Semax vs Selank
Structural and analytical comparison · research use only
Semax and Selank are frequently grouped together because both were developed in Russia and both are short synthetic peptides carrying a Pro-Gly-Pro tail. Their parent sequences are unrelated. This page compares identity and molecular profile only.
| Property | Semax | Selank |
|---|---|---|
| Classification | Synthetic ACTH(4–7) analog with a Pro-Gly-Pro extension | Synthetic tuftsin analog with a Pro-Gly-Pro extension |
| Parent sequence | Fragment of adrenocorticotropic hormone | Tuftsin, an immunologically described tetrapeptide |
| CAS number | 80714-61-0 | 129954-34-3 |
| Molecular formula | C37H51N9O10S | C33H57N11O9 |
| Molecular weight | 813.92 g/mol | 751.87 g/mol |
| Contains sulfur | Yes (methionine residue) | No |
| Supplied format | Lyophilized powder, sealed vial | Lyophilized powder, sealed vial |
| Purity standard | ≥99.2% (HPLC) | ≥99.2% (HPLC) |
The shared tail, and why it is not similarity
Both peptides append the same Pro-Gly-Pro (PGP) tripeptide to a different parent fragment. That design choice is what makes them look related in a sequence listing. The functional cores are entirely different: Semax derives from an ACTH fragment, Selank from tuftsin. Comparing them structurally is a comparison of two different molecules that happen to share a three-residue terminus.
Analytical distinction
The clearest laboratory difference is elemental: Semax contains sulfur from its methionine residue, Selank does not. Combined with a ~62 g/mol mass difference, the two are readily separated and independently confirmed by mass spectrometry.
Supplied strictly as a research reference material for in-vitro laboratory use. Not for human or veterinary use.
Frequently asked questions
Are Semax and Selank related peptides?
Only at the terminus. Both are synthetic peptides that carry a Pro-Gly-Pro tail, but their parent sequences differ entirely — Semax derives from an ACTH fragment and Selank from tuftsin.
How are they distinguished analytically?
By molecular weight (813.92 vs 751.87 g/mol) and by elemental composition — Semax contains sulfur, Selank does not. Each lot is confirmed by mass spectrometry and HPLC.