  The interaction between metal atoms and nucleobases has been a topic of high
interest due to the wide scientific and technological implications. Combining
density functional theory simulations with a literature overview, we achieved
an exhaustive study of the ground state electronic properties of DNA/RNA
nucleobases interacting with gold and silver atoms at three charge states:
neutral, cationic, and anionic. We describe the nature of the stability and
electronic properties in each hybrid metallic structure. In addition to the
metal interacting with the five isolated nucleobases, we included their
respective DNA-WC base pairs and one case with the protonated sugar-phosphate
backbone. As a general trend, we discerned that the energetic ordering of
isomers follows simple electrostatic rules as expected from previous studies.
Also, we found that although the metal localizes almost all of the extra charge
in the anionic system, a donation of charge is shared almost equally in the
cationic system. Furthermore, the frontier orbitals of the cationic system tend
to have more effects from the pairing and inclusion of the backbone than the
anionic system. Finally, the electronic gap varies greatly among all of the
considered structures and could be further used as a fingerprint when searching
DNA-metal hybrid structures.
