  We consider ion transport through protein ion channels in lipid membranes and
water-filled nanopores in silicon films. It is known that, due to the large
ratio of dielectric constants of water and the surrounding material, an ion
placed inside the channel faces a large electrostatic self-energy barrier. The
barrier leads to an exponentially large resistance of the channel. We study
reduction of the electrostatic barrier by immobile charges located on the
internal walls of the channel. We show that the barrier practically vanishes
already at relatively small concentration of wall charges.
