Complexation of bases and phosphates of nucleic acid components by transition metal ions

Abstract

Complexation of transition metal ions, Mn(II), Co(II) and Ni(II), by nucleic acid components (bases, nucleosides and nucleotides) has been studied by various polarographic methods (dc, NP, DP and ac). The Ni(II) electroreduction process was investigated in detail due to the unique effect of splitting of polarographic waves or peaks, which was attributed to the reduction of (Ni 2+—base) aq complexes and hydrated nickel ion Ni 2+ aq. The following order of stability constants of (Ni 2+—base) aq complexes was observed for the bases in nucleosides: guanine > 5-methylcytosine ∼ adenine > cytosine ∼ 5-methyluracil. Complexation of Ni(II) by phosphate groups does not lead to splitting of the Ni(II) electroreduction waves or peaks, thus enabling a distinction between complexation of bases and phosphate groups in nucleotides. Complexation of the base and phosphate group in cytosine-containing nucleotide is similar but a much stronger complexation of the base was found in guanine nucleotide, thus confirming the order of (Ni 2+—base) aq complexes derived from studies of nucleosides.