Snap-8, also designated acetyl octapeptide-3 (acetyl glutamyl heptapeptide-1), is a synthetic eight-residue peptide whose sequence mimics the N-terminal region of SNAP-25, one of the core proteins of the SNARE complex. It is an elongated relative of acetyl hexapeptide-8, carrying two additional residues at the C-terminal end. Research interest centers on how short SNAP-25-mimetic peptides compete with the native protein during SNARE assembly, which makes Snap-8 a tool for studying the molecular machinery of vesicle docking and neurotransmitter release in cell-free and cell-based systems. This overview covers its chemical identity, the biology of its target, published research context, analytical characterization and laboratory handling.
Snap-8 is an N-acetylated octapeptide amide: Ac-Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp-NH2.
Molecular formula: C41H70N16O16S. Molecular weight: 1,075.2 g/mol. Synonym: acetyl octapeptide-3. CAS: 868844-74-0. Classification: SNAP-25-derived synthetic peptide.
The sequence mimics the N-terminal region of SNAP-25. N-terminal acetylation and C-terminal amidation remove the terminal charges and improve stability against exopeptidases compared with the free peptide.
Regulated exocytosis depends on the SNARE complex, a four-helix bundle formed by synaptobrevin (VAMP) on the vesicle membrane and by syntaxin and SNAP-25 on the target membrane. Zippering of these helices brings the two membranes together and drives fusion, releasing vesicle contents such as acetylcholine.
Snap-8 reproduces a short stretch of the SNAP-25 N-terminal helix. In cell-free assembly assays, peptides of this type compete with native SNAP-25 for positions in the assembling complex, which can reduce the fraction of complexes that form correctly. The effect is concentration-dependent and reversible, in contrast to clostridial neurotoxins, which cleave SNAP-25 enzymatically.
Acetyl hexapeptide-8 (Ac-Glu-Glu-Met-Gln-Arg-Arg-NH2) is the six-residue parent sequence, from the same N-terminal region of SNAP-25. Snap-8 adds alanine and aspartate, extending the peptide toward the C-terminus of the same SNAP-25 region. The added residues change the peptide's length, charge distribution and hydrophobicity, which is why the two are compared side by side in structure–activity and SNARE-assembly studies.
Direct comparisons are usually run at equal molar concentrations in the same assay format, with a scrambled-sequence peptide as a negative control so that sequence-specific effects can be distinguished from nonspecific peptide interactions.
Snap-8 is studied in: SNARE complex biology, cell-free SNARE-assembly and liposome-fusion assays, in-vitro neurotransmitter release models, structure–activity relationship work on SNAP-25-derived peptides, and peptide stability studies.
Additional research contexts include comparative studies against acetyl hexapeptide-8 and other SNARE-modulating peptides, evaluation of liposomal carriers for in-vitro delivery experiments, and structure–activity studies exploring how N-terminal acetylation and C-terminal amidation influence peptide half-life in buffer and binding kinetics at the SNAP-25 interface. Investigators also use Snap-8 as a reference peptide when benchmarking new SNAP-25-mimetic candidates in cell-based exocytosis assays.
Reverse-phase HPLC with UV detection is used to assess purity, and electrospray mass spectrometry confirms identity against the calculated mass of about 1,075 Da. The methionine residue can oxidize to the sulfoxide (+16 Da), so oxidized variants are monitored as a specific impurity during method development.
Snap-8 is prepared by Fmoc solid-phase peptide synthesis on an amide-forming resin such as Rink amide, with N-terminal acetylation performed on-resin before cleavage. The two consecutive arginine residues and the aspartate require optimized coupling and cleavage conditions to limit deletion sequences and aspartimide formation, and these by-products are removed by preparative reverse-phase HPLC before lyophilization.
Material sold as Snap-8 is supplied as a research chemical for in-vitro laboratory research and identification purposes only. It is not approved by the FDA for human or veterinary use and is not for human consumption.
Form: lyophilized powder. Storage: 2–8°C short-term; −20°C long-term, protected from light. Minimize air exposure of opened material because of the oxidation-prone methionine residue.
For research use only. Not for human consumption.
Snap-8 is an octapeptide; acetyl hexapeptide-8 is a hexapeptide. Snap-8 carries two additional residues, alanine and aspartate, that extend the SNAP-25-mimetic sequence, which is why the two peptides are compared in SNARE-assembly research.
Snap-8 is Ac-Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp-NH2, with molecular formula C41H70N16O16S and a molecular weight of about 1,075.2 g/mol.
As a lyophilized powder at −20°C for long-term storage, protected from light and moisture. The methionine residue is susceptible to oxidation, so opened material should be kept sealed and handled with minimal air exposure.
The SNARE (soluble NSF attachment protein receptor) complex is the molecular machinery that mediates synaptic vesicle docking and neurotransmitter release at synapses. SNAP-25 is a key component of this complex.