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Nano Lett. 2012 Feb 8;12(2):1038-44. doi: 10.1021/nl204273h. Epub 2012 Jan 27.

Slowing down DNA translocation through a nanopore in lithium chloride.

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Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.


The charge of a DNA molecule is a crucial parameter in many DNA detection and manipulation schemes such as gel electrophoresis and lab-on-a-chip applications. Here, we study the partial reduction of the DNA charge due to counterion binding by means of nanopore translocation experiments and all-atom molecular dynamics (MD) simulations. Surprisingly, we find that the translocation time of a DNA molecule through a solid-state nanopore strongly increases as the counterions decrease in size from K(+) to Na(+) to Li(+), both for double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA). MD simulations elucidate the microscopic origin of this effect: Li(+) and Na(+) bind DNA stronger than K(+). These fundamental insights into the counterion binding to DNA also provide a practical method for achieving at least 10-fold enhanced resolution in nanopore applications.

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