Hydrophobic interactions modulate antimicrobial peptoid selectivity towards anionic lipid membranes

Area of Science:

• Biochemistry
• Materials Science
• Microbiology

Background:

• Hydrophobic interactions are key to natural antimicrobial peptide specificity.
• The relationship between hydrophobicity and specificity in synthetic peptoids is not well-established.
• Peptoids are synthetic mimics of antimicrobial peptides with potential therapeutic applications.

Purpose of the Study:

• To investigate the role of hydrophobicity in the membrane interaction and selectivity of synthetic peptoid macrocycles.
• To determine if hydrophobicity governs the specificity of peptoids against bacterial versus eukaryotic membranes.
• To compare the optimization schemes of synthetic peptoids with natural antimicrobial peptides.

Main Methods:

• Synthesis of peptoid macrocycles with varying aromatic groups.
• Minimum inhibitory and hemolytic concentration assays.
• Epifluorescence microscopy, atomic force microscopy, and X-ray reflectivity.
• High-performance liquid chromatography for hydrophobicity determination.
• Studies on solid-supported lipid bilayers and Langmuir monolayers.

Main Results:

• Peptoid hydrophobicity was successfully modulated by aromatic groups.
• Selective disruption of bacterial lipid membranes, but not eukaryotic membranes, was observed.
• Peptoid intercalation into lipid membranes was regulated by hydrophobicity.
• Critical levels of peptoid selectivity were demonstrated and linked to hydrophobic groups.

Conclusions:

• Hydrophobicity is a critical factor in the membrane selectivity of synthetic peptoids.
• Synthetic peptoids may require different design principles compared to natural antimicrobial peptides for optimized function.
• These findings support the development of peptoids as targeted antimicrobial agents.