Selank is a synthetic heptapeptide made by attaching a three-residue Pro-Gly-Pro extension to tuftsin, a natural four-amino-acid fragment of immunoglobulin G. The design borrows a stabilizing tail from the same Russian research program that produced Semax, and it places Selank in an unusual spot: a peptide with an immune-system ancestry that is studied mostly for its actions on brain neurochemistry.
What follows explains where tuftsin comes from, why the extension was added, and what rodent and cell studies have reported about enzyme inhibition, monoamines, neurotrophins and gene expression. A closing section is blunt about how small and geographically concentrated this evidence base is.
At a glance
- Class: Synthetic heptapeptide; tuftsin analogue
- Origin: Developed at the Institute of Molecular Genetics of the Russian Academy of Sciences
- Structure: Thr-Lys-Pro-Arg-Pro-Gly-Pro; C33H57N11O9; MW 751.9 g/mol; CAS 129954-34-3
- Main research areas: enkephalinase inhibition, serotonin and dopamine metabolism, hippocampal BDNF expression, GABA-related and immune gene expression
- Regulatory status: Not approved by the FDA for any use; research reagent only
Structure and origin
Tuftsin, Thr-Lys-Pro-Arg, is released from the Fc region of the IgG heavy chain by enzymatic cleavage. It was described around 1970 and named after Tufts University, where it was characterized as a peptide that stimulates phagocytosis by neutrophils and macrophages. Like many short peptides, tuftsin is broken down quickly by peptidases in blood and tissue.
The Selank design keeps the full tuftsin sequence at the N-terminus and adds Pro-Gly-Pro at the C-terminus. Proline-rich sequences are poor substrates for many exopeptidases, and the same tail was used in Semax, an ACTH-derived peptide from the same group of Moscow laboratories. The aim was a molecule that persists longer than tuftsin while keeping its basic, positively charged core (lysine and arginine). That charged core distinguishes Selank chemically from Semax, whose N-terminal sequence is acidic.
Mechanism: what the research shows
There is no identified receptor for Selank, and the literature describes a set of effects in assays and rodent tissue rather than a single pathway.
The clearest biochemical finding comes from enzyme kinetics. Kost and colleagues incubated Selank and Semax with human serum and measured activity of enkephalin-degrading enzymes. Both peptides inhibited these enzymes in vitro, which would be expected to slow the breakdown of endogenous opioid peptides such as leu-enkephalin (Kost et al., 2001).
A second set of findings involves serotonin. In rats pretreated with para-chlorophenylalanine (PCPA), an inhibitor of serotonin synthesis, Semenova and colleagues compared Selank with tuftsin and measured serotonin and its metabolite 5-HIAA in brain regions (Semenova et al., 2009). Narkevich and colleagues measured monoamines and their metabolites in two inbred mouse strains, BALB/c and C57BL/6, which differ in baseline behavior and neurochemistry, and compared how Selank altered these markers in each strain (Narkevich et al., 2008). Expression studies have also reported changes in genes connected to GABAergic signaling and in inflammatory mediators such as IL-6 in stress models.
Key areas of study
Peptidase inhibition and opioid peptides
The serum enzyme work places Selank among peptides that may act indirectly, by protecting other signaling molecules from degradation (Kost et al., 2001). It also matters for experimental design, since Selank can affect the stability of other peptides present in the same preparation.
Monoamine neurochemistry
The PCPA study and the two-strain mouse comparison are the main sources on Selank and monoamines. Both used HPLC measurement of tissue monoamines and metabolites, and in both the reported changes varied with the model, the strain or the brain region (Narkevich et al., 2008; Semenova et al., 2009). The comparison with tuftsin in the PCPA study is useful because it tests whether the Pro-Gly-Pro extension changes the parent peptide’s profile.
Neurotrophin expression
Inozemtseva and colleagues gave Selank intranasally to rats and measured BDNF expression in the hippocampus, reporting changes in expression after exposure (Inozemtseva et al., 2008). This finding parallels BDNF work on Semax and is one reason the two peptides are often studied side by side.
Comparative network studies
Because Selank and Semax share a stabilizing tail but have different cores, researchers have compared them directly. A functional connectivity study set the two peptides against each other using imaging methods (Panikratova et al., 2020). Such comparisons help separate effects tied to the shared Pro-Gly-Pro motif from those tied to the tuftsin or ACTH sequence.
What the evidence does not show
The Selank literature is narrow. Most papers come from a few Russian institutes, many appear in Russian-language journals with brief methods sections, and independent replication elsewhere is rare. There is no characterized receptor, so the enzyme, monoamine, BDNF and gene-expression findings remain separate observations rather than a mechanism. Rodent studies are typically small and use a range of routes and models, which makes them hard to compare. Tuftsin’s immune activity raises the question of how much of Selank’s profile is immune rather than neural, and that has not been resolved. No animal or cell result here establishes an effect in people, and none describes the material sold here.
Regulatory status
Selank is not approved by the FDA for any use. Rogue Compounds sells it as a research reagent only, not as an approved drug product.
Handling and storage in the lab
Lyophilized Selank should be kept sealed and refrigerated at 2–8°C (36–46°F), protected from light. Leave the vial closed until it is needed to limit exposure to moisture and air.
Sourcing and documentation
Rogue Compounds has Selank made in small batches. Every vial carries a batch number and a QR code that opens the independent U.S. testing lab’s own report for that batch. The same batch COA is posted on the product page and in the COA Library.
View Selank on Rogue Compounds
References
- Kost NV, et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Bioorg Khim. 2001;27(3):180-183. PMID 11443939
- Narkevich VB, et al. Effects of heptapeptide selank on the content of monoamines and their metabolites in the brain of BALB/C and C57Bl/6 mice: a comparative study. Eksp Klin Farmakol. 2008;71(5):8-12. PMID 19093364
- Inozemtseva LS, et al. Intranasal administration of the peptide Selank regulates BDNF expression in the rat hippocampus in vivo. Dokl Biol Sci. 2008;421:241-243. PMID 18841804
- Semenova TP, et al. Comparison of the effects of selank and tuftsin on the metabolism of serotonin in the brain of rats pretreated with PCPA. Eksp Klin Farmakol. 2009;72(4):6-8. PMID 19803361
- Panikratova YR, et al. Functional connectomic approach to studying Selank and Semax effects. Dokl Biol Sci. 2020;490(1):9-11. PMID 32342318
Research use only. Rogue Compounds products are sold strictly for laboratory research. They are not for human or veterinary use, and nothing in this article is medical advice. The studies cited here describe published research, not this product or any use of it.