Salt dependence of DNA translocation dynamics through silicon nanopores detected by ultraviolet excitation

Abstract

DNA translocation through nanopores was observed using ultraviolet excitation to investigate the effect of salt concentration and counterion species on the translocation speed. The translocation of 9.6-kbp DNA molecules was measured in an aqueous solvent containing KCl, NaCl, or LiCl. An increase in the KCl concentration from 0.5 to 2 M increased the DNA translocation time. Maintaining the salt concentration at 1.0 M but replacing KCl with NaCl or LiCl also increased the translocation time. These results suggest that the effective charge on the DNA changed due to the binding of counterions, decreasing the DNA electrophoretic mobility. Significant correlation was observed between the translocation time and the dwell time in the observation volume (time needed to move out of the observation volume), and a possible explanation for this observation is provided.