Slowing down DNA Translocation
through a Nanopore
in Lithium Chloride
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Abstract
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<sup>+</sup> to Na<sup>+</sup> to Li<sup>+</sup>, both for double-stranded
DNA (dsDNA) and single-stranded DNA (ssDNA). MD simulations elucidate
the microscopic origin of this effect: Li<sup>+</sup> and Na<sup>+</sup> bind DNA stronger than K<sup>+</sup>. 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