Effect of Ni(II) Binding on the Tautomerism of Guanine: A Quantum-Chemical NDDO Investigation
Journal of Molecular Structure: THEOCHEM
||NUCLEIC-ACID BASES; SCF-MO METHOD; 9-METHYLGUANINE; EQUILIBRIA; COMPLEXES; MOLECULES; ABINITIO; MODEL
Institute of Catalysis, 630090 Novosibirsk, Russian Federation
Institute of Molecular Genetics, Kurchatov sq. 46, 123182 Moscow, Russian Federation
Using the semiempirical quantum-chemical method NDDO/MC calculations were carried out on some aqua and ammine Ni(II) complexes with the guanine nucleic base. The results obtained suggest that the greatest influence of the transition metal is on the keto-enol tautomerism of guanine. The effect on the tautomerism is shown to be connected with a charge transfer from guanine to form a coordinative bond with Ni(II). In the octahedral Ni(II)-guanine complex the charge transfer from the heterocycle is small and such a complex stabilizes the keto form. Conversely, the planar complex facilitates greater charge transfer and leads to stabilization of the enol tautomer.