Molecular dynamics simulation of water between two charged layers of dipalmitoylphosphatidylserine

A molecular dynamics simulation of water between two charged layers of dipalmitoylphosphatidylserine in its liquid-crystalline state with atomic detail was carried out. From an analysis of a trajectory of 184 ps of length, we obtained information about the dynamics and structure of water between such charged layers. The most remarkable conclusions of this work indicate that the presence of counterions and charge interactions between adjacent phospholipids produce a screening of the electric field which reduces the strength of the lipid-water interactions. In this way, only minor differences of the behavior of the water compared to uncharged phospholipids were found. This conclusion was based on the calculation of the following properties: electric potential and water dipole orientation across the water layer, radial distribution function of water about lipid atoms, and diffusion and orientational relaxation time of water.