Compound comparison · 5 min read
Semax vs Selank: Two Heptapeptide Analogs Compared
Semax and Selank are both seven-residue synthetic peptides ending in Pro-Gly-Pro. How their sequences, parent peptides, molecular data and handling compare.
Semax and Selank are often mentioned together. Both are short synthetic peptides, both were developed by research groups in Russia, and both end in the same three amino acids. Their starting points, though, are different natural peptides. This guide compares them as materials.
At a glance
| Semax | Selank | |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent peptide | ACTH(4-7), a fragment of adrenocorticotropic hormone | Tuftsin (Thr-Lys-Pro-Arg), a fragment of the immunoglobulin G heavy chain |
| Added sequence | Pro-Gly-Pro at the C-terminus | Pro-Gly-Pro at the C-terminus |
| Molecular formula | C37H51N9O10S | C33H57N11O9 |
| Molecular weight | 813.9 g/mol | 751.9 g/mol |
| CAS number | 80714-61-0 | 129954-34-3 |
The shared Pro-Gly-Pro tail
Short natural peptides such as ACTH fragments and tuftsin are broken down quickly by peptidases. Adding a C-terminal Pro-Gly-Pro is a design choice described in the literature as making both sequences more resistant to that breakdown in vitro. It is the reason the two peptides look so alike on paper despite their different origins.
Semax
Semax takes the first four residues of the ACTH(4-10) fragment (Met-Glu-His-Phe) and adds Pro-Gly-Pro. The N-terminal methionine is the residue most prone to oxidation, so a COA may show a small side peak about 16 Da heavier when a sample has been exposed to air or heat. See Atlas Semax.
Selank
Selank extends tuftsin, a tetrapeptide first described in the 1970s, with the same Pro-Gly-Pro tail. With a lysine and an arginine, it carries more positive charge than Semax, which shows up as an earlier retention time on reversed-phase HPLC under the same conditions. See Atlas Selank.
Confirming identity
At under 1,000 Da, both peptides usually appear as a singly charged ion in electrospray mass spec: about 814 m/z for Semax and about 752 m/z for Selank ([M+H]+), sometimes with a doubly charged ion alongside. Because the two share three residues and similar masses, the observed mass is the clearest way to confirm which one is in the vial. Our testing guide explains the methods.
Storage
Both are supplied lyophilized: -20 °C long term, 2–8 °C short term, sealed and away from light. See the storage guide.
Compounds in this guide
Cognitive Research
Semax
Synthetic heptapeptide analog of the ACTH(4-10) fragment with a C-terminal Pro-Gly-Pro extension
813.9 g/mol · 7 aa · CAS 80714-61-0
COA on release
Cognitive Research
Selank
Synthetic heptapeptide analog of tuftsin with a Pro-Gly-Pro extension
751.9 g/mol · 7 aa · CAS 129954-34-3
COA on release
Keep reading
- How Research Peptides Are Tested: HPLC, Mass Spec and Beyond
- MOTS-c vs NAD+: Two Mitochondrial Research Compounds Compared
- Where to Buy Research Peptides Online: A 7-Point Supplier Checklist
For Research Use Only. Not for human or veterinary use. Not for diagnostic or therapeutic use. Not a drug, food, cosmetic or dietary supplement. Not for resale to consumers.
