Geometry and electronic structure of M-DNA (M=Zn2+, Co2+, and Fe2+)

We have investigated, by means of first principles calculations, modified forms of DNA with divalent Zn, Co, Fe cations bonded to the two helix strands of poly(dC)-poly(dG). We propose a common stable structure that is consistent with the experimental reports for Zn-DNA. In all three cases, the band gap is much narrower, and the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) bands are considerably wider than those in dry DNA. In Zn-DNA, the HOMO LUMO bands are formed purely by guanine cytosine states, respectively, with no weight in the Zn atoms. Their large width arise from an increased overlap between pi states of the bases, due to the helix deformation after the insertion of the Zn ion. Contrarily, the HOMO and LUMO bands of Co-DNA and Fe-DNA have a large weight on the metal atoms. These results offer promising perspectives for turning DNA into a conducting wire.