Function
While Semax is used clinically in Russia for ischemic stroke and cognitive disorders; in models it improves learning, protects dopaminergic neurons, and modulates stress responses without significant endocrine ACTH-like effects166174, Snap-8 is a cosmetic peptide studied for reducing wrinkle depth by inhibiting synaptic vesicle fusion and subsequent muscle contraction in facial expression muscles5060.
Mechanism
While Semax works as a synthetic heptapeptide, Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP), that is an analog of ACTH(4–10) with a Pro-Gly-Pro extension and exerts neurotrophic and neuroprotective actions partly via upregulation of BDNF and modulation of dopaminergic and glutamatergic systems40162165174, Snap-8 is acetyl octapeptide-3 (Ac-Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp-NH2), an extended analog of Argireline derived from the N-terminal region of SNAP-25 that competes with native SNAP-25 for binding to syntaxin-1, forming a non-functional SNARE complex and reducing neurotransmitter release5060.
Length and Sequence
Semax is 7 amino acids long, whereas Snap-8 is longer as it has a length of 8 amino acids. Semax is made up of a sequence of Methionine, Glutamic acid, Histidine, Phenylalanine, Proline, Glycine, Proline. Snap-8 is made up of a sequence of Glutamic acid, Glutamic acid, Methionine, Glutamine, Arginine, Arginine, Alanine, Aspartic acid.