Distribution of Counter Ions in Negatively-charged Lipid/Water/Air Interface: Molecular Dynamics Study

We investigated the distribution of ions around charged membranes at a lipid/water/air interface by using a molecular dynamics (MD) simulation with a sufficiently large cell size for water. It was shown that the thickness of the electronic double layer is different from the classical Debye length, which is a bit longer than the former. It was also found that the distance between the ions in the solution and the membrane charge changes depending on the difference in ionic charge owing to the water molecules around the ions. Detailed analysis of ion distribution near the lipid/water surface was presented. Molecular dynamics (MD) simulations of water/lipid/air surface were performed to investigate the distribution of ions around charged membranes. It was found that the charge distribution decays more rapid than the classical continuum model. We also the dependence of ionic valence charge on the screening of the membrane charges.