Dynamically amorphous character of electronic states in poly(dA)-poly(dT) DNA

We present theoretical work on the electronic states in a model DNA double helix of poly(dA)-poly(dT) (10 base pairs) as the molecule undergoes thermal fluctuations at room temperature. We couple state-of-the art empirical force field molecular dynamics (MD) simulations with an ab initio tight-binding formalism based on density-functional theory [Lewis et al. Phys. Rev. B 2001, 64, 195103-1]. The dynamical features of the charge density distributions and the electronic structure are presented. The periodic structure exhibits extended HOMO-LUMO electronic states; however, equivalent states are quite localized in the aperiodic structures generated as snapshots from the MD simulation. Our results show strong Anderson localization in DNA as a result of the disorder due to structural changes promoted by the thermal fluctuations.