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.
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