Semax Research Guide: Structure, COA and Handling
Semax is a synthetic seven-amino-acid peptide, Met-Glu-His-Phe-Pro-Gly-Pro. It joins a short fragment of adrenocorticotropic hormone (ACTH) to a Pro-Gly-Pro tail that slows its breakdown. Labs study it in neuropeptide and neurotrophic-signaling research models. This page covers its structure, how it differs from N-acetyl semax amidate, what a semax certificate of analysis should show, and how to handle the lyophilized powder, using FRO Peptides’ own published lot report as the example.
Semax at a glance
| Class | Synthetic ACTH-derived regulatory peptide (research compound) |
|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP), 7 amino acids |
| Molecular formula | C37H51N9O10S |
| Molecular weight | ≈ 813.9 g/mol |
| CAS number | 80714-61-0 |
| Built from | ACTH (4-7) plus a C-terminal Pro-Gly-Pro; an analog of ACTH (4-10) |
| Supplied as | Lyophilized white powder in sealed vials |
| FRO vial sizes | 5mg, 10mg, 30mg |
| FRO tested purity | 99.57% by HPLC (30mg, sample D7W9-8MTR) |
How the molecule is built
The first four residues, Met-Glu-His-Phe, are positions 4 to 7 of ACTH. On its own that fragment has no hormonal (corticotropic) activity and is broken down quickly by peptidases. Semax’s developers, at the Institute of Molecular Genetics of the Russian Academy of Sciences, added a Pro-Gly-Pro tripeptide to the end. Proline-rich sequences resist enzymatic cleavage, so the tail lets the peptide survive long enough to study.
For lab work, the main things to know are that semax is small, water-soluble and contains a methionine. Methionine is easily oxidized, which is one reason the powder should be kept sealed, cold and away from air and light. An oxidized sample can still look clean on a quick test while no longer being the intended compound.
Why labs study it
- Neurotrophic signaling. Published rodent studies report changes in BDNF and its receptor TrkB in brain tissue after semax exposure, so it is used in neurotrophin-pathway research.
- Ischemia models. It has been studied in animal models of reduced blood flow to the brain, looking at gene-expression changes in affected tissue.
- Melanocortin pathway research. Because it is derived from ACTH, it is used to study how short ACTH fragments interact with melanocortin signaling.
Worth knowing: most of the published semax literature comes from Russian research groups, and independent replication elsewhere is limited.
Semax vs. N-acetyl semax amidate
N-acetyl semax amidate is a different molecule. It is the same MEHFPGP sequence with an acetyl group on the N-terminus and an amide on the C-terminus. Those changes are meant to further slow enzymatic breakdown, and they raise the molecular weight to about 855 g/mol. FRO Peptides sells unmodified semax. If your protocol calls for the acetylated, amidated form, check the identity line of any COA before you buy. A report that says “Semax” is not a report for N-acetyl semax amidate.
How to read a semax certificate of analysis
A COA is only useful if you know what each line proves. Here is FRO’s 30mg report (AccuMark Labs, sample code D7W9-8MTR, received 05/04/2026, published 09/07/2026) line by line:
| Test | Result | What it tells you |
|---|---|---|
| Identity | Semax, conforms | The main compound in the vial matches semax. |
| HPLC purity | 99.57% (spec > 98.0%) | Share of the sample that is the target peptide, measured by UV detection at 220 nm. The chromatogram shows one sharp main peak at about 4.53 minutes. The small blip near 1 minute is the solvent front, not an impurity. |
| Quantity | 33.45 mg measured in a 30 mg vial | How much peptide is actually in the vial. This vial held about 11% more than the label. Many COAs skip this line, but it is the one that catches underfilled vials. |
The full report, chromatogram included, is free to open in the Semax COA library. Match the code on your vial to the report.
What this report doesn’t cover
This report covers identity, HPLC purity and measured quantity. It does not include endotoxin, sterility or mass spectrometry results. Mass spectrometry is the cleanest way to confirm the exact molecular weight of 813.9 and to rule out oxidized methionine or the amidated variant. FRO has additional third-party testing underway at Vanguard Laboratory, an ISO 17025 lab, and new results are added to the COA library as they come in.
Red flags on any supplier’s COA
- No lot or sample code, or a code that doesn’t match the vial.
- No lab name, or a lab you can’t find.
- Purity with no chromatogram.
- No measured quantity, only the label claim.
- A “semax” report used to sell N-acetyl semax amidate, or the reverse.
- The same report reused across several products or years.
Storage and handling for research use
- Lyophilized powder: store frozen (−20 °C), sealed and protected from light. Let the vial reach room temperature before opening to avoid condensation, and keep it closed when not in use to limit oxidation.
- Reconstitution: semax is water-soluble. Add bacteriostatic water slowly down the vial wall and swirl gently until clear. Use the peptide reconstitution calculator to work out concentration for your protocol.
- After reconstitution: refrigerate at 2–8 °C, protect from light, and use within your protocol’s defined window.
- Avoid repeated freeze-thaw. If you need to store reconstituted material frozen, split it into single-use aliquots first.
Frequently asked questions
Does FRO Peptides publish a COA for semax?
Yes. The 30mg report from AccuMark Labs, an independent lab, is published in the COA library, chromatogram included.
What purity is FRO’s semax?
The current 30mg lot tested at 99.57% by HPLC, against a specification of more than 98.0%, with 33.45 mg measured in the 30 mg vial.
Does FRO sell N-acetyl semax amidate?
No. FRO sells unmodified semax (MEHFPGP). The acetylated, amidated form is a different compound with a different molecular weight.
Is semax the same as Selank?
No. Both are synthetic heptapeptides from the same research tradition, but Selank is built on tuftsin, an immune-system peptide, not on ACTH.
What is the difference between the vial sizes?
Only the quantity of peptide. The 5mg, 10mg and 30mg vials contain the same compound.
Is semax from FRO for human use?
No. FRO sells semax strictly for laboratory and analytical research. It is not for human or veterinary use.
View Semax research peptide (5mg–30mg) →
Lot report published in the COA library. Ships next business day, FedEx 2-Day.
For laboratory research use only. Not for human or veterinary use. Not a drug, food, or cosmetic under FDA regulations. Nothing on this page is medical advice.