INTERACTION OF DNA-BASE PAIRS WITH VARIOUS METAL-CATIONS (MG2- NONEMPIRICAL AB-INITIO CALCULATIONS ON STRUCTURES, ENERGIES, AND NONADDITIVITY OF THE INTERACTION(, CA2+, SR2+, BA2+, CU+, AG+, AU+, ZN2+, CD2+, AND HG2+) )

Interaction of Watson-Crick adenine-thymine (AT) and guanine-cytosine (GC) base pairs with various metal (M) cations (Mg2+,..., Hg2+) were s tudied by nonempirical ab initio methods with inclusion of correlation energy. Cations were allowed to interact with the N7 nitrogen of aden ine and the N7 and O6 atoms of guanine. All of the cations were descri bed by Christiansen's average relativistic effective potentials using the DZ+P basis set, while the 6-31G* basis set was used for the eleme nts of base pairs. Disruption of the adenine-thymine as well as guanin e-cytosine pairs in the presence of all studied cations is energetical ly more demanding than that for isolated base pairs; the addition stab ilization of the base pair is about 100% for complexes with dication. The interaction is highly nonadditive. The three-body term is for the MGC complex considerably larger than that for MAT; the intercomplex ch arge transfer is also much larger for the former complex.