Thymulin
Also known as Serum thymic factor, FTS, Facteur thymique sérique, Zinc-thymulin
Thymulin is a defined thymic nonapeptide, also called serum thymic factor (FTS), studied in immune and immunosenescence research. Notable for its zinc dependence. A professional-use profile with no claims about effects.
Thymulin is a nonapeptide associated with the thymus — the organ where T-cells mature — and was originally characterized as a circulating thymic factor, which is where the older name serum thymic factor, or FTS, comes from. Unlike a tissue-derived fraction, it is one molecule with one sequence and one exact mass, so it can be identified against a public database entry and reported on a certificate as a single identity.
The detail most often missed is the zinc. The literature describes thymulin's characteristic form as a zinc-coupled complex, and discussions of the peptide routinely distinguish the apo-peptide from zinc-thymulin. That is a materials point rather than a claim about what it does in anything.
This page describes what thymulin is as a material and where it appears in the literature. It makes no claims about effects in a person or animal.
Thymulin is a single defined nonapeptide — pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn — with the molecular formula C33H54N12O15 and a mass of 858.86 g·mol⁻¹ (CAS 63958-90-7). One characterization point separates it from most peptides in a catalogue: thymulin is described in the literature as zinc-dependent, the peptide coupling with a zinc ion to form zinc-thymulin. The metal is treated as part of what defines the active species rather than an impurity, which is why zinc content appears in discussions of thymulin preparations.
A defined peptide, and why the name matters
Thymulin is frequently confused with thymalin, and the names are close enough that catalogues — this one included, until recently — have carried one while describing the other. They are not the same material. Thymulin is a synthetic nonapeptide with a known sequence and exact mass. Thymalin is a polypeptide preparation extracted from thymus tissue: a complex of components rather than a single molecule, with no single sequence or CAS number to print.
The practical consequence is in the paperwork. A defined peptide can be identified on a certificate by a single-peak identity check against a reference; a tissue-derived fraction cannot, and has to rely on the manufacturer's specification for that fraction. If a certificate reports one exact identity and mass, it is describing a defined peptide — whatever the label on the box says.
It is also distinct from thymosin alpha-1, a 28-residue synthetic thymic peptide. All three share a thymic theme and are routinely discussed together, which is precisely why the distinctions are worth stating plainly.
Zinc, and what it means for characterization
Thymulin's association with zinc is unusually load-bearing for a peptide. The literature describes the biologically characterized species as the zinc-coupled form, with the metal treated as part of the molecule of interest rather than a contaminant carried over from synthesis.
For anyone reading a certificate, that is worth knowing because it changes how a metals figure should be interpreted. A heavy-metals specification on a certificate is a purity control and is not the same measurement as the zinc stoichiometry discussed in the thymulin literature. The two are easy to conflate and answer different questions.
The thymic-immune research context
Thymulin appears in immune research through its thymic origin, and in immunosenescence discussions — the study of how immune function changes with age — where thymic involution is a recurring theme. It also surfaces in neuroimmune and pain-signalling literature, which is a narrower and more specialised context.
These are descriptions of where a compound appears in published work. They are not statements that it does anything, and nothing here should be read as suggesting a use.
These are research areas the compound is associated with in the literature — not medical claims or intended uses.
Handling & storage
Supplied lyophilized. Kept sealed and cold; in research settings it is reconstituted only when a protocol requires it, then refrigerated. Because the literature treats the zinc-coupled form as the characterized species, defer to the certificate and product specification for the exact lot rather than assuming a form. Handle per accepted laboratory practice.
Verify a certificate by lot →Common questions
No, and the two are easy to confuse. Thymulin is a single defined nonapeptide with a known sequence, exact mass and CAS number. Thymalin is a polypeptide preparation extracted from thymus tissue — a complex of components rather than one molecule. A certificate reporting one exact identity and mass is describing thymulin.
Both are defined synthetic peptides with a thymic association, but they are different molecules of different length — thymulin is a nonapeptide, thymosin alpha-1 is 28 residues. They are not substitutes for one another and are characterized separately.
The literature describes thymulin's characterized form as zinc-coupled, so zinc is discussed as part of the species of interest rather than as an impurity. Note this is a different question from the heavy-metals limit on a certificate, which is a purity control.
Immune research, given its thymic origin, and immunosenescence research where thymic change with age is a recurring topic. These describe research contexts, not promised effects.
This monograph is a professional-use reference. It describes composition and the contexts in which the compound has been studied — it is not medical advice, a description of effects, or a recommendation for use. Sold strictly for laboratory and research use; not for human or animal consumption.