Source-first science
Purely PeptidesResearch
A structured peptide-science reference organized by compounds, molecular classes, mechanisms, and verified bibliography.
Taxonomy
Browse by compound class
Compound class
GLP-1 receptor peptide analogs
Designed peptide analogs whose declared molecular relationship is agonism at the glucagon-like peptide-1 receptor.
3 published compounds
Compound class
Multi-receptor incretin analogs
Single peptide molecules characterized against more than one receptor in the incretin and glucagon receptor families.
4 published compounds
Compound class
Kisspeptins
Peptides derived from the KISS1 precursor that share a C-terminal RF-amide motif and bind the kisspeptin receptor.
2 published compounds
Compound class
Regenerative peptides
Synthetic peptides studied in connective-tissue and epithelial repair models, grouped by shared experimental context rather than by a common receptor.
1 published compound
Compound class
Copper-binding peptides
Peptides whose defining chemical feature is high-affinity coordination of Cu(II), forming discrete metal-peptide complexes with molecular identities distinct from the free peptide.
2 published compounds
Compound class
GHRH analogs
Synthetic analogs of growth hormone-releasing factor, typically modified fragments of the 44-residue human sequence, acting at the GHRH receptor.
3 published compounds
Compound class
Growth hormone secretagogues
Endogenous peptide ligands, synthetic peptides and nonpeptide mimetics acting at the growth hormone secretagogue receptor (the ghrelin receptor), a distinct receptor from the GHRH receptor targeted by GHRH analogs.
7 published compounds
Compound class
Mitochondrial-derived peptides
Peptides encoded by short open reading frames within the mitochondrial genome rather than the nuclear genome.
7 published compounds
Compound class
Regulatory peptide fragment analogs
Short synthetic peptides constructed from a fragment of a larger endogenous regulatory peptide, commonly extended with a stabilizing C-terminal sequence.
7 published compounds
Compound class
Thymosin-related peptides
Peptides originally isolated from thymic tissue fractions, subsequently characterized as having functions unrelated to thymic hormone activity.
2 published compounds
Compound class
Melanocortin fragment peptides
Short peptides corresponding to fragments of melanocortin hormones, retaining part of the parent sequence while lacking the residues required for melanocortin receptor binding.
1 published compound
Compound class
Nonpeptide receptor agonists
Small molecules characterized as agonists at receptors whose endogenous ligands are peptides, included here for comparison with the peptide agonists at the same receptor.
1 published compound
Compound class
Matrikine-derived peptides
Peptides corresponding to fragments of extracellular matrix proteins, typically studied for their reported effects on matrix synthesis in fibroblast culture.
5 published compounds
Compound class
Cyclic melanocortin analogs
Synthetic melanocortin receptor ligands closed into a macrocycle by a side-chain to side-chain bridge, in contrast to the linear fragment and full-length melanocortin peptides.
4 published compounds
Compound class
Amylin and calcitonin receptor agonists
Peptides that engage the calcitonin receptor and the amylin receptor complexes it forms with receptor activity-modifying proteins. Described as amylin analogs, they are not amylin-receptor-exclusive.
3 published compounds
Compound class
Linear melanocortin analogs
Full-length melanocortin peptide analogs that retain a linear backbone, distinguished from the cyclic lactam analogs and from the short melanocortin fragments.
1 published compound
Compound class
Neurotrophic peptide mimetics
Small synthetic peptides designed to mimic regions of neurotrophic factors, typically characterised through downstream pathway readouts rather than a demonstrated direct receptor target.
1 published compound
Compound class
Melanocortin receptor ligands
An umbrella for everything that acts at the melanocortin receptors regardless of chemistry — the native hormones, their fragments, cyclic analogs and nonpeptide small molecules. It exists so the native hormone is not filed as an analog of itself and a nonpeptide is not filed in a peptide class.
5 published compounds
Compound class
Incretin and glucagon receptor ligands
Endogenous hormones acting at the GLP-1, GIP and glucagon receptors, held together without any claim of common chemical ancestry. It exists so native hormones are not filed in a class of analogs of themselves.
5 published compounds
Compound class
Neuropeptides and derived fragments
A navigation class for endogenous neuropeptides and synthetic fragments derived from them. Membership does not imply a shared precursor, receptor or mechanism.
11 published compounds
Compound class
Aromatic cationic tetrapeptides
Synthetic linear tetrapeptide amides with alternating aromatic residues and basic amino-acid residues, in either aromatic–basic–aromatic–basic or basic–aromatic–basic–aromatic order.
1 published compound
Compound class
GnRH peptide analogs
Synthetic peptide analogs of the hypothalamic GnRH decapeptide with direct experimental evidence of binding the GnRH receptor. Each member carries its own substitutions, so membership does not imply identical chemistry.
4 published compounds
Entities
Compound directory
Canonical names, aliases, and scientific identifiers
Browse every published compound record without requiring client-side filtering.
Recorded relationships
Peptide Receptor Map
Library index
Explore compounds by molecular target
View recorded compound and target links together in a grid or list.
Recorded disagreements
Source Disagreements and Name Mix-ups
Library index
Where sources disagree and what gets mixed up
Every identity disagreement and name or form mix-up the records note, each quoted from its record.
Recorded relationships
Compound Relationship Map
Library index
Analogues, fragments and other forms
Which records are analogues of, contained in or other forms of each other, and which share an origin, each quoted from its record.
Cited studies
Evidence Map
Study findings
Explore study findings
Read each recorded finding with its study model, result and source paper.
Library index
Study types cited for each compound
How many of the papers cited in each record report in vitro, animal, human-participant, review or analytical work, each count linked to those papers.
Downloads
Open Research Data
Library index
The Library as JSON and CSV files
Compound records, references with their verification receipts, the relationship map and the disagreement register, free to reuse with credit under CC BY 4.0.
Molecular index
Browse mechanisms
receptor
Glucagon-like peptide-1 receptor
GLP-1R is a class B G-protein-coupled receptor. The cited structural and pharmacology records characterize semaglutide and retatrutide as peptide agonists at this receptor.
11 linked published compounds
receptor
Glucose-dependent insulinotropic polypeptide receptor
GIPR is a class B G-protein-coupled receptor. The cited discovery and trial records identify it as one of the three receptor relationships declared for retatrutide.
3 linked published compounds
receptor
Glucagon receptor
GCGR is a class B G-protein-coupled receptor. Retatrutide's LY3437943 discovery record characterizes a molecular agonist relationship at GCGR alongside GIPR and GLP-1R.
5 linked published compounds
receptor
Kisspeptin receptor
KISS1R is a G-protein-coupled receptor historically reported as GPR54 and AXOR12. Foundational records identify KISS1-derived peptides as its endogenous ligands.
2 linked published compounds
receptor
GHRH receptor
A class B G-protein-coupled receptor expressed on anterior pituitary somatotrophs. Synthetic growth hormone-releasing factor analogs are characterized by their activity at this receptor.
3 linked published compounds
binding-interaction
Cu(II) coordination
Formation of a discrete coordination complex between a peptide ligand and a Cu(II) ion. Spectroscopic study of the glycyl-L-histidyl-L-lysine complex reports a mononuclear 1:1 species at neutral pH with equatorial nitrogen coordination including the histidyl imidazole. Complex formation changes the molecular formula, mass, and analytical identity of the species relative to the free peptide, and is reversible by competing chelators.
1 linked published compound
signaling-pathway
Focal adhesion kinase signaling
A cytoskeletal signaling pathway in which focal adhesion kinase and paxillin phosphorylation coordinate cell adhesion, spreading, and migration.
1 linked published compound
receptor
Growth hormone secretagogue receptor
A G-protein-coupled receptor distinct from the GHRH receptor. Antagonist profiling reported that ipamorelin releases growth hormone through a GHRP-like receptor rather than through the GHRH receptor, establishing the two pathways as separate.
7 linked published compounds
signaling-pathway
AMPK signaling
A serine/threonine kinase complex that senses low cellular ATP and phosphorylates substrates that increase ATP generation and decrease ATP consumption. Reported as a central mediator of the cellular response to energetic stress and of multiple aspects of mitochondrial homeostasis.
1 linked published compound
binding-interaction
G-actin sequestration
Binding of monomeric globular actin by a peptide ligand, holding it in a form unavailable for filament assembly. Beta-thymosins are reported as the main intracellular G-actin-sequestering peptides in most vertebrate cells, with a dissociation constant in the micromolar range that permits rapid binding and release.
1 linked published compound
receptor
Innate repair receptor
A heteromeric receptor complex proposed in 2004 to comprise the erythropoietin receptor together with the beta common receptor (CD131), and described as distinct from the EPOR homodimer that mediates erythroid maturation. The proposal rests on co-purification and co-immunoprecipitation of the two receptors from tissue membranes, colocalization in protected cells, and the absence of erythropoietin's protective activity in beta common receptor knockout animals. It is disputed. An independent group examined the extracellular regions of the two receptors in silico and in vitro, in the presence and in the absence of erythropoietin or the erythropoietin-derived peptide cibinetide, reported that they do not specifically associate, and opens by calling the complex controversial. No biophysical demonstration of a direct association between the two receptors has been published. This record therefore describes a reported complex together with the test that failed to confirm it, not an established one. Peptides characterized as selective agonists at this complex are reported not to engage the homodimeric receptor.
1 linked published compound
receptor
Melanocortin receptors
A family of five G protein-coupled receptors, MC1R through MC5R. ACTH recognition and signaling at MC2R depend on the accessory protein MRAP. Native hormones, peptide analogs and nonpeptide ligands differ in receptor-subtype recognition and functional direction; binding affinity, agonism and antagonism must be interpreted separately in the experimental system studied.
8 linked published compounds
receptor
Amylin and calcitonin receptors
The calcitonin receptor, and the amylin receptor complexes it forms when associated with receptor activity-modifying proteins RAMP1, RAMP2 or RAMP3. Because the amylin receptors are heteromers rather than distinct gene products, receptor construct and accessory-protein expression must accompany any selectivity claim; a potency ranking is not transferable between assay systems.
3 linked published compounds
receptor
CD36 scavenger receptor
A multifunctional scavenger receptor, distinct from the growth hormone secretagogue receptor, reported as a binding target for certain synthetic secretagogue peptides. It is recorded separately here precisely because collapsing it into the ghrelin-receptor mechanism would erase the finding that these compounds are not pharmacologically interchangeable.
2 linked published compounds
receptor
Galanin receptors
The galanin receptor family comprises three G protein-coupled receptors. GALR1 and GALR3 signal through Gi/o, while GALR2 signals mainly through Gq/11. Spexin activates GALR2 and GALR3 but not GALR1 in the reported ligand panel. Structural studies compared galanin-bound GALR1-Go and GALR2-Gq with spexin-bound GALR2-Gq, providing evidence for ligand recognition and subtype-dependent coupling.
2 linked published compounds
receptor
GnRH receptor
The GnRH receptor is a G-protein-coupled receptor encoded in humans by GNRHR. The records linked here cite direct binding measurements for synthetic peptide analogs, made at the human receptor or, where stated, at the rat receptor expressed in cultured cells.
2 linked published compounds
receptor
Parathyroid hormone 1 receptor
PTH1R is a class B G-protein-coupled receptor encoded by PTH1R and also called the PTH/PTHrP receptor. The record linked here cites a direct binding measurement made at the human receptor expressed in a human kidney cell line.
1 linked published compound
receptor
Opioid receptors
Receptor sites characterized by direct opioid-ligand binding experiments. Historical peptide studies establish receptor binding without necessarily resolving a modern receptor subtype.
1 linked published compound
receptor
Cholecystokinin 1 receptor
The cholecystokinin 1 receptor is a class A G-protein-coupled receptor. Independent structural studies identify sulfated CCK-8 bound to this receptor.
1 linked published compound
receptor
Bradykinin B2 receptor
The human bradykinin B2 receptor is a G protein-coupled receptor. The cited studies characterize bradykinin-bound receptor structures and icatibant recognition in identified receptor preparations.
2 linked published compounds
receptor
Corticotropin-releasing factor receptor 1
CRFR1 is a class B G-protein-coupled receptor. Independent receptor-expression and receptor-complex studies identify binding of the human/rat-sequence corticotropin-releasing factor peptide.
1 linked published compound
receptor
Guanylate cyclase C receptor
Guanylate cyclase C is a receptor also designated GC-C. The cited studies characterize linaclotide in membrane-binding assays and evaluate peptide activity at this receptor.
1 linked published compound
receptor
Secretin receptor
The secretin receptor, encoded by SCTR, is a class B G-protein-coupled receptor. Independent structural studies characterize human secretin bound to this receptor.
1 linked published compound
receptor
Integrin αIIbβ3
A heterodimeric integrin whose interaction with eptifibatide is characterized by direct structural and solution studies.
1 linked published compound
receptor
Angiotensin receptors
The angiotensin receptor family includes the AT1 and AT2 G-protein-coupled receptors. Direct binding experiments and structures of receptor–peptide complexes establish interaction with the Ile5 angiotensin II parent. Receptor subtype, organism and engineered receptor construct are distinguished in the cited studies.
1 linked published compound
receptor
Thyrotropin-releasing hormone receptor
A class A G-protein-coupled receptor. Independent structural studies report the defined TRH tripeptide bound to human TRHR in receptor–G-protein complexes.
1 linked published compound
receptor
PACAP and VIP receptors
Receptor relationships involving PAC1, VPAC1 and VPAC2, with each ligand’s tested receptor subtype identified separately.
1 linked published compound
Reference paths
Chemistry and analytical science
Research Article
Peptide chemistry foundations
Begin with the site's existing primer, then use the glossary for precise molecular terminology.
Existing article URL preserved
Research Article
Analytical identity and purity
Continue to the existing HPLC and mass-spectrometry overview, with terminology linked through the glossary.
Existing article URL preserved
Freshness
Recently updated research
Updated monograph
Angiotensin II (Ile5, free peptide)
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.
Updated 2026-10-22
Updated monograph
Bradykinin
Bradykinin is a linear nonapeptide composed of standard amino-acid residues, with free N and C termini.
Updated 2026-10-22
Updated monograph
CCK-8 (sulfated)
Sincalide is a linear eight-residue peptide with Tyr2 O-sulfation, a free N terminus and a C-terminal phenylalanine amide.
Updated 2026-10-22
Updated monograph
Eptifibatide
Eptifibatide is a synthetic peptide containing L-homoarginine and a disulfide closure connecting an N-terminal 3-mercaptopropanoyl unit to the C-terminal cysteinamide.
Updated 2026-10-22
Updated monograph
Human corticotropin-releasing factor (1–41) amide
Corticorelin (human/rat sequence) is a 41-residue peptide with a free N terminus and an amidated C-terminal isoleucine.
Updated 2026-10-22
Updated monograph
Human secretin
Human secretin is a linear 27-residue peptide with a free N-terminal histidine and a C-terminal valine amide.
Updated 2026-10-22
Research map
Explore every research surface
Sequence Lookup
Match pasted letters to the sequences stored in Library records.
Bibliography
Verified source records and durable identifiers.
Glossary
Anchored definitions for scientific terms.
Methodology
How identity and citation records are maintained.
Research Articles
Existing long-form articles at their original URLs.
Research Journal
The existing journal tool, kept distinct from Research.
Compounds
Canonical compound monographs and identifiers.
Compound Classes
Chemistry-first controlled taxonomy.
Mechanisms
Neutral receptor and molecular relationships.
102
Published compounds
278
Verified references
27
Published mechanisms