  We report Molecular Dynamics (MD) simulations of a generic hydrophobic
nanopore connecting two reservoirs which are initially at different Na+
concentrations, as in a biological cell. The nanopore is impermeable to water
under equilibrium conditions, but the strong electric field caused by the ionic
concentration gradient drives water molecules in. The density and structure of
water in the pore are highly field dependent. In a typical simulation run, we
observe a succession of cation passages through the pore, characterized by
approximately bulk mobility. These ion passages reduce the electric field,
until the pore empties of water and closes to further ion transport, thus
providing a possible mechanism for biological ion channel gating.
