TB-500 and the Analytical Record

Peptheos

TB-500 is Ac-LKKTETQ, the N-terminally acetylated fragment corresponding to residues 17 to 23 of thymosin beta-4, molecular formula C38H68N10O14, molecular weight 889.0 g/mol. Its identity was fixed by analytical chemistry: a 2012 study by Esposito and colleagues at Ghent University ran commercial TB-500 through high-resolution mass spectrometry, identified the content as Ac-LKKTETQ, and confirmed it against a synthesised standard.

That analytical framing matters because product identity is not guaranteed. A 2023 analysis in Drug Testing and Analysis examined products sold as TB500 and TB1000 and reported that their content was not systematically consistent with prior descriptions. The parent protein, thymosin beta-4, is a separate 43-residue molecule; the reviews that anchor that field, including Goldstein and colleagues in 2005, study the full protein, not the fragment.

Supplied for laboratory research use only.

References

Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P. 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. Drug Test Anal. 2012;4(9):733-738. doi.org/10.1002/dta.1402
Delcourt V, Garcia P, Chabot B, et al. TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023;15(4):458-464. doi.org/10.1002/dta.3421
Goldstein AL, Hannappel E, Kleinman HK. Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med. 2005;11(9):421-429. doi.org/10.1016/j.molmed.2005.07.004