What it is
Thymosin alpha-1 is a peptide of twenty-eight residues, originally characterised from thymic tissue and now made synthetically. Its distinguishing structural feature is at the front of the chain: the N-terminal amine is acetylated, capped with an acetyl group rather than left free.
That cap is not a synthesis convenience. It is present in the natural molecule, and a preparation lacking it is a different substance from the one the literature describes.
| Property | Value | Where it is confirmed |
|---|---|---|
| Residue count | 28 | Synthesis record |
| N-terminal modification | Acetyl group | Synthesis record; identity result |
| Approximate mass | near 3,108 g/mol | Certificate of analysis |
| Character | Strongly acidic; many Asp and Glu residues | Structure |
| Physical form supplied | Lyophilized solid | Label and batch record |
The 42-unit check
An acetyl group adds about 42 mass units. Material that failed to receive the cap therefore weighs roughly 42 less than the finished compound — a difference far beyond any method's tolerance and trivially resolvable where identity is reported by mass.
This makes uncapped material the single most useful impurity to look for, and it belongs to a pattern that recurs across this library: a compound defined by an addition fails by that addition being absent. The DAC linker on CJC-1295, the hexenoyl group on Tesamorelin, and the acetyl cap here are the same situation three times over. In each case the impurity is itself a legitimate peptide — which is exactly why it needs ruling out rather than assuming.
What else the sequence predicts
- Twenty-eight residues is a substantial synthesis. Deletion sequences are the expected impurity class alongside uncapped material, and they elute close to the main peak.
- The chain is strongly acidic. A high proportion of aspartic and glutamic acid residues makes the molecule very polar, which affects retention and means the method has to be chosen for it. Adjacent aspartate residues also raise the backbone-rearrangement route described under BPC-157 — a species of identical mass that only chromatography separates.
- No methionine or cysteine. Oxidation is not the primary degradation route.
Where identity is reported as HPLC-RTM rather than by mass, the reference standard is what establishes that the cap is present, so the report should name it.
Storage of the lyophilized solid
Supplied as a freeze-dried solid, governed by temperature and moisture. The acidic side chains make this compound markedly hygroscopic, and adsorbed water is what enables the aspartate chemistry noted above to proceed in what looks like a dry solid.
Stability is a documented property rather than an assumed one: a laboratory establishes it by holding material under defined conditions and re-analysing at intervals. Where a retest date is stated, the question worth asking is what data supports it. See storing lyophilized research materials.
Scope of this documentation
This page concerns material identification and analytical documentation for laboratory research. It does not recommend personal, human, clinical, therapeutic or veterinary applications. Published research findings do not establish the properties of Arctic stock; use the applicable lot record and its stated methods and limitations.
Related documentation
Material on this site
The documentation this article describes is published per lot for the listings below. Match the lot number on a vial label to its record before relying on it.
- Research materials catalog — current listings with batch status
- Batch COA library — every currently published report with its verification link