Effect of local binding on stochastic transport in ion channels

Ionic Coulomb blockade is an electrostatic phenomenon recently discovered in low-capacitance ion channels/ nanopores. Depending on the fixed charge that is present, Coulomb blockade strongly and selectively influences the ease with which a given type of ion can permeate the pore. The phenomenon arises from the discreteness of the charge-carriers and it manifests itself strongly for divalent ions (e.g. Ca
²⁺
). Ionic Coulomb blockade is closely analogous to electronic Coulomb blockade in quantum dots. In addition to the non-local 1D Coulomb interaction considered in the standard Coulomb blockade model, we now propose a correction to take account of the singular part of the attraction to the binding site (i.e. local site binding) and of the local ion-ion repulsion. We show that this correction leads to a geometry-dependent shift of the single-ion barrier-less resonant conduction points M
₀
. We also show that local repulsion accounts for a splitting of Ca
²⁺
profiles observed earlier in Brownian dynamics simulations.