TB-500 is a synthetic 43-amino-acid peptide corresponding to thymosin beta-4, a naturally occurring protein first isolated from thymus tissue and subsequently found across most mammalian cell types. The material is supplied acetylated at the N-terminus, with a molecular formula of C212H350N56O78S and a molecular weight of 4963.4 g/mol.
Thymosin beta-4 is one of the most abundant intracellular proteins in many tissues, which is part of why it became a subject of sustained research interest rather than an obscure sequence.
Research context
The published literature centres on actin sequestration. Thymosin beta-4 binds monomeric G-actin and holds it in reserve, regulating the pool available for polymerisation into filaments — a mechanism relevant to cell motility, cytoskeletal reorganisation and wound-closure models.
Downstream of that, published work examines the peptide in angiogenesis, corneal and dermal repair preparations, and cardiac tissue models. The actin-binding mechanism is well characterised; the tissue-level effects reported in animal models are a more active area of investigation.
For a fuller treatment of the sequence and published models, see the TB-500 research guide. Researchers evaluating repair-model compounds may also want the BPC-157 vs TB-500 comparison, which sets out how the two differ in mechanism and in the strength of their evidence bases.
Specification
CAS number 77591-33-4. Supplied as a white lyophilized powder, soluble in water. This batch assayed at 99.36% purity, verified by HPLC and LC-MS at ILS Lab.
Handling
Reconstitute with bacteriostatic or sterile water, introducing the diluent against the vial wall and swirling gently rather than shaking. Store lyophilized at −20°C protected from light; refrigerate at 2–8°C once reconstituted.
Ships with a batch-specific Certificate of Analysis. Cross-check the batch ID printed on your vial against the CoA before use — see the guide to reading a CoA if you are unfamiliar with the format.
Frequently asked questions about TB-500
Is TB-500 the same as thymosin beta-4?
Effectively yes, though the naming is loose in circulation. TB-500 as supplied for research is the synthetic full-length 43-residue thymosin beta-4 sequence, acetylated at the N-terminus. Some suppliers use TB-500 to mean only the short LKKTETQ active fragment, which is a different molecule with a different molecular weight. Check the sequence and molecular weight on the Certificate of Analysis rather than relying on the product name — this batch is the full-length peptide at 4963.4 g/mol.
What purity should TB-500 be?
Research-grade material is typically 98% or above. This batch assayed at 99.36% by HPLC with identity confirmed by LC-MS at ILS Lab. For a 43-residue peptide, mass spectrometry matters more than it does for short sequences — longer syntheses accumulate deletion sequences that can elute close to the target peak on HPLC alone.
How should TB-500 be reconstituted and stored?
Bacteriostatic or sterile water; it is water-soluble and needs no acidic diluent. Introduce the diluent against the inner wall of the vial and swirl gently — at 43 residues this peptide is more conformationally sensitive than short sequences, and shaking or foaming risks denaturation. Store lyophilized at −20°C protected from light, refrigerate at 2–8°C once reconstituted, and avoid repeated freeze-thaw cycles.
TB-500 or BPC-157 for repair models?
Different mechanisms, so the choice follows the endpoint. TB-500 has a well-characterised molecular mechanism in G-actin sequestration, making it the more direct choice where cytoskeletal dynamics or cell migration are being measured. BPC-157 is studied largely through angiogenic and growth-factor signalling. The comparison guide covers how the evidence bases differ, and studies pairing them typically use the combined preparation.
Research use only. Not for human or veterinary use, not for use in diagnostic procedures, and not evaluated by the U.S. Food and Drug Administration.
