Peptide-lipid interactions in supported monolayers and bilayers

Abstract

This chapter describes monolayer and bilayer techniques for measuring the insertion and structure of peptides in lipid membranes. Measurements of lipid monolayer expansion, together with molecular area measurements of the peptide yield binding isotherms, thermodynamic partition coefficients, and free energies of peptide insertion. Supported bilayers on solid substrates provide a relatively new membrane model system that has become particularly useful for measuring secondary structures and orientations of peptides in lipid bilayers by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in physiological environments. The chapter also discusses the application of these and other techniques to determine the structure and interactions of the fusion peptide of the influenza hemagglutinin in lipid bilayers. Fusion peptides are an interesting class of peptides, which upon activation, become exposed from the ectodomains of fusion proteins and subsequently insert into the bilayer of target membranes, in order to fuse target and host membranes. The sequences of fusion peptides are generally highly conserved within a given class of fusion proteins. A widely studied prototype fusion peptide is that of influenza hemagglutinin, which fuses membranes at pH 5, but not at pH 7.