TB-500 (Thymosin Beta-4)

The name is the first thing to get right: "TB-500" is used loosely for a short synthetic peptide built around the LKKTETQ actin-binding motif, but the CAS number and the 4,963.44 g/mol mass on this vial belong to the complete 43-amino-acid thymosin beta-4 sequence, which is what DNA-LABS supplies. Thymosin beta-4 is the most abundant actin-sequestering protein in mammalian cells and is unusually disordered — it carries almost no fixed secondary structure in solution and folds only on contact with G-actin, which is why it binds monomeric actin one-to-one and holds it out of the polymerising pool. It was first purified from bovine thymus, though it is expressed far beyond the thymus and is not a hormone despite the name. Laboratory interest has centred on actin dynamics and cytoskeletal assembly, on cell-migration and scratch assays, on corneal and dermal wound models, and on angiogenesis work, predominantly in cell culture and in rodent systems. It is supplied as a lyophilised white powder, 10 mg in a sealed vial, at 99% purity against the certificate of analysis for that lot. Reconstitute with bacteriostatic water directed down the vial wall rather than onto the cake, swirl instead of shaking, and hold both the sealed vial and the reconstituted stock at 2–8°C away from light, avoiding repeated freeze–thaw cycles. For laboratory research use only — not for human or animal consumption.