Molecular dynamics simulation of a dipalmitoylphosphatidylcholine bilayer with NaCl

Molecular dynamics simulations are performed on two hydrated dipalmitoylphosphatidylcholine bilayer systems: one with pure water and one with added NaCl. Due to the rugged nature of the membrane/electrolyte interface, ion binding to the membrane surface is characterized by the loss of ion hydration. Using this structural characterization, binding of Na+ and Cl- ions to the membrane is observed, although the binding of Cl- is seen to be slightly weaker than that of Na+. Dehydration is seen to occur to a different extent for each type of ion. In addition, the excess binding of Na+ gives rise to a net positive surface charge density just outside the bilayer. The positive density produces a positive electrostatic potential in this region, whereas the system,without salt shows an electrostatic potential of zero.