Semax

1 Identity

Synthetic linear heptapeptide. Residues 1-4 are the ACTH(4-7) fragment Met-Glu-His-Phe; residues 5-7 are a synthetic Pro-Gly-Pro C-terminal extension. Free-acid C-terminus, free N-terminal alpha-amine, no acetyl, no amide, no acylation, no non-proteinogenic residue, no cysteine, no disulfide. All seven residues proteinogenic and L-configured. The sequence stops short of the His-Phe-Arg-Trp melanocortin core, which is why the molecule is classed with the neuroactive regulatory peptides rather than the melanocortin receptor ligands despite its ACTH derivation. The N-terminal methionine is the analytically decisive residue and it drives the packaging, the storage condition and the purity method. CAS 80714-61-0. PubChem CID 9811102. The vendor abbreviation 'NASA' is applied both to N-Acetyl Semax Amidate and to N-Acetyl Selank Amidate and identifies neither on its own.

Sequence

H-Met-Glu-His-Phe-Pro-Gly-Pro-OH; one-letter MEHFPGP, 7 residues. Free acid at the C-terminal proline, free alpha-amine at the N-terminal methionine. Supplied lyophilized as the acetate or trifluoroacetate salt.

Molecular formula

C37H51N9O10S (free base). One sulfur, in the Met1 thioether, and it is both the identity handle in the isotope envelope and the principal degradation site.

Average mass

813.928 Da (C37H51N9O10S) on IUPAC 2021 abridged conventional atomic weights. PubChem publishes 813.9, and sellers print 813.9 and 813.93; the same formula on the pre-2021 table returns 813.920. Mono-acetate formula weight 873.98 (acetate 6.87 percent w/w); mono-trifluoroacetate 927.95 (trifluoroacetate 12.29 percent w/w).

Monoisotopic mass

813.34796 Da neutral free base; [M+H]+ 814.35524; [M+2H]2+ 407.68126. A plus or minus 5 ppm window on the protonated ion is plus or minus 0.0041 Da, comfortably inside the 0.98 Da that separates this molecule from its C-terminal amide and the 41.05 Da that separates it from the N-acetylated amide. An independent laboratory reported 813.3 monoisotopic for this formula, and the formula gives 813.34796.

Salt / variant note

The Adamax problem lives on this record and it is the most important thing on the page. (1) N-Acetyl Semax Amidate, Ac-MEHFPGP-NH2, C39H54N10O10S, 854.981 avg / 854.37451 mono, [M+H]+ 855.38179 — 41.05 Da heavier than the parent, and independently given by an outside laboratory as C39H54N10O10S at 854.97. This is the most common mis-certification on this molecule, because the market uses the two trade names interchangeably and they are not interchangeable compounds. (2) N-Acetyl Semax free acid, Ac-MEHFPGP-OH, C39H53N9O11S, 855.965 avg / 855.35852 mono. Set (1) against (2): 0.98 Da apart, both round to '855' on a nominal-mass instrument, two different molecules, two different reference standards, one number on a bad certificate. (3) Semax C-terminal amide, MEHFPGP-NH2, C37H52N10O9S, 812.944 avg / 812.36394 mono — 0.98 Da lighter than the parent. (4) ADAMAX. A figure of 976.2 avg / 975.45 mono circulates for Adamax, carried with the instruction that '976.2 under a Semax label is not Semax'. That figure is withdrawn: 976.2 is simply 813.93 plus 162.23 for an adamantane-1-carbonyl on plain Semax, a mass derived from an assumed structure rather than measured, which is the exact defect this record exists to correct. Two chemically distinct molecules trade commercially as 'Adamax'. The extended non-adamantyl variant is Ac-Met-Glu-His-Phe-Pro-Gly-Pro-Ala-Gly-OH, C44H61N11O13S, 984.096 avg / 983.41710 mono, confirming the outside laboratory's 984.1 to the decimal. The full adamantane-modified article that laboratory quotes as C50H69N11O11S at 1030.23 does not reconcile: that formula computes to 1032.228 avg / 1031.48987 mono, two hydrogens above the quoted mass, while C50H67N11O11S computes to 1030.212 avg / 1029.47422 mono and matches the quoted number. Every other row from that laboratory reproduces exactly, so the discrepancy is specific to the adamantyl row — either the formula or the mass was transcribed with a two-hydrogen error — and the manufacturer must reconfirm formula and mass together in writing before either is printed. Until that letter exists, no adamantyl mass is stated as established. (5) Methionine sulfoxide, +15.995: C37H51N9O11S, 829.927 avg / 829.34287 mono — a degradant, not an analogue, and the failure the packaging exists to prevent. (6) Methionine sulfone, +31.990: C37H51N9O12S, 845.926 avg / 845.33779 mono. (7) ACTH(4-7) MEHF, C25H34N6O7S, 562.642 avg / 562.22097 mono — the 4-mer core, 251.29 Da lighter. (8) Salt forms sold under the bare name: free base 813.93 at one seller against 'Semax acetate' at another; mono-acetate 873.98 (6.87 percent w/w), mono-trifluoroacetate 927.95 (12.29 percent w/w). The commercial reality: material sold as Adamax is routinely certified at 813.9, which is plain Semax, or at 855, which is N-acetyl Semax amidate, and both directions were observed by the contract laboratory that will run this company's release testing.

2 Class & testing panel

Form

Single article

Testing panel

P1 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Rodent and in-vitro studies form the bulk of the characterized literature, alongside a Russian-language clinical literature tied to the compound's Russian registration — mostly small, often unblinded, and typically silent on the analytical characterization of the test article. English-language PubMed indexing is on the order of a hundred items including reviews and translations. No FDA-registered trial exists and ClinicalTrials.gov returned no completed controlled trial under this name. Two facts are worth recording precisely because they are structural rather than promotional: the compound is a registered pharmaceutical in the Russian Federation as 0.1 percent and 1 percent nasal drops, which is a fact about Russian regulatory practice and not an independent validation by a stringent regulatory authority; and the two human studies in healthy volunteers (n=24 and n=52) measured resting-state fMRI connectivity rather than any validated cognitive endpoint. There is also a directly relevant in-vitro report, Magri and colleagues (PMID 27586814), that N-terminal acetylation abolished a documented in-vitro activity of this peptide — which bears on the analogue trade rather than on this molecule. The citation index page carries the primary reports with study-type, language, design and sample-size badges and states what is absent in the same typeface as everything else.

4 Storage & specification

Storage

Lyophilized white to off-white powder in amber Type I glass, bromobutyl stopper, headspace displaced with nitrogen, desiccant in the shipper. Labeled condition: store at -20 degrees C plus or minus 5 degrees C, desiccated, protected from light, headspace re-blanketed with nitrogen after any subdivision. The light and oxygen conditions are not boilerplate on this record — they are the specific controls for methionine oxidation, and the label states the reason so a receiving technician cannot treat them as optional. Vials equilibrated to room temperature before opening. Shipped on dry ice or in a validated shipper holding not more than 8 degrees C for transit up to 96 hours, with a single-use electronic temperature logger in every shipper.

Shelf life

Provisional 24-month retest interval at -20 degrees C plus or minus 5 degrees C, desiccated and light-protected, held pending this company's own stability data. Because the governing failure mode is oxidative rather than hydrolytic, the protocol pulls at 0, 3, 6, 12, 18, 24 and 36 months and trends methionine sulfoxide as a named attribute; the interval is shortened if sulfoxide growth exceeds 0.3 percent per year at the labeled condition, and that trigger is written into the stability protocol rather than left to judgment.