Interaction of DNA Bases with Gold Substrates

The interaction of molecules with inorganic substrates is a crucial issue forapplications in molecular electronics. It influences important factors suchas the immobilization efficiency and the charge injection through the inter-face. Moreover, mechanical aspects connected to the unfolding of biologicalmolecules are important.We hereby present recent efforts in our group to tackle these problems,based on density functional theory calculations. In particular, we discussour results on the adsorption of cytosine on Au(111) and on the interactionof guanine, in its natural and size-expanded forms, with small Au clusters.We find that cytosine binds to the Au(111) surface with a mechanism thatinvolves charge sharing, intermediate between chemisorption and physisorp-tion. The investigation of small complexes between guanine and gold clustersreveals the formation of hydrogen bonds: these configurations with unusualbonds are relevant at the corners of nanoparticles, while they can probably beneglected when DNA binds on flat extended metal surfaces.