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ACS Nano. 2012 Aug 28;6(8):6960-8. doi: 10.1021/nn3019943. Epub 2012 Jul 13.

Molecular dynamics study of MspA arginine mutants predicts slow DNA translocations and ion current blockades indicative of DNA sequence.

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Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA.


The protein nanopore Mycobacteria smegmatis porin A (MspA), can be used to sense individual nucleotides within DNA, potentially enabling a technique known as nanopore sequencing. In this technique, single-stranded DNA electrophoretically moves through the nanopore and results in an ionic current that is nucleotide-specific. However, with a high transport velocity of the DNA within the nanopore, the ionic current cannot be used to distinguish signals within noise. Through extensive (~100 μs in total) all-atom molecular dynamics simulations, we examine the effect of positively charged residues on DNA translocation rate and the ionic current blockades in MspA. Simulation of several arginine mutations show a ~10-30 fold reduction of DNA translocation speed without eliminating the nucleotide induced current blockages. Comparison of our results with similar engineering efforts on a different nanopore (α-hemolysin) reveals a nontrivial effect of nanopore geometry on the ionic current blockades in mutant nanopores.

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