Forty-three residues, present almost everywhere
Thymosin beta-4 is a 43-amino-acid protein found in nearly every cell type and in most body fluids. Its principal known function is binding actin monomers and regulating how the cytoskeleton is assembled and reorganised.
That role puts it at the centre of cell migration, which is why it turns up in wound healing research, in corneal work and in cardiac injury models.
Actin is among the most abundant proteins in a cell, and keeping a reserve of it unpolymerised is housekeeping rather than signalling. Anything doing that work sits upstream of every process that involves cells changing shape or moving, which is why the research reaches into fields that look unrelated to one another until you notice what they have in common.
The fragment sold as TB-500
TB-500 refers to a short sequence from this protein, generally the region held to carry the actin-binding activity. It is cheaper to synthesise and easier to handle than the full protein, which is why the market settled on it.
The names then merged. Suppliers list TB-500 and describe thymosin beta-4, or the reverse. If you are buying, the certificate of analysis names the actual sequence, and that is the document to go by rather than the product title.
A fragment is not a scaled-down copy of its parent. It can keep one binding interaction and lose others, proteases treat it differently, and it does not necessarily reach the same places. Two molecules sharing a motif can therefore return genuinely different results, which is the practical reason the naming confusion is worth more than a pedantic footnote.
| Length | 43 amino acids |
| Distribution | Most cell types and body fluids |
| Primary function | Actin binding, cytoskeleton regulation |
| Research areas | Wound healing, corneal and cardiac injury |
| Relationship to TB-500 | TB-500 is a short fragment of it |
| Stocked here | The fragment only |
| Closest product | TB-500 peptide pen |
| Category | Research use only |
Facts about what is supplied. Not about what happens next.
What we actually supply
We carry the fragment, listed as TB-500, and we call it that. We do not supply the full 43-residue protein, and we are not going to describe the fragment as though we did.
If your protocol specifically requires the complete protein, we are not the supplier for it. If it requires the fragment, the product page and the compound page are linked below.
For the wider setting, the recovery and repair research area sets out where the injury-model literature on this family is substantial and where it thins to almost nothing. That is the context to have in place before deciding which of the two molecules a protocol is actually asking for.
Telling the two apart on paper
Because one name covers two molecules across this market, the paperwork carries more weight here than it does on a compound with a single unambiguous identity. A certificate that states a sequence settles the question; a certificate that repeats the product title settles nothing. Our guide to checking a certificate covers what a genuine document contains and which omissions are the ones that matter.
A purity figure will not rescue you either, because purity describes how much of a sample is the stated substance without establishing what the stated substance is. The page on what a purity number leaves out works through that distinction with cases rather than assertions.
For the underlying science, the UniProt record for the human protein gives the full sequence, and the indexed literature on PubMed returns the wound healing and cardiac work. An abstract will usually tell you within a sentence or two which of the two molecules a given study used.
Thymosin beta-4 in the catalogue
Analysed and released at 99% and above, with per-lot documentation.
Where Thymosin beta-4 fits in
What to read if this raised more questions than it settled.
About Thymosin beta-4
Your questions, answered as directly as we can.