TB-500: A Research Primer

TB-500 is a synthetic 43-amino-acid peptide, an N-acetylated fragment related to the naturally occurring protein Thymosin Beta-4. It carries CAS number 77591-33-4. That is the identity in two lines, and the rest of this page is the detail behind them.

This is an identity primer, not a usage page. It covers what the molecule is, what the numbers on the label mean, which corners of the research literature reference it, and how it is handled and tested as a reagent. It ships as a laboratory material.

What TB-500 is

TB-500 is a short synthetic peptide sold under a trade-style name, not a distinct chemical class of its own.

The name comes out of research and supplier nomenclature rather than formal chemical naming. Underneath it sits Thymosin Beta-4, a peptide that occurs naturally in cells across many tissues, 43 amino acids long, acetylated at its N-terminus. What a supplier labels TB-500 is a synthetic peptide built to correspond to that structure. Chemists assemble the chain from scratch rather than extracting anything from tissue.

Here is the wrinkle worth knowing before you buy: "TB-500" and "Thymosin Beta-4" get used loosely, and sometimes interchangeably, across catalogs. The trade name on its own does not pin down exactly which chain is in the vial. The registry number does, which is why the chemistry section leads with it.

The chemistry on the label

The one label value that resolves the naming ambiguity is the CAS number, so match it first.

• CAS number: 77591-33-4
• Class: peptide, N-acetylated, related to Thymosin Beta-4
• Length: 43 amino acids
• N-terminus: acetylated
• Other names: Thymosin Beta-4, TB4, T-beta-4

CAS 77591-33-4 registers the 43-residue Thymosin Beta-4 entity, so a certificate that cites it is telling you which molecule the lot is meant to be. Molecular formula and exact molecular weight are worth reading straight off the certificate of analysis rather than off any product description, because sources define their "TB-500" against slightly different boundaries and the mass on the COA is measured against the actual material in the vial. Match the CAS number, then check the reported mass against that specific report. A name can be written a dozen ways; a registry number cannot.

Where it appears in the research literature

TB-500 and Thymosin Beta-4 show up mainly in two areas of published research: tissue research and cell-migration research.

Both are named here as subject areas, nothing more. Naming the field a compound has been studied in is a statement about what researchers have chosen to look at, not about any outcome, and a primer stays on that side of the line. I am deliberately not summarizing what any of those papers reported. This category has a hard boundary between describing a molecule's identity and describing what anyone claims about it, and everything above is on the identity side of that boundary.

If you want to read the underlying studies, "Thymosin Beta-4", "TB-500", and the CAS number are the search terms that surface them faster than the trade name alone.

How it is supplied and handled

It is supplied as a lyophilized, or freeze-dried, solid, stored cold and kept sealed.

TB-500 ships lyophilized because a dry solid travels far better than a solution. Store it at -20C, keep the vial sealed until you are working with it, and limit its exposure to moisture and repeated temperature swings. Kept cold, dark, and sealed, a freeze-dried peptide holds its integrity over long periods. As with most lyophilized peptides there is often a bulking agent in the vial so there is something visible to work with, and a proper certificate accounts for that filler in the reported mass.

That is the whole handling story: storage temperature, an intact seal, and protection from light. None of it is preparation guidance.

How each lot is tested

Every lot gets its own third-party certificate of analysis, and the two figures that matter are identity and purity.

Mass spectrometry confirms the molecule matches the label, which for a 43-residue peptide is the test that actually settles whether you have the intended chain rather than something shorter. HPLC measures purity, meaning how much of the sample is the target peptide versus related impurities, read at 220 nm, the standard wavelength for peptide bonds. Our [TB-500](/products/tb-500) lots are tested at independent third-party laboratories, with the full per-lot COA PDF published on each batch page.

If you have not read one of these documents before, we wrote a walkthrough on [how to read a peptide COA](/research/how-to-read-a-peptide-coa) using two of our own reports, plus a [checklist for buying research peptides in Canada](/research/buying-research-peptides-canada) that covers what else to verify before you order. Kits Peptides ships tracked from Vancouver, BC across Canada.

*All products are supplied as laboratory reagents for research use only. Not for human or veterinary use.*