Colloquium: Dr. Syvio MayDepartment of Physics North Dakota State University Fargo, ND
Electrostatics of Lipid Membranes
To describe the electrostatic properties of a lipid membrane, mean-field continuum electrostatics is widely used. Its fundamental implementation - the classical Poisson-Boltzmann model - predicts the structure and corresponding free energy of the diffuse layer of counterions and coions in the vicinity of a uniformly charged surface. The mean-field character of the Poisson-Boltzmann approach and its ability to predict free energies make the model an ideal starting point for extensions and applications to complex soft matter systems. In this talk, we briefly discuss one specific extension that is related to the dipolar character of zwitterionic lipids. We demonstrate how mobile surface dipoles can be included into the Poisson-Boltzmann framework. To this end, we suggest an extended mean-field model that can be used to describe mixed charged-zwitterionic membranes, their stability with respect to lateral phase separation, and their interactions with macroions such as DNA and proteins.