TB-500 is a synthetic N-terminally acetylated heptapeptide, Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, corresponding to residues 17–23 of thymosin beta-4 (Tβ4). This segment contains the central LKKTET motif, the actin-binding region of the 43-residue parent peptide. Analytical characterization of commercial material has identified this acetylated fragment as the principal component sold under the TB-500 designation.

The LKKTET motif has been characterized as the core of the Tβ4 interaction with monomeric (G-) actin, through which the full-length molecule sequesters actin and regulates filament assembly. Short synthetic peptides spanning this region have been reported to reproduce several in vitro activities of the parent molecule, including endothelial cell migration and tube formation in culture assays.

TB-500 is cited in research on actin cytoskeleton dynamics, structure–activity mapping of β-thymosin active sites, endothelial cell-migration and tube-formation assays, and analytical chemistry, including LC-MS methods for the fragment and its metabolites. The heptapeptide is distinct from full-length Tβ4, which is listed separately.

Research use only. This material is sold for in-vitro laboratory research and development purposes exclusively. It is not a drug, food, or dietary supplement, has not been evaluated by the FDA, and must not be used in humans or animals.