TB-500 5 mg

What is TB-500?

TB-500 is the usual name for a short synthetic fragment of thymosin β4. Thymosin β4 itself is a protein of 43 amino acids that binds monomeric actin (G-actin) in cells and thereby keeps it from being incorporated into actin filaments. The analytical literature and substance databases define TB-500 as an N-terminally acetylated heptapeptide with the sequence Ac-LKKTETQ. It corresponds to positions 17 to 23 of the mature human protein. Common spellings are TB500 and TB 500; a more systematic name is N-acetyl-thymosin β4 (17–23).

Structure and key data

• Sequence (literature definition): Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH
• Chain length: 7 amino acids
• End groups: acetyl group at the N-terminus, free carboxylic acid at the C-terminus
• Origin of the sequence: positions 17–23 of thymosin β4 (gene TMSB4X, UniProt P62328)
• Parent protein for comparison: thymosin β4, 43 amino acids, around 4963 g/mol, CAS 77591-33-4

With two lysines, two threonines, one glutamate and one glutamine, the sequence is predominantly polar; the N-terminal leucine is the only residue with a non-polar side chain. The acetyl group at the start of the chain is part of the definition of the fragment and distinguishes it from the unmodified sequence LKKTETQ.

Classification: TB-500, thymosin β4 and BPC-157

The fragment should not be equated with full-length thymosin β4: it contains seven of the 43 amino acids, roughly one sixth of the chain. The tetrapeptide Ac-SDKP, which covers positions 1 to 4 and does not overlap with the TB-500 section, also derives from the same protein. Within the range, TB-500 belongs to the Peptide Fragments category. There it sits alongside BPC-157, an unmodified pentadecapeptide of different origin. For work with both molecules there is also the BPC-157 + TB500 set.

Research context

The literature describes the sequence LKKTETQ as the actin-binding region of thymosin β4 and associates it with cell migration. The fragment is therefore investigated in in-vitro work on cell migration and the dynamics of the actin cytoskeleton, as well as in preclinical angiogenesis models. There is also an analytical strand of research: LC-MS methods have been described for the acetylated heptapeptide that allow it to be detected in biological samples.

Analytics at GPeptides

Mass spectrometry is particularly important for TB-500 because the name is not used consistently. In product descriptions on the market, full-length thymosin β4 sometimes appears under this name as well. The two molecules differ in mass by more than a factor of five: around 0.9 kDa for the acetylated heptapeptide, around 5 kDa for the full protein. An MS measurement therefore identifies the contents of a vial unambiguously, while HPLC indicates the proportion of the target compound in the sample as a whole.

TB-500 is regularly tested externally by HPLC and mass spectrometry in an independent laboratory. Published certificates are available in the lab area; where a document is missing, the product is listed there as pending. How both methods work is explained in the guide HPLC and mass spectrometry.