  We investigate the ionic current modulation in DNA nanopore translocation
setups by numerically solving the electrokinetic mean-field equations for an
idealized model. Specifically, we study the dependence of the ionic current on
the relative length of the translocating molecule. Our simulations show a
significantly smaller ionic current for DNA molecules that are shorter than the
pore at low salt concentrations. These effects can be ascribed to the
polarization of the ion cloud along the DNA that leads to an opposing electric
dipole field. Our results for DNA shine light on the observed discrepancy
between infinite pore models and experimental data on various sized DNA
complexes.
