Intermittent permeation of cylindrical nanopores by water.

Molecular-dynamics simulations of water molecules in nanometer sized cylindrical channels connecting two reservoirs show that the permeation of water is very sensitive to the channel radius and to electric polarization of the embedding material. At threshold, the permeation is intermittent on a nanosecond time scale, and strongly enhanced by the presence of an ion inside the channel, providing a possible mechanism for gating. Confined water remains surprisingly fluid and bulklike. Its behavior differs strikingly from that of a reference Lennard-Jones fluid, which tends to contract into a highly layered structure inside the channel.