TB-500 Frag 17-23

TB-500 Frag 17-23 (Ac-LKKTETQ) designates residues 17–23 of thymosin beta-4 with an N-terminal acetyl group. It is important to understand this compound in its correct context: **TB-500 Frag 17-23 is not a purposefully designed therapeutic peptide.** It was identified analytically by anti-doping researchers as a fragment present in commercial TB-500 (thymosin beta-4) lyophilized preparations — a manufacturing-related impurity or degradation product, not a designed active pharmaceutical ingredient.

Some research peptide vendors sell TB-500 Frag 17-23 as an independent product, but this practice reflects commercial opportunism rather than independent therapeutic evidence. The entirety of published data on this fragment is from a single anti-doping analytical study (PMID 22962027) that characterized its presence in commercial TB-500 vials for the purpose of developing urine/plasma detection methods.

Researchers and users seeking the therapeutic effects described for TB-500 should refer to the TB-500 (thymosin beta-4) entry, which covers the full protein with its established wound healing, tissue repair, and cardioprotective evidence.

The LKKTET motif (residues 17–22 of thymosin beta-4) overlaps with the actin-binding domain of full thymosin beta-4. Full Tβ4 binds G-actin via this region, sequestering monomeric actin and modulating actin polymerization dynamics. However, the isolated heptapeptide Ac-LKKTETQ has not been independently characterized for: - G-actin binding affinity - Cellular uptake - Any functional biological activity in cell or animal models

The better-characterized N-terminal fragment of thymosin beta-4 is Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline, residues 1–4) — a distinct compound with documented anti-fibrotic, anti-inflammatory, and angiogenic activity in published peer-reviewed studies. TB-500 Frag 17-23 is not Ac-SDKP and should not be conflated with it.