AFM Determination of the Elasticity of Model Biomembranes

Abstract

The utility of AFM (Atomic Force Microscopy) to study surface morphologies and molecular level forces is well known. It is also possible to apply well-defined small forces on soft surfaces using the AFM. The latter is being used here to determine the elasticity (Young's modulus) of model membrane lipid bilayers. The mechanical properties of biological membranes are of interest in understanding various biologically related processes like cell hemolysis, viral fusion and pore formation, etc. and are closely related to the cell stability. The method involves determination of the force curves by compressing the lipid bilayer by indenting the AFM tip on the bilayer surface, and the resulting elastic response of the bilayer to the applied force (load) is analysed using theoretical models for the tip geometry. We will discuss the sample preparation technique and the results of our experiments on coexisting fluid-phase domains in typical ‘lipid raft’ mixtures, as well as the effects of varying the level of unsaturation of the lipid carbon chains.