  We develop a correlation-corrected transport theory in order to predict ionic
and polymer transport properties of membrane nanopores in physical conditions
where mean-field electrostatics breaks down. The experimentally observed low
KCl conductivity of open alpha-Hemolysin pores is quantitatively explained by
the presence of surface polarization effects. Upon the penetration of a DNA
molecule into the pore, these polarization forces combined with the
electroneutrality of DNA sets a lower boundary for the ionic current,
explaining the weak salt dependence of blocked pore conductivities at dilute
ion concentrations. The addition of multivalent counterions into the solution
results in the reversal of the polymer charge and the direction of the
electroosmotic flow. With trivalent spermidine or quadrivalent spermine
molecules, the charge inversion is strong enough to stop the translocation of
the polymer and to reverse its motion. This mechanism can be used efficiently
in translocation experiments in order to improve the accuracy of DNA sequencing
by minimizing the translocation velocity of the polymer.
