  DNAs charge transfer and self-assembly characteristics have made it a
hallmark of molecular electronics for the past two decades. A fast and
efficient charge transfer mechanism with programmable properties using DNA
nanostructures is required for DNA-based nanoelectronics applications and
devices. The ability to integrate DNA with inorganic substrates becomes
critical in this process. Such integrations may effect the conformation of DNA,
altering the charge transport properties. Thus, using molecular dynamics
simulations and first-principles calculations in conjunction with Greens
function approach, we explore the impact of Au (111) substrate on the
conformation of DNA and analyze its effect on the charge transport. Our results
indicate that DNA sequence, leading its molecular conformation on Au substrate,
is critical to engineer charge transport properties. We demonstrate that DNA
can fluctuate on a gold substrate, sampling various distinct conformations over
time. The energy levels, spatial locations of molecular orbitals and the DNA/Au
contact atoms can differ between these distinct conformations. Depending on the
sequence, at HOMO, the charge transmission differs up to 60 times between the
top ten conformations. We demonstrate that the relative positions of the
nucleobases are critical in determining the conformations and the coupling
between orbitals. We anticipate these results can be extended to other
inorganic surfaces and pave the way for understanding DNA inorganic interface
interaction for future DNA-based electronic devices.
