Electrostatic interactions in symmetric and asymmetric charged free-standing membranes

Phospholipid bilayer elastic properties govern numerous biological processes, ranging from the deformation necessary during endocytosis and exocytosis, to the lateral diffusion of membrane proteins. In this presentation, we will discuss recent advances in our lab applying a novel technique to create free-standing charge asymmetric membranes with controlled composition on either membrane leaflet. Capacitance measurements characterize the degree of charge asymmetry, indicating transmembrane potentials approaching the biological case of 100 mV. Electrostriction experiments detail the effect of charge on the membrane Young's modulus, showing that as the overall charge in the membrane increases so does the membrane stiffness. However, asymmetric membranes are less stiff than their symmetric counterparts. The measured membrane Young's modulus is then related to the membrane bending rigidity by applying thin plate theory in the framework of linear elasticity. We critically examine our results in comparison with measurements of bending rigidity using other methods (supported lipid bilayers and giant unilamellar vesicles), with a particular focus on the impact of phospholipid composition, preparation method, and asymmetry.