Perturbation theory analysis for electronic response of DNA base pairs

The electronic responses of duplex B-DNA sequences are investigated using perturbation theory analyses. The electronic polarizability and effective mass are computed for base pair doublets and triplets and the electronic structures are calculated according to density functional theory. High polarizability and a light effective mass are obtained in a sequence such as 5′-GGG-3′. The results indicate that the concentration of GC base pairs causes a high response of the electronic states, and molecular orbitals that are very responsive to the electric field tend to be reactive with other orbitals or conducting hole carriers. Furthermore, the interaction between the electronic states and a positively charged wavepacket is discussed, assuming hole injection in the DNA sequences. The sequence of 5′-GGG-3′ responds sensitively to the external hole approach, which is presumably injected to a guanine site.