Stepwise Transport of Stretched ssDNA Through Graphene Nanopores

Abstract

Among various biological and solid-state nanopores employed for DNA sensing, graphene nanopores have the greatest potential to be successful for DNA sequencing because graphene's single-atom-thin layer may offer single-base resolution recognition. However, the identification of individual bases could not be achieved yet by means of graphene nanopores, mainly because DNA translocation through the pore is too fast and thermal motion of bases is too strong to permit individual bases to be resolved. Here we demonstrate by means of molecular dynamics simulations that stretch-induced stepwise translocation of single-stranded DNA (ssDNA) through graphene nanopores can permit single-base resolution detection. The intrinsic stepwise DNA motion is brought about through alternating conformational changes between spontaneous adhesion of DNA bases to the rim of the graphene nanopore and unbinding due to mechanical force or electric field. A graphene membrane shaped as a quantum point contact permits, by means of transverse electronic conductance measurement, detection of the stepwise translocation of the DNA as predicted through quantum mechanical Green's function-based transport calculations. The measurement scheme described opens a route to enhance the signal-to-noise ratio by not only slowing down DNA translocation to provide sufficient time for base recognition, but also by stabilizing single DNA bases and, thereby, reducing thermal noise.