No abstract

The B3LYP/6-311+G(2df,2p) density functional approach was used to study the interaction that aluminum trication, in the bare and hydrated forms, establishes with the nucleic acid bases and the corresponding monophosphate nucleotides. In this investigation, we determine equilibrium geometry of all possible complexes resulting from the attachment of the ion on the different binding sites selected on each ligand. The relative energies of complexes and metal ion affinities are also given. The most meaningful aspect was found to lie in the energetics of this interaction that underlines a very high affinity of aluminum ion for the examined biological systems.

ABSTRACT:The interaction of uracil, thymine, cytosine, adenine, and guanine with zinc ion was studied at the density functional B3LYP/6-311ϩG(2df,2p) level. Different binding sites allowing both mono-metal and bi-metal coordination were considered for the different low-lying tautomers of nucleic acid bases. Zinc ion forms stable compounds with all nucleobases. Except for cytosine, mono-coordination appears to be less favored than bi-coordination in the other pyrimidines. Instead, the preferred sites in the case of adenine and guanine were found to be the N7 and O6 and N7 and N6 pairs of atoms, respectively. Zinc ion affinity was evaluated for all the complexes and compared with values previously obtained for other transition metal ions. In the present case, the following order of metal ion affinity (MIA) was found: GϾAϾCϾTϾU.