Selank vs SNAP-8 (Acetyl Octapeptide-3)

Selank

Selank is a synthetic seven-residue peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, made by adding Pro-Gly-Pro to the tetrapeptide tuftsin. Tuftsin is a fragment of the heavy chain of immunoglobulin G, studied in immunology for its actions on phagocytic cells; the Pro-Gly-Pro extension was added to slow enzymatic breakdown. Selank was developed in Russia, and most published work on it comes from Russian groups. That literature consists mainly of rodent behavioural and gene-expression studies, with some small clinical studies, many of them published in Russian-language journals. Independent work outside Russia is limited.

SNAP-8 (Acetyl Octapeptide-3)

SNAP-8, or acetyl octapeptide-3, is a synthetic eight-residue peptide modelled on the N-terminal region of the neuronal protein SNAP-25. Its sequence, Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp, extends the related acetyl hexapeptide-3 by two residues, and both ends are capped: acetylated at the N-terminus and amidated at the C-terminus. It was developed as a cosmetic ingredient, and most available data come from ingredient-level testing and small studies of topical formulations rather than independent research. Biochemical work has looked at its interaction with the SNARE complex in vitro. Whether a peptide of this size crosses intact skin to reach nerve terminals in meaningful amounts has not been well established.

How Selank acts

No single receptor for Selank has been identified. Rodent studies have reported that it changes the expression of genes involved in GABAergic neurotransmission, and some experiments suggest it modulates GABA-A receptor function allosterically. It has also been reported to inhibit enkephalin-degrading enzymes in blood serum, to affect monoamine metabolism in the brain, and to alter the expression of cytokines including interleukin-6. Increased expression of brain-derived neurotrophic factor (BDNF) in the rat hippocampus has also been described. Much of this evidence comes from a small number of laboratories and awaits independent replication.

How SNAP-8 (Acetyl Octapeptide-3) acts

Release of neurotransmitter from a nerve terminal depends on the SNARE complex, a bundle of helices contributed by SNAP-25, syntaxin and synaptobrevin (VAMP) that draws vesicle and plasma membranes together. Acetyl octapeptide-3 copies a short stretch of the SNAP-25 N-terminus and has been proposed to compete with the native protein for a place in that bundle. Reports, mostly from ingredient developers, describe less efficient assembly of stable complexes and reduced neurotransmitter release from cultured cells. These data come largely from simplified systems, and evidence that the same interaction occurs in intact tissue is limited.

The records side by side

• Type: Selank, Synthetic tuftsin analog (heptapeptide); SNAP-8 (Acetyl Octapeptide-3), Acetylated octapeptide with C-terminal amidation
• Length: Selank, 7 amino acids; SNAP-8 (Acetyl Octapeptide-3), 8 amino acids
• Molecular weight: Selank, 751.9 g/mol; SNAP-8 (Acetyl Octapeptide-3), 1075.2 g/mol
• Molecular formula: Selank, C33H57N11O9; SNAP-8 (Acetyl Octapeptide-3), C41H70N16O16S

Reading a comparison

A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.