TB-500

The distinction between TB-500 and thymosin beta-4 is the single most important thing to establish before reading this literature, and it is routinely collapsed in secondary sources. Thymosin beta-4 is an endogenous, 43-amino-acid, highly conserved protein present at high intracellular concentration in most mammalian cell types, and essentially all of the peer-reviewed research is conducted on it. TB-500 is a research-supply designation for a synthetic peptide based on the actin-binding region of that protein, most often given as the heptapeptide motif around residues 17 to 23. Papers describing outcomes for Tβ4 should not be read as describing outcomes for the shorter construct without checking which material was actually used.

The Tβ4 literature has two distinct strands. The first is structural cell biology: Tβ4 is the major G-actin sequestering peptide in mammalian cells, maintaining a monomeric actin pool and thereby influencing the rate at which filaments can be assembled. The second strand, which drew far wider attention, is repair biology. A 2004 report in Nature by Bock-Marquette and colleagues described systemic administration of Tβ4 following experimental myocardial infarction in mice and reported improved cardiac function, reduced scar size and increased neovascularisation, with integrin-linked kinase activation proposed as the pathway. Goldstein, Hannappel and Kleinman reviewed the broader repair literature in 2005 under the framing that an actin-sequestering protein appeared to moonlight in tissue repair, covering dermal wound healing, corneal repair and post-ischaemic cardiac signalling.

Human clinical evidence for the shorter synthetic construct is not established in the peer-reviewed record, and readers should treat the cardiac and dermal findings as belonging to the endogenous 43-mer in animal models. Merit Sciences supplies this material strictly for laboratory research use. Nothing here describes use in humans or animals, and no preparation, dosing or administration guidance is published.

The established biochemistry is actin sequestration: thymosin beta-4 binds monomeric G-actin in a one-to-one complex and holds it in a polymerisation-incompetent state, which buffers the free monomer pool available for filament assembly. Because cell migration depends on controlled, local actin polymerisation, this buffering role is the proposed starting point for the migration and repair observations reported downstream. In the cardiac work, integrin-linked kinase and Akt activation were reported as the signalling route associated with cardiomyocyte survival and migration. Reported here as proposed mechanism from animal and cell-culture models, and predominantly for the full-length endogenous protein rather than the shorter synthetic construct.

• G-actin sequestration and cytoskeletal dynamics studies
• Cell migration and wound-closure assays in vitro
• Preclinical cardiac repair and neovascularisation models
• Corneal and dermal repair models
• Comparative work distinguishing full-length Tβ4 from shorter synthetic fragments

TB-500 ships as a sealed, lyophilized (freeze-dried) powder. Supplied lyophilised, commonly as the acetate salt. Reported as soluble in water and in aqueous buffers. The actin-binding motif is strongly polar, carrying multiple lysine and glutamate residues, and contains no cysteine, so there is no disulfide chemistry to manage. Physicochemical context only. Merit Sciences publishes no reconstitution or preparation procedures. Store sealed, light-protected, and follow your institution’s handling procedures for research materials.

1. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Bock-Marquette I, Saxena A, White MD, DiMaio JM, Srivastava D. Nature, 2004 · PMID 15565145
2. Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Goldstein AL, Hannappel E, Kleinman HK. Trends in Molecular Medicine, 2005