What TB-500 is
TB-500 is a synthetic form of thymosin beta-4 (Tβ4), a 43-amino-acid peptide present in most mammalian cell types and one of the most abundant intracellular peptides in the body. Its principal established function is actin sequestration: it binds monomeric G-actin and maintains the unpolymerised pool from which cells assemble actin filaments.
That single biochemical role explains most of the research interest. Cell migration depends on rapid, controlled actin polymerisation at the leading edge, and anything governing the available monomer pool sits upstream of motility — which in turn sits upstream of wound closure, angiogenesis and tissue remodelling.
The naming problem
The label "TB-500" is used inconsistently across the research chemical market, and it is worth being explicit about it:
| Material | Length | Approximate mass |
|---|---|---|
| Full-length thymosin β4 | 43 residues | ~4,963 Da |
| Ac-LKKTETQ fragment | 7 residues | ~889 Da |
Both are sold as "TB-500". They are not equivalent, they do not cost the same to synthesise, and the difference is invisible in the vial. The fragment corresponds to the actin-binding domain of the full peptide, which is the usual justification given for the substitution — but it is a different molecule and should be sold as one.
This is a mass spectrometry question, and only a mass spectrometry question. Four thousand daltons is not a subtle difference; any real MS result resolves it immediately. A certificate reporting purity alone cannot, which is exactly why this compound is a useful test of whether a supplier's documentation means anything. Tested Peptides supplies full-length thymosin β4, and the observed mass on each batch certificate is the evidence for that.
Molecular profile
| Property | Value |
|---|---|
| Also known as | Thymosin β4, Tβ4 |
| CAS number | 77591-33-4 |
| Length | 43 amino acids |
| Molecular weight | ~4,963 Da |
| Principal known function | G-actin sequestration |
| Appearance | White lyophilised powder |
Research context
Published work on thymosin β4 spans:
- Cell migration — the mechanistic core, following directly from actin monomer regulation.
- Angiogenesis — endothelial cell migration and tube formation in vitro.
- Tissue repair models — dermal, corneal and cardiac injury models, largely preclinical.
- Inflammatory signalling — reported effects on cytokine expression in cultured cells.
Supplied for in-vitro laboratory research only. No therapeutic claim is made and no dosing or administration guidance is provided.
Analytical notes
At 43 residues, thymosin β4 is a demanding solid-phase synthesis. Longer chains accumulate more opportunities for incomplete coupling, so the deletion-sequence impurity profile is richer than it is for a short peptide, and the separation between a 43-mer and a 42-mer on reversed-phase chromatography is narrow.
Two consequences follow. First, the chromatogram is worth more than the purity figure — a well-resolved trace with a clean baseline says more than "99.2%" detached from it. Second, mass spectrometry is doing double duty here: confirming identity against the fragment ambiguity above, and confirming that the main peak is the full-length species rather than a truncation.
Handling and storage
Store sealed at −20 °C, protected from light and moisture, and bring to room temperature before opening. Reconstitute by adding diluent down the vial wall and swirling gently. Longer peptides are more susceptible to aggregation on agitation than short ones — see peptide aggregation and handling. Store reconstituted solution at 2–8 °C, protected from light, and avoid repeated freeze-thaw.
What we supply
Full-length thymosin β4, released against a ≥99% purity specification, with HPLC purity and mass spectrometry identity confirmation on every batch and a batch-specific Certificate of Analysis on which the observed mass is stated explicitly. Select batches additionally receive independent third-party purity verification.