Semax vs Selank: Two Synthetic Heptapeptides Compared
Quick Answer
Semax and Selank are synthetic heptapeptides that share one design idea: a native short peptide extended with a Pro-Gly-Pro sequence that slows enzymatic breakdown. They come from different parents. Semax is built from the ACTH(4-7) fragment of adrenocorticotropic hormone, and Selank from tuftsin, a tetrapeptide fragment of immunoglobulin G. In the literature, Semax appears mostly in neurotrophin (BDNF, TrkB) and melanocortin-receptor research, and Selank in GABAergic signaling, enkephalinase activity and cytokine expression work.
Key Takeaways
- Both are seven residues long and end in Pro-Gly-Pro.
- Semax = ACTH(4-7) + PGP. Selank = tuftsin (Thr-Lys-Pro-Arg) + PGP.
- Different molecular weights: 813.9 g/mol (Semax) vs 751.9 g/mol (Selank).
- They are studied in different signaling systems, and are often ordered together for comparison work.
Semax vs Selank 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) | Tuftsin |
| Molecular formula | C37H51N9O10S | C33H57N11O9 |
| Molecular weight | 813.9 g/mol | 751.9 g/mol |
| CAS number | 80714-61-0 | 129954-34-3 |
| Common research areas | BDNF/TrkB expression, melanocortin receptors | GABAergic signaling, enkephalinases, cytokines |
What Is Semax?
Semax is a synthetic peptide made by joining the ACTH(4-7) sequence (Met-Glu-His-Phe) to a Pro-Gly-Pro tail. ACTH(4-7) is a short stretch of adrenocorticotropic hormone that keeps some melanocortin-receptor binding but has no corticotropic activity of its own. The added tail protects the N-terminal fragment from rapid breakdown by peptidases, which is why it is a common design element in this family.
In published cell-culture and receptor studies, Semax is examined for its effect on brain-derived neurotrophic factor (BDNF) and its TrkB receptor, for melanocortin-receptor binding, and in neuronal culture assays.
What Is Selank?
Selank applies the same Pro-Gly-Pro extension to tuftsin, the tetrapeptide Thr-Lys-Pro-Arg released from the Fc region of immunoglobulin G. Tuftsin itself is short-lived in biological fluids; the tail is meant to extend its stability.
Selank appears in research on GABAergic signaling, on the enzymes that break down enkephalins, and on cytokine gene expression in immune-cell models.
How They Differ
The shared tail is the only structural overlap. The N-terminal four residues decide what each peptide binds: an ACTH fragment for Semax, an immunoglobulin fragment for Selank. That is why the two show up in different assay systems, and why labs that compare them usually run them side by side rather than treating one as a substitute for the other. Our Selank + Semax + NAD+ research stack and Semax + Selank + Thymosin Alpha-1 bundle supply both with separate lot numbers.
Storage of the Sealed Vial
All of these compounds ship as lyophilized (freeze-dried) solids in sealed vials. Store sealed vials as stated on the label, protected from light and moisture, and see our storage and handling guide for temperature ranges. Each vial is labelled with its lot number, which ties it to its certificate.
Analytical Verification and Documentation
Each lot is tested by Testides, an independent laboratory, for HPLC purity and content. Certificates are published with their report numbers so they can be checked against the lab’s own record:
New to certificates? Our guide on how to read a COA walks through each field.
Frequently Asked Questions
What is the difference between Semax and Selank?
They share a Pro-Gly-Pro tail but have different parent sequences: Semax is built from ACTH(4-7), Selank from tuftsin. That gives them different molecular weights (813.9 vs 751.9 g/mol) and different research applications.
What is the molecular weight of Semax?
Semax (C37H51N9O10S) has a molecular weight of 813.9 g/mol. Its CAS number is 80714-61-0.
What is the molecular weight of Selank?
Selank (C33H57N11O9) has a molecular weight of 751.9 g/mol. Its CAS number is 129954-34-3.
Why do both peptides end in Pro-Gly-Pro?
The Pro-Gly-Pro tail slows breakdown by peptidases, so short native fragments stay intact longer in assay conditions.
All compounds discussed are sold for in-vitro laboratory research only. They are not for human or animal use and not for diagnostic or therapeutic procedures. Nothing here describes or suggests use in people.
For Research Use Only. Not for use in diagnostic or therapeutic procedures.
