Semax - Frequently Asked Questions

Semax is a synthetic melanocortin / ACTH(4-10)-derived neuropeptide, specifically a heptapeptide. It combines the ACTH(4-7) fragment (Met-Glu-His-Phe) with a C-terminal Pro-Gly-Pro tripeptide, placing it in the melanocortin/ACTH-fragment family while lacking the N-terminal corticotropic residues of full ACTH.

The sequence is Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP), written H-Met-Glu-His-Phe-Pro-Gly-Pro-OH. The first four residues are the ACTH(4-7) fragment and the final Pro-Gly-Pro is a stability-conferring C-terminal tail.

Semax has an average molecular weight of 813.92 g/mol as the free base and the molecular formula C37H51N9O10S. The single sulfur atom corresponds to the methionine residue.

The CAS Registry Number is 80714-61-0, per Cayman Chemical and ChemicalBook references in the entry. This provides a unique, supplier-independent identifier for verifying received reference material.

In rat basal forebrain membranes, tritium-labeled Semax shows specific, reversible, time-dependent binding with a dissociation constant KD of 2.4 +/- 1.0 nM and a binding-site density BMAX of 33.5 +/- 7.9 fmol/mg protein (Dolotov et al., J Neurochem 2006, PMID 16635254).

Ex-vivo rat hippocampus studies report roughly a 1.4-fold increase in BDNF protein, about 1.6-fold TrkB tyrosine phosphorylation, approximately 3-fold exon III BDNF mRNA, and around 2-fold trkB mRNA after a single application (Dolotov et al., Brain Research 2006, PMID 16996037), implicating downstream neurotrophin-receptor cascades such as MAPK/ERK and PI3K/Akt.

The C-terminal Pro-Gly-Pro shields the peptide from aminopeptidase degradation, increasing metabolic stability relative to native ACTH(4-10). This is the structural rationale for the tail, supported by a 2006 degradation study (Amino Acids) and multiple reviews.

According to the provided data, Semax lacks the corticotropic N-terminal ACTH residues and is therefore described as devoid of classical adrenal-stimulating hormonal activity, despite being derived from an ACTH fragment.

The cited studies examined BDNF/TrkB neurotrophin signaling in rat hippocampus and basal forebrain, melanocortin/ACTH-fragment receptor binding, neurotrophin and receptor gene transcription in cerebral ischemia models (including a genome-wide transcriptional analysis), monoaminergic modulation, and in-vitro enzymatic stability, all in rodent, ex-vivo, or cell-free systems.

For in-vitro handling, the lyophilized peptide is reconstituted by adding a measured volume of bacteriostatic water to yield a stock of known concentration (mass divided by volume). It is aliquoted, stored cold and protected from light, and the defined molecular weight (813.92 g/mol) allows conversion to molar concentration. This is laboratory preparation only, not a dosing protocol.

No numeric half-life value is provided in the entry. The data instead emphasizes enzymatic stability: the Pro-Gly-Pro tail confers aminopeptidase resistance, prolonging in-vitro and ex-vivo stability versus native ACTH(4-10). General peptide-class storage principles (aliquoting, cold storage, light protection) apply for reconstituted stock.

Semax is presented strictly as a research-use-only (RUO) reference compound. All described properties pertain to in-vitro, ex-vivo, receptor-binding, and preclinical rodent contexts; the entry supports no human, therapeutic, or dosing applications.