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TB-500 is a synthetic heptapeptide based on a short region of thymosin beta-4 (Tβ4), not the full protein. PubChem records it as Ac-LKKTETQ: residues 17–23 of Tβ4 with an acetyl group added to the N-terminus.1 The fragment weighs about 889 g/mol and the full 43-residue protein about 4,963 g/mol, so the two are easy to tell apart analytically and should never be confused in the literature.1
This profile describes the compound as a laboratory chemical: identity, structure, analytical checks, handling and regulation. Titan Peptides supplies it for laboratory and research use only; it is not for human consumption.
Analytical laboratories that examined products sold under the TB-500 name identified the key ingredient by liquid chromatography with high-resolution mass spectrometry as the N-terminally acetylated 17–23 fragment of human Tβ4, and confirmed the assignment by making the same peptide by solid-phase synthesis. PubChem's record for TB-500 lists the same structure, Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH.1
| Property | TB-500 | Thymosin beta-4 (full length) |
|---|---|---|
| Class | Synthetic N-acetylated heptapeptide | Naturally occurring 43-residue peptide, N-terminally acetylated |
| Sequence (one-letter) | Ac-LKKTETQ | Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES |
| Molecular formula (PubChem) | C38H68N10O14 | C212H350N56O78S |
| Molar mass (PubChem) | 889.0 g/mol | 4963 g/mol |
| CAS number | 885340-08-9 | 77591-33-4 |
| PubChem CID | 62707662 | 16132341 |
| Origin | Synthetic copy of Tβ4 residues 17–23 with an added N-terminal acetyl group | Encoded by the TMSB4X gene |
| Other names | TB 500 | Tβ4, timbetasin, Fx peptide |
Values are from the PubChem records for each compound; the sequence and gene are from UniProt entry P62328.12
Tβ4 is a highly conserved, acidic peptide of 43 amino acids. Its best-established role is structural: it binds monomeric (G-) actin and is regarded as the main G-actin-sequestering peptide in mammalian cells, which affects how cells build and remodel their actin cytoskeleton. The LKKTETQ region sits at the centre of the molecule: a 2010 review describes it as the central actin-binding domain plus one additional amino acid, which is why that short sequence was singled out.3 The fragment lacks the rest of the protein.
Because TB-500 is a product name rather than a pharmacopoeial substance, identity checks matter more than usual. Documentation should state the sequence and an observed mass that matches it: about 889 g/mol for Ac-LKKTETQ, or about 4,963 g/mol for full-length Tβ4. The two differ by more than 4,000 g/mol, which mass spectrometry resolves easily. A missing N-terminal acetyl group lowers the mass by 42 Da, enough to tell the acetylated fragment from the free heptapeptide. Our explainer on how HPLC and mass spectrometry test peptide identity and purity covers what those figures mean in practice.
Store the sealed vial dry, dark and frozen at −20 °C or colder (−50 to −80 °C for long-term storage), and let it warm to room temperature in a desiccator before opening. The C-terminal glutamine is one of the residues the storage literature flags as prone to deamidation, which is a reason not to keep TB-500 in solution for long: split a reconstituted stock into single-use aliquots, freeze them, and do not refreeze a thawed aliquot. See storing lyophilised and reconstituted peptides.
In the June 2026 Poisons Standard, TB-500 and thymosin beta 4 each have their own entry in Schedule 4 (prescription-only medicines), and each is also listed in Appendix D, clause 5, which covers poisons that "must not be possessed by a person without authority".4 The TGA's 13 April 2026 safety advisory names TB-500 among its examples of unapproved peptide products and states that a "research use only" disclaimer does not make supply lawful.5 Scheduling is implemented through state and territory legislation; our guide are research peptides legal in Australia? explains how that works.
No. Products sold as TB-500 contain Ac-LKKTETQ, a synthetic, N-acetylated copy of residues 17 to 23 of thymosin beta-4, which is itself a 43-residue peptide. The fragment weighs about 889 g/mol against about 4,963 g/mol for the full protein, so data on one should not be attributed to the other.
PubChem identifies TB-500 as Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, written Ac-LKKTETQ, with molecular formula C38H68N10O14, molar mass 889.0 g/mol and CAS number 885340-08-9. It corresponds to residues 17 to 23 of mature thymosin beta-4, with an acetyl group added to the N-terminal leucine.
By mass. Ac-LKKTETQ is about 889 g/mol and full-length thymosin beta-4 about 4,963 g/mol, a difference mass spectrometry resolves easily. A missing N-terminal acetyl group would lower the fragment mass by 42 Da, so the observed mass also confirms the acetylation.
In the June 2026 Poisons Standard, TB-500 and thymosin beta 4 are both listed in Schedule 4 and both appear in Appendix D, clause 5, which covers poisons that must not be possessed without authority. The TGA names TB-500 as an unapproved peptide product. Scheduling is applied through state and territory legislation.
A chemical profile of BPC-157: the 15-residue sequence and its identifiers, salt forms, how identity is checked in the laboratory, storage, and its place in the Australian Poisons Standard.
How reverse-phase HPLC and mass spectrometry are used to test peptide purity and identity, how to read a chromatogram and a mass spectrum, and what each method cannot tell you.
What the TGA, the June 2026 Poisons Standard, the Therapeutic Goods Act and customs law actually say about peptides, "research use only" labels, import controls and advertising in Australia.
