Research use only. The information below concerns laboratory reference materials for in-vitro research and makes no medical, therapeutic, diagnostic, cosmetic or performance claims.
“TB-500” and “Thymosin β4” are often treated as synonyms, but for reference-material labelling they can denote two different molecules. This note explains the distinction so the correct identity data is used.
The fragment
“TB-500” most precisely denotes the N-acetylated fragment of Thymosin β4 containing the actin-binding motif (residues 17-23), with its own molecular formula, molecular weight and CAS number.
The full-length protein
Full-length Thymosin β4 is a 43-amino-acid peptide with a substantially higher molecular weight and a different CAS number. Some suppliers label full-length material as “TB-500”.
Why it matters for the lab
Because the two forms differ in mass, a concentration calculated for one is incorrect for the other. Always confirm which molecule a COA and its mass-spectrometry identity describe before using the data. VERIPHASE lists the fragment and the full-length form as separate reference materials.