26H30N6O3", "molecularWeightDa": 474.56, "terminalModifications": [ "N-formyl gem-diamino terminus" ], "structuralModifications": [ "gem-diamino linkage", "D-tryptophan-derived unit" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor" ], "relatedCompoundIds": [ "anamorelin", "octanoyl-ghrelin" ], "referenceIds": [ "pmid-12646029", "pmid-40542284", "pmid-34417468" ], "identityOverview": "Macimorelin is a gem-diamino peptidomimetic agonist at the ghrelin receptor.", "nomenclatureNotes": "Macimorelin is neither a ghrelin fragment nor an ordinary unmodified tripeptide; the peptidomimetic connectivity is what defines it. Acetate in a salt preparation must not become a covalent N-acetyl modification in the structural record.", "structuralNotes": "A cryo-EM structure of the ghrelin receptor bound to macimorelin, determined alongside an anamorelin-bound structure, shows both occupying a bifurcated pocket divided by a conserved salt bridge, with mutagenesis identifying the residues behind their differing affinities. That permits a direct structural comparison rather than an assumption that all ghrelin mimetics bind alike. An assay-independent signalling-bias designation is not established.", "analyticalNotes": "An amino-acid composition result or a peptide search-engine match is insufficient for this terminus. NMR is needed to establish gem-diamino connectivity and N-formyl placement, with a chiral method for the defined stereocentres. Counterion content for acetate material is a separate measurement; the parent ion establishes neither acetate stoichiometry nor peptide-equivalent content.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-09-13" }, { "id": "anamorelin", "url": "https://purelypeptides.org/research/compounds/anamorelin/", "displayName": "Anamorelin", "canonicalName": "Anamorelin", "moleculeType": "small-molecule", "aliases": [], "developmentCodes": [ "ONO-7643", "RC-1291", "ST-1291" ], "externalIds": { "cas": "249921-19-5", "pubChemCid": "9828911", "unii": "DD5RBA1NKF" }, "sequence": { "notes": "Not a conventional peptide and no sequence string is published here. A 3R-substituted piperidine-3-carbohydrazide bearing a benzyl group and an N,N',N'-trimethylhydrazide, acylated through a D-Trp-derived 2R centre and an Aib-derived aminoacyl unit. No lipid conjugation and no macrocycle." }, "molecularFormula": "C31H42N6O3", "molecularWeightDa": 546.72, "terminalModifications": [], "structuralModifications": [ "trimethylhydrazide", "2R and 3R stereocentres" ], "compoundClassIds": [ "growth-hormone-secretagogues" ], "mechanismIds": [ "ghs-receptor" ], "relatedCompoundIds": [ "macimorelin", "octanoyl-ghrelin" ], "referenceIds": [ "pmid-40542284", "pmid-39833471", "pmid-39128804" ], "identityOverview": "Anamorelin is a nonpeptide small-molecule agonist at the ghrelin receptor, structurally unrelated to the peptide secretagogues that share its target.", "nomenclatureNotes": "The CAS recorded here is the parent free base. The hydrochloride requires separate salt accounting; chloride is not part of this formula. Describing anamorelin as a ghrelin mimetic says nothing about sequence homology with ghrelin, of which it has none.", "structuralNotes": "Receptor-bound structural work reports anamorelin behaving as a superagonist in the system studied, and separate structures place it alongside macimorelin in the same bifurcated binding pocket. A comparison across two assay formats found it a full agonist in both. 'Full agonist' versus 'superagonist' is a question of assay context, not two chemical identities; a single assay-independent intrinsic-activity or signalling-bias label is not established.", "analyticalNotes": "Matching molecular mass excludes neither epimers nor connectivity isomers, and a receptor activation assay cannot distinguish anamorelin from macimorelin or any other active ligand. NMR should establish the piperidine, hydrazide and aminoacyl connectivity, with a chiral method for the 2R and 3R centres. For hydrochloride material, quantify chloride independently rather than inferring it from the parent ion.", "publishedDate": "2026-09-13", "lastVerifiedDate": "2026-09-13" }, { "id": "alpha-msh", "url": "https://purelypeptides.org/research/compounds/alpha-msh/", "displayName": "alpha-MSH", "canonicalName": "alpha-Melanocyte-stimulating hormone", "moleculeType": "peptide", "aliases": [ "α-MSH", "alpha-MSH", "alpha-melanotropin", "Melanotropin alpha" ], "developmentCodes": [], "externalIds": { "cas": "581-05-5", "pubChemCid": "16133793", "unii": "OVF025LA77" }, "sequence": { "oneLetter": "SYSMEHFRWGKPV", "threeLetter": [ "Ser", "Tyr", "Ser", "Met", "Glu", "His", "Phe", "Arg", "Trp", "Gly", "Lys", "Pro", "Val" ], "notes": "Thirteen residues, all L, linear, N-terminally acetylated and C-terminally amidated. The 'Ac' is the acetyl cap, not amino-acid letters." }, "molecularFormula": "C77H109N21O19S", "molecularWeightDa": 1664.91, "terminalModifications": [ "N-terminal acetylation", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [ "melanocortin-receptor-ligands" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "melanotan-i", "melanotan-ii", "pt-141", "kpv", "cosyntropin", "setmelanotide", "shu9119", "thiq" ], "referenceIds": [ "pmid-12750433", "pmid-21211532", "pmid-34453129", "pmid-34433901" ], "identityOverview": "alpha-MSH is the endogenous thirteen-residue melanocortin peptide hormone from which several of the synthetic compounds in this library are derived.", "nomenclatureNotes": "This is the native hormone, not an analog. It is not afamelanotide: the parent retains Met4 and L-Phe7, and the analog's norleucine and D-phenylalanine substitutions must not migrate into the parent's identity fields. Nor is it simply 'ACTH(1-13)' — the N-acetyl and C-amide processing distinguish it from an uncapped fragment. KPV is its C-terminal tripeptide sequence and nothing more; see structuralNotes.", "structuralNotes": "An agonist at MC1R, MC3R, MC4R and MC5R, with receptor-bound structures establishing MC1R and MC4R recognition; it is not the canonical agonist at MC2R, which responds to ACTH. One caution matters for this library specifically: a fragment of alpha-MSH does not inherit its receptor profile. Comparative work reports that the C-terminal tripeptide KPV retains an anti-inflammatory effect that was NOT blocked by the MC3/4R antagonist SHU9119 and did not raise cAMP, and concludes it likely acts through a mechanism other than the melanocortin receptors. Sequence ancestry is a structural relationship, not a pharmacological one.", "analyticalNotes": "Confirmation requires the thirteen-residue sequence, Met4, the N-acetyl cap and the C-terminal amide, plus a methionine-oxidation assessment. The parent must be distinguished from the Nle4/D-Phe7 analog: those differ compositionally and are separable by mass, but mass alone establishes no D/L configuration. Detecting KPV after hydrolysis or degradation does not show the intact parent was present.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "setmelanotide", "url": "https://purelypeptides.org/research/compounds/setmelanotide/", "displayName": "Setmelanotide", "canonicalName": "Setmelanotide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "RM-493", "BIM-22493", "IRC-022493" ], "externalIds": { "cas": "920014-72-8", "pubChemCid": "11993702", "unii": "N7T15V1FUY" }, "sequence": { "threeLetter": [ "Arg", "Cys", "D-Ala", "His", "D-Phe", "Arg", "Trp", "Cys" ], "notes": "Eight residues closed by a Cys2-Cys8 DISULFIDE. No linear string is published here. This is not a head-to-tail ring and not an Asp-Lys lactam — the distinction from the Melanotan II scaffold is the point of the entry. Gary et al. (PMID 39394922) describe setmelanotide as cyclized by a disulfide bond formed through its two cysteine residues, here Cys2 and Cys8.", "rings": [ { "kind": "disulfide", "from": { "position": 2, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 8, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-39394922" } ] }, "molecularFormula": "C49H68N18O9S2", "molecularWeightDa": 1117.32, "terminalModifications": [ "N-terminal acetylation at Arg1", "C-terminal amide at Cys8" ], "structuralModifications": [ "Cys2-Cys8 intramolecular disulfide", "D-Ala3", "D-Phe5" ], "compoundClassIds": [ "cyclic-melanocortin-analogs", "melanocortin-receptor-ligands" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "melanotan-ii", "pt-141", "shu9119", "alpha-msh", "thiq" ], "referenceIds": [ "pmid-33858992", "pmid-34561620", "pmid-34433901", "pmid-38834138", "pmid-39394922" ], "identityOverview": "Setmelanotide is a synthetic disulfide-cyclized octapeptide characterised as an MC4R-preferring melanocortin receptor agonist. A review by Swan et al. (PMID 38834138) describes setmelanotide as an analogue of alpha-melanocyte-stimulating hormone; that is a review-level parent attribution, not a residue-by-residue design account.", "nomenclatureNotes": "'Cyclic melanocortin' does not identify the cyclization chemistry. A disulfide ring and a side-chain lactam are different molecules with different stability and different analytical handling, and a linear sequence with the word cyclic appended describes neither.", "structuralNotes": "A cryo-EM structure of the setmelanotide-bound MC4R signalling complex reveals the activation switch, and reports that calcium is required for agonist but not antagonist activity — the same cofactor identified in the antagonist-bound structure of the same receptor. MC4R-preferring should not be upgraded to MC4R-exclusive, and no assay-independent subtype-selectivity or signalling-bias value is established.", "analyticalNotes": "Combine intact high-resolution MS with sequence analysis and a reducing versus nonreducing comparison; reduction of the single intramolecular disulfide adds 2.0157 Da before alkylation. Verify Cys2-Cys8 connectivity specifically and exclude intermolecular disulfide dimers, which share the monomer's amino-acid composition. D-Ala3 and D-Phe5 need a stereochemical method; neither a mass match nor an area-purity figure addresses them.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "cosyntropin", "url": "https://purelypeptides.org/research/compounds/cosyntropin/", "displayName": "Cosyntropin (ACTH 1-24)", "canonicalName": "Cosyntropin", "moleculeType": "peptide", "aliases": [ "Tetracosactide", "ACTH(1-24)", "alpha 1-24 corticotropin" ], "developmentCodes": [], "externalIds": { "cas": "16960-16-0", "pubChemCid": "16133751", "unii": "72YY86EA29" }, "sequence": { "oneLetter": "SYSMEHFRWGKPVGKKRRPVKVYP", "notes": "Twenty-four residues, all L, with a free N-terminus and a free C-terminal carboxyl. No acetylation, no amidation, no ring. Note the first thirteen residues are shared with alpha-MSH — the terminal processing is what differs." }, "molecularFormula": "C136H210N40O31S", "molecularWeightDa": 2933.48, "terminalModifications": [ "Free Ser1 amino terminus", "Free Pro24 carboxyl terminus" ], "structuralModifications": [], "compoundClassIds": [ "melanocortin-receptor-ligands" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "alpha-msh", "kpv" ], "referenceIds": [ "pmid-26424796", "pmid-21211532", "pmid-36588120" ], "identityOverview": "Cosyntropin is the synthetic 1-24 fragment of adrenocorticotropic hormone, the melanocortin ligand of the MC2R branch.", "nomenclatureNotes": "Cosyntropin is ACTH(1-24). It is not full-length ACTH(1-39), not ACTH(4-10), and not alpha-MSH. A shared N-terminal sequence does not erase chain-length or terminal-processing differences, and 'ACTH' in a paper's abstract does not establish which preparation was used — some melanocortin experiments use capped or norleucine-substituted analogs. PubChem CID 16129617, the entry titled Cosyntropin, and CID 16129674 encode Lys15, Lys16, Arg17 and Arg18 as D-residues and leave the configuration of Ser1 undefined; this record therefore cites CID 16133751, which encodes the all-L chain.", "structuralNotes": "MC2R is the melanocortin receptor that responds to ACTH rather than to the shorter melanocortin pharmacophore, and its function depends on the accessory protein MRAP. Work fixing MRAP orientation establishes that the requirement is for MRAP acting on the EXTRACELLULAR face of the membrane, not merely for trafficking the receptor to the surface. Receptor-chimera experiments explicitly using ACTH(1-24) locate the regions responsible for ligand specificity and MRAP dependence. A structural study of an ACTH-bound MC2R-MRAP1 complex is cited as Class B: whether its experimental ligand is equivalent to unmodified cosyntropin is not established here.", "analyticalNotes": "Confirmation needs the basic internal sequence and the Pro24 terminus, with explicit tests for Met4 versus a substituted analog and for the absence of an N-acetyl cap or C-terminal amide. An ACTH immunoassay may recognise several ACTH-containing fragments and does not establish 24-residue identity. Conversely, a negative result in an MC2R assay lacking functional MRAP is not evidence that the material is wrong.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-12", "lastVerifiedDate": "2026-09-13" }, { "id": "shu9119", "url": "https://purelypeptides.org/research/compounds/shu9119/", "displayName": "SHU9119", "canonicalName": "SHU9119", "moleculeType": "peptide", "aliases": [ "SHU-9119", "SHU 9119" ], "developmentCodes": [], "externalIds": { "cas": "168482-23-3", "pubChemCid": "9898183" }, "sequence": { "threeLetter": [ "Nle", "Asp", "His", "D-2-Nal", "Arg", "Trp", "Lys" ], "notes": "Seven residues closed by a LACTAM between the Asp2 side-chain carboxyl and the Lys7 epsilon-amino group. D-2-Nal is 3-(naphthalen-2-yl)-D-alanine, one residue. No disulfide, no head-to-tail closure, and no safe linear string. Hruby et al. (PMID 7658432) write it as Ac-Nle4-c[Asp5,D-Nal(2)7,Lys10]alpha-MSH-(4-10)-NH2, which places the lactam between Asp2 and Lys7 of this chain.", "rings": [ { "kind": "side-chain lactam", "from": { "position": 2, "residue": "Asp", "atom": "side-chain carboxyl (Cγ)" }, "to": { "position": 7, "residue": "Lys", "atom": "side-chain ε-amino nitrogen (Nζ)" }, "sourceNumbering": "Asp5–Lys10 in alpha-MSH numbering", "referenceId": "pmid-7658432" } ] }, "molecularFormula": "C54H71N15O9", "molecularWeightDa": 1074.26, "terminalModifications": [ "N-terminal acetylation at Nle1", "C-terminal amide at Lys7" ], "structuralModifications": [ "Asp2-Lys7 side-chain lactam", "D-2-naphthylalanine at position 4" ], "compoundClassIds": [ "cyclic-melanocortin-analogs", "melanocortin-receptor-ligands" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "melanotan-ii", "pt-141", "setmelanotide", "alpha-msh" ], "referenceIds": [ "pmid-7658432", "pmid-32327598", "pmid-34453129", "pmid-12750433", "pmid-35404053" ], "identityOverview": "SHU9119 is a cyclic lactam melanocortin analog whose receptor behaviour is subtype-dependent: antagonist at some melanocortin receptors and agonist at others. Gimenez et al. (PMID 35404053) describe SHU9119 as a cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone.", "nomenclatureNotes": "SHU9119 shares the Melanotan II ring architecture and differs by a single substitution, D-Phe to D-2-Nal, a net C4H2 or 50.0157 Da. Shared ring architecture does not mean shared pharmacological direction — see structuralNotes. Calling it 'the melanocortin blocker' conceals the central experimental limitation of the compound. PubChem CID 6440621, the entry titled Shu 9119 and the one its CAS number resolves to, encodes a different ring system; this record cites CID 9898183, which encodes the Asp2-Lys7 lactam with the same formula.", "structuralNotes": "The original structure-activity work reports it as a potent MC4R antagonist and a less potent MC3R antagonist, both with minimal agonist activity, while behaving as a FULL AGONIST at MC1 and MC5 receptors. It is therefore not a pan-melanocortin antagonist, and its antagonism must not be transferred from MC4R to every experiment involving a melanocortin receptor. Receptor-bound structures exist at both MC4R — where calcium was identified as a ligand-binding cofactor — and MC1R, giving an unusually direct structural account of why one scaffold can act in opposite directions at two subtypes.", "analyticalNotes": "Establishing the Asp2-Lys7 lactam requires NMR or a validated orthogonal method; disulfide reduction is not a ring-opening strategy for a lactam and will not report on it. Verify D-2-Nal stereochemistry and the naphthyl attachment position. The expected mass separates SHU9119 from Melanotan II but not from every stereochemical or positional isomer, and an MC4R antagonist response is supportive functional evidence rather than chemical identification.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "thiq", "url": "https://purelypeptides.org/research/compounds/thiq/", "displayName": "THIQ", "canonicalName": "THIQ (MC4R agonist)", "moleculeType": "small-molecule", "aliases": [], "developmentCodes": [], "externalIds": { "cas": "312637-48-2", "pubChemCid": "9938402" }, "sequence": { "notes": "Not a peptide. A stereodefined tetrahydroisoquinoline-carboxamide with a 4-chlorophenyl-substituted aminoacyl unit and a piperidine bearing cyclohexyl and triazolylmethyl groups, with two R-configured centres. No peptide shorthand should stand in for the structure." }, "molecularFormula": "C33H41ClN6O2", "molecularWeightDa": 589.18, "terminalModifications": [], "structuralModifications": [ "Two R-configured stereocentres", "Aryl chloride" ], "compoundClassIds": [ "melanocortin-receptor-ligands" ], "mechanismIds": [ "melanocortin-receptors" ], "relatedCompoundIds": [ "alpha-msh", "setmelanotide" ], "referenceIds": [ "pmid-16114870", "pmid-19303903", "pmid-34433901" ], "identityOverview": "THIQ is a nonpeptide small-molecule agonist at the melanocortin-4 receptor, included here as the nonpeptide comparator to the melanocortin peptides.", "nomenclatureNotes": "THIQ is ALSO the generic abbreviation for the tetrahydroisoquinoline scaffold, an entire chemical class. The generic scaffold and this defined MC4R agonist are not the same substance, and a name-only search imports unrelated chemistry — at least one supplier listing conflates them. The chlorine in the formula is a covalent aryl chloride, NOT evidence of a hydrochloride salt.", "structuralNotes": "Alanine-scanning mutagenesis at MC4R shows the nonpeptide agonists depend on residues across several transmembrane helices, while a linear peptide agonist's binding was substantially reduced by only two of the same substitutions — direct evidence that peptide and nonpeptide routes to the same receptor are not equivalent. Chimeric-receptor work identifies conserved residues required for binding and non-conserved residues in the third transmembrane helix contributing to MC4R selectivity. A receptor-bound structure places it alongside peptide agonists in the same complex study. Selectivity was examined in the comparisons tested; that is not the absence of every off-target interaction.", "analyticalNotes": "High-resolution MS should show the chlorine isotope pattern, which is the quickest confirmation that the halogen is present and covalent. NMR establishes the substituted scaffold and chiral chromatography the two stereocentres. Neither the name THIQ, nor a tetrahydroisoquinoline substructure match, nor a positive MC4R assay establishes identity — the first because the abbreviation is ambiguous, the last because other MC4R agonists give the same response.", "publishedDate": "2026-09-13", "lastVerifiedDate": "2026-09-13" }, { "id": "ac-sdkp", "url": "https://purelypeptides.org/research/compounds/ac-sdkp/", "displayName": "Ac-SDKP (Goralatide)", "canonicalName": "Goralatide", "moleculeType": "peptide", "aliases": [ "Ac-SDKP", "Seraspenide", "N-acetyl-seryl-aspartyl-lysyl-proline" ], "developmentCodes": [], "externalIds": { "cas": "120081-14-3", "pubChemCid": "65938", "unii": "H041538E9P" }, "sequence": { "oneLetter": "SDKP", "threeLetter": [ "Ser", "Asp", "Lys", "Pro" ], "notes": "Four residues, all L, N-terminally acetylated with a free C-terminal carboxyl. The acetyl sits on the serine alpha-amino group. An acetyl on the lysine side chain instead would preserve the elemental composition while describing a different molecule." }, "molecularFormula": "C20H33N5O9", "molecularWeightDa": 487.51, "terminalModifications": [ "N-terminal acetylation", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "thymosin-related-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "thymosin-beta-4", "tb-500" ], "referenceIds": [ "pmid-26962108", "pmid-15037553", "pmid-23739235" ], "identityOverview": "Ac-SDKP is the acetylated N-terminal tetrapeptide of thymosin beta-4, generated from the parent by sequential enzymatic processing.", "nomenclatureNotes": "Ac-SDKP is not thymosin beta-4 and not a generic TB-500 fragment. It is one specifically processed N-terminal tetrapeptide and is not a stand-in for the parent's other sequence regions. Release and degradation are also different processes: meprin-alpha and prolyl oligopeptidase participate in generating it, while angiotensin-converting enzyme hydrolyses it. ACE must not be recorded as the releasing mechanism.", "structuralNotes": "The release pathway is the best-characterised thing about this compound, and it is sequential rather than direct. In a purified system neither meprin-alpha nor prolyl oligopeptidase alone released Ac-SDKP from intact thymosin beta-4; only both together did, supported by inhibitor experiments and by kidneys from meprin-alpha knockout animals failing to release it. Earlier work had identified prolyl oligopeptidase as responsible, and the later finding refines that rather than overturning it. Separate work comparing parent, fragment, and cleavage inhibition supports a conditional statement — that some thymosin beta-4-associated effects depend on Ac-SDKP being generated — and does not support the converse, that activity measured with isolated Ac-SDKP can be attributed to the intact parent. No direct cognate receptor is established.", "analyticalNotes": "Confirmation needs N-terminal rather than lysine-side-chain acetylation established by an orthogonal method, since the two are identical by mass. Ordinary aspartate versus isoaspartate connectivity also survives an intact-mass match. A terminal acid and an amide differ in exact mass and should be distinguished explicitly. When studying formation from the parent, measure both the intact parent and the released tetrapeptide; a downstream cellular response is not evidence that cleavage occurred.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "ghk", "url": "https://purelypeptides.org/research/compounds/ghk/", "displayName": "GHK (Prezatide)", "canonicalName": "Prezatide", "moleculeType": "peptide", "aliases": [ "GHK", "Glycyl-L-histidyl-L-lysine", "Tripeptide-1" ], "developmentCodes": [ "NSC-379527" ], "externalIds": { "cas": "49557-75-7", "pubChemCid": "73587", "unii": "39TG2H631E" }, "sequence": { "oneLetter": "GHK", "threeLetter": [ "Gly", "His", "Lys" ], "notes": "Three residues with a free N-terminal amine and a free C-terminal carboxyl. No modifications. Copper is NOT part of this entry — see nomenclatureNotes." }, "molecularFormula": "C14H24N6O4", "molecularWeightDa": 340.38, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "copper-binding-peptides", "matrikine-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "ghk-cu", "pal-ghk", "kttks" ], "referenceIds": [ "pmid-858356", "pmid-7514608", "pmid-6303307" ], "identityOverview": "GHK is the uncomplexed tripeptide ligand of the GHK-copper complex, identified in 1977 as a growth-modulating tripeptide from human plasma.", "nomenclatureNotes": "GHK, GHK-Cu and Pal-GHK are three different substances: an uncomplexed peptide, a copper coordination species, and a covalently lipidated derivative. CAS 49557-75-7 belongs to THIS entry, the free tripeptide. The copper complex is 89030-95-5. That distinction has practical consequences — certificates of analysis in this market have carried the free-tripeptide number on copper-complex product, which describes the wrong substance.", "structuralNotes": "Its matrix provenance is sourced: proteolysis of SPARC, a matrix-associated protein, yields KGHK, GHK and longer peptides. That provenance is the basis for its secondary matrikine classification. Two cautions belong with it. Most of the angiogenic activity in that work mapped to KGHK rather than to the GHK tripeptide, and was reported as sequence-specific and apparently independent of bound copper — so neither the longer-fragment results nor a copper dependence should be transferred to GHK. Separately, spectroscopic work on Cu(II) coordination reports three nitrogen atoms and one oxygen in a square-planar arrangement, with the major and minor species present varying by pH. Copper binding is therefore established; a single invariant coordination structure is not.", "analyticalNotes": "For material specified as uncomplexed GHK, quantitative metal analysis is an identity-relevant measurement rather than a cosmetic one — the peptide ion alone does not establish the absence of copper, and acidic chromatography can change the coordination state before detection. Any experiment described as copper-independent must also account for metals already present in the medium. Neither solution colour nor amino-acid composition establishes the complete identity.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "kttks", "url": "https://purelypeptides.org/research/compounds/kttks/", "displayName": "KTTKS (Pentapeptide-4)", "canonicalName": "KTTKS", "moleculeType": "peptide", "aliases": [ "Pentapeptide-4", "Collagen pentapeptide" ], "developmentCodes": [], "externalIds": { "cas": "149128-48-3", "pubChemCid": "9959565", "unii": "69B8BD4H9G" }, "sequence": { "oneLetter": "KTTKS", "threeLetter": [ "Lys", "Thr", "Thr", "Lys", "Ser" ], "notes": "Five residues, all L, free at both termini. No palmitoylation, no ring, no metal." }, "molecularFormula": "C23H45N7O9", "molecularWeightDa": 563.65, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "matrikine-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "matrixyl", "ghk" ], "referenceIds": [ "pmid-8486721", "pmid-25143811", "pmid-19393372" ], "identityOverview": "KTTKS is the unmodified pentapeptide from type I procollagen that forms the peptide backbone of the palmitoylated cosmetic ingredient Matrixyl.", "nomenclatureNotes": "KTTKS is not Matrixyl. Matrixyl is the palmitoylated derivative, Pal-KTTKS, and N-palmitoylation adds C16H30O — 238.2297 Da — changing both the covalent structure and the physicochemical behaviour. 'Pentapeptide-4' alone does not distinguish them, which is why the sequence should always accompany the name. GSRS UNII 69B8BD4H9G identifies unmodified, all-L, free-terminal KTTKS and includes CAS 149128-48-3 and PubChem CID 9959565.", "structuralNotes": "It was identified as residues 212 to 216 of the type I procollagen carboxyl-terminal propeptide, and as the minimum sequence within a larger propeptide subfragment that produced the reported matrix effect in fibroblasts. Two limits follow. Identifying an active synthetic five-residue segment does not establish that free KTTKS is routinely released as an endogenous product. And 'signal peptide' is a functional description, not identification of a receptor: no direct molecular target is established. Its relationship to GHK is shared matrix-derived provenance, not a shared precursor protein or receptor — the two come from different parent proteins.", "analyticalNotes": "Tandem MS must distinguish KTTKS from sequence permutations, and the palmitoylated species should be tested for explicitly rather than accepting 'pentapeptide-4' as sufficient identity. Threonine stereochemistry is not resolved by intact mass. A collagen hydrolysate containing compatible amino acids is not evidence of a purified KTTKS molecule. A direct comparison of KTTKS and pal-KTTKS in hairless mouse skin found both degraded rapidly, the palmitoylated form more stable, and only the palmitoylated form detectable in skin layers. Neither compound was detected in the receptor solution under the experimental conditions, so retention in skin layers should not be read as full-thickness permeation.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "pal-ghk", "url": "https://purelypeptides.org/research/compounds/pal-ghk/", "displayName": "Pal-GHK (Palmitoyl Tripeptide-1)", "canonicalName": "Palmitoyl tripeptide-1", "moleculeType": "peptide", "aliases": [ "Pal-GHK", "N-palmitoyl-GHK", "C16-GHK", "Palmitoyl oligopeptide" ], "developmentCodes": [], "externalIds": { "cas": "147732-56-7", "pubChemCid": "10231864", "unii": "RV743D216M" }, "sequence": { "threeLetter": [ "Gly", "His", "Lys" ], "notes": "The GHK tripeptide with a hexadecanoyl (palmitoyl) cap on the glycine alpha-amino group. In the shorthand Pal-GHK, 'Pal' names the acyl cap, not an amino-acid residue. The lysine side-chain amine and the C-terminal carboxyl remain free. No copper is part of this identity." }, "molecularFormula": "C30H54N6O5", "molecularWeightDa": 578.8, "terminalModifications": [ "N-terminal palmitoylation", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "matrikine-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "ghk", "ghk-cu", "matrixyl" ], "referenceIds": [ "pmid-23822110", "pmid-19393372", "pmid-7514608" ], "identityOverview": "Pal-GHK is the N-palmitoylated derivative of the GHK tripeptide, used as a cosmetic ingredient and as an analytical internal standard.", "nomenclatureNotes": "'Palmitoyl oligopeptide' is not a unique identifier and should be kept only as a qualified alias; it is used for other lipidated peptides too. Pal-GHK is also not GHK-Cu with a delivery modification bolted on: acylating the N-terminal amine alters a group that participates in GHK's copper coordination, so copper behaviour must be measured for this molecule rather than inherited from the free ligand.", "structuralNotes": "The exact-compound evidence here is physicochemical rather than biological. A direct comparison of three palmitoylated peptides found that C16-KTTKS forms flat tapes and extended fibrils with high beta-sheet content and stains with Congo red, while C16-GHK forms crystal-like aggregates with lower beta-sheet content — all three sharing similar critical aggregation concentrations governed by the lipid chain. That is a real, measured difference between Pal-GHK and Matrixyl, and it is not a shared receptor. No direct biological receptor is established for this compound, and effects demonstrated for Pal-KTTKS or for multi-ingredient formulations must not be assigned to it.", "analyticalNotes": "Establish both the GHK sequence and palmitoylation on the GLYCINE alpha-amino group: a lysine-side-chain-palmitoylated positional isomer has the same elemental composition. Tandem MS, and NMR where connectivity stays ambiguous. Confirm the acyl chain identity and assess residual unmodified GHK separately. Aggregation measurements supplement chemical identity testing rather than replacing it — differences in concentration-dependent assembly are not evidence of a different sequence. Note that this compound serves as the internal standard in a published LC-MS/MS method for pal-KTTKS in cosmetic formulations, which is a use that depends on its identity being unambiguous.", "publishedDate": "2026-09-13", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-13" }, { "id": "amylin", "url": "https://purelypeptides.org/research/compounds/amylin/", "displayName": "Amylin (human IAPP)", "canonicalName": "Amylin", "moleculeType": "peptide", "aliases": [ "Human islet amyloid polypeptide", "IAPP", "hIAPP", "Amlintide" ], "developmentCodes": [], "externalIds": { "cas": "122384-88-7", "pubChemCid": "16132430", "unii": "U3U3114NE1" }, "sequence": { "oneLetter": "KCNTATCATQRLANFLVHSSNNFGAILSSTNVGSNTY", "notes": "Thirty-seven residues with a Cys2-Cys7 disulfide and a C-terminal Tyr37 amide. The backbone string alone is not a complete description: both the disulfide and the amide are required, and neither is visible in a linear sequence. Young et al. (PMID 28970890) describe human IAPP as containing a disulfide bond between Cys-2 and Cys-7 and an amidated C-terminus. The IUPHAR/BPS Guide to Pharmacology (ligand 687, release 2026.3.1) names an amidated C-terminal proline in its modification text while its own sequence ends in amidated tyrosine; this record keeps the Tyr37 amide.", "rings": [ { "kind": "disulfide", "from": { "position": 2, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-28970890" } ] }, "molecularFormula": "C165H261N51O55S2", "molecularWeightDa": 3903.3, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Tyr37" ], "structuralModifications": [ "Cys2-Cys7 disulfide" ], "compoundClassIds": [ "amylin-and-calcitonin-receptor-agonists" ], "mechanismIds": [ "amylin-and-calcitonin-receptors" ], "relatedCompoundIds": [ "pramlintide", "cagrilintide", "hng", "shlp2" ], "referenceIds": [ "pmid-3035556", "pmid-3317417", "pmid-10026261", "pmid-34288673", "pmid-40204768", "pmid-28798389", "pmid-28970890" ], "identityOverview": "Amylin is the endogenous 37-residue human pancreatic peptide hormone, co-secreted with insulin, from which pramlintide and cagrilintide are both derived.", "nomenclatureNotes": "Amylin and IAPP are the same molecule under two names when both refer to this mature human peptide. They are NOT synonyms for the IAPP gene, for proIAPP, for a processing intermediate, for the reduced peptide, or for rodent amylin — rat amylin differs in sequence and is a common substitute in structural work. The FDA substance record uses 'amlintide' as a preferred name for this peptide; amlintide is NOT pramlintide, which carries three proline substitutions and is a separate entry in this library.", "structuralNotes": "It was identified twice in 1987 by independent groups — once from human insulinoma and cat islet amyloid, once from amyloid-rich pancreatic extracts — reaching the same 37-residue sequence, with roughly 40 to 46 percent identity to calcitonin gene-related peptide. That evolutionary relationship to CGRP is why its receptors are calcitonin receptor complexes rather than a receptor of its own. Amylin receptors are CALCR associated with receptor activity-modifying proteins: AMY1, AMY2 and AMY3 correspond to RAMP1, RAMP2 and RAMP3. CALCRL is a different gene and must not be substituted for CALCR, and there is no standalone IAPP receptor gene to name. Two mitochondrial-derived peptides in this library, HNG and SHLP2, were tested against this peptide's misfolding: thioflavin T fluorescence, seeded fluorescence and co-sedimentation supported binding to misfolded, seeding-capable IAPP species, while electron paramagnetic resonance and circular dichroism did not support binding to IAPP monomers. That distinction belongs on this record rather than only on theirs, because this entry specifies the mature monomeric peptide and the reported interaction is with aggregated species, not with the molecule described here.", "analyticalNotes": "Sequence identity, disulfide connectivity, terminal amidation and AGGREGATION STATE are four separate attributes and a matching intact mass establishes only the first. This peptide was discovered in amyloid deposits; a correct mass says nothing about whether a given preparation is monomeric or already contains higher-order assemblies, and the library should not assert an aggregation state it has not measured. Rat amylin is a frequent comparator in structural work and differs in sequence, so a structure obtained with it is not evidence about this molecule.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-13" }, { "id": "pramlintide", "url": "https://purelypeptides.org/research/compounds/pramlintide/", "displayName": "Pramlintide", "canonicalName": "Pramlintide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "AC137" ], "externalIds": { "cas": "151126-32-8", "pubChemCid": "70691388", "unii": "D3FM8FA78T" }, "sequence": { "oneLetter": "KCNTATCATQRLANFLVHSSNNFGPILPPTNVGSNTY", "notes": "Thirty-seven residues, Cys2-Cys7 disulfide, C-terminal Tyr37 amide — identical to human amylin except at three positions, where alanine 25 and serines 28 and 29 are each replaced by proline. It is not lipidated.", "rings": [ { "kind": "disulfide", "from": { "position": 2, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "registrySource": "FDA GSRS UNII D3FM8FA78T; PubChem CID 70691388" } ] }, "molecularFormula": "C171H267N51O53S2", "molecularWeightDa": 3949.4, "terminalModifications": [ "Free N-terminus", "C-terminal amide at Tyr37" ], "structuralModifications": [ "Cys2-Cys7 disulfide", "A25P", "S28P", "S29P" ], "compoundClassIds": [ "amylin-and-calcitonin-receptor-agonists" ], "mechanismIds": [ "amylin-and-calcitonin-receptors" ], "relatedCompoundIds": [ "amylin", "cagrilintide" ], "referenceIds": [ "pmid-17879973", "pmid-27665170", "pmid-10026261", "pmid-34288673", "pmid-40204768", "pmid-33727283" ], "identityOverview": "Pramlintide is an engineered analog of human amylin carrying three proline substitutions, designed to address the aggregation behaviour of the native human sequence.", "nomenclatureNotes": "Pramlintide is not another name for human amylin and not identical to rat amylin. It differs from human amylin at exactly three positions: A25P, S28P, S29P. The CAS recorded here is the peptide; a pramlintide acetate record describes a salt and must not replace this identity.", "structuralNotes": "Why this molecule exists belongs at the front of any description of it: human amylin aggregates, and the three prolines were introduced to reduce that propensity. The substitutions place it structurally between human amylin and cagrilintide — cagrilintide retains all three prolines and adds N14E, V17R, a Pro37 amide and N-terminal lipidation. The corpus records that chain as a structural relationship only; it is not a claim that the three molecules have interchangeable receptor profiles or physical behaviour. The receptor-comparison study PMID 33727283 tests pramlintide itself alongside selective and nonselective calcitonin-family receptor agonists. Its native amylin comparator is rat amylin, whose sequence differs from human amylin; those comparator data are not evidence for the human-amylin sequence.", "analyticalNotes": "THE AGGREGATION CLAIM NEEDS CARE, and this is the entry where the library should be most explicit. Pramlintide is widely described as non-aggregating. Exact-compound work reports it assembling into multimers and forming amyloid fibrils in vitro in a pH-dependent process, characterised by thioflavin T binding, loss of soluble peptide, transmission electron microscopy, atomic force microscopy and X-ray diffraction. Separate biophysical work reported pH-dependent stability and aggregation. Reduced propensity relative to human amylin is real; categorical immunity is not established. Neither the three prolines nor a chromatographic purity figure establishes the absence of higher-order assemblies in a given sample. Identity confirmation should also target positions 25, 28 and 29 specifically rather than relying on regions shared with human amylin.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-09-13" }, { "id": "glp-1-7-36-amide", "url": "https://purelypeptides.org/research/compounds/glp-1-7-36-amide/", "displayName": "GLP-1(7-36) amide", "canonicalName": "Glucagon-like peptide-1 (7-36) amide", "moleculeType": "peptide", "aliases": [ "GLP-1(7-36)amide", "GLP-1 7-36 amide" ], "developmentCodes": [], "externalIds": { "cas": "107444-51-9", "pubChemCid": "16133831", "unii": "0JS9125PIZ" }, "sequence": { "oneLetter": "HAEGTFTSDVSSYLEGQAAKEFIAWLVKGR", "notes": "Thirty residues ending in an amidated arginine. The conventional 7-36 numbering is retained rather than renumbering the mature N-terminal histidine as residue 1 — every modification table for every GLP-1 analog in this library uses that convention, and silently renumbering produces wrong records." }, "molecularFormula": "C149H226N40O45", "molecularWeightDa": 3297.7, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [ "incretin-and-glucagon-receptor-ligands" ], "mechanismIds": [ "glp-1-receptor" ], "relatedCompoundIds": [ "glp-1-7-37", "gip-1-42", "oxyntomodulin", "exenatide", "orforglipron", "tirzepatide", "retatrutide", "survodutide", "mazdutide", "glp-2" ], "referenceIds": [ "pmid-2890903", "pmid-8482423", "pmid-8100523", "pmid-7556682", "pmid-37528104" ], "identityOverview": "GLP-1(7-36) amide is an endogenous processing form of glucagon-like peptide-1 and the native ligand against which the GLP-1 receptor agonists in this library are compared. Deacon et al. (PMID 7556682) isolated this form from human colon and conclude that it is a product of proglucagon processing. Horváth et al. (PMID 37528104) place GLP-1 among the gastrointestinal peptides of the glucagon family.", "nomenclatureNotes": "'GLP-1(7-36)' without an amidation designation is not sufficiently specified. This entry is the AMIDATED form; GLP-1(7-37) is a separate molecule with an additional terminal glycine and a free carboxyl, recorded separately in this library. Amidation is not a counterion difference. GLP-1(1-37) is the N-terminally extended proform and is not this hormone; describing it as an inactive precursor is appropriate only in the sense that it is not the conventional mature insulinotropic form. The name Insulinotropin belongs to GLP-1(7-37) and is recorded on that entry; it is not an alias of this amidated form.", "structuralNotes": "Its N-terminal His-Ala is a substrate for dipeptidyl peptidase IV, which removes the dipeptide to give the des-His-Ala product. The enzymology was characterised directly, with kinetics consistent with degradation at nanomolar concentrations, and the released His-Ala identified. Since an intact N-terminus is required for activity in this peptide family, that cleavage is an identity question and not merely sample ageing. It is also the reason essentially every GLP-1-derived analog in this library carries a substitution at position 8.", "analyticalNotes": "The C-terminal modification must be part of the identity record; a generic GLP-1 measurement is not form-specific without demonstrated assay discrimination. Intact peptide must also be distinguished from the DPP-IV product; total GLP-1 immunoreactivity does not establish intact-molecule identity. This entry and GLP-1(7-37) are distinct native processing forms, not aliases — though note that the source comparing them directly found them equipotent, so the distinction recorded here is chemical rather than functional.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-14" }, { "id": "glp-1-7-37", "url": "https://purelypeptides.org/research/compounds/glp-1-7-37/", "displayName": "GLP-1(7-37)", "canonicalName": "Glucagon-like peptide-1 (7-37)", "moleculeType": "peptide", "aliases": [ "GLP-1 7-37", "GLP-I(7-37)", "Insulinotropin" ], "developmentCodes": [], "externalIds": { "cas": "106612-94-6", "pubChemCid": "16133830", "unii": "PI470C66NT" }, "sequence": { "oneLetter": "HAEGTFTSDVSSYLEGQAAKEFIAWLVKGRG", "notes": "Thirty-one residues ending in glycine with a FREE C-terminal carboxyl. Distinct from both the amidated 30-residue form and from GLP-1(1-37). Conventional 7-37 numbering retained: Ala8 is the second residue of the mature peptide, Lys26 the twentieth, Lys34 the twenty-eighth. Mixing numbering systems silently produces incorrect modification records for every analog derived from this scaffold." }, "molecularFormula": "C151H228N40O47", "molecularWeightDa": 3355.7, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "incretin-and-glucagon-receptor-ligands" ], "mechanismIds": [ "glp-1-receptor" ], "relatedCompoundIds": [ "glp-1-7-36-amide", "semaglutide", "liraglutide", "glp-2" ], "referenceIds": [ "pmid-3543057", "pmid-8482423", "pmid-37528104" ], "identityOverview": "GLP-1(7-37) is an endogenous processing form of glucagon-like peptide-1 retaining a C-terminal glycine, and the structural reference for several acylated GLP-1 analogs. Mojsov et al. (PMID 3543057) describe the glucagon-like peptides as liberated from proglucagon in both the pancreas and the intestine. Horváth et al. (PMID 37528104) place GLP-1 among the gastrointestinal peptides of the glucagon family.", "nomenclatureNotes": "This is the reference scaffold for the acylated GLP-1 analogs in this library, because they retain the C-terminal glycine. 'Both are GLP-1 analogs' is not sufficient for this corpus: which native form an analog is built on determines whether its modification table is right. GSRS UNII PI470C66NT and primary CAS 106612-94-6 describe the free 31-residue peptide represented by PubChem CID 16133830, although the GSRS CID cross-reference points to acetate CID 91820613. Mojsov et al. (PMID 3543057) named this glycine-extended form Insulinotropin; the name does not denote the amidated GLP-1(7-36) form.", "structuralNotes": "Work in the isolated perfused rat pancreas established this form as a potent stimulator of insulin secretion at concentrations as low as 5 x 10^-11 M, while the N-terminally extended GLP-1(1-37) had no effect at concentrations four orders of magnitude higher. That contrast is what makes the processing-form distinction a real identity question rather than a matter of notation. A separate human comparison of this form against the amidated form found them equipotent and concluded that C-terminal amidation is important for neither metabolism nor pancreatic effect — so this library records two distinct molecules on chemical grounds while reporting that the source examining them found no functional difference.", "analyticalNotes": "Terminal glycine, terminal carboxyl state and N-terminal processing state must each be independently visible. An ambiguous GLP-1 identity cannot be resolved by matching only the internal sequence segment shared by both active forms, since that segment is identical.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-14" }, { "id": "gip-1-42", "url": "https://purelypeptides.org/research/compounds/gip-1-42/", "displayName": "GIP(1-42)", "canonicalName": "Glucose-dependent insulinotropic polypeptide", "moleculeType": "peptide", "aliases": [ "GIP", "Gastric inhibitory polypeptide", "Glucose-dependent insulinotropic peptide" ], "developmentCodes": [], "externalIds": { "cas": "100040-31-1", "pubChemCid": "131954558", "unii": "1O4H75S7H2" }, "sequence": { "oneLetter": "YAEGTFISDYSIAMDKIHQQDFVNWLLAQKGKKNDWKHNITQ", "notes": "Forty-two residues, free at both termini. Note residue 1 is TYROSINE — the N-terminal Tyr-Ala distinguishes this hormone from GLP-1's His-Ala and is the single quickest way to tell a GIP-derived scaffold from a GLP-1-derived one." }, "molecularFormula": "C226H338N60O66S", "molecularWeightDa": 4983.6, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "incretin-and-glucagon-receptor-ligands" ], "mechanismIds": [ "gip-receptor" ], "relatedCompoundIds": [ "glp-1-7-36-amide", "glucagon", "tirzepatide", "retatrutide", "glp-2" ], "referenceIds": [ "pmid-6745415", "pmid-8100523", "pmid-37528104" ], "identityOverview": "GIP is a 42-residue endogenous incretin hormone and the native ligand of the GIP receptor. Horváth et al. (PMID 37528104) place GIP among the gastrointestinal peptides of the glucagon family.", "nomenclatureNotes": "'Gastric inhibitory polypeptide' is the historical name for this same hormone, not a different peptide. Species must stay explicit: human GIP differs from porcine at residues 18 and 34. Full-length GIP must not be merged with GIP(3-42), GIP(1-30)amide, or proGIP — DPP-IV cleavage changes the molecule and its pharmacology. GSRS UNII 1O4H75S7H2 assigns primary CAS 100040-31-1 to the human 42-residue free peptide, while PubChem CID 131954558 matches its connectivity and formula but leaves all 46 atom stereocentres undefined.", "structuralNotes": "Human GIP was isolated from small-intestinal extracts and sequenced by Edman degradation, together with the N-terminally truncated forms GIP(10-42), GIP(11-42) and GIP(17-42). Its N-terminal Tyr-Ala is a DPP-IV substrate; the enzyme releases Tyr-Ala to give GIP(3-42), and the same work identified this as the main degradation route in human serum. Because an intact N-terminus is required for activity in this peptide family, the truncated form is a different substance rather than degraded material of the same one.", "analyticalNotes": "Require human species, full length and an intact N terminus. A total-GIP assay is not automatically an intact-GIP assay. For any comparison against a GIP-derived analog, retain explicit residue numbering — Ala13, Met14, Ile17 and His18 are positions where off-by-one errors in modification tables are common, because the analogs substitute at several of them.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-14" }, { "id": "glucagon", "url": "https://purelypeptides.org/research/compounds/glucagon/", "displayName": "Glucagon", "canonicalName": "Glucagon", "moleculeType": "peptide", "aliases": [ "Glucagon(1-29)" ], "developmentCodes": [], "externalIds": { "cas": "16941-32-5", "pubChemCid": "16132283", "unii": "76LA80IG2G" }, "sequence": { "oneLetter": "HSQGTFTSDYSKYLDSRRAQDFVQWLMNT", "notes": "Twenty-nine residues, free at both termini, no modifications." }, "molecularFormula": "C153H225N43O49S", "molecularWeightDa": 3482.8, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "incretin-and-glucagon-receptor-ligands" ], "mechanismIds": [ "glucagon-receptor" ], "relatedCompoundIds": [ "oxyntomodulin", "gip-1-42", "retatrutide", "survodutide", "mazdutide", "glp-2" ], "referenceIds": [ "pmid-32193322", "pmid-40385697", "pmid-36356832", "pmid-37528104" ], "identityOverview": "Glucagon is the endogenous 29-residue pancreatic hormone and the native ligand of the glucagon receptor. Horváth et al. (PMID 37528104) place glucagon among the gastrointestinal peptides of the glucagon family.", "nomenclatureNotes": "Mature glucagon, not proglucagon and not a generic glucagon-family peptide. PubChem CID 16132283 encodes the free 29-residue peptide, whereas CAS-associated CIDs 91820614 and 16186213 include acetate and hydrochloride components, respectively. Glucagon, GLP-1 and oxyntomodulin are related through processing of a shared precursor but are not aliases. Note particularly that this entire 29-residue sequence is contained within oxyntomodulin, which extends it by eight residues — that containment is exactly why the two are analytically difficult to separate.", "structuralNotes": "Cryo-electron microscopy structures of glucagon bound to the human glucagon receptor in complex with two different heterotrimeric G proteins establish exact-hormone receptor recognition, with conformational differences in the receptor intracellular loops identified as selectivity determinants and supported by mutagenesis. Being an agonist at this receptor does not, in the other direction, establish a glucagon-derived backbone: compounds in this library activate the glucagon receptor from scaffolds that are not glucagon-derived at all.", "analyticalNotes": "A shared glucagon-region epitope or internal sequence is insufficient to discriminate glucagon from larger proglucagon-derived peptides that contain it in full. Identity work should target intact-molecule specificity and calibrant identity rather than assuming all glucagon-reactive material is mature glucagon. A validated mass-spectrometric method separating glucagon from oxyntomodulin exists and is the appropriate reference point for that problem. GSRS UNII 76LA80IG2G matches the peptide sequence but reports C153H225N43O48S, one oxygen below PubChem CID 16132283 and this record’s formula.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-14" }, { "id": "oxyntomodulin", "url": "https://purelypeptides.org/research/compounds/oxyntomodulin/", "displayName": "Oxyntomodulin", "canonicalName": "Oxyntomodulin", "moleculeType": "peptide", "aliases": [ "OXM", "Glucagon-37" ], "developmentCodes": [], "externalIds": { "pubChemCid": "121494088", "unii": "LV7ELH7V16" }, "sequence": { "oneLetter": "HSQGTFTSDYSKYLDSRRAQDFVQWLMNTKRNRNNIA", "notes": "Thirty-seven residues, free at both termini. The first twenty-nine are the complete glucagon sequence; the C-terminal extension is KRNRNNIA. Species and the extension must both be explicit." }, "molecularFormula": "C192H295N61O60S", "molecularWeightDa": 4449.9, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "incretin-and-glucagon-receptor-ligands" ], "mechanismIds": [ "glp-1-receptor", "glucagon-receptor" ], "relatedCompoundIds": [ "glucagon", "glp-1-7-36-amide", "mazdutide", "glp-2" ], "referenceIds": [ "pmid-3189794", "pmid-40385697", "pmid-22421924", "pmid-25115338" ], "identityOverview": "Oxyntomodulin is an endogenous proglucagon-derived peptide containing the complete glucagon sequence plus an eight-residue C-terminal extension, with reported activity at both the GLP-1 and glucagon receptors. A review by Bataille and Dalle (PMID 25115338) describes oxyntomodulin as a member of the glucagon family; that is a review-level family attribution.", "nomenclatureNotes": "Oxyntomodulin is ONE peptide, not a mixture of GLP-1 and glucagon. It is also not glicentin, which is a larger processing product that contains the oxyntomodulin region — and both carry the same KRNRNNIA C-terminus, so recognising that region does not distinguish them. Separately, 'oxyntomodulin-like' is a description of GLP-1R/GCGR pharmacology and does not establish oxyntomodulin-derived chemistry; a compound can have that pharmacology from a different scaffold entirely. PubChem CID 121494088 encodes the human 37-residue free peptide ending KRNRNNIA, whereas CID 16144019 ends KRNKNNIA and contains Lys33 in place of Arg33. Arginine carries two more nitrogens than lysine, which is why that record shows N59 against this entry's N61. Its formula and mass describe a variant and must not be applied to the human sequence.", "structuralNotes": "Its dual-receptor character was dissected using a single-residue variant: replacing glutamine with glutamate at position 3 retained comparable potency at the murine GLP-1 receptor while removing significant murine glucagon-receptor agonist activity in vitro and reducing the ability to stimulate glycogenolysis in perfused mouse liver by roughly one hundred-fold. These receptor and liver assays distinguish the GLP-1R and GCGR components of oxyntomodulin signaling. The library cites that work for this receptor dissection specifically. There is no separate established oxyntomodulin receptor to name; the mechanism is the two receptors it shares with other proglucagon-derived peptides.", "analyticalNotes": "Identity work must discriminate oxyntomodulin from BOTH glucagon and glicentin. An internal glucagon-derived segment cannot identify it uniquely, because glucagon's entire sequence is contained within it. A C-terminal antibody does not solve this either: antisera raised against the KRNRNNIA extension cross-react completely with both oxyntomodulin and glicentin while showing none toward glucagon. Chromatographic or mass-spectrometric separation is therefore the appropriate approach, and a validated LC-MS/MS method distinguishing oxyntomodulin from glucagon exists. GSRS UNII LV7ELH7V16 matches the human sequence but reports C192H291N61O60S, four hydrogens below PubChem CID 121494088 and this record’s formula.", "publishedDate": "2026-09-14", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-14" }, { "id": "humanin", "url": "https://purelypeptides.org/research/compounds/humanin/", "displayName": "Humanin (HN)", "canonicalName": "Humanin", "moleculeType": "peptide", "aliases": [ "HN" ], "developmentCodes": [], "externalIds": { "cas": "330936-69-1", "pubChemCid": "16131438", "unii": "H975EUX36G" }, "sequence": { "oneLetter": "MAPRGFSCLLLLTSEIDLPVKRRA", "notes": "Twenty-four residues with free termini and one cysteine at position 8. This record specifies the standard-code form; it does not identify the mature product of mitochondrial translation." }, "molecularFormula": "C119H204N34O32S2", "molecularWeightDa": 2687.3, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "hng", "hngf6a", "shlp2", "shlp3", "shlp6", "mots-c" ], "referenceIds": [ "pmid-11371646", "pmid-12732850", "pmid-19386761", "pmid-15465011", "pmid-19477263", "pmid-37644144", "pmid-25738459" ], "identityOverview": "Humanin is a 24-residue peptide encoded within the mitochondrial 16S ribosomal RNA gene, and the first-described member of the mitochondrial-derived peptide family.", "nomenclatureNotes": "The humanin coding sequence lies within MT-RNR2, the mitochondrial 16S rRNA gene. A mitochondrial coding locus does not establish where translation occurs. This record specifies the 24-residue standard-code form; a mitochondrial-code prediction is a distinct sequence. Nuclear humanin-like loci further complicate assigning endogenous origin. HNG carries S14G, and HNGF6A carries F6A and S14G. N-formyl humanin is a distinct chemical form. MTRNR2L gene names denote nuclear loci and are not peptide aliases.", "structuralNotes": "Functional expression screening identified humanin cDNA, and the corresponding peptide was detected in culture medium. Humanin binds BAX, an intracellular partner, and limits its association with isolated mitochondria. Cell-binding and reconstituted-protein experiments implicate CNTFR-alpha, WSX-1 and gp130 in a separate cell-surface complex. A comparison of unmodified and N-formyl humanin measured receptor binding and activation; the chemical forms must be distinguished. Analysis of synonymous codon bias reports strong bias and conservation for humanin, consistent with amino-acid sequence constraint within the rRNA gene.", "analyticalNotes": "Fragments spanning positions 14 and 16 and the C-terminal RRA segment distinguish the recorded sequence from related forms. A short shared fragment or immunoassay signal cannot identify the intact 24-mer or its transcript of origin. One cysteine permits an intermolecular disulfide but no intramolecular disulfide. Routine intact mass does not distinguish leucine from isoleucine or establish stereochemistry.", "publishedDate": "2026-09-16", "lastVerifiedDate": "2026-09-15" }, { "id": "hng", "url": "https://purelypeptides.org/research/compounds/hng/", "displayName": "HNG ([Gly14]-Humanin)", "canonicalName": "[Gly14]-humanin", "moleculeType": "peptide", "aliases": [ "HNG", "S14G-humanin", "S14G-HN", "Humanin-G" ], "developmentCodes": [], "externalIds": { "cas": "330936-70-4", "pubChemCid": "16135997" }, "sequence": { "oneLetter": "MAPRGFSCLLLLTGEIDLPVKRRA", "notes": "Twenty-four residues, free at both termini. Identical to humanin except at position 14, where serine is replaced by glycine." }, "molecularFormula": "C118H202N34O31S2", "molecularWeightDa": 2657.2, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "S14G" ], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "humanin", "hngf6a", "shlp2", "amylin" ], "referenceIds": [ "pmid-19386761", "pmid-23836030", "pmid-28798389" ], "identityOverview": "HNG is a synthetic single-substitution analog of humanin carrying glycine in place of serine at position 14.", "nomenclatureNotes": "HNG, S14G-HN and [Gly14]-humanin name the same substitution. 'Humanin-G' denotes substitution at position 14, not a glycine extension. HNGF6A additionally replaces Phe6 with alanine. These synthetic analogs require sequence-specific attribution; mitochondrial family membership does not establish endogenous expression.", "structuralNotes": "Cell-binding experiments tested biotin-labeled humanin and HNG separately; receptor-subunit knockdown reduced HNG binding, and reconstituted-protein assays examined both peptides. In a separate biophysical study, HNG and SHLP2 associated with misfolded IAPP seeds. Fluorescence and co-sedimentation supported seed binding, while EPR and circular dichroism did not support binding to IAPP monomers. Rodent disposition experiments compared HNG with HNGF6A and included an IGFBP-3-deficient group; plasma measurements used a humanin ELISA, so immunoreactivity is distinct from intact-peptide identification.", "analyticalNotes": "Verify glycine at position 14 with fragments spanning it. Relative to humanin the substitution removes CH2O, a calculated monoisotopic difference of 30.011 Da — small, and a fragment that omits position 14 cannot distinguish the two molecules at all. A humanin immunoassay or a shared biological response cannot establish which analog was supplied.", "publishedDate": "2026-09-16", "lastVerifiedDate": "2026-09-15" }, { "id": "hngf6a", "url": "https://purelypeptides.org/research/compounds/hngf6a/", "displayName": "HNGF6A", "canonicalName": "[Ala6,Gly14]-humanin", "moleculeType": "peptide", "aliases": [ "HNGF6A", "F6A/S14G-humanin" ], "developmentCodes": [], "externalIds": { "cas": "1093111-54-6", "pubChemCid": "90489015" }, "sequence": { "oneLetter": "MAPRGASCLLLLTGEIDLPVKRRA", "notes": "Twenty-four residues, free at both termini. Two substitutions relative to humanin: F6A and S14G. Chain length is unchanged, so '24-residue humanin analog' does not identify it." }, "molecularFormula": "C112H198N34O31S2", "molecularWeightDa": 2581.1, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "F6A", "S14G" ], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "humanin", "hng" ], "referenceIds": [ "pmid-23836030", "pmid-23995290" ], "identityOverview": "HNGF6A is a synthetic humanin analog with F6A and S14G substitutions, described as non-IGFBP-3-binding in a comparative disposition study.", "nomenclatureNotes": "HNGF6A is not an alias of humanin or HNG. F6A-humanin alone is a third molecule again — it retains Ser14. Some records collapse humanin and its derivatives under broad substance names, so the sequence must control assignment rather than the label.", "structuralNotes": "A rodent study compared HNGF6A with HNG in wild-type animals and HNG in animals lacking IGFBP-3. Its non-IGFBP-3-binding designation defines the comparison; plasma humanin immunoreactivity does not establish intact-peptide identity. A separate study explicitly examined HNGF6A in isolated islets and cultured murine beta cells with scrambled-peptide controls and assessed K-ATP channel dependence. Those experimental systems do not establish a direct receptor assignment for this double-substituted peptide.", "analyticalNotes": "Require fragments establishing BOTH Ala6 and Gly14; either alone leaves it indistinguishable from HNG or from F6A-humanin. Relative to HNG the F6A substitution removes C6H4, a calculated monoisotopic difference of 76.031 Da. Testing IGFBP-3 binding characterises function and cannot substitute for chemical identity — degradation, aggregation or assay failure would all produce an apparent absence of binding.", "publishedDate": "2026-09-16", "lastVerifiedDate": "2026-09-15" }, { "id": "shlp2", "url": "https://purelypeptides.org/research/compounds/shlp2/", "displayName": "SHLP2", "canonicalName": "Small humanin-like peptide 2", "moleculeType": "peptide", "aliases": [ "SHLP-2" ], "developmentCodes": [], "externalIds": { "cas": "1191923-93-9", "pubChemCid": "171716852" }, "sequence": { "oneLetter": "MGVKFFTLSTRFFPSVQRAVPLWTNS", "notes": "Twenty-six residues, free at both termini. One methionine, no cysteine. Position 4 is LYSINE in this form; a naturally occurring variant carries arginine there and is a different molecule." }, "molecularFormula": "C142H214N36O35S", "molecularWeightDa": 3017.6, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "humanin", "hng", "shlp3", "shlp6", "mots-c", "amylin" ], "referenceIds": [ "pmid-27070352", "pmid-28798389", "pmid-37468558", "pmid-38167865", "pmid-37644144", "pmid-25738459" ], "identityOverview": "SHLP2 is a 26-residue peptide assigned to a small open reading frame within the mitochondrial 16S rRNA region. Its experimental characterization includes receptor screening, protein-interaction assays and targeted peptide detection.", "nomenclatureNotes": "'Humanin-like' describes the genomic neighbourhood, not the sequence: SHLP2 is not a humanin fragment and shares no substantial sequence with it. K4R-SHLP2 is a distinct variant arising from a mitochondrial single-nucleotide polymorphism and is not an alias for this Lys4 form. The mature endogenous terminal chemistry is UNKNOWN; the free-acid termini recorded here specify the synthetic reference molecule.", "structuralNotes": "Structural complementation screening identified CXCR7 binding and activation by SHLP2. Separate experiments detected a tryptic fragment in neuronal cells and supported association with mitochondrial complex I. Biophysical assays also support binding to misfolded IAPP seeds. These experimental findings coexist with weaker evolutionary evidence: the synonymous-codon analysis found no significant bias and poor conservation for SHLP2, unlike humanin and SHLP6. Because the coding sequence lies within an rRNA gene, amino-acid conservation is the expected signature of peptide-level functional constraint. This analysis argues against that constraint for SHLP2; it does not erase the reported experimental observations.", "analyticalNotes": "Targeted proteomics detected the internal tryptic fragment FFPSVQR. It omits position 4 and both termini, so it cannot distinguish Lys4 from the Arg4 variant or establish intact endogenous terminal chemistry. Intact-sequence assignment requires additional coverage. Peptide-affinity capture of partner proteins is a separate experiment from endogenous-peptide identification.", "publishedDate": "2026-09-16", "lastVerifiedDate": "2026-09-15" }, { "id": "shlp3", "url": "https://purelypeptides.org/research/compounds/shlp3/", "displayName": "SHLP3", "canonicalName": "Small humanin-like peptide 3", "moleculeType": "peptide", "aliases": [ "SHLP-3" ], "developmentCodes": [], "externalIds": {}, "sequence": { "oneLetter": "MLGYNFSSFPCGTISIAPGFNFYRLYFIWVNGLAKVVW", "notes": "Thirty-eight residues with free termini and a cysteine at position 11. The recorded sequence has valine at position 29; substitution with tryptophan would change both formula and mass." }, "molecularFormula": "C214H301N47O49S2", "molecularWeightDa": 4380.2, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "shlp2", "shlp6", "humanin", "mots-c" ], "referenceIds": [ "pmid-27070352", "pmid-37644144", "pmid-25738459" ], "identityOverview": "SHLP3 is a 38-residue peptide from the same mitochondrial region as humanin, characterised principally through the study that named the series.", "nomenclatureNotes": "The number denotes a distinct peptide, not an activity rank and not a shortened humanin. PubChem and GSRS searches found no exact registry identifier for the specified 38-residue free peptide with C214H301N47O49S2; this bounded result does not establish that registration is impossible or excluded by molecular size. Mature endogenous termini and intact endogenous sequence confirmation are UNKNOWN; a synthetic peptide showing activity does not demonstrate that the same mature molecule is produced physiologically.", "structuralNotes": "The discovery study identified small open reading frames in the mitochondrial 16S rRNA region and found different cellular responses among the SHLP peptides. SHLP3 induced ERK phosphorylation without detectable STAT3 phosphorylation in the reported comparison. No direct receptor assignment is established here. The conservation analysis found no significant synonymous codon bias and poor conservation for SHLP3, arguing against amino-acid sequence constraint despite the reported cellular observations.", "analyticalNotes": "Sequence confirmation should distinguish valine from tryptophan at position 29 and establish both termini. One cysteine permits intermolecular disulfide formation, and methionine oxidation changes mass. A matching retention time or nominal mass does not establish residue order or leucine/isoleucine assignments.", "publishedDate": "2026-09-16", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-09-15" }, { "id": "shlp6", "url": "https://purelypeptides.org/research/compounds/shlp6/", "displayName": "SHLP6", "canonicalName": "Small humanin-like peptide 6", "moleculeType": "peptide", "aliases": [ "SHLP-6" ], "developmentCodes": [], "externalIds": { "pubChemCid": "16208939" }, "sequence": { "oneLetter": "MLDQDIPMVQPLLKVRLFND", "notes": "Twenty residues, free at both termini. TWO methionines, at positions 1 and 8, and NO cysteine — so it carries two sulfur atoms without any thiol." }, "molecularFormula": "C107H177N27O30S2", "molecularWeightDa": 2385.9, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "mitochondrial-derived-peptides" ], "mechanismIds": [], "relatedCompoundIds": [ "shlp2", "shlp3", "humanin", "mots-c" ], "referenceIds": [ "pmid-27070352", "pmid-37644144", "pmid-25738459" ], "identityOverview": "SHLP6 is a 20-residue peptide assigned to the mitochondrial 16S rRNA region and distinguished from other SHLP members by its sequence and reported cellular response.", "nomenclatureNotes": "SHLP6 is twenty residues; descriptions that give all SHLPs a common length range are wrong. PubChem CID 16208939 encodes the free 20-residue sequence MLDQDIPMVQPLLKVRLFND; its CAS 368431-25-8 synonym remains independently unconfirmed, and no exact GSRS UNII was found. It is neither a truncated humanin nor interchangeable with SHLP2 or SHLP3, and it does not behave like them — see structuralNotes.", "structuralNotes": "The discovery comparison found different cellular responses across the SHLP series: SHLP6 increased apoptosis in the assay where SHLP2 and SHLP3 reduced it. Family membership does not establish a common cellular effect. Separately, SHLP6 and humanin showed strong synonymous codon bias and sequence conservation, consistent with amino-acid sequence constraint. This support does not extend to SHLP2 or SHLP3. No direct receptor or molecular target is established here.", "analyticalNotes": "Fragmentation should cover methionine 8 and the C-terminal aspartate. With two methionines, singly and doubly oxidised species are relevant identity impurities rather than incidental ones. The peptide contains no cysteine, so any proposed disulfide structure contradicts this sequence outright. Antibody detection and coding-sequence conservation each establish something real and neither establishes intact endogenous termini, which remain unknown.", "publishedDate": "2026-09-16", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-09-15" }, { "id": "spexin", "url": "https://purelypeptides.org/research/compounds/spexin/", "displayName": "Spexin", "canonicalName": "Spexin", "moleculeType": "peptide", "aliases": [ "SPX", "Spexin-1", "NPQ" ], "developmentCodes": [], "externalIds": { "cas": "1370290-58-6", "pubChemCid": "122705996" }, "sequence": { "oneLetter": "NWTPQAMLYLKGAQ", "threeLetter": [ "Asn", "Trp", "Thr", "Pro", "Gln", "Ala", "Met", "Leu", "Tyr", "Leu", "Lys", "Gly", "Ala", "Gln" ], "notes": "Fourteen residues with a C-terminal amide, free N-terminus and no disulfide, lactam or lipid conjugation." }, "molecularFormula": "C74H114N20O19S", "molecularWeightDa": 1619.9, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [ "galanin-receptors" ], "relatedCompoundIds": [ "galanin", "kisspeptin-14" ], "referenceIds": [ "pmid-17284679", "pmid-24517231", "pmid-35594396" ], "identityOverview": "Spexin is an endogenous fourteen-residue amidated neuropeptide identified by computational screening of the human proteome, and a ligand of galanin receptors 2 and 3.", "nomenclatureNotes": "Spexin and spadin are unrelated peptides. Mature spexin has fourteen residues, and PE 22-28 is derived from the sortilin propeptide. The former alias Spexin (22-28) incorrectly assigned that fragment to spexin. NPQ is a discovery-era designation that may refer to the precursor; it does not by itself identify the mature amidated peptide.", "structuralNotes": "A hidden Markov model screen identified the spexin precursor, followed by secretory-granule localization and recovery from cell supernatant. These observations concern precursor expression and secretion; they do not alone identify intact mature spexin. Ligand-receptor experiments found spexin activation of GALR2 and GALR3, with no GALR1 activation in the reported panel and greater potency at GALR3 than the galanin comparator. A cryo-EM study determined a spexin-bound GALR2-Gq complex. Evolutionary analysis supports local duplication of spexin, galanin and kisspeptin genes before two rounds of vertebrate whole-genome duplication.", "analyticalNotes": "Confirmation needs the fourteen-residue sequence and the terminal amide together; the free acid is 0.98 Da heavier than the amide and deamidation must be localised rather than inferred from intact mass. Include a methionine-oxidation assessment. Precursor-derived intermediates extended at the N-terminus or carrying the amidation-donor glycine should be looked for explicitly, since detecting precursor expression or immunoreactivity does not establish that the mature amidated peptide is present.", "publishedDate": "2026-09-19", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-17" }, { "id": "spadin", "url": "https://purelypeptides.org/research/compounds/spadin/", "displayName": "Spadin", "canonicalName": "Spadin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "cas": "1270083-24-3", "pubChemCid": "91826106" }, "sequence": { "oneLetter": "YAPLPRWSGPIGVSWGLR", "notes": "Eighteen residues with free termini. This record specifies the Tyr-extended form YAPLPRWSGPIGVSWGLR. The seventeen-residue sortilin-propeptide segment PE(12-28) is APLPRWSGPIGVSWGLR; the added tyrosine changes the residue composition by 163.06 Da." }, "molecularFormula": "C96H142N26O22", "molecularWeightDa": 2012.3, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [ "pe-22-28" ], "referenceIds": [ "pmid-20405001", "pmid-28955242" ], "identityOverview": "Spadin is a sortilin-propeptide-derived peptide reported to interact with sortilin and to inhibit the TREK-1 potassium channel, and the parent design from which PE 22-28 was derived.", "nomenclatureNotes": "Spadin derives from the propeptide released during sortilin maturation. Sortilin is also called neurotensin receptor 3. This entry specifies the eighteen-residue Tyr-extended form; the unqualified name spadin and the label PE(12-28) do not resolve the seventeen-versus-eighteen-residue distinction. The founding study describes a Tyr0 radioiodination site. Its labeled binding probe is a separate reagent, and an assay described only as spadin does not establish that every experiment used the same terminal form. PE 22-28 is a seven-residue designed truncation of the same propeptide sequence.", "structuralNotes": "The founding study reported reciprocal immunoprecipitation of sortilin and TREK-1 and colocalization in cortical neurons. Binding assays reported approximately 10 nM affinity, and electrophysiology measured inhibition of TREK-1 activity in transfected cells, cultured hippocampal neurons and brain slices. A later study designed PE 22-28 from blood degradation products and measured TREK-1 inhibition in hTREK-1/HEK cells at approximately 0.1 nM, against 40-60 nM for the spadin comparator. That source is internally inconsistent about which peptide carries which value: its abstract and results report 0.12 nM for PE 22-28 and 0.10 nM for the Gly22-Ala analog, while its figure legend and discussion transpose the two. No single figure is reproduced here as though the source agreed with itself. These results establish the experimental design relationship; they do not establish endogenous production of the seven-residue peptide. The Tyr extension and radioiodination state must be tracked when comparing reagents.", "analyticalNotes": "The first question for any sample is whether it begins Tyr-Ala or Ala: the tyrosine residue adds 163.06 Da monoisotopic, 163.18 Da average, and N-terminal fragmentation localises it. State which convention a reported figure uses; the recorded mass on this entry is an average mass. Radioiodinated Tyr-containing binding probes used in this literature are separate reagents and are not chemically identical to unlabelled spadin. For PE 22-28, verify the exact seven residues and the free acid, and exclude the Gly22-Ala analog and the biotinylated derivatives used in the same experiments — a shared TREK-1 response does not distinguish them.", "publishedDate": "2026-09-19", "lastVerifiedDate": "2026-09-17" }, { "id": "kisspeptin-14", "url": "https://purelypeptides.org/research/compounds/kisspeptin-14/", "displayName": "Kisspeptin-14", "canonicalName": "Kisspeptin-14", "moleculeType": "peptide", "aliases": [ "KP-14", "Metastin(41-54)" ], "developmentCodes": [], "externalIds": { "cas": "374675-19-1", "pubChemCid": "171916517" }, "sequence": { "oneLetter": "DLPNYNWNSFGLRF", "notes": "Fourteen residues with a C-terminal amide, free N-terminus, no cyclization or nonstandard residue. The final ten residues are the entire kisspeptin-10 sequence; the distinguishing part is the N-terminal DLPN." }, "molecularFormula": "C82H112N22O21", "molecularWeightDa": 1741.9, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [ "kisspeptins" ], "mechanismIds": [ "kisspeptin-receptor" ], "relatedCompoundIds": [ "kisspeptin-10", "spexin" ], "referenceIds": [ "pmid-11457843", "pmid-38935498", "pmid-24517231" ], "identityOverview": "Kisspeptin-14 is a KISS1-derived peptide isolated from human placental extracts, containing kisspeptin-10 as its C-terminal decapeptide, and an agonist at the kisspeptin receptor.", "nomenclatureNotes": "A fourteen-residue kisspeptin was isolated from human placenta alongside the 54- and 13-residue forms. KP-14 contains the kisspeptin-10 sequence at its C terminus. Removing its initial aspartate gives the 13-residue sequence; removing DLPN gives the 10-residue sequence. These are different molecular forms even where receptor responses are similar.", "structuralNotes": "The 54-, 14- and 13-residue kisspeptins were isolated from human placenta together, share a common C-terminal RF-amide, and bound rat and human GPR54 with low nanomolar affinity. A cryo-EM structure of the receptor exists but was determined with kisspeptin-10; the shared C-terminal pharmacophore makes it useful context for this entry rather than evidence about how KP-14's four additional N-terminal residues behave when bound. Whether KP-14 is produced in vivo from a longer form, and by which enzyme, is not established, and shared sequence is not by itself evidence of a serial processing pathway.", "analyticalNotes": "Sequence coverage must span the DLPN extension, not only the shared ten-residue tail, or the result cannot distinguish KP-14 from KP-13 or KP-10. Asparagine deamidation and loss of the terminal amide each produce a change near 0.98 Da, so intact mass can detect that something happened but not where. A receptor response is useful functional evidence and identifies no particular chain length.", "publishedDate": "2026-09-19", "updatedDate": "2026-10-14", "lastVerifiedDate": "2026-09-17" }, { "id": "gonadorelin", "url": "https://purelypeptides.org/research/compounds/gonadorelin/", "displayName": "Gonadorelin (GnRH-I)", "canonicalName": "Gonadorelin", "moleculeType": "peptide", "aliases": [ "GnRH-I", "Gonadotropin-releasing hormone", "LHRH", "LH-RH" ], "developmentCodes": [], "externalIds": { "cas": "33515-09-2", "pubChemCid": "638793", "unii": "9O7312W37G" }, "sequence": { "threeLetter": [ "pGlu", "His", "Trp", "Ser", "Tyr", "Gly", "Leu", "Arg", "Pro", "Gly" ], "notes": "Ten residues. NO one-letter string is published here because position 1 is pyroglutamate, not glutamine or glutamate, and any standard letter would name a different residue. The C-terminal glycine is amidated. The pyroglutamate ring is internal to that residue; this is NOT a head-to-tail macrocycle." }, "molecularFormula": "C55H75N17O13", "molecularWeightDa": 1182.3, "terminalModifications": [ "N-terminal pyroglutamate", "C-terminal amide" ], "structuralModifications": [ "Pyroglutamate at position 1" ], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [ "kisspeptin-10", "leuprolide", "triptorelin" ], "referenceIds": [ "pmid-4946067", "pmid-16339030" ], "identityOverview": "Gonadorelin is the ten-residue hypothalamic releasing hormone GnRH-I, carrying an N-terminal pyroglutamate and a C-terminal amide.", "nomenclatureNotes": "GnRH-I is not GnRH-II and not any of the long-acting synthetic GnRH analogs; a generic 'GnRH' label does not identify this decapeptide. Kisspeptin does not become GnRH by cleavage — they are different sequences acting at different receptors, connected by a neuronal circuit.", "structuralNotes": "The decapeptide structure was established by conventional sequential analysis of porcine hypothalamic material. Human GnRH-I has the same sequence; the founding determination was not a human isolation. Separate electrophysiology used human kisspeptin-10 to depolarize GnRH neurons in mouse brain slices, with a larger responsive fraction in adults than in juvenile animals. This supplies circuit context for gonadorelin, not evidence that gonadorelin binds KISS1R or that kisspeptin binds the GnRH receptor.", "analyticalNotes": "Verify pyroglutamate at position 1 and the C-terminal amide specifically, not merely a mass-compatible decapeptide. A single-position substitution, or a D-amino acid in place of its L counterpart, can leave the elemental composition unchanged, so an intact-mass match does not exclude either. A gonadotropin-release response is a functional assay and does not distinguish native GnRH from an active analog.", "publishedDate": "2026-09-19", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-17" }, { "id": "galanin", "url": "https://purelypeptides.org/research/compounds/galanin/", "displayName": "Galanin (human 1-30)", "canonicalName": "Galanin", "moleculeType": "peptide", "aliases": [ "GAL", "Galanin(1-30)" ], "developmentCodes": [], "externalIds": { "cas": "119418-04-1", "pubChemCid": "16133823" }, "sequence": { "oneLetter": "GWTLNSAGYLLGPHAVGNHRSFSDKNGLTS", "notes": "Thirty residues with a FREE C-terminal carboxyl — not an amide. That distinguishes the human peptide from the 29-residue amidated galanins of several other species, which are widely used as comparators." }, "molecularFormula": "C139H210N42O43", "molecularWeightDa": 3157.4, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [ "galanin-receptors" ], "relatedCompoundIds": [ "spexin" ], "referenceIds": [ "pmid-35594396", "pmid-24517231" ], "identityOverview": "Galanin is a thirty-residue human neuropeptide acting through the galanin receptor family, and the reference ligand against which spexin's receptor selectivity is measured.", "nomenclatureNotes": "Human galanin is thirty residues with a free acid terminus and is NOT interchangeable with the 29-residue amidated galanins from other species that appear throughout this literature as comparators; length, C-terminal sequence and terminal chemistry all differ. Galanin-like peptide is a different molecule, not an alias. PubChem CID 16133823 is retained for fully stereospecified human galanin(1–30) with free termini; CID 74765466 has the same connectivity but leaves stereochemistry undefined. And spexin is not a proteolytic fragment of galanin — the two are separate gene products that happen to share receptors.", "structuralNotes": "The cryo-EM study used galanin(1-30) and determined galanin-bound GALR1-Go and GALR2-Gq complexes, alongside a spexin-bound GALR2-Gq complex. The resolved galanin N-terminal region adopts a largely alpha-helical conformation in the extracellular vestibule, roughly parallel to the membrane. Its N-terminal residues 1-17 were well resolved; this does not establish structural detail for the entire human C-terminal segment. Functional measurements in the same study identified zinc as a negative allosteric regulator of GALR1 but not GALR2. The evolutionary comparison supplies family context; it does not establish a matched GALR3 potency comparison for this exact human thirty-residue free acid.", "analyticalNotes": "Establish the human C-terminal sequence and the free acid at serine 30 specifically; conserved N-terminal coverage is the region shared with other species' galanins and cannot identify the human peptide. Look explicitly for amidated contaminants and for species substitutions against sequence-defined standards. Similar receptor activation does not distinguish human galanin from other active galanin sequences, and a generic galanin immunoassay may resolve neither length nor terminal processing.", "publishedDate": "2026-09-19", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-09-17" }, { "id": "tb-500", "url": "https://purelypeptides.org/research/compounds/tb-500/", "displayName": "TB-500", "canonicalName": "TB-500", "moleculeType": "peptide", "aliases": [ "N-acetyl-thymosin beta-4 (17-23)" ], "developmentCodes": [], "externalIds": { "cas": "885340-08-9", "pubChemCid": "62707662", "unii": "QHK6Z47GTG" }, "sequence": { "oneLetter": "LKKTETQ", "threeLetter": [ "Leu", "Lys", "Lys", "Thr", "Glu", "Thr", "Gln" ], "notes": "The residue sequence LKKTETQ corresponds to positions 17-23 of mature human thymosin beta-4 and positions 18-24 of UniProt P62328, whose initiator methionine is removed. The fragment's N-terminal acetyl modification is attached to leucine, rather than to the serine that begins the mature parent." }, "terminalModifications": [ "N-terminal acetylation at Leu1", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [ "thymosin-beta-4", "ac-sdkp" ], "referenceIds": [ "pmid-22962027", "pmid-23084823", "pmid-36482504" ], "identityOverview": "Analytical studies have identified an N-terminally acetylated heptapeptide with the residue sequence LKKTETQ in material labeled TB-500. The designation alone does not establish the complete molecular identity of another preparation.", "nomenclatureNotes": "TB-500 is a product designation whose use does not uniquely specify a molecular structure. This dossier concerns the acetylated LKKTETQ referent identified in analytical literature. PubChem CID 62707662 and GSRS UNII QHK6Z47GTG, which lists CAS 885340-08-9, identify Ac-LKKTETQ-OH; these identifiers describe the defined fragment and do not establish the composition of another preparation labeled TB-500. It does not establish the identity or composition of a commercial preparation.", "analyticalNotes": "The retrieved registry representations disagree on molecular formula and molecular weight. Their reported properties are retained as conflicting observations; no settled formula or average molecular weight is assigned here. A calculation for a specified terminal structure characterizes that structure and does not resolve the source disagreement. PubChem CID 62707662 explicitly represents the acetylated seven-residue fragment with a free Gln7 carboxyl, so that end can be declared for this structure without settling the retained inter-registry formula disagreement. PubChem CID 62707662 reports C38H68N10O14, whereas GSRS UNII QHK6Z47GTG reports C36H66N10O13 despite specifying N-acetylation, leaving the registry property disagreement explicit.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-28" }, { "id": "n-acetyl-semax-amidate", "url": "https://purelypeptides.org/research/compounds/n-acetyl-semax-amidate/", "displayName": "N-Acetyl Semax Amidate", "canonicalName": "N-Acetyl Semax Amidate", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "pubChemCid": "172638603" }, "sequence": { "oneLetter": "MEHFPGP", "threeLetter": [ "Met", "Glu", "His", "Phe", "Pro", "Gly", "Pro" ], "notes": "The seven residue positions are unchanged from Semax. In shorthand, Ac and NH2 denote the N-terminal acetyl and C-terminal amide groups; they are not additional residues." }, "molecularFormula": "C39H54N10O10S", "molecularWeightDa": 855, "terminalModifications": [ "N-terminal acetylation at Met1", "C-terminal amide at Pro7" ], "structuralModifications": [], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [ "semax" ], "referenceIds": [ "pmid-31667971" ], "identityOverview": "N-Acetyl Semax Amidate is the Semax heptapeptide with an acetyl group on the N-terminal methionine residue and an amide at the C-terminal proline. These covalent terminal changes define a distinct molecule.", "nomenclatureNotes": "The complete name specifies both terminal groups. A bare N-acetyl Semax label does not specify the C-terminal group and is not an alias here. Acetate salt terminology does not establish covalent N-acetylation. PubChem CID 172638603 represents the recorded amidate structure. No CAS or UNII is assigned here because no authoritative assignment was verified. PubChem CID 172638603 includes CAS 2920938-90-3 among deposited synonyms, but that association has not independently established the CAS assignment for the N-acetylated, C-amidated species.", "structuralNotes": "The residue sequence preserves the ACTH(4-7)-plus-Pro-Gly-Pro construction of Semax. N-terminal acetylation adds C2H2O to the free-terminal parent; C-terminal amidation adds H and N and removes O. Together the changes add C2H3N and yield C39H54N10O10S. The direct parent link identifies this structural relationship.", "analyticalNotes": "Table 1 of Vanhee et al. (PMID 31667971) corroborates the C39H54N10O10S formula for a custom-synthesized reference standard from Thermo Fisher Scientific. The sequence column describes the ordered standard, not a sequence established for a seized amidate sample. This citation supplies formula corroboration only for this record; the Selank-specific rLys-C discrimination does not apply here. Table 1 reports 854.3745 Da monoisotopic mass. The library records 855.0 Da average mass, derived from the formula using its conventional atomic weights. The paper is not the original source of the name-to-sequence mapping.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-28" }, { "id": "n-acetyl-selank-amidate", "url": "https://purelypeptides.org/research/compounds/n-acetyl-selank-amidate/", "displayName": "N-Acetyl Selank Amidate", "canonicalName": "N-Acetyl Selank Amidate", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": {}, "sequence": { "oneLetter": "TKPRPGP", "threeLetter": [ "Thr", "Lys", "Pro", "Arg", "Pro", "Gly", "Pro" ], "notes": "The seven residue positions are unchanged from Selank. In shorthand, Ac and NH2 denote the N-terminal acetyl and C-terminal amide groups; they are not additional residues." }, "molecularFormula": "C35H60N12O9", "molecularWeightDa": 792.9, "terminalModifications": [ "N-terminal acetylation at Thr1", "C-terminal amide at Pro7" ], "structuralModifications": [], "compoundClassIds": [ "regulatory-peptide-fragment-analogs" ], "mechanismIds": [], "relatedCompoundIds": [ "selank" ], "referenceIds": [ "pmid-31667971" ], "identityOverview": "N-Acetyl Selank Amidate is the Selank heptapeptide with an acetyl group on the N-terminal threonine residue and an amide at the C-terminal proline. These covalent terminal changes define a distinct molecule.", "nomenclatureNotes": "The complete name specifies both terminal groups. A bare N-acetyl Selank label does not specify the C-terminal group and is not an alias here. Acetate salt terminology does not establish covalent N-acetylation. PubChem CID 133082488 and UNII J3PM702O93 describe the N-acetyl Selank free acid, C35H59N11O10, and are not identifiers for this amidate. No CAS, PubChem CID or UNII is assigned here because no matching authoritative record was verified.", "structuralNotes": "The residue sequence preserves the tuftsin-plus-Pro-Gly-Pro construction of Selank. N-terminal acetylation adds C2H2O to the free-terminal parent; C-terminal amidation adds H and N and removes O. Together the changes add C2H3N and yield C35H60N12O9. The direct parent link identifies this structural relationship.", "analyticalNotes": "Table 1 of Vanhee et al. (PMID 31667971) corroborates the C35H60N12O9 formula for a custom-synthesized reference standard from Thermo Fisher Scientific. The sequence column describes the ordered standard, not a sequence established for a seized amidate sample. This citation supplies formula corroboration only for this record; the Selank-specific rLys-C discrimination does not apply here. Table 1 reports 792.4606 Da monoisotopic mass. The library records 792.9 Da average mass, derived from the formula using its conventional atomic weights. The paper is not the original source of the name-to-sequence mapping.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-28" }, { "id": "oxytocin", "url": "https://purelypeptides.org/research/compounds/oxytocin/", "displayName": "Oxytocin", "canonicalName": "Oxytocin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": {}, "sequence": { "notes": "Numbering begins at the mature N-terminal residue. The complete sequence is withheld because the source descriptions disagree at residue 4; complete stereochemical admission also remains unresolved.", "rings": [ { "kind": "disulfide", "from": { "position": 1, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 6, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-37649440" } ] }, "terminalModifications": [ "Free N-terminus", "C-terminal amidation at Gly9" ], "structuralModifications": [ "Cys1-Cys6 intramolecular disulfide" ], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [ "desmopressin" ], "referenceIds": [ "pmid-8111231", "pmid-37649440" ], "identityOverview": "Oxytocin is a mature nine-residue peptide with an intramolecular disulfide and a terminal carboxamide. This identity record is scoped to the Leu8 form.", "nomenclatureNotes": "OXT and OT are ambiguous abbreviations and are not retained as aliases. The name does not establish the identity of every species variant or commercial preparation. PubChem CID 439302 and GSRS UNII 1JQS135EYN, which lists CAS 50-56-6, specify Gln4, Leu8, Cys1–Cys6 disulfide and Gly9-amide; these remain registry candidates while this record’s sequence and stereochemical admission are unresolved.", "structuralNotes": "The disulfide links mature positions 1 and 6, and the C-terminal glycine is amidated. Layden et al. (PMID 37649440) describe oxytocin as a cyclic peptide with a disulfide bond between Cys1 and Cys6. The Gln4 versus glutamyl4 source disagreement leaves the complete sequence, molecular formula and average molecular mass unresolved; those fields are withheld.", "analyticalNotes": "The mature amide, glycine-extended forms and counterion-containing preparations are distinct molecular states. Elemental composition alone does not establish sequence order or complete stereochemistry.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-09-28" }, { "id": "desmopressin", "url": "https://purelypeptides.org/research/compounds/desmopressin/", "displayName": "Desmopressin", "canonicalName": "Desmopressin", "moleculeType": "peptide", "aliases": [ "dDAVP", "1-deamino-8-D-arginine vasopressin", "1-desamino-8-D-arginine vasopressin" ], "developmentCodes": [], "externalIds": { "cas": "16679-58-6", "pubChemCid": "5311065", "unii": "ENR1LLB0FP" }, "sequence": { "threeLetter": [ "Mpa", "Tyr", "Phe", "Gln", "Asn", "Cys", "Pro", "D-Arg", "Gly" ], "notes": "Mpa denotes 3-mercaptopropanoyl, an achiral acyl unit at conventional position 1; Tyr is position 2. The C-terminal amide is recorded as a terminal group and is not another residue. Standard one-letter notation cannot specify Mpa1 and D-Arg8 faithfully. The N-terminal acyl chemistry and Mpa1-Cys6 disulfide are outside the automated sequence-formula model.", "rings": [ { "kind": "disulfide", "from": { "position": 1, "residue": "Mpa", "atom": "thiol sulfur" }, "to": { "position": 6, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "registrySource": "FDA GSRS UNII ENR1LLB0FP; PubChem CID 5311065" } ] }, "terminalModifications": [ "N-terminal 3-mercaptopropanoyl acyl unit; no free N-terminal alpha-amino group", "C-terminal amidation at Gly9" ], "structuralModifications": [ "Intramolecular disulfide between Mpa1 and L-Cys6", "D-Arg at position 8" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [ "oxytocin" ], "referenceIds": [ "pmid-9546658" ], "identityOverview": "Desmopressin is a synthetic cyclic peptide construction containing eight amino-acid units and an N-terminal 3-mercaptopropanoyl unit. Its conventional numbering spans nine positions. This record describes the anhydrous parent without acetate or water of crystallization.", "nomenclatureNotes": "The abbreviation dDAVP identifies the D-Arg8 compound in the structural literature. The abbreviation dAVP is also used for its L-Arg8 counterpart and is not retained as an alias. The position-1 unit is 3-mercaptopropanoyl, rather than cysteine. PubChem CID 5311065 and GSRS UNII ENR1LLB0FP, which lists CAS 16679-58-6, encode the anhydrous parent with D-Arg8, the Mpa1–Cys6 disulfide and Gly9-amide; acetate CAS 62288-83-9 identifies a separate form.", "structuralNotes": "Position 1 and glycine at position 9 are achiral. The specified amino-acid stereocentres include D-Arg at position 8. Average molecular mass remains unestablished under the dossier evidence requirements; the molecular formula and mass fields are both withheld.", "analyticalNotes": "Elemental composition and mass alone cannot distinguish this molecule from its L-Arg8 counterpart. The cited NMR characterization does not certify the identity or stereochemical purity of an untested sample.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-28" }, { "id": "thymosin-alpha-1", "url": "https://purelypeptides.org/research/compounds/thymosin-alpha-1/", "displayName": "Thymosin alpha-1", "canonicalName": "Thymalfasin", "moleculeType": "peptide", "aliases": [ "Thymosin alpha1", "Thymosin α1" ], "developmentCodes": [], "externalIds": {}, "sequence": { "notes": "The primary structural candidate corresponds to residues 2-29 of reviewed human prothymosin alpha, using precursor numbering that includes the initiator methionine. Mature-peptide numbering starts at Ser1. The complete sequence is withheld because collected source renderings remain conflicted." }, "terminalModifications": [ "N-terminal acetylation at Ser1", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-22115779" ], "identityOverview": "Thymalfasin, also called thymosin alpha-1, is a linear 28-residue peptide. Its primary structural candidate corresponds to the N-terminal region of prothymosin alpha after the initiator methionine.", "nomenclatureNotes": "Thymalfasin is the recommended international nonproprietary name; thymosin alpha-1 is the common scientific display name. The shared historical thymosin designation does not establish a common structural family with beta-thymosins. PubChem CID 16130571 and GSRS UNII W0B22ISQ1C, which lists CAS 62304-98-7, describe the conventional N-acetylated 28-mer with a free C-terminal acid; these candidates do not resolve this record’s held complete-sequence assignment.", "structuralNotes": "The defined candidate has an acetylated N-terminus and a free C-terminal carboxyl group. It is linear, with standard L-amino-acid residues and no cysteine or disulfide. The complete sequence, molecular formula and average molecular mass remain conflicted and are withheld.", "analyticalNotes": "The acetyl cap is not an additional amino-acid residue. Average molecular mass, neutral monoisotopic mass and an ion mass are different quantities; agreement of a calculated candidate with one reported value does not resolve the held identity fields.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-09-28" }, { "id": "elamipretide", "url": "https://purelypeptides.org/research/compounds/elamipretide/", "displayName": "Elamipretide", "canonicalName": "Elamipretide", "moleculeType": "peptide", "aliases": [ "Bendavia" ], "developmentCodes": [ "SS-31" ], "externalIds": { "cas": "736992-21-5", "pubChemCid": "11764719", "unii": "87GWG91S09" }, "sequence": { "threeLetter": [ "D-Arg", "Dmt", "Lys", "Phe" ], "notes": "Positions are numbered from the N-terminus. Dmt denotes 2′,6′-dimethyltyrosine; the primes identify aromatic-ring positions. In shorthand, NH2 denotes the C-terminal amide rather than another residue. A standard one-letter string is withheld because it cannot preserve D-Arg1 or the two ring methyl groups of Dmt2; this chemistry is outside the automated sequence-formula model." }, "molecularFormula": "C32H49N9O5", "molecularWeightDa": 639.802, "terminalModifications": [ "Free N-terminus", "C-terminal amidation at Phe4" ], "structuralModifications": [ "D-Arg at position 1", "Two aromatic-ring methyl substituents at positions 2′ and 6′ of L-tyrosine at peptide position 2" ], "compoundClassIds": [ "aromatic-cationic-tetrapeptides" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-31780923", "pmid-35913044" ], "identityOverview": "Elamipretide is a synthetic linear tetrapeptide with D-arginine, L-2′,6′-dimethyltyrosine, L-lysine and L-phenylalanine in that order, a free N-terminal amino group and a C-terminal primary carboxamide.", "nomenclatureNotes": "SS-31 is the admitted laboratory designation. Bendavia is a historical investigational designation. The parent registry identifiers do not identify the trihydrochloride salt.", "structuralNotes": "The molecular formula and average mass describe the unsalted, unhydrated parent peptide. Two ring methyl substitutions contribute C2H4 relative to tyrosine. The defined structure has no disulfide.", "analyticalNotes": "The CIAAW 2024 abridged calculation gives an average mass of 639.802 Da. The dossier preserves a numerical discrepancy with the GSRS value of 639.79 whose atomic-weight convention was not established. Equal formula and mass do not distinguish SS-31 from the differently ordered SS-02 peptide.", "publishedDate": "2026-09-28", "updatedDate": "2026-10-15", "lastVerifiedDate": "2026-09-28" }, { "id": "angiotensin-1-7", "url": "https://purelypeptides.org/research/compounds/angiotensin-1-7/", "displayName": "Angiotensin-(1-7)", "canonicalName": "Talfirastide", "moleculeType": "peptide", "aliases": [ "Angiotensin (1-7)", "Ang-(1-7)", "Talfirastidum", "Talfirastida" ], "developmentCodes": [ "TXA127" ], "externalIds": { "cas": "51833-78-4", "pubChemCid": "123805", "unii": "IJ3FUK8MOF" }, "sequence": { "oneLetter": "DRVYIHP", "threeLetter": [ "Asp", "Arg", "Val", "Tyr", "Ile", "His", "Pro" ], "notes": "Seven standard proteinogenic residues, all L; Ile denotes the natural L-isoleucine stereoisomer. The sequence begins at Asp and ends at Pro." }, "molecularFormula": "C41H62N12O11", "molecularWeightDa": 899.02, "terminalModifications": [ "Free N-terminal amino group", "Free C-terminal carboxyl group" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-34452239", "pmid-17904691" ], "identityOverview": "Talfirastide, also called Angiotensin-(1-7), is a linear all-L heptapeptide with sequence Asp–Arg–Val–Tyr–Ile–His–Pro, an uncapped amino terminus and a C-terminal carboxyl group.", "nomenclatureNotes": "Talfirastide and Angiotensin-(1-7) denote the same defined peptide parent. Fragment notation does not specify a preparation’s counterion or hydration state.", "structuralNotes": "The defined parent contains six conventional peptide bonds and no covalent macrocycle or disulfide bridge.", "publishedDate": "2026-09-29", "lastVerifiedDate": "2026-09-29" }, { "id": "glp-2", "url": "https://purelypeptides.org/research/compounds/glp-2/", "displayName": "Human GLP-2(1-33)", "canonicalName": "Human glucagon-like peptide-2 (1-33)", "moleculeType": "peptide", "aliases": [ "GLP-2", "Glucagon-like peptide-2", "Human GLP-2", "hGLP-2" ], "developmentCodes": [], "externalIds": { "cas": "223460-79-5", "pubChemCid": "71300624", "unii": "0825W549JC" }, "sequence": { "oneLetter": "HADGSFSDEMNTILDNLAARDFINWLIQTKITD", "threeLetter": [ "His", "Ala", "Asp", "Gly", "Ser", "Phe", "Ser", "Asp", "Glu", "Met", "Asn", "Thr", "Ile", "Leu", "Asp", "Asn", "Leu", "Ala", "Ala", "Arg", "Asp", "Phe", "Ile", "Asn", "Trp", "Leu", "Ile", "Gln", "Thr", "Lys", "Ile", "Thr", "Asp" ], "notes": "Thirty-three residues numbered from His1 to Asp33. Every chiral residue is in the L configuration; Gly4 is achiral." }, "molecularFormula": "C165H254N44O55S", "molecularWeightDa": 3766.16, "terminalModifications": [ "Free N-terminal amino group", "Free C-terminal carboxyl group" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [ "glucagon", "oxyntomodulin", "glp-1-7-36-amide", "glp-1-7-37", "gip-1-42", "exenatide" ], "referenceIds": [ "pmid-10704722", "pmid-21167157", "pmid-9348213", "pmid-2714431", "pmid-37528104" ], "identityOverview": "Human GLP-2(1-33) is a linear 33-residue peptide with a free amino terminus and a C-terminal carboxyl group. This record describes the unmodified parent covalent structure. Orskov et al. (PMID 2714431) characterize human and pig intestinal GLP-2 as a proglucagon processing product. Horváth et al. (PMID 37528104) place GLP-2 among the gastrointestinal peptides of the glucagon family.", "nomenclatureNotes": "“GLP-2” on its own specifies neither species nor whether a peptide is intact or shortened, so this record keeps the human (1-33) form explicit. Fragment notation does not specify a preparation’s counterion or hydration state. GSRS UNII 0825W549JC lists primary CAS 223460-79-5 for the free human 33-mer; PubChem CIDs 71300624 and 90488755 encode the same stereospecified structure, with 71300624 selected here.", "structuralNotes": "The chain runs from His1 to Asp33 with no cysteine, so it has no intramolecular disulfide bond and no covalent macrocycle.", "analyticalNotes": "The molecular formula and the 3766.16 Da average mass are calculated from the sequence with CIAAW 2024 abridged atomic weights. Two published average-mass values differ and remain unreconciled: 3769.136 in the PDB entity metadata for entry 2L63, and 3760.0 as the GSRS estimated calculated weight. The sequence rests on Edman, mass-spectrometric and NMR characterization of separate material sets; this is not a lot-specific certificate.", "publishedDate": "2026-09-30", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-09-30" }, { "id": "hcg", "url": "https://purelypeptides.org/research/compounds/hcg/", "displayName": "hCG (Human chorionic gonadotropin)", "canonicalName": "Human chorionic gonadotropin", "moleculeType": "glycoprotein", "aliases": [ "hCG" ], "developmentCodes": [], "externalIds": {}, "sequence": { "notes": "Two chains, described separately and never joined into one string. Alpha subunit: the cDNA encodes a 24-amino-acid presequence (Fiddes and Goodman, 1979), and protein sequencing reported a 92-residue chain in which a fraction of the chains lacked the first two or three residues (Morgan et al., 1975). The two crystal-structure depositions differ at alpha position 4: PDB entry 1HRP records threonine and PDB entry 1HCN records valine. Beta subunit: the cDNA encodes a 145-amino-acid chain with a 20-amino-acid presequence (Fiddes and Goodman, 1980), while an earlier protein-sequencing report described 147 residues (Carlsen et al., 1973). No single sequence is recorded here because these sources have not been reconciled." }, "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-4795659", "pmid-1150658", "pmid-481597", "pmid-6774259", "pmid-7922031", "pmid-8202136" ], "identityOverview": "Human chorionic gonadotropin (hCG) is a glycoprotein hormone made of two different subunits, alpha and beta, that associate without a covalent bond between the chains. This record describes the intact two-chain hormone. It is not a record of either subunit alone or of any fragment.", "nomenclatureNotes": "“hCG” on its own does not specify a preparation, a glycoform or a subunit. Names of the individual subunits, and of the genes that encode them, are not names of the intact hormone and are not aliases of this record. GSRS registrations 20ED16GHEB and 6413W06WR3 specify distinct chorionic-gonadotropin substances, but neither establishes an exact identifier for this record’s unresolved chains and unspecified preparation or glycoform.", "structuralNotes": "Wu et al. (1994) and Lapthorn et al. (1994) each report a crystal structure in which both subunits have a cystine-knot fold. Wu et al. determined theirs on recombinant selenomethionyl protein after partial deglycosylation, so that material is not the fully glycosylated native hormone.", "analyticalNotes": "No molecular formula or molecular mass is recorded. hCG is glycosylated, the attached glycans vary between preparations, and the chain descriptions above are not reconciled, so a single calculated value would describe no particular material.", "publishedDate": "2026-10-03", "updatedDate": "2026-10-13", "lastVerifiedDate": "2026-10-03" }, { "id": "leuprolide", "url": "https://purelypeptides.org/research/compounds/leuprolide/", "displayName": "Leuprolide (leuprorelin)", "canonicalName": "Leuprorelin", "moleculeType": "peptide", "aliases": [ "Leuprolide", "Leuprorelinum" ], "developmentCodes": [], "externalIds": { "cas": "53714-56-0", "pubChemCid": "657181", "unii": "EFY6W0M8TG" }, "sequence": { "threeLetter": [ "pGlu", "His", "Trp", "Ser", "Tyr", "D-Leu", "Leu", "Arg", "Pro" ], "notes": "Nine residues numbered pGlu1 to Pro9. pGlu is L-pyroglutamyl (5-oxo-L-prolyl), a residue whose side chain is cyclized onto its own amino group; it is not open-chain glutamate or glutamine. Position 6 is D-leucine and every other chiral residue is L. The C-terminal N-ethylamide is a terminal group, not a tenth residue. No one-letter string is published because the chain contains a nonstandard residue and a D residue." }, "molecularFormula": "C59H84N16O12", "molecularWeightDa": 1209.421, "terminalModifications": [ "N-terminal pyroglutamate", "C-terminal N-ethylamide at Pro9" ], "structuralModifications": [ "Pyroglutamate at position 1", "D-leucine at position 6" ], "compoundClassIds": [ "gnrh-peptide-analogs" ], "mechanismIds": [ "gnrh-receptor" ], "relatedCompoundIds": [ "gonadorelin", "triptorelin" ], "referenceIds": [ "pmid-20354741", "pmid-10722088", "pmid-26398856", "pmid-24490142" ], "identityOverview": "Leuprorelin, also called leuprolide, is a synthetic nine-residue peptide with an L-pyroglutamyl residue at position 1, D-leucine at position 6 and an N-ethylamide on the C-terminal proline. This record describes the parent peptide without counterion or hydrate.", "nomenclatureNotes": "Leuprorelin is the WHO international nonproprietary name (Latin leuprorelinum) and leuprolide the United States adopted name; both denote this parent peptide. Salt-qualified names such as leuprolide acetate describe the peptide together with a counterion and are not aliases of this record: the Japanese Pharmacopoeia specifies a monoacetate, while an FDA chemistry review describes one or two acetate equivalents. Development codes and trade names are not listed because no two independent sources tie them to this exact species.", "structuralNotes": "The WHO proposed-INN entry and the Japanese Pharmacopoeia monograph give the full structure with explicit configuration at every residue. Laimou et al. (PMID 20354741) studied leuprolide in solution by two-dimensional NMR, and Sanz-Nebot et al. (PMID 10722088) characterized crude synthesis products by liquid chromatography-mass spectrometry. Nederpelt et al. (PMID 26398856) measured leuprolide binding at the human GnRH receptor; Morgan et al. (PMID 24490142) measured it at the rat GnRH receptor expressed in cultured cells. The pyroglutamyl ring lies within residue 1; there is no ring closure between residues.", "analyticalNotes": "The molecular formula and the 1209.421 Da average mass are calculated for the neutral parent from its structure with CIAAW 2024 abridged atomic weights; the Japanese Pharmacopoeia lists 1209.40 using an earlier atomic-weight table. D-leucine and L-leucine at position 6 have the same composition, so an intact-mass match does not confirm the configuration. One acetate equivalent adds C2H4O2, about 60.05 Da, so salt preparations do not share the parent's mass.", "publishedDate": "2026-10-15", "lastVerifiedDate": "2026-10-15" }, { "id": "triptorelin", "url": "https://purelypeptides.org/research/compounds/triptorelin/", "displayName": "Triptorelin", "canonicalName": "Triptorelin", "moleculeType": "peptide", "aliases": [ "Triptorelinum" ], "developmentCodes": [], "externalIds": { "cas": "57773-63-4", "pubChemCid": "25074470", "unii": "9081Y98W2V" }, "sequence": { "threeLetter": [ "pGlu", "His", "Trp", "Ser", "Tyr", "D-Trp", "Leu", "Arg", "Pro", "Gly" ], "notes": "Ten residues numbered pGlu1 to Gly10. pGlu is L-pyroglutamyl (5-oxo-L-prolyl), not open-chain glutamate or glutamine. Position 6 is D-tryptophan and every other chiral residue is L; Gly10 is achiral and carries the C-terminal amide. No one-letter string is published because the chain contains a nonstandard residue and a D residue." }, "molecularFormula": "C64H82N18O13", "molecularWeightDa": 1311.473, "terminalModifications": [ "N-terminal pyroglutamate", "C-terminal amide at Gly10" ], "structuralModifications": [ "Pyroglutamate at position 1", "D-tryptophan at position 6" ], "compoundClassIds": [ "gnrh-peptide-analogs" ], "mechanismIds": [ "gnrh-receptor" ], "relatedCompoundIds": [ "gonadorelin", "leuprolide" ], "referenceIds": [ "pmid-40726784", "pmid-11404838", "pmid-11802711", "pmid-26398856" ], "identityOverview": "Triptorelin is a synthetic ten-residue peptide with an L-pyroglutamyl residue at position 1, D-tryptophan at position 6 and a C-terminal glycinamide. This record describes the parent peptide without counterion.", "nomenclatureNotes": "Triptorelin is the WHO international nonproprietary name (Latin triptorelinum). Triptorelin acetate and triptorelin pamoate (embonate) are salt forms with their own registry entries and are not aliases of this record. Bracketed substitution names of the D-Trp6 type, development codes and trade names are not listed because no two independent sources tie each of them to this exact species.", "structuralNotes": "Li et al. (PMID 40726784) synthesized triptorelin and report its full stereochemical structure with chromatographic and mass-spectrometric characterization. Sanz-Nebot et al. (PMID 11404838) characterized a synthesis crude and its side products by liquid chromatography-mass spectrometry. Hövelmann et al. (PMID 11802711) and Nederpelt et al. (PMID 26398856) measured triptorelin binding at the human GnRH receptor. The pyroglutamyl ring lies within residue 1; there is no ring closure between residues.", "analyticalNotes": "The molecular formula and the 1311.473 Da average mass are calculated for the counterion-free parent from its structure with CIAAW 2024 abridged atomic weights, and the formula agrees with the WHO and FDA disclosures. The GSRS record for this UNII also lists a non-defining calculated weight of 1140 Da that does not correspond to this structure. The acetate and pamoate registry definitions each add one acid equivalent, so salt preparations differ in mass from the parent.", "publishedDate": "2026-10-15", "lastVerifiedDate": "2026-10-15" }, { "id": "teriparatide", "url": "https://purelypeptides.org/research/compounds/teriparatide/", "displayName": "Teriparatide", "canonicalName": "Teriparatide", "moleculeType": "peptide", "aliases": [ "Human parathyroid hormone (1-34)" ], "developmentCodes": [], "externalIds": { "cas": "52232-67-4", "pubChemCid": "16133850", "unii": "10T9CSU89I" }, "sequence": { "oneLetter": "SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF", "threeLetter": [ "Ser", "Val", "Ser", "Glu", "Ile", "Gln", "Leu", "Met", "His", "Asn", "Leu", "Gly", "Lys", "His", "Leu", "Asn", "Ser", "Met", "Glu", "Arg", "Val", "Glu", "Trp", "Leu", "Arg", "Lys", "Lys", "Leu", "Gln", "Asp", "Val", "His", "Asn", "Phe" ], "notes": "Thirty-four residues numbered Ser1 to Phe34, corresponding to residues 1-34 of the mature human hormone. Every chiral residue is L; Gly12 is achiral." }, "molecularFormula": "C181H291N55O51S2", "molecularWeightDa": 4117.773, "terminalModifications": [ "Free N-terminal amino group", "Free C-terminal carboxyl group" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [ "parathyroid-hormone-1-receptor" ], "relatedCompoundIds": [], "referenceIds": [ "pmid-10837469", "pmid-9933468", "pmid-4509319", "pmid-4521809", "pmid-31595483" ], "identityOverview": "Teriparatide is the linear 34-residue peptide corresponding to residues 1-34 of human parathyroid hormone, with a free amino terminus and a free C-terminal carboxyl group. This record describes the peptide without counterion.", "nomenclatureNotes": "PTH(1-34) without a species prefix, and PTH alone, do not identify this molecule: other species' fragments differ in sequence, and the intact hormone has 84 residues. Acetate-containing preparations are separate species. Brewer et al. (PMID 4509319) reported a 1972 human sequence with glutamine at position 22, lysine at 28 and leucine at 30; Niall et al. (PMID 4521809) reported a sequence differing at those three positions and concluded theirs was correct. This record follows the sequence in the 2000 crystal structure and current regulatory disclosures, with glutamate at 22, leucine at 28 and aspartate at 30. PubChem CIDs 16133850 and 16132393 encode this structure with different histidine tautomer representations; 16133850 is used here.", "structuralNotes": "Jin et al. (PMID 10837469) determined the crystal structure of human parathyroid hormone 1-34 at 0.9 Å resolution. Frolik et al. (PMID 9933468) measured binding of recombinant human PTH(1-34) at the human PTH/PTHrP receptor expressed in a human kidney cell line. The chain contains no cysteine and no covalent ring.", "analyticalNotes": "The molecular formula and the 4117.773 Da average mass are calculated from the sequence with CIAAW 2024 abridged atomic weights; the neutral monoisotopic mass calculated from the same formula is 4115.131 Da. Kovács et al. (PMID 31595483) reported a theoretical monoisotopic mass of 4115.1309 Da for the teriparatide molecule. The GSRS record for this UNII lists a non-defining estimated formula, C181H287N55O50S2, which lacks four hydrogens and one oxygen relative to this structure. Oxidized, deamidated and truncated forms are separate species; oxidation of one methionine adds 16 Da.", "publishedDate": "2026-10-15", "updatedDate": "2026-10-16", "lastVerifiedDate": "2026-10-16" }, { "id": "carnosine", "url": "https://purelypeptides.org/research/compounds/carnosine/", "displayName": "L-Carnosine", "canonicalName": "Carnosine", "moleculeType": "peptide", "aliases": [ "β-Alanyl-L-histidine" ], "developmentCodes": [], "externalIds": { "cas": "305-84-0", "pubChemCid": "439224", "unii": "8HO6PVN24W" }, "sequence": { "threeLetter": [ "β-Ala", "His" ], "notes": "β-Ala is one β-alanine (3-aminopropanoic acid) unit, not α-alanine. Its carboxyl group forms the amide bond to the α-amino nitrogen of L-histidine at position 2. β-Alanine is achiral; His2 is L. No standard one-letter string encodes this nonstandard first unit." }, "molecularFormula": "C9H14N4O3", "molecularWeightDa": 226.236, "terminalModifications": [ "Free N-terminal amino group", "Free C-terminal carboxyl group" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-16742772", "pmid-35761267" ], "identityOverview": "Carnosine is the dipeptide β-alanyl-L-histidine. This record describes the free parent, with an uncapped amino end and a free carboxyl end.", "nomenclatureNotes": "This record denotes the free parent containing L-histidine. D-carnosine, salts, metal complexes and substituted derivatives are distinct identities.", "structuralNotes": "Barger and Tutin examined residue order by derivatization and hydrolysis. She et al. described synthesis using L-histidine, with chromatographic and mass-spectrometric product confirmation. The chain contains one inter-residue amide bond and no inter-residue ring closure.", "analyticalNotes": "The formula and 226.236 Da average mass follow the parent structure with CIAAW 2024 abridged atomic weights. PubChem displays 226.23; that printed value differs by 0.006 Da. The source calculation convention is not established, and the displayed number is not substituted for the defined calculation.", "publishedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "noopept", "url": "https://purelypeptides.org/research/compounds/noopept/", "displayName": "Noopept (Omberacetam)", "canonicalName": "Omberacetam", "moleculeType": "peptide", "aliases": [ "N-phenylacetyl-L-prolylglycine ethyl ester", "omberacetamum", "ombéracétam" ], "developmentCodes": [ "GVS-111" ], "externalIds": { "cas": "157115-85-0", "pubChemCid": "180496", "unii": "4QBJ98683M" }, "sequence": { "oneLetter": "PG", "threeLetter": [ "Pro", "Gly" ], "notes": "The chain is L-Pro1–Gly2. Glycine is achiral. PG denotes only the residue chain; the N-terminal phenylacetyl group and C-terminal ethyl ester are declared separately and are necessary to identify the complete molecule. The proline ring is intrinsic to its residue." }, "molecularFormula": "C17H22N2O4", "molecularWeightDa": 318.373, "terminalModifications": [ "N-terminal phenylacetylation at Pro1", "C-terminal ethyl ester at Gly2" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-39298839" ], "identityOverview": "Omberacetam is N-phenylacetyl-L-prolylglycine ethyl ester, a terminally modified dipeptide. This record describes the neutral parent.", "nomenclatureNotes": "Omberacetam is the nonproprietary name. The chemical alias identifies the terminally modified L-Pro–Gly entity; descriptions without explicit stereochemistry do not establish the same sample configuration. Salts, solvates and other solid forms require separate specification.", "structuralNotes": "Araj et al. reported NMR, diffraction and other physicochemical characterization. The accessible structural evidence is partial: the full experimental article and supplementary crystallographic detail were not audited in the source dossier. The phenylacetyl cap is attached to proline nitrogen; the ethyl ester is at glycine carboxyl.", "analyticalNotes": "The recorded 318.373 Da is the CIAAW 2024 average mass calculated from C17H22N2O4. Jia et al. (PMID 21986202; DOI 10.1016/j.jmb.2011.10.005) report MW 319 in their materials section without specifying its mass convention or ion/species basis. That divergent statement remains unreconciled and is non-defining for this formula-derived field; agreement is not established, and no protonated-ion assignment is inferred. Formula agreement alone does not establish sample enantiomeric purity or equivalence of solid forms.", "publishedDate": "2026-10-20", "updatedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "glutathione", "url": "https://purelypeptides.org/research/compounds/glutathione/", "displayName": "Glutathione (reduced)", "canonicalName": "Glutathione", "moleculeType": "peptide", "aliases": [ "Reduced glutathione", "GSH", "γ-L-Glutamyl-L-cysteinylglycine" ], "developmentCodes": [], "externalIds": { "cas": "70-18-8", "pubChemCid": "124886", "unii": "GAN16C9B8O" }, "sequence": { "threeLetter": [ "γ-Glu", "Cys", "Gly" ], "notes": "γ-Glu is one L-glutamyl unit whose γ-carboxyl carbonyl, rather than its α-carboxyl group, forms the amide bond to Cys2 nitrogen. Cys2 is L and forms the ordinary carboxyl-to-amino bond to achiral Gly3. No one-letter string is supplied because it would conceal the γ linkage." }, "molecularFormula": "C10H17N3O6S", "molecularWeightDa": 307.321, "terminalModifications": [ "Free N-terminal amino group", "Free C-terminal carboxyl group" ], "structuralModifications": [ "Acyclic γ-glutamyl linkage between residues 1 and 2", "Free cysteine thiol at position 2" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-19806629" ], "identityOverview": "Reduced glutathione is γ-L-glutamyl-L-cysteinylglycine, an acyclic three-unit peptide with a free cysteine thiol. The first amide bond uses the glutamyl γ-carboxyl group.", "nomenclatureNotes": "GSH denotes the reduced, unconjugated parent in this record. Glutathione disulfide, sodium-containing material and covalent conjugates are separate chemical identities.", "structuralNotes": "The γ-glutamyl linkage is an acyclic isopeptide bond; it does not form a side-chain lactam ring. Ko et al. examined mass-selected gas-phase anions and inferred neutral-parent structures by spectroscopy and calculations. That experiment does not independently determine residue stereochemistry or bulk crystal composition.", "analyticalNotes": "The recorded 307.321 Da is the CIAAW 2024 average mass calculated from C10H17N3O6S. Görbitz (1987) reports a formula weight of 307.33, while Hübschle et al. (2018) report 307.32; GSRS records mwt 307.325. Their calculation tables or conventions remain unestablished. These source numbers are non-defining for the formula-derived field, and the 307.33 value differs from that calculation. No oxidized, salt or conjugate composition is included in the parent formula.", "publishedDate": "2026-10-20", "updatedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "dermorphin", "url": "https://purelypeptides.org/research/compounds/dermorphin/", "displayName": "Dermorphin", "canonicalName": "Dermorphin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "cas": "77614-16-5", "pubChemCid": "5485199", "unii": "2SEC01B703" }, "sequence": { "threeLetter": [ "Tyr", "D-Ala", "Phe", "Gly", "Tyr", "Pro", "Ser" ], "notes": "Residues are numbered from the N-terminus. Ala2 is D; Tyr1, Phe3, Tyr5, Pro6 and Ser7 are L; Gly4 is achiral. No one-letter string is supplied because it would conceal D-alanine at position 2." }, "molecularFormula": "C40H50N8O10", "molecularWeightDa": 802.886, "terminalModifications": [ "Free N-terminal amino group", "C-terminal amide" ], "structuralModifications": [ "D-alanine at position 2" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-19476389", "pmid-27822705" ], "identityOverview": "Dermorphin is a seven-residue peptide with D-alanine at position 2, an uncapped N-terminus and a C-terminal amide. This record describes the neutral parent separately from modified derivatives and counterion-containing preparations.", "nomenclatureNotes": "The PubMed abstract of Montecucchi et al. (1981; PMID 7287299) prints Try at the first position, while the publisher abstract for DOI 10.1111/j.1399-3011.1981.tb01993.x prints Tyr. This record follows the publisher-supported Tyr sequence; the indexed Try spelling is retained here as a noted transcription error.", "structuralNotes": "Linear seven-residue peptide; no interresidue covalent ring closure is specified. Sachon et al. compared prepared peptide isomers by mass spectrometry. Pang et al. independently examined dermorphin monomers and oligomers by ion-mobility mass spectrometry. Preparation-level stereochemical and counterion limitations remain specific to those studies.", "publishedDate": "2026-10-20", "updatedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "goserelin", "url": "https://purelypeptides.org/research/compounds/goserelin/", "displayName": "Goserelin", "canonicalName": "Goserelin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "pubChemCid": "5311128", "unii": "0F65R8P09N" }, "sequence": { "threeLetter": [ "pGlu", "His", "Trp", "Ser", "Tyr", "D-Ser(O-tBu)", "Leu", "Arg", "Pro" ], "notes": "pGlu is one L-pyroglutamyl (5-oxo-L-prolyl) unit. D-Ser(O-tBu) is one O-tert-butyl-D-seryl unit, with the ether on side-chain oxygen. Chiral positions 1–5 and 7–9 are L; position 6 is D. The stored chain contains nine amino-acid-derived units; the aza-glycinamide end is declared as terminal chemistry. Its full connectivity is Pro9–C(=O)–NH–NH–C(=O)–NH2. No one-letter string is supplied." }, "molecularFormula": "C59H84N18O14", "molecularWeightDa": 1269.433, "terminalModifications": [ "N-terminal pyroglutamate", "C-terminal aza-glycinamide at Pro9" ], "structuralModifications": [ "O-tert-butyl ether on D-Ser6" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-364060", "pmid-10985544" ], "identityOverview": "Goserelin is a synthetic peptide parent containing an L-pyroglutamyl first unit, an O-tert-butyl-D-seryl unit at position 6 and a carbamoylhydrazide terminus. This record excludes counterions and water components.", "nomenclatureNotes": "The parent and acetate-containing material have distinct composition boundaries. Nine conventional amino-acid-derived units plus a semicarbazide end and a ten-position notation including azaglycine describe the stated connectivity; this record stores the end group separately from the residue chain.", "structuralNotes": "Dutta et al. reported synthesis of substituted aza analogues. Sanz-Nebot et al. reported chromatographic separation and mass-spectrometric identification of a goserelin synthesis mixture. The inspected abstracts do not establish a complete stereochemical audit of every preparation. The pyroglutamyl ring lies within residue 1; there is no inter-residue ring closure.", "analyticalNotes": "The formula and 1269.433 Da average mass follow the defined parent structure using CIAAW 2024 abridged atomic weights. The terminal carbamoylhydrazide is neither a simple proline amide nor a proline ethylamide. A fixed acetate or hydrate composition is not assigned to the parent.", "publishedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "cetrorelix", "url": "https://purelypeptides.org/research/compounds/cetrorelix/", "displayName": "Cetrorelix", "canonicalName": "Cetrorelix", "moleculeType": "peptide", "aliases": [ "cetrorelixum" ], "developmentCodes": [], "externalIds": { "cas": "120287-85-6", "pubChemCid": "25074887", "unii": "OON1HFZ4BA" }, "sequence": { "threeLetter": [ "D-Nal(2)", "D-Phe(4-Cl)", "D-Pal(3)", "Ser", "Tyr", "D-Cit", "Leu", "Arg", "Pro", "D-Ala" ], "notes": "Ten residues numbered from the first D residue. D-Nal(2) is D-3-(naphthalen-2-yl)alanine; D-Phe(4-Cl) is D-4-chlorophenylalanine; D-Pal(3) is D-3-(pyridin-3-yl)alanine. D-Cit is D-citrulline, or N5-carbamoyl-D-ornithine. Positions 1, 2, 3, 6 and 10 are D; positions 4, 5, 7, 8 and 9 are L. Every nonstandard token denotes one residue. No one-letter string is supplied." }, "molecularFormula": "C70H92ClN17O14", "molecularWeightDa": 1431.061, "terminalModifications": [ "N-terminal acetylation", "C-terminal amide" ], "structuralModifications": [ "D configuration at positions 1, 2, 3, 6 and 10" ], "compoundClassIds": [ "gnrh-peptide-analogs" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-8005749", "pmid-40386934" ], "identityOverview": "Cetrorelix is a synthetic linear decapeptide with defined D/L configuration and nonstandard residues, an acetylated N terminus and an amidated C terminus. This record describes the parent without counterion.", "nomenclatureNotes": "Cetrorelixum is the issued Latin name. Acetate-qualified names describe separately specified material and are excluded from the parent aliases and identifiers. No development code is admitted from the source dossier.", "structuralNotes": "Müller et al. reported MS and NMR structural characterization; Aluri et al. reported synthesis and differentiation of epimeric impurities in acetate material. Their accessible abstracts are partial structural evidence and do not establish an independent experimental configuration measurement at every residue. The stored chain is linear, with no inter-residue ring closure.", "analyticalNotes": "The formula and 1431.061 Da average mass are calculated for the neutral parent using CIAAW 2024 abridged atomic weights. PubChem displays 1431.0; the 0.061 Da numerical discrepancy is retained and that value is not substituted for the defined calculation. Acetate components and impurity modifications are excluded.", "publishedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "degarelix", "url": "https://purelypeptides.org/research/compounds/degarelix/", "displayName": "Degarelix", "canonicalName": "Degarelix", "moleculeType": "peptide", "aliases": [ "Degarelixum" ], "developmentCodes": [], "externalIds": { "cas": "214766-78-6", "pubChemCid": "16136245", "unii": "SX0XJI3A11" }, "sequence": { "threeLetter": [ "D-2Nal", "D-4Cpa", "D-3Pal", "Ser", "4Aph(L-Hor)", "D-4Aph(Cbm)", "Leu", "Lys(iPr)", "Pro", "D-Ala" ], "notes": "D-2Nal is D-3-(naphthalen-2-yl)alanine; D-4Cpa is D-4-chlorophenylalanine; D-3Pal is D-3-(pyridin-3-yl)alanine. 4Aph(L-Hor) is L-4-aminophenylalanine with its para amino group acylated by L-hydroorotic acid, whose additional stereocentre is 4S. D-4Aph(Cbm) is D-4-aminophenylalanine with a para carbamoylated amino group. Lys(iPr) is N6-isopropyl-L-lysine. Positions 1, 2, 3, 6 and 10 are D; positions 4, 5, 7, 8 and 9 are L. Each token is one residue; no one-letter string is supplied." }, "molecularFormula": "C82H103ClN18O16", "molecularWeightDa": 1632.286, "terminalModifications": [ "N-terminal acetylation", "C-terminal amide" ], "structuralModifications": [ "D configuration at residues 1, 2, 3, 6 and 10", "Residue-5 para-amino acylation with L-hydroorotyl, including its 4S stereocentre", "Residue-6 para-amino carbamoylation", "Residue-8 N6-isopropyl substitution" ], "compoundClassIds": [ "gnrh-peptide-analogs" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-28504858" ], "identityOverview": "Degarelix is a synthetic linear decapeptide with an acetylated N terminus, an amidated C terminus and explicitly configured nonstandard residues. This record describes the parent without acetate or hydrate components.", "nomenclatureNotes": "Degarelixum is the issued Latin name. The parent identifiers exclude the distinct acetate and hydrated acetate registry representations. No fixed acetate or water stoichiometry is assigned to all preparations bearing a salt-qualified name.", "structuralNotes": "Takahashi, Inomata and Fukui reported independent peptide synthesis with chromatographic product characterization. That evidence does not independently establish all stereocentres. The stated parent has eleven specified stereocentres, including the residue-5 side-chain centre. The proline and hydroorotyl rings are within their units; neither is an inter-residue closure.", "analyticalNotes": "The formula and 1632.286 Da average mass follow the parent structure using CIAAW 2024 abridged atomic weights. The neutral monoisotopic calculation is a different mass convention. Counterion, hydrate, isotope-labelled and conjugated compositions are not transferred to the parent.", "publishedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "larazotide", "url": "https://purelypeptides.org/research/compounds/larazotide/", "displayName": "Larazotide", "canonicalName": "Larazotide", "moleculeType": "peptide", "aliases": [ "larazotidum", "larazotida" ], "developmentCodes": [], "externalIds": { "cas": "258818-34-7", "pubChemCid": "9810532", "unii": "ZN3R5560ZV" }, "sequence": { "oneLetter": "GGVLVQPG", "threeLetter": [ "Gly", "Gly", "Val", "Leu", "Val", "Gln", "Pro", "Gly" ], "notes": "Eight standard residues numbered from Gly1. All chiral residues are L; glycine is achiral. The chain has seven ordinary peptide bonds and free termini. No counterion or hydration component is included." }, "molecularFormula": "C32H55N9O10", "molecularWeightDa": 725.845, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-34502335" ], "identityOverview": "Larazotide is a linear octapeptide with free N and C termini. This record describes the defined parent peptide composition separately from counterion-containing and hydrated preparations.", "nomenclatureNotes": "Larazotidum and larazotida are WHO language forms of the parent name. WHO Recommended INN List 61 defines the parent; US9051349B2 describes synthesis and distinguishes salt and hydrated preparations. Acetate-qualified names and shared development codes are not admitted as exact parent aliases.", "structuralNotes": "The defined parent is a linear octapeptide with free amino and carboxyl termini. The patent synthesis and Di Micco et al. synthesis and supplementary analytical material support the covalent parent. A separate January 2021 synthesis account gives conflicting Gly-Wang and Ile-Wang resin descriptions; its actual material remains unresolved and is not used to redefine this parent.", "analyticalNotes": "The formula matches WHO Recommended INN List 61; the 725.845 Da average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem reports 725.8 at one-decimal precision. GSRS estimates 726.0 under an unestablished mass convention; that number is non-defining. Di Micco et al. report an ESI [M+H]+ value of 726.4125, compared with the calculated 726.41446547480; analytical acceptance tolerance is not established. Ion m/z, neutral monoisotopic mass and average molecular mass are distinct.", "publishedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "salmon-calcitonin", "url": "https://purelypeptides.org/research/compounds/salmon-calcitonin/", "displayName": "Salmon calcitonin", "canonicalName": "Salmon calcitonin", "moleculeType": "peptide", "aliases": [ "Calcitonin salmon" ], "developmentCodes": [], "externalIds": { "cas": "47931-85-1", "unii": "7SFC6U2VI5" }, "sequence": { "oneLetter": "CSNLSTCVLGKLSQELHKLQTYPRTNTGSGTP", "threeLetter": [ "Cys", "Ser", "Asn", "Leu", "Ser", "Thr", "Cys", "Val", "Leu", "Gly", "Lys", "Leu", "Ser", "Gln", "Glu", "Leu", "His", "Lys", "Leu", "Gln", "Thr", "Tyr", "Pro", "Arg", "Thr", "Asn", "Thr", "Gly", "Ser", "Gly", "Thr", "Pro" ], "notes": "Positions count the 32-residue mature chain. All chiral residues are L; glycine is achiral. Val8, Lys11 and Pro32 are retained explicitly. Terminal amidation and the Cys1-Cys7 disulfide are recorded separately.", "rings": [ { "kind": "disulfide", "from": { "position": 1, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-2043752" } ] }, "molecularFormula": "C145H240N44O48S2", "molecularWeightDa": 3431.895, "terminalModifications": [ "Free N-terminus", "C-terminal amidation" ], "structuralModifications": [ "Cys1-Cys7 intramolecular disulfide" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-5261048", "pmid-2043752" ], "identityOverview": "Salmon calcitonin is a 32-residue peptide with a free N terminus, C-terminal prolinamide and a Cys1-Cys7 disulfide. This record describes the parent without counterion or hydration components.", "nomenclatureNotes": "Calcitonin salmon is an admitted word-order alias. This record identifies the full-length parent peptide; production method alone does not establish a distinct molecular species or universal equivalence between preparations. No unique PubChem CID is admitted because competing issuer records remain unresolved.", "structuralNotes": "The 32-residue backbone has a free N terminus at Cys1 and a C-terminal amide at Pro32. Meyer et al. and the Japanese Pharmacopoeia XVIII connectivity diagram support the Cys1-Cys7 disulfide. Niall et al. provide sequence and terminal characterization; their tentative disulfide discussion is not used as the sole connectivity proof. Counterions, hydration components, synthetic intermediates and sulfur-modified derivatives are excluded from this parent.", "analyticalNotes": "The formula and 3431.895 Da average mass are calculated using CIAAW 2024 abridged atomic weights. Japanese Pharmacopoeia XVIII reports 3431.85, a non-defining difference of 0.045 Da (13.1125 ppm). PubChem reports 3431.9 under an average-mass convention; DailyMed prints 3432 without an established convention in the inspected description. Neither replaces the defined calculation. Niall et al. sequence determination and Meyer et al. synthetic-peptide NMR provide complementary identity evidence; a preparation-independent solution conformation is not assigned.", "publishedDate": "2026-10-20", "lastVerifiedDate": "2026-10-20" }, { "id": "met-enkephalin", "url": "https://purelypeptides.org/research/compounds/met-enkephalin/", "displayName": "Met-enkephalin", "canonicalName": "Metenkefalin", "moleculeType": "peptide", "aliases": [ "Methionine enkephalin", "Methionine-enkephalin", "[Met5]enkephalin" ], "developmentCodes": [], "externalIds": { "cas": "58569-55-4", "pubChemCid": "443363", "unii": "9JEZ9OD3AS" }, "sequence": { "oneLetter": "YGGFM", "threeLetter": [ "Tyr", "Gly", "Gly", "Phe", "Met" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C27H35N5O7S", "molecularWeightDa": 573.665, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-1207728", "pmid-1065904", "pmid-1066668", "pmid-3458181" ], "identityOverview": "Met-enkephalin is a linear five-residue peptide with the sequence Tyr-Gly-Gly-Phe-Met and free amino and carboxyl termini.", "nomenclatureNotes": "Metenkefalin is the WHO Recommended INN List 59 name for this parent. A D-tyrosyl synonym collected by PubChem conflicts with its specified structure and is excluded. PubMed and Nature give different ending pages for Hughes et al.; that pagination discrepancy remains unresolved.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem reports 573.7 Da at one-decimal precision: the calculated minus displayed difference is -0.035 Da (-61.0075 ppm), consistent with that display precision. Hydrated crystal associations do not add covalent peptide rings.", "publishedDate": "2026-10-21", "updatedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "cck-8", "url": "https://purelypeptides.org/research/compounds/cck-8/", "displayName": "CCK-8 (sulfated)", "canonicalName": "Sincalide", "moleculeType": "peptide", "aliases": [ "Sulfated cholecystokinin octapeptide", "O-sulfated CCK-8" ], "developmentCodes": [], "externalIds": { "cas": "25126-32-3", "pubChemCid": "9833444", "unii": "M03GIQ7Z6P" }, "sequence": { "threeLetter": [ "Asp", "Tyr(SO3H)", "Met", "Gly", "Trp", "Met", "Asp", "Phe" ], "notes": "Positions count the eight-residue chain from Asp1. Tyr(SO3H) is L-tyrosine with a phenolic O-sulfate ester at position 2; it is one residue. All chiral residues are L and Gly4 is achiral. The sulfate is covalent; it is neither a counterion nor an inter-residue ring. A one-letter string would omit its identity." }, "molecularFormula": "C49H62N10O16S3", "molecularWeightDa": 1143.269, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [ "Residue-2 phenolic O-sulfation" ], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-3245972" ], "identityOverview": "Sincalide is a linear eight-residue peptide with Tyr2 O-sulfation, a free N terminus and a C-terminal phenylalanine amide.", "nomenclatureNotes": "The CCK-8 designation requires a sulfation qualifier. Sincalide is the issued name linked by GSRS to WHO Proposed INN List 32. Unqualified short names and unsupported development codes are withheld.", "structuralNotes": "Positions count the eight-residue chain from Asp1. Tyr(SO3H) is L-tyrosine with a phenolic O-sulfate ester at position 2; it is one residue. All chiral residues are L and Gly4 is achiral. The sulfate is covalent; it is neither a counterion nor an inter-residue ring. A one-letter string would omit its identity.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem displays 1143.3 Da: -0.031 Da (-27.1145 ppm), consistent with one-decimal rounding. GSRS reports 1143.2742 (-0.0052 Da, -4.54834 ppm); its precise mass convention is unestablished. The FDA description prints 1143.27 (-0.001 Da, -0.874684 ppm), also under an unestablished convention.", "publishedDate": "2026-10-21", "updatedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "bradykinin", "url": "https://purelypeptides.org/research/compounds/bradykinin/", "displayName": "Bradykinin", "canonicalName": "Bradykinin", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "cas": "58-82-2", "pubChemCid": "439201", "unii": "S8TIM42R2W" }, "sequence": { "oneLetter": "RPPGFSPFR", "threeLetter": [ "Arg", "Pro", "Pro", "Gly", "Phe", "Ser", "Pro", "Phe", "Arg" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C50H73N15O11", "molecularWeightDa": 1060.228, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-5908746" ], "identityOverview": "Bradykinin is a linear nonapeptide composed of standard amino-acid residues, with free N and C termini.", "nomenclatureNotes": "This record describes the covalent parent without counterion or hydration components.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem displays 1060.2 Da at one-decimal precision. FDA GSRS estimates 1060.0 Da under an unestablished mass convention; that figure is non-defining. A patent intermediate heading and an earlier octapeptide assignment do not redefine the admitted final nonapeptide.", "publishedDate": "2026-10-21", "updatedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "angiotensin-ii", "url": "https://purelypeptides.org/research/compounds/angiotensin-ii/", "displayName": "Angiotensin II (Ile5, free peptide)", "canonicalName": "Angiotensin II", "moleculeType": "peptide", "aliases": [ "AII", "AngII" ], "developmentCodes": [], "externalIds": { "pubChemCid": "172198", "unii": "M089EFU921" }, "sequence": { "oneLetter": "DRVYIHPF", "threeLetter": [ "Asp", "Arg", "Val", "Tyr", "Ile", "His", "Pro", "Phe" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C50H71N13O12", "molecularWeightDa": 1046.197, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-12603318" ], "identityOverview": "Angiotensin II is a linear octapeptide composed of eight L-amino-acid residues. This record describes the Ile5 free peptide with unmodified amino and carboxyl termini.", "nomenclatureNotes": "The record fixes Ile at position 5 and excludes counterion-containing and substituted species. CAS is withheld because the dossier did not complete the required issuer qualification.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. ", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "trh", "url": "https://purelypeptides.org/research/compounds/trh/", "displayName": "TRH (thyrotropin-releasing hormone)", "canonicalName": "Protirelin", "moleculeType": "peptide", "aliases": [ "Thyrotropin-releasing hormone", "TRH", "Thyrotropin-releasing factor", "TRF" ], "developmentCodes": [], "externalIds": { "cas": "24305-27-9", "pubChemCid": "638678", "unii": "5Y5F15120W" }, "sequence": { "threeLetter": [ "pGlu", "His", "Pro" ], "notes": "pGlu denotes L-pyroglutamyl at position 1, rather than open-chain Glu or Gln. His2 and Pro3 are L. The pyroglutamyl lactam is within the first unit and is not an inter-residue ring. Terminal prolinamide is recorded separately; no one-letter sequence is supplied." }, "molecularFormula": "C16H22N6O4", "molecularWeightDa": 362.39, "terminalModifications": [ "N-terminal pyroglutamate", "C-terminal amide" ], "structuralModifications": [ "Pyroglutamate at position 1" ], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-4982117", "pmid-4985794" ], "identityOverview": "Protirelin is a tripeptide comprising L-pyroglutamyl, L-histidyl and L-prolinamide units in that order.", "nomenclatureNotes": "Protirelin names the parent without counterion or hydrate. A D-His-qualified name is excluded. The additional CAS lead remains unqualified. An unresolved historical erratum linkage and receptor-bound model differences do not establish an alternative free-parent structure.", "structuralNotes": "pGlu denotes L-pyroglutamyl at position 1, rather than open-chain Glu or Gln. His2 and Pro3 are L. The pyroglutamyl lactam is within the first unit and is not an inter-residue ring. Terminal prolinamide is recorded separately; no one-letter sequence is supplied.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. Japanese Pharmacopoeia XVIII prints 362.38, a non-defining difference of +0.010 Da (+27.595 ppm). PubChem also displays 362.38, without an established explanation of its atomic-weight table. An early incompletely characterized isolation preparation had a tentative mass around 1000; its equivalence to the exact parent is unresolved.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "apelin-13", "url": "https://purelypeptides.org/research/compounds/apelin-13/", "displayName": "Apelin-13 (unmodified)", "canonicalName": "Apelin-13", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "pubChemCid": "25078060" }, "sequence": { "oneLetter": "QRPRLSHKGPMPF", "threeLetter": [ "Gln", "Arg", "Pro", "Arg", "Leu", "Ser", "His", "Lys", "Gly", "Pro", "Met", "Pro", "Phe" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C69H111N23O16S", "molecularWeightDa": 1550.852, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-30092142", "pmid-29412822", "pmid-36562292" ], "identityOverview": "Apelin-13 is a 13-residue peptide with an N-terminal glutamine and a C-terminal phenylalanine. This record describes the unmodified parent with free terminal groups.", "nomenclatureNotes": "This record specifies the unmodified free-terminal parent. Pyroglutamyl and amidated forms are distinct chemistry and are excluded as aliases. CAS and UNII are withheld under the dossier issuer-evidence limits.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem reports 1550.8: +0.052 Da (+33.531 ppm), a mismatch as printed and a non-defining registry number. Published theoretical and observed analytical numbers retain their source conventions; no ion assignment is inferred.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "icatibant", "url": "https://purelypeptides.org/research/compounds/icatibant/", "displayName": "Icatibant", "canonicalName": "Icatibant", "moleculeType": "peptide", "aliases": [ "Icatibantum" ], "developmentCodes": [ "HOE 140" ], "externalIds": { "cas": "130308-48-4", "pubChemCid": "6918173", "unii": "7PG89G35Q7" }, "sequence": { "threeLetter": [ "D-Arg", "Arg", "Pro", "Hyp", "Gly", "Thi", "Ser", "D-Tic", "Oic", "Arg" ], "notes": "The ten tokens are ordered from D-Arg1, which is D-arginine (R). Arg2, Pro3, Ser7 and Arg10 are L; Gly5 is achiral. Hyp4 is (2S,4R)-4-hydroxyproline. Thi6 is (S)-3-(thiophen-2-yl)alanine, the 2-thienyl isomer. D-Tic8 is the (3R)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid unit. Oic9 is the (2S,3aS,7aS)-octahydroindole-2-carboxylic acid unit. Intrinsic unit rings are not inter-residue closures. No standard one-letter string can encode these units faithfully." }, "molecularFormula": "C59H89N19O13S", "molecularWeightDa": 1304.541, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "D configuration at residues 1 and 8", "Residue-4 (2S,4R)-4-hydroxyproline", "Residue-6 (S)-3-(thiophen-2-yl)alanine", "Residue-8 (3R)-tetrahydroisoquinoline-3-carboxylic acid unit", "Residue-9 (2S,3aS,7aS)-octahydroindole-2-carboxylic acid unit" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-41642875", "pmid-30849486" ], "identityOverview": "Icatibant is a synthetic linear decapeptide containing D-configured and nonproteinogenic amino-acid units. This record describes its counterion-free parent peptide.", "nomenclatureNotes": "Icatibantum is the WHO Latin name. HOE 140 is admitted with a form boundary and does not fix acetate stoichiometry. Acetate identifiers are excluded. An IUPHAR DL/underspecified encoding conflicts with the fully assigned WHO/FDA/EMA parent and is not imported.", "structuralNotes": "The ten tokens are ordered from D-Arg1, which is D-arginine (R). Arg2, Pro3, Ser7 and Arg10 are L; Gly5 is achiral. Hyp4 is (2S,4R)-4-hydroxyproline. Thi6 is (S)-3-(thiophen-2-yl)alanine, the 2-thienyl isomer. D-Tic8 is the (3R)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid unit. Oic9 is the (2S,3aS,7aS)-octahydroindole-2-carboxylic acid unit. Intrinsic unit rings are not inter-residue closures. No standard one-letter string can encode these units faithfully.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. FDA prints 1304.55 (-0.009 Da, -6.899 ppm); EMA prints 1304.52 (+0.021 Da, +16.098 ppm). Both are non-defining published figures with unestablished precise conventions. They are not averaged. Mass alone cannot distinguish the N-terminal epimer.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "plecanatide", "url": "https://purelypeptides.org/research/compounds/plecanatide/", "displayName": "Plecanatide", "canonicalName": "Plecanatide", "moleculeType": "peptide", "aliases": [ "plecanatidum", "plécanatide", "plecanatida" ], "developmentCodes": [], "externalIds": { "cas": "467426-54-6", "pubChemCid": "70693500", "unii": "7IK8Z952OK" }, "sequence": { "oneLetter": "NDECELCVNVACTGCL", "threeLetter": [ "Asn", "Asp", "Glu", "Cys", "Glu", "Leu", "Cys", "Val", "Asn", "Val", "Ala", "Cys", "Thr", "Gly", "Cys", "Leu" ], "notes": "Positions count the mature 16-residue chain, Asn1 through Leu16. All chiral residues are L and glycine is achiral. The free amino and carboxyl termini remain open. Disulfides join Cys4-Cys12 and Cys7-Cys15. Li et al. form Cys7-Cys15 first; Kremsmayr et al. use the opposite folding order and report a reverse-order topoisomer. Exact final conformer equivalence is unestablished; the pairings do not specify a unique three-dimensional conformer.", "rings": [ { "kind": "disulfide", "from": { "position": 4, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 12, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-32275447" }, { "kind": "disulfide", "from": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 15, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-32275447" } ] }, "molecularFormula": "C65H104N18O26S4", "molecularWeightDa": 1681.887, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "Cys4-Cys12 intramolecular disulfide", "Cys7-Cys15 intramolecular disulfide" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-32275447", "pmid-35420805" ], "identityOverview": "Plecanatide is a synthetic 16-residue peptide with free termini and two intramolecular disulfide bridges.", "nomenclatureNotes": "This record describes the covalent parent without counterion or hydration components.", "structuralNotes": "Positions count the mature 16-residue chain, Asn1 through Leu16. All chiral residues are L and glycine is achiral. The free amino and carboxyl termini remain open. Disulfides join Cys4-Cys12 and Cys7-Cys15. Li et al. form Cys7-Cys15 first; Kremsmayr et al. use the opposite folding order and report a reverse-order topoisomer. Exact final conformer equivalence is unestablished; the pairings do not specify a unique three-dimensional conformer.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem reports 1681.9 Da (-0.013 Da, -7.729 ppm). FDA prints 1682 Daltons (-0.113 Da, -67.182 ppm) under an unestablished mass convention. Li et al. report calculated [M+H]+ 1681.6324 and found 1681.6325; these are ion values, separate from average molecular mass.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "crf", "url": "https://purelypeptides.org/research/compounds/crf/", "displayName": "Human corticotropin-releasing factor (1–41) amide", "canonicalName": "Corticorelin (human/rat sequence)", "moleculeType": "peptide", "aliases": [ "hCRF", "Human corticotropin-releasing factor", "Rat corticotropin-releasing factor" ], "developmentCodes": [], "externalIds": { "cas": "86784-80-7", "unii": "305OE8862Y" }, "sequence": { "oneLetter": "SEEPPISLDLTFHLLREVLEMARAEQLAQQAHSNRKLMEII", "threeLetter": [ "Ser", "Glu", "Glu", "Pro", "Pro", "Ile", "Ser", "Leu", "Asp", "Leu", "Thr", "Phe", "His", "Leu", "Leu", "Arg", "Glu", "Val", "Leu", "Glu", "Met", "Ala", "Arg", "Ala", "Glu", "Gln", "Leu", "Ala", "Gln", "Gln", "Ala", "His", "Ser", "Asn", "Arg", "Lys", "Leu", "Met", "Glu", "Ile", "Ile" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C208H344N60O63S2", "molecularWeightDa": 4757.517, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-6354254", "pmid-6335980", "pmid-7692441", "pmid-32004469" ], "identityOverview": "Corticorelin (human/rat sequence) is a 41-residue peptide with a free N terminus and an amidated C-terminal isoleucine.", "nomenclatureNotes": "The issued name Corticorelin is qualified here for the human/rat sequence. CRF requires organism and form qualification. Salt formulations and differently qualified organism sequences are excluded. PubChem CID is withheld because the dossier did not complete the full graph match.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. GSRS estimates 4757.0 Da, a non-defining difference of +0.517 Da (+108.682 ppm). The calculation does not certify a physical preparation. The synthetic human-sequence preparation and native rat sequencing are distinct evidence; partial native human sequencing is not represented as a complete independent determination.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "bnp", "url": "https://purelypeptides.org/research/compounds/bnp/", "displayName": "Human brain natriuretic peptide (1–32)", "canonicalName": "Nesiritide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "cas": "124584-08-3", "unii": "P7WI8UL647" }, "sequence": { "oneLetter": "SPKMVQGSGCFGRKMDRISSSSGLGCKVLRRH", "threeLetter": [ "Ser", "Pro", "Lys", "Met", "Val", "Gln", "Gly", "Ser", "Gly", "Cys", "Phe", "Gly", "Arg", "Lys", "Met", "Asp", "Arg", "Ile", "Ser", "Ser", "Ser", "Ser", "Gly", "Leu", "Gly", "Cys", "Lys", "Val", "Leu", "Arg", "Arg", "His" ], "notes": "Positions count the mature human chain from Ser1 to His32. All chiral residues are L and glycine is achiral. The backbone has 31 peptide bonds and the Cys10-Cys26 disulfide is an additional side-chain closure.", "rings": [ { "kind": "disulfide", "from": { "position": 10, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 26, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "registrySource": "WHO Recommended INN List 42, nesiritide, printed page 198; FDA GSRS UNII P7WI8UL647 disulfide definition" } ] }, "molecularFormula": "C143H244N50O42S4", "molecularWeightDa": 3464.073, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "Cys10-Cys26 intramolecular disulfide" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-2136732", "pmid-2138890" ], "identityOverview": "Human brain natriuretic peptide (1–32) is a 32-residue peptide with free termini and one intramolecular disulfide between Cys10 and Cys26.", "nomenclatureNotes": "Nesiritide is the WHO-issued name for the qualified human parent. The routing abbreviation does not combine precursor or formulation identities. PubChem CID is withheld because two issuer records match without a resolved single assignment.", "structuralNotes": "Positions count the mature human chain from Ser1 to His32. All chiral residues are L and glycine is achiral. The backbone has 31 peptide bonds and the Cys10-Cys26 disulfide is an additional side-chain closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. GSRS records the non-defining estimated formula C143H246N50O42S4, differing from the derived composition by H2. Its non-defining average is 3464.0 Da: +0.073 Da (+21.0739 ppm). FDA prints 3464 Da under an unestablished mass convention. These source figures do not replace the derived formula or mass.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "linaclotide", "url": "https://purelypeptides.org/research/compounds/linaclotide/", "displayName": "Linaclotide", "canonicalName": "Linaclotide", "moleculeType": "peptide", "aliases": [ "Linaclotidum", "Linaclotida" ], "developmentCodes": [], "externalIds": { "cas": "851199-59-2", "pubChemCid": "16158208", "unii": "N0TXR0XR5X" }, "sequence": { "oneLetter": "CCEYCCNPACTGCY", "threeLetter": [ "Cys", "Cys", "Glu", "Tyr", "Cys", "Cys", "Asn", "Pro", "Ala", "Cys", "Thr", "Gly", "Cys", "Tyr" ], "notes": "Numbering begins at Cys1 of the 14-residue chain. All chiral residues are L; Gly12 is achiral. Disulfides join Cys1-Cys6, Cys2-Cys10 and Cys5-Cys13. The peptide backbone remains open at both termini.", "rings": [ { "kind": "disulfide", "from": { "position": 1, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 6, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-36770675" }, { "kind": "disulfide", "from": { "position": 2, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 10, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-36770675" }, { "kind": "disulfide", "from": { "position": 5, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "to": { "position": 13, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-36770675" } ] }, "molecularFormula": "C59H79N15O21S6", "molecularWeightDa": 1526.725, "terminalModifications": [ "Free N-terminus", "Free C-terminal carboxyl" ], "structuralModifications": [ "Cys1-Cys6 intramolecular disulfide", "Cys2-Cys10 intramolecular disulfide", "Cys5-Cys13 intramolecular disulfide" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-36770675", "pmid-33558523", "pmid-33979161" ], "identityOverview": "Linaclotide is a synthetic 14-residue peptide with free termini and three intramolecular disulfide bridges.", "nomenclatureNotes": "This record describes the covalent parent without counterion or hydration components.", "structuralNotes": "Numbering begins at Cys1 of the 14-residue chain. All chiral residues are L; Gly12 is achiral. Disulfides join Cys1-Cys6, Cys2-Cys10 and Cys5-Cys13. The peptide backbone remains open at both termini.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. WHO and FDA formulas match the derived C59H79N15O21S6. GSRS carries the non-defining estimate C59H85N15O21S6, differing by H6, beside its matching 1526.725 Da mass. FDA prints 1526.8 (-0.075 Da, -49.122 ppm). Laps et al. Figure 5d gives calculated 1525.1 and observed 1525.1 ± 0.1 under an average-isotope caption: +1.625 Da (+1065.504 ppm) from 1525.1. Those numerical figures are non-defining; 1525.1 is not relabeled as an accurate monoisotopic mass.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "pacap-38", "url": "https://purelypeptides.org/research/compounds/pacap-38/", "displayName": "PACAP-38", "canonicalName": "PACAP38", "moleculeType": "peptide", "aliases": [ "PACAP 38" ], "developmentCodes": [], "externalIds": { "cas": "124123-15-5", "unii": "LK78T72MLT" }, "sequence": { "oneLetter": "HSDGIFTDSYSRYRKQMAVKKYLAAVLGKRYKQRVKNK", "threeLetter": [ "His", "Ser", "Asp", "Gly", "Ile", "Phe", "Thr", "Asp", "Ser", "Tyr", "Ser", "Arg", "Tyr", "Arg", "Lys", "Gln", "Met", "Ala", "Val", "Lys", "Lys", "Tyr", "Leu", "Ala", "Ala", "Val", "Leu", "Gly", "Lys", "Arg", "Tyr", "Lys", "Gln", "Arg", "Val", "Lys", "Asn", "Lys" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C203H331N63O53S", "molecularWeightDa": 4534.329, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [ "neuropeptides-and-derived-fragments" ], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-2803320", "pmid-32323126" ], "identityOverview": "PACAP-38 is a linear 38-residue peptide with a free N-terminal histidine and a C-terminal lysinamide.", "nomenclatureNotes": "Length and terminal state qualify the parent identity. PACAP(1-38) is withheld as an unestablished alias. PubChem CID is withheld because three matching issuer records remain unresolved. No blanket species or salt equivalence is assigned.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. GSRS carries the non-defining estimated formula C203H329N63O52S, differing by H2O, and estimated average 4530 Da: +4.329 Da (+955.629 ppm). PubChem displays 4534 Da: +0.329 Da (+72.563 ppm), consistent with whole-unit display rounding. An analytical table prints calculated 4534.3 (+0.029 Da, +6.396 ppm) under an unestablished mass convention; a patent reports SIMS (M+H) 4530 under an incompletely specified ion convention. None defines the neutral average.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "secretin", "url": "https://purelypeptides.org/research/compounds/secretin/", "displayName": "Human secretin", "canonicalName": "Secretin human", "moleculeType": "peptide", "aliases": [], "developmentCodes": [], "externalIds": { "cas": "108153-74-8", "unii": "A0426J905J" }, "sequence": { "oneLetter": "HSDGTFTSELSRLREGARLQRLLQGLV", "threeLetter": [ "His", "Ser", "Asp", "Gly", "Thr", "Phe", "Thr", "Ser", "Glu", "Leu", "Ser", "Arg", "Leu", "Arg", "Glu", "Gly", "Ala", "Arg", "Leu", "Gln", "Arg", "Leu", "Leu", "Gln", "Gly", "Leu", "Val" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C130H220N44O40", "molecularWeightDa": 3039.458, "terminalModifications": [ "Free N-terminus", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-32217097", "pmid-11060443" ], "identityOverview": "Human secretin is a linear 27-residue peptide with a free N-terminal histidine and a C-terminal valine amide.", "nomenclatureNotes": "The name is species-qualified and identifies the mature human parent separately from precursor and salt forms. PubChem CID is withheld because competing human-parent assignments remain unresolved; the generic-name registry encoding is excluded.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. The derived formula matches the WHO entry and matching PubChem structures. DailyMed prints C130H220N44O39, whose CIAAW average is 3023.459 Da, 15.999 Da below the derived value; its printed 3039.44 differs by +0.018 Da (+5.922 ppm) under an unestablished convention. GSRS gives the non-defining estimate C130H222N44O41, differing by H2O, and sequence-calculated 3038.0 Da: +1.458 Da (+479.921 ppm). PubChem reports 3039.4 Da: +0.058 Da (+19.083 ppm). These divergent values are non-defining.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "enfuvirtide", "url": "https://purelypeptides.org/research/compounds/enfuvirtide/", "displayName": "Enfuvirtide", "canonicalName": "Enfuvirtide", "moleculeType": "peptide", "aliases": [], "developmentCodes": [ "T20", "T-20", "DP-178" ], "externalIds": { "cas": "159519-65-0", "pubChemCid": "16130199", "unii": "19OWO1T3ZE" }, "sequence": { "oneLetter": "YTSLIHSLIEESQNQQEKNEQELLELDKWASLWNWF", "threeLetter": [ "Tyr", "Thr", "Ser", "Leu", "Ile", "His", "Ser", "Leu", "Ile", "Glu", "Glu", "Ser", "Gln", "Asn", "Gln", "Gln", "Glu", "Lys", "Asn", "Glu", "Gln", "Glu", "Leu", "Leu", "Glu", "Leu", "Asp", "Lys", "Trp", "Ala", "Ser", "Leu", "Trp", "Asn", "Trp", "Phe" ], "notes": "Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately." }, "molecularFormula": "C204H301N51O64", "molecularWeightDa": 4491.945, "terminalModifications": [ "N-terminal acetylation", "C-terminal amide" ], "structuralModifications": [], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-22228771", "pmid-19073602", "pmid-30096076" ], "identityOverview": "Enfuvirtide is a synthetic linear peptide comprising 36 L-amino-acid residues, with an acetylated N terminus and a C-terminal amide.", "nomenclatureNotes": "The historical codes T20, T-20 and DP-178 are admitted for the defined parent. Acetyl and amide caps are terminal modifications rather than chain tokens. No salt or hydrate equivalence is inferred.", "structuralNotes": "The chain contains standard L-amino-acid residues and no inter-residue covalent closure.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem formula C204H301N51O64 matches the covalent derivation. GSRS carries non-defining estimated C204H302N51O66 and 4450.0 Da: +41.945 Da (+9425.842697 ppm). DailyMed displays 4492, a non-defining difference of -0.055 Da (-12.243989 ppm) if compared as an average; its exact convention is unestablished. Neutral monoisotopic mass and MS ion values are separate quantities.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" }, { "id": "eptifibatide", "url": "https://purelypeptides.org/research/compounds/eptifibatide/", "displayName": "Eptifibatide", "canonicalName": "Eptifibatide", "moleculeType": "peptide", "aliases": [ "Eptifibatidum", "Eptifibatida" ], "developmentCodes": [], "externalIds": { "pubChemCid": "448812", "unii": "NA8320J834" }, "sequence": { "threeLetter": [ "Mpa", "Har", "Gly", "Asp", "Trp", "Pro", "Cys" ], "notes": "Conventional numbering counts Mpa1, Har2, Gly3, Asp4, Trp5, Pro6 and Cys7. Mpa is the achiral N-terminal 3-mercaptopropanoyl acyl unit, not an amino acid. Har is L-homoarginine, equivalently N6-amidino-L-lysine. The six amino acids contain five L chiral units and achiral Gly. Cysteinamide is a terminal group; no one-letter string is supplied. Source amino-acid-only numbering Har1-Cys6 maps to conventional positions 2-7.", "rings": [ { "kind": "disulfide", "from": { "position": 1, "residue": "Mpa", "atom": "thiol sulfur" }, "to": { "position": 7, "residue": "Cys", "atom": "thiol sulfur (Sγ)" }, "referenceId": "pmid-21031361" } ] }, "molecularFormula": "C35H49N11O9S2", "molecularWeightDa": 831.965, "terminalModifications": [ "N-terminal 3-mercaptopropanoyl acyl unit; no free N-terminal alpha-amino group", "C-terminal amide" ], "structuralModifications": [ "Intramolecular disulfide between Mpa1 and L-Cys7" ], "compoundClassIds": [], "mechanismIds": [], "relatedCompoundIds": [], "referenceIds": [ "pmid-21031361" ], "identityOverview": "Eptifibatide is a synthetic peptide containing L-homoarginine and a disulfide closure connecting an N-terminal 3-mercaptopropanoyl unit to the C-terminal cysteinamide.", "nomenclatureNotes": "WHO Recommended INN List 40 names the parent and its language forms. Six amino acids plus one non-amino-acid acyl unit occupy seven conventional positions. CAS provenance and historical codes remain withheld. FDA uses the literal term interchain, while WHO and analytical ring-scission evidence establish an intramolecular disulfide. EMA prose says (L)propyl, whereas its sequence representation and the other admitted structures identify proline. These editorial wording conflicts remain unresolved and do not define additional bonds or residues.", "structuralNotes": "Conventional numbering counts Mpa1, Har2, Gly3, Asp4, Trp5, Pro6 and Cys7. Mpa is the achiral N-terminal 3-mercaptopropanoyl acyl unit, not an amino acid. Har is L-homoarginine, equivalently N6-amidino-L-lysine. The six amino acids contain five L chiral units and achiral Gly. Cysteinamide is a terminal group; no one-letter string is supplied. Source amino-acid-only numbering Har1-Cys6 maps to conventional positions 2-7.", "analyticalNotes": "The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. FDA prints 831.96: +0.005 Da (+6.0099 ppm). EMA prints 831.32: +0.645 Da (+775.8745 ppm) against the average; neither source explicitly establishes its precise mass convention. PubChem displays 832.0 Da: -0.035 Da (-42.0673 ppm), consistent with one-decimal rounding. Those published figures are non-defining; reduced and altered MS products are separate material.", "publishedDate": "2026-10-21", "lastVerifiedDate": "2026-10-21" } ] }