Selank Peptide: Molecular Structure, Mechanism, and Research Overview

What Selank is

Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow ^[2]. It is built from tuftsin, a naturally occurring tetrapeptide, with three extra residues attached to slow its breakdown. In the chemical literature it also appears as TP-7.

Its public record is unusually well defined for a research peptide. PubChem lists Selank under CID 11765600 with the molecular formula C33H57N11O9, a molecular weight of 751.9 and CAS number 129954-34-3 ^[1]. Those three values give anyone holding a certificate of analysis something concrete to check it against, which is where this guide starts.

Precise Pep Labs sells Selank 10mg for in vitro research use only. Nothing here describes or recommends use in people or animals, and nothing here is a protocol.

Structure: a tuftsin fragment with a stabilising tail

Tuftsin, the parent sequence

Tuftsin is the tetrapeptide Thr-Lys-Pro-Arg, a fragment released from the heavy chain of immunoglobulin G. It has its own substantial literature as an immunomodulator, and a large family of synthetic analogues has been built from it over several decades ^[3]. PubChem gives tuftsin the formula C21H40N8O6 and a molecular weight of 500.6 ^[4].

What the Pro-Gly-Pro extension changes

Selank is tuftsin with Pro-Gly-Pro added at the carboxyl end. The purpose of that extension is pharmacokinetic rather than pharmacological: short peptides are cleaved rapidly by peptidases, and the proline-rich tail is intended to slow that degradation. The same design appears in Semax, which takes a fragment of adrenocorticotropic hormone and adds the identical Pro-Gly-Pro tail; the two compounds share a stabilisation strategy but start from unrelated parent sequences ^[17].

This is worth stating carefully. A longer half-life is a property of the molecule's chemistry. It is not, by itself, evidence of any biological effect, and the published work on the extension's consequences is discussed further down rather than assumed here.

The three molecules side by side

Selank and Semax are frequently sold and discussed together. They are different molecules from different origins, and a result for one says nothing about the other.

Checking a certificate against the public record

Most compound guides stop at naming the sequence. For a laboratory receiving a vial, the more useful exercise is checking whether the paperwork is internally consistent with a public reference.

Three fields make that possible for Selank: the molecular formula, the CAS number and the molecular weight. All three are in PubChem ^[1], so a certificate that prints a formula or CAS can be compared directly. Our own Selank certificate prints C33H57N11O9 and CAS 129954-34-3, and both match the PubChem record exactly.

That check is worth doing and worth not overstating. Matching a formula confirms that the document describes the compound it claims to describe. It does not confirm that the powder in the vial is that compound; only a measurement on the material can speak to that, and what such a measurement does and does not establish is covered in the analytical section below and in our guide to reading a certificate of analysis.

What the research investigates

The published work on Selank is mostly preclinical. The sections below describe what was measured, in what system, and what the authors concluded. None of it describes an effect in a person outside the specific clinical studies named later.

Enkephalin-degrading enzymes

The earliest mechanistic proposal concerns enkephalinases. Zozulya and colleagues reported that Selank inhibited enzymatic hydrolysis of plasma enkephalin in a concentration-dependent manner with an IC50 of 15 μM, and was more potent in that assay than the peptidase inhibitors bacitracin and puromycin ^[5]. The same report observed shortened enkephalin half-life and reduced total enkephalinase activity in the blood of patients with generalised anxiety, but not in panic disorder or agoraphobia.

A mouse study then linked the two observations. In BALB/c mice, Selank produced an anxiolytic effect in the open-field test and increased the half-life of plasma leu-enkephalin; in C57Bl/6 mice, the same treatment changed neither behaviour nor enkephalinase activity ^[6]. The strain dependence is the interesting part: the effect was not uniform across genetic backgrounds, which is a constraint on how far any single rodent result can be generalised.

The GABA system, and where the evidence disagrees

The most cited mechanistic claim is that Selank acts on GABAergic signalling. Radioligand work from the originating institute reported that Selank affects [3H]GABA binding as a positive allosteric modulator, that its joint action with certain benzodiazepines is not simply additive, and that it can block the modulatory activity of diazepam and olanzapine — leading the authors to propose subtype-selective, concentration-dependent allosteric modulation of GABA receptors ^[2].

Two gene-expression studies then reached results that do not line up neatly:

• In rat frontal cortex, Selank altered the expression of a large number of genes involved in neurotransmission, with changes in 45 of 84 genes measured at one hour and 22 at three hours, correlating with the changes produced by GABA itself ^[7].
• In cultured human IMR-32 neuroblastoma cells, Selank alone produced no change in the mRNA levels of the GABAergic genes studied. Combined with GABA it largely suppressed the changes GABA produced on its own, and combined with olanzapine it was associated with more altered genes than olanzapine alone ^[8].

The authors of the second study read their own result as partially consistent with an effect on GABA's interaction with its receptor rather than on gene transcription directly. For a reader, the honest summary is narrower: a whole-animal brain region and an isolated human cell line gave different answers, and the mechanism should not be described as settled. Electrophysiology adds a further wrinkle — in rat hippocampal slices Selank increased the amplitude and rate of spontaneous inhibitory postsynaptic currents in CA1 neurons, but across the 1–8 μM range tested the authors reported no significant concentration dependence ^[9].

BDNF and neurotrophic signalling

Two rat studies report effects on brain-derived neurotrophic factor. One found that Selank regulates BDNF expression in the hippocampus in vivo ^[10]. A later study in rats given ethanol as their only fluid for 30 weeks reported that Selank produced a cognitive-stimulating effect in the object recognition test in animals not exposed to ethanol, prevented memory and attention disturbances developing during withdrawal, and prevented an ethanol-induced increase in BDNF in the hippocampus and frontal cortex ^[11].

Note the direction in that last result: Selank prevented an increase in BDNF. "Affects BDNF" is accurate; "raises BDNF" would not be.

Immune and inflammation-related genes

Selank's tuftsin ancestry makes immune endpoints a natural line of enquiry. In mouse spleen, Selank and its short Gly-Pro fragment both altered the expression of C3, Casp1, Il2rg and Xcr1, with a roughly three-fold fall in C3 mRNA thirty minutes after administration. The expression profiles after Selank and after Gly-Pro alone coincided in most cases, which the authors took to suggest that the dipeptide fragment contributes substantially to the parent peptide's effect ^[12].

That last point matters for interpretation. If a breakdown product reproduces much of the observed profile, attributing the result to the intact heptapeptide is not straightforward.

Other preclinical models

Selank has also been examined in a naloxone-precipitated morphine withdrawal model in rats, where it reduced the total withdrawal index by 39.6 % and raised the tactile sensitivity threshold, performing somewhat below diazepam in the same model ^[13].

Human research: what exists, and what it does not establish

Human studies of Selank exist, and they should be described precisely rather than waved at.

Four limitations apply to this body of work, and all four are visible from the records themselves:

1. Scale. Sixty-two and sixty participants are small by the standards of psychiatric drug evaluation.
2. Language and access. The two clinical reports are published in Russian in a single national journal; the English-language records available internationally are abstracts.
3. Independence. The clinical work, the mechanistic work and the compound's development share authors and institutions, which is common for a nationally developed compound but limits the value of apparent replication.
4. Regulatory status. Selank is registered as a medicine in the Russian Federation. It holds no such approval elsewhere, and no finding above describes an approved use in any other jurisdiction.

Nothing in this section supports a use of Selank in people outside those studies, and none of it should be read as evidence of benefit.

Where the literature comes from

Almost every primary source cited here lists the Institute of Molecular Genetics of the Russian Academy of Sciences, or a collaborating Moscow institution, among its affiliations. That is not a criticism of the work; a compound developed at one institute will naturally be studied there first. It is, however, a material fact about the evidence base, because independent replication by unconnected groups is one of the main ways a preclinical finding becomes durable. For Selank, that independent layer is thin, and the IMR-32 result ^[8] is a reminder that different systems can give different answers.

Analytical identification and purity testing

What the methods can and cannot show

Reversed-phase HPLC with ultraviolet detection, the technique on most peptide certificates, separates components by their interaction with the column and reports each as a share of total detected peak area. It is a purity measure, not an identity measure: it says how much of what was detected corresponds to the main peak, not what that peak is. Compendial chromatography practice is described in the United States Pharmacopeia's general chapter on chromatography ^[18]. Identity needs a separate measurement, typically mass spectrometry, and our guide to reading a certificate of analysis sets out how the fields relate.

Our Selank certificate

The certificate on file for Selank 10mg is Kovera Labs report KVR-2026-78418E, certified 20 July 2026 and added to our COA Library on 5 August 2026. Those are two different dates and neither is the date the laboratory performed the analysis, which the certificate does not state.

Three observations follow. Each records what the document does and does not state.

The net content is above the nominal label amount. The laboratory reported 11.61 mg where the label is a nominal 10 mg, which is 16.1 % above the label figure, and marked that row as meeting its reference. The reference itself is printed as "~10mg" — a nominal value, not a numeric acceptance range. No tolerance, upper limit or lower limit for net content appears anywhere on the certificate, so the size of the difference cannot be assessed against a documented acceptance criterion, and this guide therefore does not describe the result as passing, failing or otherwise. Purity and net content answer different questions in any case; our guide to purity versus net content explains why.

The report number is not a lot number. KVR-2026-78418E is the laboratory's report identifier: it identifies the document, not the material it describes. The certificate's own Batch field reads "N/A", so no lot identifier is recorded, the report cannot by itself be tied to a particular production lot, and the report number should not be read as a verified lot. Where the lot printed on a vial is not represented in our library, contact us with that lot number rather than assuming a given certificate applies to it.

The identity line prints no observed mass. It records confirmation by LC-MS without a measured value or a theoretical value to compare against. A complete identity result for a 751.9 Da peptide would ordinarily print the observed mass against the calculated one; this certificate does not, so a reader cannot independently verify the conclusion. The same reasoning, applied to a differently named analogue, appears in our IGF-1 LR3 guide.

Endotoxin is a separate question

Bacterial endotoxin testing is a different measurement from chromatographic purity and answers a different question. This guide makes no endotoxin claim about Selank and presents no endotoxin result, because our editorial review of the available endotoxin documentation is unresolved. Purity and endotoxin claims should be kept distinct in any case; a purity percentage says nothing about endotoxin content, and the reverse is equally true.

Limitations and open questions

• The mechanism is not settled. GABAergic involvement is proposed and supported in some systems ^[2][7][9], but a human cell line showed no direct transcriptional effect ^[8].
• A fragment may carry part of the effect. Gly-Pro alone reproduced much of Selank's gene-expression profile in mouse spleen ^[12].
• Rodent results are strain-dependent. The enkephalinase-linked behavioural effect appeared in BALB/c but not C57Bl/6 mice ^[6].
• Human evidence is small, concentrated and mostly non-English. Two controlled comparisons with roughly 60 participants each ^[14][15].
• The evidence base is institutionally concentrated, with limited independent replication.
• Our certificate records no lot identifier and no observed mass. Its net content is 16.1 % above the nominal label amount, against a reference that states no range, so that margin cannot be judged against a documented criterion.
• Sources read. The findings above were verified against the published abstracts and bibliographic records of each paper through PubMed, and the identity values against PubChem. Full texts were not obtained for this article, so results reported only in figures or supplementary material are not represented here. The PubMed record for reference ^[10] carries no abstract, so that study is described from its title and bibliographic record only.

Where to find the certificate

The Kovera Labs report for Selank 10mg is in our COA Library, and it is linked from the product page. The separate Semax 10mg certificate is in the same library. If the lot printed on a vial you hold does not appear there, contact us with the lot number and we will locate the corresponding report.