Effects of hydrated Mg++ interacting with the guanine site in cytosine-guanine nucleic acid-base pair: an ab initio Hartree-Fock study in the absence of basis set superposition error

The structures and energetics of complexes between guanine· · ·cytosine Watson–Crick (GCWC) DNA base pair and the hydrated Mg11 cation were investigated by an ab initio Hartree–Fock study in the absence of basis set superposition error. The explicit hydration of the cation with four and five water molecules was considered. The various charged fragments were allowed to interact with the N7 and O6 sites of guanine. The BSSE-free gradient geometry optimisation were performed in the framework of the SCF-MI (self-consistent field for molecular interactions) theory. The structures of the complexes were analysed showing that the coordination of the GC pair can generate highly distorted non-Watson–Crick hydrogen bonding patterns.