In brief: Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a synthetic peptide that extends fragment 4–10 of adrenocorticotropic hormone (ACTH) with the stabilising sequence Pro-Gly-Pro – the same “protective cap” that Selank carries. In research it is used as a model compound for neurotrophic and neuroprotective signalling pathways; it is not approved as a medicinal product in the EU and is available exclusively for research use. When sourcing it, what counts is a batch-specific COA with HPLC and mass spectrometry, the net peptide content and oxidation-aware storage, because Semax contains methionine, a sensitive residue.
What is Semax?
Semax was developed – like Selank – at the Institute of Molecular Genetics of the Russian Academy of Sciences. The starting point is the ACTH fragment 4–10 (Met-Glu-His-Phe-Arg-Trp-Gly), which has been investigated in animal models in studies of learning and attention paradigms without producing the hormonal effect of full-length ACTH. Replacing the C-terminal end with Pro-Gly-Pro produced a heptapeptide with markedly higher enzymatic stability. Semax is registered as a medicinal product in Russia, but not in the EU or the United States.
In the scientific literature, Semax is studied above all in connection with:
- the expression of neurotrophic factors (BDNF, NGF) and their receptors in the hippocampus
- neuroprotective mechanisms in ischaemia models
- modulation of the melanocortin system and of gene expression in the CNS
Structure, receptor profile and literature references are summarised on the Semax page in the peptide library.
Semax and Selank compared
The two peptides are often mentioned in the same breath, because they come from the same institute and carry the same stabilising sequence. As research tools, however, they address different questions:
| Semax | Selank | |
|---|---|---|
| Origin | ACTH fragment 4–10 | Tuftsin (IgG fragment) |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Molecular mass | approx. 814 Da | approx. 751 Da |
| Typical research fields | Neurotrophic factors, neuroprotection, melanocortin system | GABAergic modulation, stress models, immune-nervous axis |
| Sensitive residue | Methionine (prone to oxidation) | – |
| Formats at Peptélia | Vial 5 mg / 10 mg | Vial 5 mg / 10 mg, ready-made solution 20 mg / 10 ml |
Anyone planning to compare the two compounds in one model should choose batches with comparable documentation – ideally from the same testing laboratory. The guide to the second compound is available at Buying Selank: vial or ready-made solution?.
What labs should check when sourcing
- Batch-specific COA with HPLC and MS. The lot number on the certificate has to match the vial; the chromatogram shows the purity, and mass spectrometry confirms the identity (target mass around 814 Da). A percentage figure without a chromatogram is not evidence – see the COA guide.
- Oxidation status. The methionine residue in position 1 can oxidise to the sulfoxide; in the mass spectrum this shows up as a +16 Da signal. A clean COA shows this peak either not at all or only minimally. If you cannot place this point in the chromatogram, the basics are covered in the article on degradation pathways in the mass spectrum.
- Net peptide content. As with all small peptides, what counts for the concentration calculation is the net content, not the HPLC purity. Calculation aid: peptide calculator.
- Legal framework. Semax is not approved as a medicinal product in the EU and is supplied exclusively for research use (Research Use Only; not legal advice, observe national regulations). Background in our research use disclaimer.
Storage: methionine calls for care
Lyophilised Semax belongs at −20 °C, dry, dark and as far as possible protected from atmospheric oxygen – so do not leave the vial open any longer than necessary after opening it. Reconstitute with bacteriostatic water, slowly down the vial wall and without shaking; the solution is kept refrigerated and frozen in aliquots, to avoid repeated thawing. General rules in storing peptides correctly.
Semax at Peptélia
Peptélia stocks Semax as a lyophilised vial in 5 mg (€29.90) and 10 mg (€34.90). Every batch is tested in our own lab by HPLC and UV/Vis spectroscopy, and the COA can be viewed before purchase. Dispatch on the next business day from the EU, free shipping from €100, and bacteriostatic water is included with every order. For an overview: buy Semax.
Note: For research use only (Research Use Only) – not for use in humans or animals.
