In Situ Mapping of Membranolytic Peptide-Membrane Interactions by Coupled Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy-Atomic Force Microscopy (ATR-FTIR-AFM)

Abstract

The mechanisms by which membranolytic peptides may exert their action are highly complex and specific. They may involve peptide self-association, membrane-induced refolding, or targeting of specific lipid domains or components. Insights into these behaviours are critical for the de novo design of peptide-based antimicrobial agents. To better understand these mechanisms, we have applied coupled attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR)-atomic force microscopy (AFM) to directly visualize and characterize the interactions of two different classes of model membranolytic peptides with supported planar lipid bilayers. Our studies provided direct evidence of membrane rearrangement and peptide aggregation by a de novo cationic antimicrobial peptide designed to adopt a helical motif in bacterial membranes. We also obtained in situ evidence of specific secondary structure motifs associated with a membrane-induced fibrillization of peptides derived from haemolytic proteins obtained from sea anemone. This coupled approach provides a unique opportunity to directly link spectroscopic details associated with peptide-membrane interactions with in situ structural insights obtained on nanometer length scales.