Selank and Semax are two synthetic peptides that recur throughout the neurochemistry and neuropharmacology research literature. Both were developed in Russia, both are built on short regulatory-peptide sequences, and both carry a distinctive design feature — a C-terminal Pro-Gly-Pro motif — yet they descend from entirely different parent molecules and are studied in largely different research systems. This overview sets them side by side.
The material below summarises how each peptide is described in peer-reviewed laboratory and animal-model studies, for orientation within the research community. It does not describe human use, clinical effects, dosing, or outcomes of any kind. Both compounds are supplied strictly for laboratory research use only — they are not medicines, and nothing here should be read as a claim about anxiety, cognition, memory, or any effect in people.
- Selank is a synthetic analogue of the immunomodulatory peptide tuftsin; Semax is a synthetic analogue of a fragment of ACTH (ACTH(4-10)).
- Both carry a C-terminal Pro-Gly-Pro motif that is studied as a way to improve resistance to enzymatic breakdown.
- In laboratory and animal models they are examined for effects on neuromodulator systems, BDNF expression, and — for Selank — immune signalling.
- Both are supplied for laboratory research use only and are not approved medicines in the EU, US, or most jurisdictions.
Two peptides, one design idea
Selank and Semax belong to a family of short peptide analogues developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. The design strategy behind both is similar: take a naturally occurring regulatory-peptide sequence that is biologically interesting but rapidly degraded, and attach a short stabilising fragment — here the tripeptide Pro-Gly-Pro (proline-glycine-proline) at the C-terminus — to slow enzymatic breakdown. Proline-rich termini resist many peptidases, so the appended Pro-Gly-Pro is studied as a way to extend how long the peptide persists in laboratory and biological media.
Beyond that shared motif the two diverge. Their parent molecules come from different signalling systems — one immune, one melanocortin/corticotropin — and the research questions asked of each reflect those origins.
Selank: a tuftsin analogue
Selank is a synthetic heptapeptide based on tuftsin, a naturally occurring tetrapeptide (threonine-lysine-proline-arginine) classically described as an immunomodulatory fragment of the immunoglobulin heavy chain. Selank preserves the tuftsin sequence and adds the C-terminal Pro-Gly-Pro motif, giving the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. The tuftsin lineage is why part of the Selank research literature concerns immune signalling rather than the nervous system alone.
In laboratory and animal models, Selank has been examined for several distinct activities. Because it derives from tuftsin, studies have looked at its influence on immune markers — the expression of interleukins and interferons in cell and animal models. A separate strand of work examines its interaction with monoamine systems, including serotonergic signalling, and with GABA-related neurotransmission. Researchers have also reported effects on the activity of enkephalin-degrading enzymes, and on the expression of genes including BDNF in rodent brain tissue. These are mechanistic observations in research models and are not demonstrated effects in humans.
