Model Bio-Membranes Investigated by AFM and AFS: A Suitable Tool to Unravel Lipid Organization and their Interaction with Proteins

The study of the biological membrane has largely benefitted from the exploitation of model bilayer systems. These simplified models of the complex biological membrane composed of thousands of different types of molecules allow both to understand basic physical principles underlying the membrane functioning and to test new techniques that will be subsequently applied to biological membranes. Here we concentrate on one of the most used model systems for this kind of investigations: the Supported Lipid Bilayer (SLB). In particular, we analyze the possibilities of investigation offered by Atomic Force Microscopy and Spectroscopy (AFM/AFS) on this model system. We discuss the information that this techniques is able to provide on the phase behavior of the lipid bilayers and on the partitioning of membrane proteins relative to the bilayer lateral heterogeneity. We discuss also the possibility to characterize the mechanical properties of lipid bilayers on the nanometer scale lateral resolution.