TB-500 Analytical Identity: Ac-LKKTETQ, Fragment Names, and MS Records

Research use only. The cited records concern analytical terminology and measurement methods. They do not provide human or veterinary use, dosing, administration, safety, or outcome guidance.

TB-500 in the cited analytical records

Three primary analytical papers use TB-500 with a specific fragment designation. Esposito et al. (2012; PMID 22962027) reports identification of the N-terminally acetylated 17-23 fragment of human thymosin beta-4 as Ac-LKKTETQ in a preparation described as TB-500. Ho et al. (2012; PMID 23084823) calls TB-500 a synthetic version of an active region of thymosin beta-4 and describes N-acetylated LKKTETQ in its analytical method. Rahaman et al. (2024; PMID 38382158) also names TB-500 as Ac-LKKTETQ.

These records support an analytical source note for the acetylated seven-residue fragment. They do not make the term TB-500 interchangeable with the full-length human thymosin beta-4 protein or with every material sold under a related name.

What each method measured

PMID 22962027 used high-performance liquid chromatography and high-resolution mass spectrometry to detect and identify Ac-LKKTETQ in the reported TB-500 preparation. The authors also synthesized Ac-LKKTETQ and described a separate HPLC/triple-quadrupole strategy for detection in plasma and urine.

PMID 23084823 reports liquid-chromatography mass-spectrometry analysis of N-acetylated LKKTETQ and metabolites in equine urine and plasma. The analytes were identified through retention time and relative abundances of major product ions. Its study system is equine biological matrices and the stated LC/MS method.

PMID 38382158 describes simultaneous UHPLC-Q-Exactive Orbitrap MS/MS quantification of TB-500 and metabolites. Its methods include human serum, in-vitro enzyme systems, rat urine samples, and authentic standards. The paper names Ac-LK and Ac-LKK among the detected metabolite records. Those findings remain tied to the reported analytical systems and samples.

Fragment name and full protein name

The fragment notation `17-23` refers to a segment of thymosin beta-4 in the cited papers. A full-protein record and a fragment-specific analytical record answer different identity questions. The publications above provide neither a sequence confirmation nor a purity result for an unrelated sample, and they do not establish the composition of a catalogue lot from its product name alone.

Material-document boundary

A material-specific record requires the actual label, lot identifier, and the documents supplied for that lot. The analytical sources can be cited for their fragment terminology, matrices, and instrument methods; they cannot replace a certificate of analysis or establish that another preparation contains Ac-LKKTETQ. TB-500 and Thymosin Beta-4: Nomenclature, Source Scope and Documentation Review provides separate broader context.