Catalogue / Semax
Semax
A heptapeptide combining the ACTH 4-7 fragment with a C-terminal Pro-Gly-Pro tail that resists enzymatic cleavage.
| Molecular formula | C37H51N9O10S |
| Average mass | 813.92 Da |
| Monoisotopic mass | 813.348 Da |
| Residues | 7 |
| Termini | C-terminal free acid |
| Class | Short bioregulator peptides |
| Determination | Peptide analysis, catalogue compound |
| Price | 341 USD |
Computed at build time from the composition shown on this page, not transcribed from a supplier datasheet.
Semax has an average molecular weight of 813.92 daltons and a monoisotopic mass of 813.348 daltons. Identity is confirmed by matching the measured deconvoluted mass to that figure, and purity is reported separately by reversed-phase chromatography at 214 nm. The two numbers answer different questions and neither substitutes for the other.
| One letter | MEHFPGP |
| Three letter | Met-Glu-His-Phe-Pro-Gly-Pro |
| Modifications | C-terminal free acid |
The formula and both masses in the table above are derived from this sequence and these terminal modifications. A reader who believes a figure is wrong can check the composition rather than take the number on trust, which is the point of publishing it this way.
A sequence is not an identity result. It is the expected composition against which a measured mass is compared, and the comparison is what appears on the certificate.
| Charge | m/z |
|---|---|
| [M+1H]+ | 814.355 |
| [M+2H]2+ | 407.681 |
These are the ions an electrospray source is expected to produce for a neutral mass of 813.348 daltons, computed from the monoisotopic mass and the proton mass. They are what a raw spectrum should show before deconvolution.
A report that gives only a deconvoluted mass without the charge states it was derived from cannot be checked. Deconvolution is a calculation, and a calculation whose inputs are not shown is an assertion.
| The N-terminal methionine oxidises to the sulfoxide, adding 16 daltons, and this is the dominant degradation product in aged material. |
| N-acetylated Semax is a distinct product 42 daltons heavier and is sold alongside the plain form. The two are frequently interchanged. |
| The Pro-Gly-Pro tail is shared with several other bioregulators, so a fragment-based identification without the intact mass can be ambiguous. |
Every compound fails in its own way. A generic peptide method applied without regard to these specifics produces a number that looks like a result and is not one.
Di, tri and tetrapeptides. Low molecular weight makes them the hardest class to quantify honestly: at this size the counter-ion and residual water can outweigh the peptide itself.
LC-MS identity, purity by RP-HPLC with a polar-retentive column since these peptides are barely retained on standard C18, and net peptide content because a purity figure alone is close to meaningless here.
Where the delivered milligram figure matters rather than the percentage, net peptide content by combustion analysis and water by Karl Fischer are added, and the certificate carries a closed mass balance instead of a single purity number.
| LC-MS identity | Measured mass |
| RP-HPLC purity | Area at 214 nm |
| Net peptide content | Milligrams |
| Water content | Karl Fischer |
| Counter-ion | Ion chromatography |
| Bacterial endotoxins | USP <85> |
What is the molecular weight of Semax?
The average molecular weight is 813.92 daltons and the monoisotopic mass is 813.348 daltons, computed from the sequence MEHFPGP shown on this page. Both figures are calculated rather than transcribed, so they can be checked against the stated composition.
How is Semax tested for purity and identity?
LC-MS identity, purity by RP-HPLC with a polar-retentive column since these peptides are barely retained on standard C18, and net peptide content because a purity figure alone is close to meaningless here. Purity describes the chromatographable fraction only and is not the same quantity as the peptide mass delivered per vial.
What goes wrong when Semax is analysed?
The N-terminal methionine oxidises to the sulfoxide, adding 16 daltons, and this is the dominant degradation product in aged material.
What does Semax analysis cost at ANALYTON?
Peptide analysis, catalogue compound is priced at 341 US dollars, covering the determinations described on this page. Content, safety and elemental determinations are ordered alongside and are priced separately on the price list.
Updated 2026-09-01. Masses computed at build, not transcribed.