  Fast, reliable and inexpensive DNA sequencing is an important pursuit in
healthcare, especially in personalized medicine with possible deep societal
impacts. Despite significant progress of various nanopore-based sequencing
configurations, challenges remain in resolution (due to thermal fluctuations or
to sensitivity to molecular orientation) and speed, which are calling for new
approaches. Here we propose a sequencing protocol for DNA translocation through
a nanopore with side-embedded N-terminated carbon nanotube electrodes.
Employing DFT and Non-Equilibrium Green's Function formalism, we show that the
rectification ratio (response to square pulses of alternating bias) bears high
nucleobase specificity. The rectification arises due to bias-dependent
resistance asymmetry on the deoxyribonucleotide-electrode interfaces. The
asymmetry induces molecular charging and HOMO pinning to the electrochemical
potential of one of the electrodes, assisted by an in-gap electric field effect
caused by dipoles at the terminated electrode ends. This sequencing protocol is
sensitive, selective with orders of magnitude, has high resolution, and it is
robust to molecular orientation.
