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Research Catalog

fragment of

TB-500 vs Thymosin beta-4

The Library's TB-500 record concerns an N-terminally acetylated seven-residue fragment, distinct from the 43-residue thymosin beta-4 parent. This identity relationship establishes neither a processing pathway nor the identity of commercial material.

Published: 2026-10-05Library record comparison: 2026-10-05

01

Identity side by side

Recorded molecular identities of TB-500 and Thymosin beta-4
Recorded fieldTB-500Thymosin beta-4
Canonical nameTB-500Timbetasin
AliasesN-acetyl-thymosin beta-4 (17-23)Thymosin b4; Tbeta4; TB4
Development codesnot recordednot recorded
CASnot recorded77591-33-4
UNIInot recorded2D5MRE3SSY
PubChem CIDnot recorded16132341
Molecular formulanot recordedC212H350N56O78S
Molecular weight (Da)not recorded4963
Sequence length (residues)7not recorded
Terminal modificationsN-terminal acetylation at Leu1N-terminal acetyl
Structural modificationsnot recordednot recorded

TB-500: nomenclature notes

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. It does not establish the identity or composition of a commercial preparation.

Thymosin beta-4: nomenclature notes

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 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.

02

Recorded modification details

An aligned one-letter sequence is not recorded for this pair. The stored modification and sequence notes are shown below.

TB-500

Terminal modifications
N-terminal acetylation at Leu1
Structural modifications
not recorded
Stored three-letter notation
Ac · Leu · Lys · Lys · Thr · Glu · Thr · Gln
Sequence 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.

Thymosin beta-4

Terminal modifications
N-terminal acetyl
Structural modifications
not recorded

03

Recorded mechanisms

These lists show the links recorded in each monograph. An unlisted link does not establish its absence from the molecule’s biology.

Shared recorded links

not recorded

Recorded only for TB-500

not recorded

Recorded only for Thymosin beta-4

04

Recorded compound classes

Shared recorded links

not recorded

Recorded only for TB-500

Recorded only for Thymosin beta-4

05

References for the relationship

  1. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential.

    Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P

    Drug testing and analysis · 2012-09-07 · Journal Article

    current
    PMID 22962027DOI 10.1002/dta.1402TB-500
  2. Doping control analysis of TB-500, a synthetic version of an active region of thymosin β₄, in equine urine and plasma by liquid chromatography-mass spectrometry.

    Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, Schiff PJ, Stewart BD

    Journal of chromatography. A · 2012-09-23 · Journal Article

    current
    PMID 23084823DOI 10.1016/j.chroma.2012.09.043TB-500

06

Read the full monographs

TB-500 →Thymosin beta-4 →