Membrane interactions of designed cyclic RW peptides by solid-state NMR spectroscopy

Area of Science:

• Biochemistry
• Molecular Biology
• Membrane Biophysics

Background:

• Increasing microbial resistance necessitates novel antimicrobial agents.
• Antimicrobial peptides (AMPs) show promise as antibiotic complements.
• Designed cyclic hexapeptides rich in arginine and tryptophan target cell membranes.

Purpose of the Study:

• To elucidate the molecular mechanisms of membrane perturbation by two designed cyclic AMPs: cyclic RRRWWW and cyclic RWRWRW.
• To investigate the differential interactions of these AMPs with model membranes mimicking bacterial and eukaryotic lipid compositions.
• To understand how AMP structure influences membrane interaction and disruption.

Main Methods:

• Utilized ³¹P and ²H solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Analyzed peptide interactions with various model membranes, including those composed of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG).
• Quantified changes in lipid chain order parameters and assessed vesicle morphology.

Main Results:

• The two cyclic AMPs exhibited distinct interactions with phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) lipid components.
• A significant decrease in deuterium order parameters was observed, indicating peptide-induced membrane structural disturbance.
• Deformation of vesicle shapes further supported the membrane-perturbing activity of the AMPs.

Conclusions:

• The study provides molecular-level insights into the distinct mechanisms by which cyclic AMPs interact with and perturb model lipid membranes.
• Findings highlight the structure-dependent nature of AMP-membrane interactions.
• This research contributes to the understanding and design of novel antimicrobial peptides for therapeutic applications.