Semax: a hormone fragment plus three residues

Semax consists of a fragment of an endogenous hormone plus three added residues. The first residue in the chain is methionine, which is why storage matters more here than for most short chains.

Met-Glu-His-Phe plus Pro-Gly-Pro

The sequence is Met-Glu-His-Phe-Pro-Gly-Pro, MEHFPGP in one-letter code. The first four residues correspond to a fragment of adrenocorticotropic hormone, the last three are a stabilising addition: the same Pro-Gly-Pro as in Selank.

The molecular formula is C₃₇H₅₁N₉O₁₀S, the molar mass 813.92 g/mol and the CAS number 80714-61-0. All of it is on the product page.

The parent sequences of Semax and Selank have nothing to do with each other; what they share is length, end piece and research tradition. Where the Selank sequence comes from is set out in Selank explained.

The S in the formula

The single sulphur atom in C₃₇H₅₁N₉O₁₀S comes from the methionine at position one. Of all the standard amino acids, methionine reacts most readily with oxygen, and oxidation raises the mass measurably.

For mass spectrometry that is rather helpful: a second signal then appears beside the expected one, and the finding is unambiguous. For storage it means that keeping this substance cool and away from light is not optional (see Storing lyophilised peptides in the laboratory). The same applies to MOTS-c, which carries two methionines.

Three certificates, all with a figure

The certificate library holds three certificates of analysis for this substance, all from 10 mg lots, the same fill size that is sold here. They report a measured purity of 98.64%, 99.8% and 98.367%.

Three certificates is not many; for CJC-1295 no DAC there are seven. That says nothing about the material, only about the number of lots documented so far, and it is stated here because a library you can count for yourself is worth more than one that is merely talked about. This shop does not state a blanket minimum purity; what counts is the measured value in the certificate for each lot.

Seven residues, two prolines

Six coupling steps in solid-phase synthesis are few, and the high values follow from that. The two prolines in the end piece make coupling at their positions slower, because their ring binds into the backbone and stiffens that point.

Purity should not be confused with peptide content, which is lower because of counterions and residual moisture. The product is supplied as a lyophilised powder; it goes into solution with bacteriostatic water, and the glossary entries on reconstitution and concentration explain the terms.

In brief

Seven residues with one sulphur atom, 813.92 g/mol, CAS 80714-61-0, three certificates of analysis from the matching vial size.

Questions

Where does the Semax sequence come from?

The first four residues correspond to a fragment of adrenocorticotropic hormone. The three added residues, Pro-Gly-Pro, are a stabilising addition.

Why does storage matter more for Semax?

Because of the methionine at position one. It is the standard amino acid most sensitive to oxygen, and oxidation changes the measurable mass.

Why are there only three certificates of analysis?

Because only three lots of this substance have been documented so far. All come from 10 mg lots and can be viewed in the library without an account.