Thymosin alpha-1 (thymalfasin) CAS, molecular weight and sequence: analytical reference for lab procurement

Use CAS 62304-98-7, formula C129H215N33O55 and an average mass of 3108.3 g/mol. PubChem CID 16130571 is the structure record behind those values, and UniProt P06454 shows where the sequence comes from: residues 2–29 of prothymosin alpha, with the serine at position 2 acetylated.

PubChem also carries two other CAS-format numbers among its depositor synonyms. Keep 62304-98-7 as the primary identifier so receiving logs and certificates match.

1. CAS 62304-98-7 and the names thymosin alpha-1 / thymalfasin on the PO.
2. Formula C129H215N33O55 and MW 3108.3 g/mol on the analytical worksheet.
3. The full sequence with the N-acetyl group written out, so a non-acetylated product cannot pass as identical.

García-Ramos et al. describe thymosin alpha-1 as a difficult sequence for stepwise solid-phase synthesis: it has runs of β-branched residues (Val, Ile, Thr), a tendency to form β-sheet structures on the resin, and needs up to 20 side-chain protecting groups. Difficult couplings tend to leave deletion peptides that are one residue short and elute close to the main peak.

Schmidt et al. describe a chemo-enzymatic route that joins two 14-residue halves. Whatever the route, the analytical questions are the same: is the N-terminal acetyl present, are any residues missing, and have any aspartate residues rearranged.

1. −42.01 Da: des-acetyl peptide (free N-terminal serine).
2. −18.01 Da: aspartimide (succinimide) at an Asp residue; it can reopen to iso-Asp at the original mass, which only chromatography resolves.
3. +0.984 Da: deamidation of the C-terminal Asn.
4. Whole-residue losses, for example −99.07 Da (Val) or −101.05 Da (Thr): deletion sequences.

Thymosin alpha-1 contains no tryptophan, tyrosine or phenylalanine, so it has essentially no absorbance at 280 nm. Purity must be measured at the peptide-bond wavelength (214–220 nm), and concentration cannot be estimated from an A280 reading. A certificate that reports purity at 280 nm for this peptide should be questioned.

The peptide is strongly acidic (about −6 at pH 7) and highly polar. Reversed-phase C18 methods with 0.1% TFA in water and acetonitrile are the usual starting point; a useful report states the column, gradient, wavelength and the integration rule behind the area-percent number.

Electrospray spectra show a charge-state series rather than one ion. Calculated monoisotopic values are m/z 1036.51 (3+), 777.63 (4+) and 622.31 (5+). On a low-resolution instrument the observed peak tops sit nearer the average-mass values (about 1037.1, 778.1 and 622.7) because the isotope envelope is broad at this size.

Deconvolute the series to a neutral mass and compare it with 3106.50 Da (monoisotopic) or 3108.3 Da (average), stating which one the report uses. A result about 42 Da low points to the des-acetyl form.

No third-party lot report for thymosin alpha-1 is published on this site yet. A lab report is available on request for the lot you would receive, and the batch number on the vial can be checked on the lot lookup page. Only some lots have a published COA.

Self-serve orders from the United States (Canada and Mexico are paused) use US fulfillment and usually ship within 5 business days of confirmed payment. Credentialed laboratories in other eligible countries can request an institutional export review through the international lab orders page. Self-serve shipping is not offered to Australia, New Zealand or OFAC-sanctioned destinations.