Chapter Five Liposome-Based Biomembrane Mimetic Systems: Implications for Lipid–Peptide Interactions

Abstract

Abstract The fundamental structural unit of biological membranes is mostly a highly dynamic, liquid-crystalline phospholipid bilayer that acts as a permeability barrier. The concept of a characteristic lipid composition for a given cell membrane is well-accepted and is of considerable interest, when studying the molecular mechanism(s) of membrane damage by membrane-active agents such as toxins or antimicrobial peptides. Despite the wealth of information and experimental data we still do not fully understand at a molecular level how these peptides disrupt the barrier function of cell membranes. Therefore, lipid model membranes mimicking the more complex biological membranes have attracted scientists from various fields. Structural and thermodynamic characterization of these biomembrane mimetic systems such as liposomes is a prerequisite for the understanding of lipid–peptide interactions. The focus of this contribution will be on how X-ray scattering techniques contribute to the characterization of liposomes and in turn to the elucidation of the mechanisms of peptide–membrane interaction. First, we summarize the current models for the mode of action of antimicrobial peptides as well as general aspects of model membranes followed by a detailed description of X-ray scattering in combination with a global data analysis. The applicability of this new approach is exemplary shown on selected model membrane and lipid–peptide systems demonstrating a tight coupling between the peptide properties and those of the lipid bilayer.