Nano-domain formation in charged membranes: Beyond Debye-Huckel approximation

We investigate the microphase separation in a membrane composed of charged lipid, by taking into account explicitly the electrostatic potential and the ion densities in the surrounding solvent. While the overall (membrane and solvent) charge neutrality is assumed, the membrane can have a non-zero net charge. The static structure factor in the homogeneous state is analytically obtained without using the Debye-Huckel approximation and is found to have a peak at an intermediate wave number. For a binary membrane composed of anionic and neutral lipids, the characteristic wave number corresponds to a scale from several to tens of nanometers. Our numerical calculation further predicts the existence of nano-domains in charged membranes.