† Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
‡ Department of Physics and Beckman Institute for Advances Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
Nano Lett., Article ASAP
DOI: 10.1021/nl204273h
Publication Date (Web): January 9, 2012
Copyright © 2012 American Chemical Society
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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