Counterion-hopping along the backbone of single-stranded DNA in nanometer pores: a mechanism for current conduction.

Molecular dynamics calculations are performed to investigate ionic current conduction through nanopores in the presence of single-stranded DNA. We find the counterions to be strongly attracted to the phosphate groups of the DNA, with resident time on the order of nanoseconds, while coions are strongly excluded. The diffusion constant of the counterions is calculated and used to estimate the ionic current through the pore, which gives a similar magnitude as in experiment. The results suggest a counterion-hopping mechanism along the ssDNA backbone in the current conduction through nanopores.