Ion distribution in the vicinity of phase-separated membrane

The physical properties of multi-component phospholipid layers have attracted increasing attention as a result of their potential benefits in medicine. We consider a phase-separated multi-component phospholipid plane with one half consisting of charged lipids and the other half of non-charged lipids in contact with an electrolyte solution composed of monovalent ions. Coarse-grained molecular dynamics (MD) simulations were performed to simulate the phase transition between charged and non-charged lipids. In addition, the modified Poisson-Boltzmann (PB) approach was used to consider the distribution of ions with finite size in the vicinity of the charge discontinuity in the lipid layer. The passage between charged and non-charged parts of the plane was described by a sigmoid function obtained from MD simulations. In the vicinity of the lipid layer, in the transition from the uncharged to the charged part, a continuous transition to an increased concentration of counterions is visible