Self-energy limited ion transport in sub-nanometer channels
  The current-voltage characteristics of the alpha-Hemolysin protein pore during the passage of single-stranded DNA under varying ionic strength, C, are studied experimentally. We observe strong blockage of the current, weak super-linear growth of the current as a function of voltage, and a minimum of the current as a function of C. These observations are interpreted as the result of the ion electrostatic self-energy barrier originating from the large difference in the dielectric constants of water and the lipid bilayer. The dependence of DNA capture rate on C also agrees with our model. 
Douwe Jan Bonthuis, Jingshan Zhang, Breton Hornblower, Jerome Mathe,   Boris I. Shklovskii, and Amit Meller