Selank: Sequence, Published Studies and What Is Still Unknown
For laboratory research use only. The compounds discussed here are sold strictly for in vitro research. They are not drugs, supplements or cosmetics and are not for human or animal use. This article summarizes published literature for reference and is not medical or usage advice.
Selank is a synthetic heptapeptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, built by adding a Pro-Gly-Pro tail to tuftsin, the tetrapeptide TKPR that comes from the Fc region of immunoglobulin G. N-acetyl Selank is the acetylated variant of the same sequence. It was developed at the Institute of Molecular Genetics in Moscow, almost all of the primary literature is Russian, and the honest summary is that this peptide is far less characterised than its popularity suggests. Here is what the published work measured, and where it stops.
Key findings
- Sequence: Thr-Lys-Pro-Arg-Pro-Gly-Pro, a heptapeptide. The TKPR portion is tuftsin, an endogenous immunoglobulin-derived fragment [1].
- No characterised receptor. A 2021 pharmacology review places Selank among GABA-receptor-related agents and calls it poorly studied [4].
- At 0.3 mg/kg daily for 7 days, Selank prevented an ethanol-associated rise in BDNF content in rat hippocampus and frontal cortex [1].
- A single 0.3 mg/kg exposure lowered a composite morphine withdrawal index by 39.6 percent in rats and raised the tactile sensitivity threshold ninefold versus active control, slightly behind diazepam at 2 mg/kg [2].
- In 52 healthy volunteers, resting-state fMRI showed altered functional connectivity between the right amygdala and a right temporal region after Selank, with some effects shared with Semax and some specific [3].
- Selank and Semax have both been identified in seized preparations by a validated LC-MS/MS screening method, and the analysts noted neither peptide has completed clinical trials [5].
The sequence and where it came from
Tuftsin is TKPR, a four residue fragment released from IgG. Selank adds Pro-Gly-Pro to that, which gives the seven residue molecule [1]. The same Pro-Gly-Pro motif is attached to Semax, which is otherwise a completely unrelated ACTH-derived sequence. Russian papers often call these molecules glyprolines after that motif [6].
Proline-rich short peptides are awkward to synthesise cleanly and awkward to analyse, which is part of why identity confirmation matters here more than for a simple linear sequence. Vanhee and colleagues ran into exactly that problem from the regulatory side and built an LC-MS/MS method covering ten peptides of this type, Selank included [5]. Their paper is the best published description of how these molecules get identified analytically.
What is actually known about mechanism
Not much, and we would rather say so than pad it out. There is no cloned receptor for Selank, no published binding affinity, no concentration-response curve at a named target. The GABAergic association that appears in nearly every secondary write-up traces back to inference from behavioural pharmacology rather than to receptor data. Doyno and White group Selank with GABA-receptor-affecting compounds in their 2021 review and describe it, with phenibut, as poorly studied [4].
So when you read that Selank modulates several neurotransmitter systems at once, ask which paper measured which system. In most cases the answer is a tissue monoamine assay after a behavioural protocol, which is downstream evidence, not mechanism.
Rodent studies, with their endpoints
BDNF content
Kolik and colleagues used outbred rats given 10 percent ethanol as their only fluid for 30 weeks, then 0.3 mg/kg Selank daily for 7 days, and ran object recognition testing plus ex vivo BDNF measurement. Selank prevented the ethanol-associated increase in BDNF content in hippocampus and frontal cortex, and object recognition scores differed from control in the ethanol-exposed group [1]. The direction is the interesting part: the peptide held BDNF down relative to the ethanol group, rather than driving it up.
Withdrawal signs
In a naloxone-precipitated morphine withdrawal model in outbred rats, a single 0.3 mg/kg exposure cut the total withdrawal index by 39.6 percent, attenuated convulsive reactions, ptosis and posture disturbances, and raised the tactile sensitivity threshold ninefold against active control. Diazepam at 2 mg/kg produced a 49.3 percent reduction and a thirteenfold threshold change in the same study [2]. One model, one comparator, one laboratory, so treat it as a single data point.
Cytokine measurements
A separate rat study used a sensory-contact confrontation protocol over 20 days with 100 micrograms per kilogram per day of Selank, and measured interleukin concentrations by ELISA [6]. Given the tuftsin origin of the sequence, immune-related readouts are a reasonable thing to measure, though the model is behavioural and the sample descriptions are thin.
The one modern human dataset
Panikratova and colleagues scanned 52 healthy participants with resting-state fMRI three times: before, and at 5 and 20 minutes after Selank, Semax or placebo. Regions of interest were the amygdala and dorsolateral prefrontal cortex in both hemispheres. They reported group and condition differences in connectivity between the right amygdala and a right-hemisphere region spanning fusiform, inferior and middle temporal and parahippocampal gyri, and described both shared and peptide-specific effects [3].
It is a short exploratory study with a 20 minute window and no replication that we could find. Still, it is one of the very few human measurements that exist for this molecule, and the authors present the comparison as a first.
Identity and purity
For a proline-rich heptapeptide, reversed phase HPLC supplies the chromatographic purity figure and mass spectrometry confirms the molecular mass against the expected sequence. Acetylation shifts that mass, so N-acetyl Selank and Selank are distinguishable by MS when the method is set up for it, which is precisely what the Sciensano group’s screening work demonstrates [5]. A purity percentage only means something attached to its method, its batch and its date. Ours are published at wholesalepeptide.com/coas, with every batch tested by a U.S.-based third-party laboratory, and you can read more on our third-party testing page.
Frequently asked questions
What is the Selank sequence?
Thr-Lys-Pro-Arg-Pro-Gly-Pro. The first four residues are tuftsin, an IgG-derived fragment, and Pro-Gly-Pro is the synthetic addition [1].
Does Selank have a known receptor?
No characterised receptor appears in the literature we reviewed. A 2021 review associates it with GABA receptor mechanisms while describing it as poorly studied [4].
How is Selank identified analytically?
By liquid chromatography with tandem mass spectrometry. A validated LC-MS/MS screening method covering Selank and nine related peptides was published in 2020 [5].
References
- Kolik LG, Nadorova AV, Antipova TA, et al. Selank, peptide analogue of tuftsin, protects against ethanol-induced memory impairment by regulating of BDNF content in the hippocampus and prefrontal cortex in rats. Bull Exp Biol Med. 2019. PMID 31625062
- Konstantinopolsky MA, Chernyakova IV, Kolik LG. Selank, a peptide analog of tuftsin, attenuates aversive signs of morphine withdrawal in rats. Bull Exp Biol Med. 2022. PMID 36322304
- Panikratova YR, Lebedeva IS, Sokolov OY, et al. Functional connectomic approach to studying Selank and Semax effects. Dokl Biol Sci. 2020. PMID 32342318
- Doyno CR, White CM. Sedative-hypnotic agents that impact gamma-aminobutyric acid receptors: focus on flunitrazepam, gamma-hydroxybutyric acid, phenibut, and selank. J Clin Pharmacol. 2021. PMID 34396551
- Vanhee C, Francotte A, Janvier S, Deconinck E. The occurrence of putative cognitive enhancing research peptides in seized pharmaceutical preparations. Drug Test Anal. 2020. PMID 31667971
- Leonidovna YA, Aleksandrovna SM, Aleksandrovna TA, et al. The influence of Selank on the level of cytokines under the conditions of “social” stress. Curr Rev Clin Exp Pharmacol. 2021. PMID 32621722
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