Last reviewed: October 2026 · Cleared Peptides research team
TB-500 is the name commonly used by research suppliers for Thymosin Beta-4 (Tβ4), a 43-amino-acid, N-terminally acetylated peptide. Tβ4 is one of the most abundant intracellular peptides and the principal G-actin-sequestering molecule in many cell types, which makes it a fundamental reference compound in cytoskeleton research.
In this guide:
TB-500 Structure and Identifiers
| Name | Thymosin Beta-4 (TB-500) |
|---|---|
| Synonyms | Tβ4; Thymosin β4 acetate |
| CAS number | 77591-33-4 |
| PubChem CID | 16132341 |
| Molecular formula | C212H350N56O78S |
| Molecular weight | ≈4963.4 g/mol |
| Length | 43 amino acids, N-acetylated (Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES) |
| Physical form | Lyophilized white powder |
Note: some suppliers use “TB-500” for a short synthetic fragment (e.g. Ac-LKKTETQ) rather than the full-length peptide. Cleared Peptides’ TB-500 is the full 43-residue Thymosin Beta-4, confirmed by mass spectrometry on each lot.
Actin-Binding Function
Tβ4 binds monomeric G-actin in a 1:1 complex and inhibits its polymerization into F-actin, maintaining a pool of unpolymerized actin in the cell. The central LKKTETQ motif is the core actin-binding region and the subject of extensive structure–function work.
In-Vitro Research Applications
- Actin polymerization and cytoskeletal-dynamics assays
- Cell-migration and adhesion assays
- Angiogenesis-signaling models in endothelial cells
- Studies of the N-terminal Ac-SDKP tetrapeptide fragment
Available formats: TB-500, BPC-157 + TB-500 blend, GLOW and KLOW. COAs are posted on our COA page.
Research materials referenced in this guide
Frequently Asked Questions
Is TB-500 the same as Thymosin Beta-4?
TB-500 is a supplier name for Thymosin Beta-4. Ours is the full-length 43-residue acetylated peptide, CAS 77591-33-4.
What does Thymosin Beta-4 do in cells?
In cell biology it sequesters G-actin, regulating the pool of actin available for filament assembly.
Is TB-500 for human use?
No. It is supplied for laboratory research use only.
Selected References
Peer-reviewed literature on the compounds discussed in this guide, listed as scientific background for laboratory researchers. Citation does not imply endorsement by the authors or any use other than in-vitro research.
- Nachmias VT. Small actin-binding proteins: the beta-thymosin family. Curr Opin Cell Biol. 1993;5(1):56-62. PubMed 8448031 · DOI
- Dedova IV, et al. Thymosin beta4 induces a conformational change in actin monomers. Biophys J. 2006;90(3):985-92. PubMed 16272441 · DOI
Laboratory note: solubility depends on salt form and solvent. This guide does not state a single solubility figure. Handling of lyophilized material is described in the peptide storage guide.
Research Use Only Notice
This guide is provided for educational and laboratory reference purposes. It summarizes published, primarily in-vitro and structural research literature and does not describe, recommend or imply any use in humans or animals. Products sold by Cleared Peptides are for laboratory research use only; they are not drugs, foods, cosmetics or dietary supplements, are not FDA-approved, and are not intended to diagnose, treat, cure, mitigate or prevent any disease. No dosing, administration or therapeutic information is provided.
