Is tuftsin the same as Selank?

No. Tuftsin is the four-residue peptide Thr-Lys-Pro-Arg. Selank is tuftsin plus a Pro-Gly-Pro extension, making seven residues.

Where does tuftsin come from?

It is released by enzymatic cleavage from the heavy chain of immunoglobulin G — the antibody itself serves as the precursor.

Does tuftsin have neurological activity?

Its classical characterisation is immunological, centred on phagocytic stimulation. How that relates to Selank's reported central effects is not fully resolved.

Selank (Tuftsin Analogue)

What Is Tuftsin? An Immunopeptide From Antibody

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-233 cited sources

Tuftsin is a tetrapeptide, Thr-Lys-Pro-Arg, released by enzymatic cleavage from the heavy chain of immunoglobulin G. It stimulates phagocytic activity in macrophages and neutrophils, and forms the first four residues of Selank. Its literature is roughly five times larger than Selank's.

Key facts

Sequence: Thr-Lys-Pro-Arg (TKPR)
Length: 4 residues
Molecular weight: 500.6 Da
Molecular formula: C21H40N8O6
PubChem CID: 156080
Origin: IgG heavy chain, Fc region
Classical activity: Stimulates phagocytosis
PubMed records: ~690

A peptide that comes out of an antibody

Tuftsin is not synthesised as an independent gene product. It is liberated by enzymatic cleavage from a specific region of the immunoglobulin G heavy chain, meaning the antibody itself acts as a precursor for a short signalling peptide. That is an unusual arrangement, and it is why tuftsin is described as an immunopeptide rather than a hormone.

What it was found to do

The classical activity, characterised across decades of work summarised in Fridkin's 1989 review in Critical Reviews in Biochemistry and Molecular Biology, is stimulation of phagocytic activity in macrophages and neutrophils — enhancing their capacity to engulf and destroy targets. This places tuftsin squarely in innate immune signalling rather than in neuropharmacology.

Research material referenced

Selank 10mg — third-party HPLC tested

View — £24.99

Why a peptide named for immunity ended up in a neuroactive compound

This is the part worth understanding. Selank's reported activity is largely neurochemical — enkephalin stabilisation, GABAergic effects, BDNF expression — which is not what tuftsin's immunological characterisation would predict. The honest position is that appending Pro-Gly-Pro produced a molecule whose reported profile is not simply a longer-lasting tuftsin, and that the relationship between the parent's immune activity and the analogue's reported central effects is not fully resolved in the literature.

The parent is better studied than the analogue

PubMed indexes roughly 690 tuftsin records against approximately 135 for Selank. That inversion is unusual and worth noting: for most designed analogues the derivative accumulates the literature. Here the naturally occurring parent has five times more, reflecting decades of immunological interest predating Selank entirely.

Why tuftsin itself is not used

Rapid enzymatic degradation. A four-residue peptide with no protective modification is cleared very quickly, which limits what can be done with it experimentally and rules it out as a practical agent. That constraint is the entire reason the Pro-Gly-Pro extension exists.

Extended research context

The Selank (Tuftsin Analogue) deep dive

Deep dive: preserving a signal rather than supplying one

Selank's most specifically characterised activity is not receptor binding. Work published in the Bulletin of Experimental Biology and Medicine in 2001 and 2002 reported that it inhibits enkephalin-degrading enzymes, measured directly on plasma enkephalinase activity, thereby extending the half-life of endogenous enkephalins rather than acting at opioid receptors itself. That distinction is routinely muddled and it matters: an agonist activates the receptor wherever the drug reaches, at whatever concentration is given, while a degradation inhibitor only lets the ligand the body is already releasing persist longer. The effect is bounded by endogenous release and occurs only where that release happens. The same logic underlies DPP-4 inhibitors in the incretin field, which prolong native GLP-1 rather than supplying an analogue - and instructively, that class produces much smaller effects than the receptor agonists do.

Deep dive: what the sequence does and does not contain

TKPRPGP is unusual among research peptides for what is absent from it. There is no cysteine, so no disulfide bonds form or scramble and no reducing agent is needed. There is no methionine, so the thioether oxidation that adds 16 Da and dominates handling guidance for MOTS-c and Semax does not apply. There is no asparagine or glutamine either, ruling out deamidation. What remains is straightforward hydrolysis, and three prolines in seven residues resist even enzymatic cleavage well, because proline locks the backbone rotation peptidases require. One practical cost of that composition: no aromatic residues means almost no absorbance at 280 nm, so the standard spectrophotometric quantification method does not work on it.

Deep dive: reading a two-literature evidence base

PubMed indexes roughly 135 Selank records against about 690 for its parent peptide tuftsin - an inversion worth noticing, since most designed analogues eventually outgrow the parent they replaced. Most of the tuftsin literature is immunological and predates Selank entirely, so it is not evidence about Selank. Within Selank's own record the split is the same one Semax shows: mechanistic work in internationally indexed journals, assessable directly; clinical work concentrated in Russian-language publications, indexed by translated title and often without accessible English full text. That is evidence which is hard to verify independently, which is not the same as evidence that is absent, and not the same as evidence that is established.

Research applications

▸Enkephalin and enkephalinase pathway research
▸GABAergic receptor expression studies in rodent models
▸BDNF expression research, including intranasal administration routes
▸Comparative work on proline-stabilised peptide design
▸Tuftsin and immunopeptide structure-activity research

Handling checklist

✓Store lyophilised material cold, dry and protected from light
✓No reducing agent needed — the sequence contains no cysteine
✓No methionine oxidation to expect; a +16 Da satellite warrants explanation
✓Do not rely on 280 nm absorbance — there are no aromatic residues
✓Introduce diluent gently against the vial wall; swirl rather than shake
✓Aliquot to avoid repeated freeze-thaw cycles

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Describing Selank as an opioid or opioid agonist

Fix: Reported work describes inhibition of enkephalin-degrading enzymes, not receptor binding. It preserves endogenous enkephalins rather than supplying an agonist.

✗ Treating the benzodiazepine contrast as a safety claim

Fix: The mechanistic difference is real — expression-level rather than direct allosteric modulation — but it supports no comparative claim about safety or dependence.

✗ Citing tuftsin literature as evidence about Selank

Fix: Tuftsin has roughly five times more papers, most of them immunological and predating Selank. They are different compounds.

✗ Reading a BDNF expression change as a demonstrated outcome

Fix: The work measured expression in rat hippocampus. Expression is upstream of function and upstream again of any clinical claim.

✗ Treating Russian registration as equivalent to MHRA approval

Fix: Authorisations are jurisdictional and do not transfer. Selank has never been assessed by the MHRA, EMA or FDA.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

Is tuftsin the same as Selank?: No. Tuftsin is the four-residue peptide Thr-Lys-Pro-Arg. Selank is tuftsin plus a Pro-Gly-Pro extension, making seven residues.
Where does tuftsin come from?: It is released by enzymatic cleavage from the heavy chain of immunoglobulin G — the antibody itself serves as the precursor.
Does tuftsin have neurological activity?: Its classical characterisation is immunological, centred on phagocytic stimulation. How that relates to Selank's reported central effects is not fully resolved.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

How we write and check this content Report a factual error in this article

More Selank (Tuftsin Analogue) articles

Popular across the research hub

One flagship guide from every other research category — keep exploring.

← Back to Forum