Chemical Structure and Physical Properties of Acetyl Octapeptide-3/SNAP-8

 Acetyl Octapeptide-3/SNAP-8 is a synthetic peptide used in cosmetic formulations as a topical anti-wrinkle ingredient. It is an acetylated octapeptide derived from the N-terminal end of the protein SNAP-25, which is involved in neurotransmitter release through the SNARE complex.

1. Chemical Structure of Acetyl Octapeptide-3 (SNAP-8)

Acetyl Octapeptide-3/SNAP-8 is a synthetic peptide composed of eight amino acids, designed as an extended analog of Acetyl Hexapeptide-8. It mimics a fragment of the SNAP-25 protein involved in the SNARE complex responsible for neurotransmitter release.

Molecular Composition

• Peptide Type: Synthetic oligopeptide

• Number of amino acids: 8

• Amino-acid sequence: Ac-Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp-NH₂

Where:

• Ac- = N-terminal acetyl group

• -NH₂ = C-terminal amide group

Structural Characteristics

1. N-terminal acetylation

• Increases stability and resistance to enzymatic degradation.

2. C-terminal amidation

• Neutralizes the terminal charge and improves bioactivity.

3. Linear peptide chain

• Acetyl Octapeptide-3/SNAP-8 is not cyclic; it is a linear oligopeptide.

4. SNAP-25 mimic fragment

• The sequence corresponds to part of the N-terminal domain of SNAP-25, enabling interference with SNARE complex formation.

Simplified Structural Representation

Ac–Glu–Glu–Met–Gln–Arg–Arg–Ala–Asp–NH2

This peptide fragment competes with SNAP-25 during SNARE complex assembly, reducing neurotransmitter release and thereby relaxing facial muscle contraction.

2. Physical Properties of Acetyl Octapeptide-3/SNAP-8

Property	Description
Molecular formula	C₄₁H₇₀N₁₆O₁₆S
Molecular weight	~1075.2 g/mol
Appearance	White to off-white powder
Solubility	Highly soluble in water
Odor	Odorless or very faint
pH stability	Stable around pH 4–7
Thermal stability	Stable at low–moderate temperatures; degrades at high heat
Charge	Slightly negative/neutral depending on pH
Hydrophilicity	Highly hydrophilic

3. Physicochemical Characteristics Relevant to Cosmetics

(1) Water-soluble peptide

Allows easy incorporation into:

• serums

• creams

• gel formulations

(2) Large molecular size

Molecular weight >1000 Da

Limited skin penetration

Often delivered using:

• liposomes

• nano-carriers

• peptide boosters

3. Biologically active peptide fragment

Acts as a competitive inhibitor in the SNARE protein complex to reduce muscle contraction.

4. Stability Characteristics

Factor	Stability
Light	Generally stable
Heat	Sensitive to high temperatures
Enzymes	Protected somewhat by acetylation
pH	Optimal stability pH 4–7

For cosmetic formulations:

• Best added during cool-down phase (<40 °C).

Summary

Acetyl Octapeptide-3/SNAP-8 is an acetylated linear octapeptide derived from a fragment of SNAP-25.

Its structure (Ac-Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp-NH₂) enables it to interfere with the SNARE complex, reducing neurotransmitter release and facial muscle contraction. Physically, it is a water-soluble, hydrophilic peptide powder with a molecular weight of ~1075 Da, commonly used in anti-wrinkle cosmetic formulations.

If you want, I can also explain:

• 3D molecular structure of Acetyl Octapeptide-3/SNAP-8

• Detailed physicochemical parameters (logP, isoelectric point, stability constants)

• Comparison of Acetyl Octapeptide-3/SNAP-8 vs Argireline molecular structure (very useful for cosmetic R&D).