TB-500 (Thymosin β4 fragment)

TB-500 most commonly denotes the synthetic heptapeptide Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH (Ac-LKKTETQ), the N-terminally acetylated 17–23 fragment of thymosin β4. The LKKTETQ motif lies within the central actin-binding region of thymosin β4, a 43-residue peptide that is a major G-actin-sequestering molecule in mammalian cells.

The acetylated fragment was synthesised and characterised by liquid chromatography–mass spectrometry after it was identified in material circulating under the TB-500 name. Validated methods for detecting it in equine urine and plasma have since been published for doping-control research. The acetylated fragment has been tested in in-vitro fibroblast scratch assays, and the non-acetylated LKKTETQ sequence has been examined in rodent dermal-repair models. Because N-terminal acetylation can change a peptide's stability and binding properties, results for one form should not be assumed to transfer to the other. The fragment is used in research on actin-binding motifs and in analytical reference work.

Supplied as a sealed, lot-numbered vial with a lot-matched Certificate of Analysis (HPLC purity and MS identity).

For laboratory research use only. Not for human or veterinary use.