What Selank actually is
Selank is a seven-amino-acid synthetic peptide. Its sequence in single-letter code is TKPRPGP - threonine, lysine, proline, arginine, proline, glycine, proline. Three prolines in seven positions is a striking ratio and matters for the pharmacology: prolines resist enzymatic cleavage by most aminopeptidases and confer the stability that makes Selank usable in research where the parent tuftsin tetrapeptide degrades in minutes.
The parent peptide is tuftsin: Thr-Lys-Pro-Arg, a four-residue immunostimulant that occurs naturally in the Fc region of immunoglobulin G heavy chains. Tuftsin was characterised in the early 1970s but its therapeutic potential was capped by its very short half-life in serum - a few minutes at most. The Russian team led by Andronati and later Mjasoedov added the Pro-Gly-Pro tripeptide tail and obtained a heptapeptide with serum half-life measured in tens of minutes and biological activity preserved at the tuftsin-family receptor.
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro (single-letter: TKPRPGP) |
| Parent peptide | Tuftsin (Thr-Lys-Pro-Arg, residues 289-292 of human IgG Fc) |
| Molecular weight | 751.42 g/mol (monoisotopic) |
| CAS number | 129954-34-3 |
| Class | Synthetic regulatory heptapeptide; tuftsin-family receptor (TFR) ligand |
| Reported half-life (intranasal) | ~10-20 minutes in serum; central effects sustained for hours |
| Visible appearance | White lyophilised cake (no chromophore - Selank is not coloured) |
| Stability (lyophilised) | 24+ months at 2–8 °C, sealed and protected from light |
| Most-studied route | Intranasal aqueous solution |
The story: from tuftsin to Selank
Tuftsin was first isolated in 1970 by Najjar and Nishioka at Tufts University (which is where the name came from, not from a Russian connection). The molecule's biological CV included macrophage activation, phagocytosis enhancement and a documented role in innate immune signalling. But the metabolic instability problem - half-life of minutes - meant Western pharmaceutical interest faded by the late 1970s.
Russian peptide chemistry kept working on the molecule. By the early 1990s, work at the V.V. Zakusov Research Institute of Pharmacology of the Russian Academy of Medical Sciences had produced Selank by appending a Pro-Gly-Pro tripeptide to tuftsin. The Pro-Gly-Pro motif is also the carboxy-terminal fragment of another well-studied Russian peptide, Semax - the same lab's other major output. The shared motif is not coincidental; both compounds use it as a metabolic-stability tail.
The Russian regulatory pathway approved Selank as an over-the-counter anxiolytic medication in 2009 under the trade name Selank, formulated as a 0.15% intranasal aqueous solution. Western regulatory bodies have never approved or formally evaluated it. The compound therefore exists in two parallel realities - registered medicine in Russia, completely unknown research-grade reagent in the West.
Why Selank is so under-represented in Western research
The under-coverage problem.
Most of the Selank literature is published in Russian-language pharmacology journals - Eksperimental'naya i Klinicheskaya Farmakologiya, the Bulletin of the Russian State Medical University, Journal of Higher Nervous Activity. PubMed indexes some of these, often as English-translation abstracts only, which means full-text access is limited and Western reviewers tend to skip the citations.
Add to that: no Western marketing authorisation, no Western pharma company developing it, no NIH or EMA-funded clinical trials, and no large language-translation programme bridging the source material into English. The result is a compound with thirty years of accumulated clinical and preclinical evidence that sits almost completely outside the Western research conversation.
For a researcher willing to read the source material - or even just the English-language reviews from authors like Inozemtsev, Kozlovskaya, Semenova, and the Mjasoedov-Andronati lineage - Selank is one of the better-characterised regulatory peptides in the literature. It just looks like an obscure compound from inside the English-language bubble.
Mechanism: what the literature actually says
The Selank mechanism papers describe four interconnected pathways. None of these is a clean single-receptor story - Selank is a regulatory peptide that nudges several systems at once, which makes it interesting and also harder to summarise.
1. Tuftsin-family receptor (TFR) binding
Like its parent tuftsin, Selank binds the tuftsin-family receptor expressed on monocytes, macrophages and several CNS cell types. The Pro-Gly-Pro tail does not abolish binding; the Thr-Lys-Pro-Arg tetrapeptide is the recognition motif. TFR engagement is the upstream event in most of the cascade - immunomodulation, BDNF effects, GABAergic modulation downstream.
2. GABAergic modulation
The most cited finding in the Russian literature is that Selank produces anxiolytic-class effects in animal behavioural paradigms (elevated plus maze, open field, conditioned fear) at intensities comparable to medazepam (a benzodiazepine), but without the sedation or muscle-relaxation associated with direct GABA-A potentiation. The mechanism is not direct binding to the benzodiazepine site but indirect modulation of GABAergic tone, possibly via altered expression of GABA-A subunits in limbic regions. Kozlovskaya et al. and several follow-up papers walk through the displacement-binding evidence.
3. BDNF and synaptic plasticity
Multiple animal studies report that Selank administration upregulates brain-derived neurotrophic factor (BDNF) expression in the hippocampus and prefrontal cortex. BDNF is the canonical mediator of activity-dependent synaptic plasticity, which would account for the cognitive and learning-related effects observed in animal cohort studies.
4. Cytokine downregulation
The immunomodulatory leg of the Selank story is the most consistent with the parent tuftsin's known biology. Selank has been reported to downregulate pro-inflammatory cytokines including IL-6 and TNF-alpha while upregulating anti-inflammatory IL-4 in animal models of stress and infection. This is the connection between the "immune compound" framing of tuftsin and the "anxiolytic compound" framing of Selank - both effects flow downstream from the same TFR engagement.
Routes of administration in the published literature
The dominant route in both Russian human research and most animal studies is intranasal aqueous solution. The 0.15% intranasal preparation registered as a medicine in Russia is dosed at 1-3 sprays per nostril, two to three times daily, in the source clinical literature. The intranasal route is preferred because:
- Selank reaches the central nervous system via olfactory and trigeminal pathways, bypassing first-pass metabolism in the liver
- The heptapeptide is small and hydrophilic enough to cross the nasal mucosa effectively
- Onset of measurable behavioural effects is fast (minutes to tens of minutes in animal studies)
Subcutaneous administration also appears in animal studies, particularly for displacement-binding work where systemic exposure rather than CNS penetration is the experimental variable. Oral administration is reported but bioavailability is low because of peptidase activity in the gut. We supply Selank as a lyophilised research reagent for in-vitro and laboratory contexts only and do not provide human-use or veterinary administration guidance.
Selank vs Semax: the same lab's two children
If Selank looks familiar to anyone who knows Semax, it should - both peptides came out of the same V.V. Zakusov research programme in roughly the same period, both use a Pro-Gly-Pro stabilising tail, and both are administered intranasally in the Russian clinical literature.
The two compounds are distinct, however, in receptor preference and behavioural profile:
- Selank (TKPRPGP) is the tuftsin-family receptor ligand. The behavioural literature emphasises anxiolytic and immunomodulatory effects.
- Semax (MEHFPGP) is a synthetic ACTH-fragment analogue (the first four residues correspond to ACTH(4-7)). The literature emphasises nootropic and neuroprotective effects.
For a compound-selection write-up we have Semax vs Selank side by side. They are commonly studied together; researchers often cite both in the same paragraph as the canonical Russian regulatory-peptide pair.
What to look for on the Certificate of Analysis
For Selank specifically, the things that matter on a Janoshik HPLC report (or any third-party COA) are:
1. The single dominant peak at the Selank retention time
On a reversed-phase HPLC chromatogram Selank elutes relatively early because the hydrophilic profile (lots of polar residues, three prolines, no aromatic amino acids) gives short retention. You should see one tall peak at the expected RT and a flat baseline elsewhere, with purity reported as 99%+ in the analytical summary.
2. Mass spectrometry confirmation
The molecular ion for Selank lands near m/z 752.4 in positive ion mode (monoisotopic mass 751.42 g/mol). Because Selank has no aromatic side chains and contains seven prolines (which fragment characteristically), the MS pattern is distinctive and easy to verify against a reference spectrum.
3. Visible appearance
Selank has no chromophore, so the lyophilised cake should be a clean white porous puck. Unlike GHK-Cu, where the colour itself is a quality signal, Selank cannot be assessed visually beyond confirming that the cake is white and structurally intact (a porous freeze-dried solid, not a heap of grains).
If you want the full walkthrough of how to read the COA, our Janoshik HPLC report explainer covers it line by line.
Storage and handling at your bench
- Refrigerate at 2–8 °C in the original sealed vial. The lyophilised cake is stable for 24+ months under these conditions.
- Reconstitute with bacteriostatic water by adding the water slowly down the inside wall of the vial and gently swirling (do not shake or vortex) until the cake fully dissolves. The resulting solution is clear and colourless.
- Reconstituted shelf life is shorter than the lyophilised form. The Russian intranasal preparation is rated for several weeks refrigerated, but for analytical research stick to the timeframe specified by your assay protocol.
- The intranasal route in published research uses a saline-buffered solution at a defined concentration. We do not supply pre-formulated nasal spray - Selank ships as lyophilised research-grade powder for laboratory work only.
Common red flags when sourcing Selank
Walk-away signals when buying Selank
- The supplier offers Selank pre-formulated as a nasal spray product - that crosses into a regulated medicines category and a research-reagent supplier should not be doing it.
- No batch-specific Certificate of Analysis included with the order, only a generic "we test our products" statement on the website.
- Mass spectrometry confirmation is absent - Selank's seven-proline structure has a distinctive MS signature and any reputable lab will have run it.
- The COA reports purity as ">95%" without a numerical value. For a relatively short and easily synthesised heptapeptide, real purity should be 99%+; sub-99 implies cheap synthesis or poor purification.
- The supplier conflates Selank with Semax in marketing copy. They are distinct compounds and a supplier that mixes them up casually will mix them up at the bench too.
- The lyophilised cake arrived as a fine loose powder rather than a solid puff or disc - freeze-drying done correctly produces a porous cake, not granules.
- Pricing is suspiciously low. Selank synthesis is well-established but it still requires standard solid-phase peptide synthesis chemistry; rock-bottom pricing usually means cut corners.
Where Selank fits in the wider catalogue
Selank sits in the neuropeptide-research family alongside Semax, DSIP, Melatonin, Oxytocin, Kisspeptin-10 and PT-141. The Russian regulatory-peptide pair (Selank + Semax) is the most under-studied subset by a wide margin in Western research markets, which is precisely why the published literature offers a useful edge to researchers willing to read it.
If you are picking between Selank and a comparable compound for a particular research context, the Semax vs Selank comparison is the closest direct write-up. Browse the full neuropeptide research category for the broader set.
What we supply
We stock Selank as a lyophilised cake in 10mg amber-glass vials, independently HPLC-verified by Janoshik Analytical. The Janoshik Certificate of Analysis ships in the box with every order where one is available for the current batch, and the report is also published on our Purity page for independent reference. The product page with current pricing, vial-or-pen format, sizing and the integrated dose calculator is at /peptides/selank.html.
Research use only. The compound information described above is drawn from published peer-reviewed analytical, biochemical and behavioural literature and is provided for laboratory and in-vitro research context. Black & White Peptides Ltd does not provide therapeutic claims, dosing guidance, administration protocols, or any content relating to human or veterinary use.