Semax and Selank are both short synthetic peptides with a stabilizing Pro-Gly-Pro tail, and both are studied in preclinical neuroscience. They come from different parent peptides, though, and researchers study them in different pathways.
Semax
Semax is a heptapeptide analog of the ACTH(4-10) fragment of adrenocorticotropic hormone. It has no hormonal ACTH activity. Research has focused on its relationship to BDNF and other neurotrophic factor expression, and on neuroprotection endpoints in animal models.
Selank
Selank is a heptapeptide built from tuftsin (Thr-Lys-Pro-Arg), an immunomodulatory tetrapeptide, extended with Pro-Gly-Pro. Studies look at GABAergic signaling, enkephalin-degrading enzyme activity, and gene expression in stress-response models.
Comparison
| Semax | Selank | |
|---|---|---|
| Parent peptide | ACTH(4-10) | Tuftsin |
| Main research focus | Neurotrophic / BDNF signaling | GABAergic and stress pathways |
| Form | Lyophilized | Lyophilized |
Related Neuropeptides
DSIP is studied in sleep-architecture models, and Pinealon in neuronal oxidative-stress research. Browse Cognitive & Sleep Research.
Study Design Notes for Neuropeptides
Short neuropeptides break down quickly in biological fluids, so researchers often run stability tests in their assay medium before they start functional experiments. The Pro-Gly-Pro extension on both Semax and Selank was designed to slow that breakdown. Comparative designs commonly measure BDNF and NGF expression, monoamine metabolites, and stress-response gene panels. Researchers studying sleep-related pathways add DSIP. For aging-related neuronal models, Pinealon and Epithalon are frequent comparators.
Origins of Both Peptides
Semax and Selank both came out of research programs at the Institute of Molecular Genetics in Moscow, where scientists modified naturally occurring regulatory peptides to make them more stable. The approach was the same in both cases: keep the biologically relevant core and add a short, protease-resistant extension. That shared design is why the two compounds are so often grouped together, even though their parent molecules (ACTH and tuftsin) come from entirely different biological systems. For researchers, this makes the pair an interesting case study in how small sequence changes redirect a peptide toward a new research pathway. Comparing the two in the same model, with matched concentrations and time points, is one of the clearest ways to see how those design choices play out experimentally.
Analytical methods for the two are similar. Reverse-phase HPLC separates each heptapeptide cleanly, and mass spectrometry confirms the expected molecular weight, about 813 Da for Semax and about 751 Da for Selank.
Common Readouts in Semax and Selank Studies
Semax studies frequently measure BDNF and TrkB expression by qPCR or western blot in hippocampal or cortical tissue. Selank studies more often look at GABA-A receptor-related gene expression and enkephalinase activity. Because both are short peptides, researchers often confirm compound integrity in the assay medium by LC-MS before interpreting functional data.
Separating the Two in Your Records
Semax and Selank names, vial sizes and appearance are similar, so label them clearly, for example with different-colored caps, and record lot numbers for each. A mix-up between two heptapeptides would be hard to spot afterwards.
Semax vs Selank FAQ
Why do both have a Pro-Gly-Pro tail? The tripeptide was added to slow enzymatic breakdown of the parent fragments.
Does Semax act like ACTH? The ACTH(4-10) fragment lacks the hormonal corticotropic activity of full-length ACTH.
Summary
- Semax: an ACTH(4-10) analog, with neurotrophic research focus
- Selank: a tuftsin analog, with GABAergic and stress-pathway focus
- Explore Cognitive & Sleep Research
- Related: choosing third-party tested peptides
Research Use Only. All compounds referenced in this article are sold by Genetic Peptides USA strictly for in-vitro and laboratory research. They are not for human or animal consumption, are not drugs, foods, or cosmetics, and are not intended to diagnose, treat, cure, or prevent any disease. This article summarizes published scientific context for educational purposes and contains no dosing guidance.