TB-500: Two Different Substances, One Name

For laboratory research use only. Not for human or veterinary use.

“TB-500” is sold by dozens of suppliers. It refers to two chemically different substances that differ by a factor of five and a half in molecular mass, cost very different amounts to make, and are routinely listed at the same price under the same name.

A mass spectrum separates them instantly. Most certificates in this market never show one.

The two substances

Both are real compounds and both appear in the literature. LKKTETQ is the actin-binding region of Thymosin β4, and it is studied in its own right — it is not a fake. The problem is not that the fragment exists. The problem is that it is sold as the protein.

Why the confusion is profitable

Solid-phase peptide synthesis costs roughly in proportion to chain length, and yield falls with every coupling step. A seven-residue peptide is cheap and easy. A forty-three residue protein is neither.

So a supplier who lists “TB-500 10mg” and ships the fragment has a very large margin advantage over one who ships the protein, at the same shelf price, with no visible difference in the vial. Both are white lyophilised powder. Both dissolve. Nothing about the physical product tells you which you have.

How to tell, in one number

Ask for a certificate that reports mass, and read it:

• A mass near 4963 — full-length Thymosin β4.
• A mass near 889 — the acetylated fragment.
• A mass near 847 — the fragment without its acetyl group, which is a third thing again.
• No mass at all — you cannot tell, and neither can the supplier.

There is no ambiguity here and no rounding to argue about. 4963 and 889 are not close. This is the easiest identity check in the whole peptide market, and it is skipped because a purity figure alone looks like documentation while saying nothing about what was 99% pure.

More on that distinction: a purity figure is not an identity test, and how to read a certificate of analysis.

What we supply, and how to check us

Our TB-500 is the full-length Thymosin β4 acetate, 4963.44 g/mol, and our product page states that formula and weight. Our manufacturer’s certificate for the source material identifies the full-length protein.

Do not take that on trust — it is precisely the claim this page is telling you to verify. Ask us for the batch certificate before you order, check the mass on it, and if it does not say 4963, ask us why. That is a reasonable question and we would rather answer it than have you assume.

Where we are not yet able to show you everything

Stated plainly, because a page about verification is worthless if it is selective.

The certificates we publish in the COA library for our two-component and four-component blends report the quantity of each component, not the mass of each. Quantity answers “how much”; it does not answer “of what”. We have gone back to the laboratory to confirm what was measured against for the TB-500 component in those blends, and we will publish the answer here when we have it, whichever way it goes.

Until then: the identity claim above rests on the manufacturer’s certificate for the source material, not on a published independent mass for every blend batch. That is a weaker chain than we would like and you are entitled to know it is weaker.

Handling

Supplied lyophilised. Store the sealed vial at −20°C, protected from light. Reconstitute with bacteriostatic or sterile water run down the vial wall, never onto the powder; swirl, do not shake. A 43-residue protein has structure to lose, so foaming is denaturation rather than a cosmetic problem — see how much is actually in the vial for why the bigger molecule is the more fragile one, and how to reconstitute research peptides for technique.

What this page does not claim

Nothing here concerns what either substance does in an organism. Thymosin β4 is the subject of a research literature that is overwhelmingly preclinical, the fragment more so, and neither is a licensed medicine in the United Kingdom. This page is about which molecule is in the vial — a question that has a definite answer, unlike most of the claims made about this compound.

In our catalogue

We supply the full-length form. The product page states the formula and the mass, which is the claim this page tells you to check:

• TB-500 — full-length Thymosin β4 acetate, 4963.44 g/mol
• BPC-157 / TB-500 Blend — the two-component blend
• KLOW Blend — the four-component blend
• GLOW Blend — BPC-157 + GHK-Cu + TB-500

Pioneer Research Peptides — UK supplier of research peptides and laboratory solvents.

For laboratory research use only — not for human consumption. 18+.