"TB-500" is one of the most searched names in the research peptide market, and one of the least precise. It is a trade name, not a scientific one, and different suppliers use it for different molecules. This reference explains what Thymosin Beta-4 is, what TB-500 can refer to, and how to confirm what a given vial contains.
Thymosin Beta-4
Thymosin Beta-4 was first characterised from the same calf thymus extract, thymosin fraction 5, that yielded Thymosin Alpha-1. Its complete amino acid sequence was reported in 1981 by Low, Hu and Goldstein in the Proceedings of the National Academy of Sciences. Despite the name, it turned out to be found in nearly every cell type, not just the thymus.
- Length: 43 amino acids, with an acetylated N-terminus.
- Molecular weight: approximately 4,963 Da.
- Best-known role: it binds monomeric (G-) actin and is one of the main actin-sequestering molecules in cells, which is why it appears so often in cell-migration and cytoskeleton research.
The stretch of the sequence most associated with actin binding is a short motif, LKKTETQ, at residues 17 to 23.
What "TB-500" can mean
Across the research market, TB-500 is used for at least two different materials:
- Full-length synthetic Thymosin Beta-4 (43 residues, about 4,963 Da).
- A short synthetic fragment built around the LKKTETQ actin-binding region, sometimes N-acetylated. These fragments weigh well under 1,000 Da.
Both are legitimate research materials, but they are not interchangeable, and a study designed around one will not translate to the other.
How to tell which one you have
The certificate of analysis answers this immediately. Look at the mass spectrometry result:
- An observed mass near 4,960 Da means full-length Thymosin Beta-4.
- An observed mass in the hundreds of daltons means a short fragment.
If the certificate gives only a purity figure and no mass, it hasn't confirmed what the material is. What a certificate of analysis shows covers this in detail.
Handling
Store lyophilized material sealed at -20°C, protected from light and moisture. See how lyophilized peptides should be stored and shipped.
Reference
Low TLK, Hu SK, Goldstein AL. Complete amino acid sequence of bovine thymosin β4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations. Proceedings of the National Academy of Sciences USA, 1981.
Related
Browse TB-500, the BPC-157 pairings, or the full Angiogenesis & Vascular Biology collection.
For research use only. Not for human consumption. This article describes the published chemistry of a research compound and is not guidance for any human or veterinary use.
