Semax vs. Selank: Neuropeptide Comparison

Both peptides were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in the late 1980s–1990s. Semax is a synthetic fragment of adrenocorticotropic hormone (ACTH 4-10) with a Pro-Gly-Pro C-terminal extension added to increase proteolytic stability. Selank is a synthetic analog of the immune peptide tuftsin (Thr-Lys-Pro-Arg) with the same Pro-Gly-Pro stabilizing tail. The C-terminal extension is a shared design pattern; the N-terminal segments come from unrelated parent molecules.

Semax has been examined in rodent models of ischemic stroke, cognitive-performance tasks, and stress-response paradigms. Reported observations include modulation of BDNF/NGF expression and dopaminergic signaling in the CNS. Selank has been studied in rodent anxiolytic paradigms including the elevated plus maze and open-field test, with additional literature on immune-peptide activity (tuftsin-family effects on macrophage function). Both bodies of research are primarily preclinical.

Both peptides ship as lyophilized powders in sealed sterile vials. Researchers typically reconstitute them in bacteriostatic water for intranasal spray preparation. Store the lyophilized powder at 2–8 °C, and the reconstituted solution at 2–8 °C for short-term use or aliquotted at −20 °C for longer storage. Both peptides are relatively small and stable, but repeated freeze–thaw cycles should still be avoided.