Electronic Structure of Wet DNA

Abstract

The electronic properties of a $Z$-DNA crystal synthesized in the laboratory are investigated by means of density-functional theory Car-Parrinello calculations. The electronic structure has a gap of only 1.28 eV. This separates a manifold of 12 occupied states which came from the $\ensuremath{\pi}$ guanine orbitals from the lowest empty states in which the electron is transferred to the $\mathrm{N}{\mathrm{a}}^{\mathrm{+}}$ from $\mathrm{P}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{\ensuremath{-}}}$ groups and water molecules. We have evaluated the anisotropic optical conductivity. At low frequency the conductivity is dominated by the $\ensuremath{\pi}\ensuremath{\rightarrow}\mathrm{N}{\mathrm{a}}^{\mathrm{+}}$ transitions. Our calculation demonstrates that the cost of introducing electron holes in wet DNA strands could be lower than previously anticipated.