a cut-and-paste research zine ~ zinc-bound thymic nonapeptide
Every study on thymulin — the zinc-bound thymic nonapeptide — clipped, taped down, and labelled.
Nine amino acids. Active only when a zinc ion clips on. We pin each finding to the board, tag what it shows, and leave the human-data gaps in plain sight.
The short version
Most of what circulates online about thymulin mixes it up with two other thymic peptides. Here is the molecule itself, plainly. Thymulin is a small hormone made by the thymus (the immune-training gland behind the breastbone). It is a nonapeptide — a chain of nine amino-acid building blocks — and it only switches on when a single zinc atom clips onto it. No zinc, no activity. It is not a supplement, not FDA-approved, and not the same thing as thymosin alpha-1 or thymosin beta-4. This site clips out the actual studies and labels what each one really shows.
What Is Thymulin?
Thymulin is a zinc-dependent thymic nonapeptide hormone with the sequence pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, produced exclusively by thymic epithelial cells (the gland's lining cells that actually build the peptide) [4]. Its biological activity depends entirely on one bound zinc ion per molecule; chelate the zinc away and the activity disappears, add zinc back and it returns [1]. That single fact — zinc on, switch on; zinc off, switch off — is the defining feature of the molecule [2].
Thymulin circulates from birth, peaks in childhood, and falls with age and with zinc deficiency [2][4]. It is handled strictly as a research peptide for laboratory use. It is not approved by the FDA for any indication, it is not a dietary supplement, and the bulk of its record sits in cell and animal models. We do not sell it, dose it, or tell you to take it; we clip the literature and label it.
The other thing worth saying up front: this peptide gets confused with thymosin alpha-1 and with thymalin (a bovine thymic complex) constantly. They are chemically and pharmacologically distinct. This site describes thymulin only, and never borrows another peptide's data for it.
Thymulin Peptide: Identity and Sequence
The thymulin peptide is a linear nonapeptide — nine residues, sequence <Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, molecular formula C33H54N12O15, molecular weight about 858.9 Da [4]. Its registry identifiers are CAS 63958-90-7, UNII 9H198D04WL, and PubChem CID 3085284. Those are the stamps on the specimen label; the science is the zinc.
A couple of the residue names are worth unpacking, because they explain the "pyroGlu" you keep seeing. The chain starts with a pyroglutamate (written pyroGlu or <Glu) — a glutamate whose end has curled into a ring — and ends in asparagine, with a lysine, two serines, a glutamine, and three glycines in between. Nine building blocks, in that fixed order; change them and it is a different peptide [4]. The thymulin peptide is produced by thymic epithelial cells and nothing else, which is part of why it is a clean marker of thymic activity [4].
When zinc binds in a 1:1 molar ratio, the peptide folds into a specific three-dimensional shape that nuclear magnetic resonance (NMR) studies can detect — and that conformation is what makes it active [2]. The zinc-free version, sometimes called apothymulin, has the same nine residues but none of the activity [1]. So "thymulin" is, precisely, the zinc-bound form of an otherwise inert peptide. The chemistry and the biology are the same sentence: the metal is the on-switch. The deep dive lives on the zinc-dependence of thymulin page.
Thymulin and Serum Thymic Factor (FTS)
If you have read older papers, you have met thymulin under a different name. "Serum thymic factor" — FTS, from the French facteur thymique serique — is the original label for this molecule. The two names are two states of one peptide: FTS is the bare peptide, thymulin is FTS with zinc clipped on [1].
The 1982 work that nailed down the zinc requirement is also where the name changed: after showing that chelating the metal abolished activity and that equimolar zinc restored it, the authors proposed calling the zinc-bound active form "thymulin" (FTS-Zn) [1]. So every time you see FTS in a citation here, read it as the same molecule, one zinc ion shy of its active self. It is a small palimpsest — the previous name struck through, the new one taped over it — and it is the honest history of the compound.
How Thymulin Is Different from Thymosin Alpha-1 (Distinct Peptides)
This is the section we most want you to read, because the internet gets it wrong constantly. Thymulin vs thymosin alpha 1 is not a comparison of two doses of the same thing — they are two different molecules. Thymulin is a zinc-dependent nonapeptide that is active only when zinc-bound [1]. Thymosin alpha-1 is a separate, larger thymic peptide with a different sequence, a different mechanism, and an entirely different research literature.
Thymulin is also distinct from thymosin beta-4 (the parent protein behind the TB-500 fragment) and from thymalin, the bovine thymic polypeptide complex. Consumer sources routinely blur all of these into one "thymic peptide" bucket; the studies do not. The confusion is not harmless: it leads people to attach one peptide's findings to another, and to assume a result shown for one molecule applies to thymulin. It does not. They differ in size, in sequence, in mechanism, and in the conditions they have been studied in.
On this site, when we cite a thymulin finding, it is a thymulin finding — we never describe thymulin's research using another peptide's data, and we never claim thymulin is one of them. Where a study used a thymulin analog rather than the native peptide (the 1980s human trials used synthetic nonathymulin), we say so on the clipping [14]. If you want the thymulin research findings themselves, they are clipped, dated, and tagged on the research page.
What the Clippings Cover
The literature on thymulin is thin and patched-together, which is exactly why a clip-and-label format fits it. The strongest, best-grounded findings are the chemistry: zinc is required for activity (1982) [1], serum thymulin activity tracks zinc status in humans and is corrected by zinc repletion (1988) [3], and the zinc-bound form adopts a defined conformation (1994 review) [2].
Beyond the chemistry, the dealt lens here is metabolic and autoimmune research — preclinical work in mice and in patient-cell assays. In animal models thymulin has shown anti-inflammatory activity through suppression of NF-kB (a master switch that turns inflammation genes on) [6], and a single inhaled gene-therapy dose reversed established asthma pathology in mice [7]. Those are findings in models, not human treatments. The thymulin immune-function research page lays them out with the limits stencilled on. Doses live on the thymulin dosage in the literature page — as study findings in named species, never as a protocol. Quick questions get quick answers in the thymulin FAQ.