Complexes between nucleic acid bases and bivalent metal ions. II. Complexes formed by guanine or cytosine, and zinc(II).

Abstract

The new 2 : 1 guaninium-zinc chloride, 2 : 1 cytosinium-zinc chloride, 1 : 1 cytosine-zinc hydroxy chloride, or 2 : 1 cytosine-zinc chloride complex was obtained from a diluted hydrochloric acid, 70% ethanol, or ethanol solution. The infrared and proton magnetic resonance spectra of these complexes were characterized to assign the binding site of zinc to guanine or cytosine. On the basis of these data, it was suggested that the N9 site of guanine was bound to zinc in the guaninium-zinc chloride complex, and that the N3 site of cytosine was coordinated with zinc in the 2 : 1 cytosine-zinc chloride and 1 : 1 cytosine-zinc hydroxy chloride. It was indicated that the N3 site of cytosine was protonated in the 2 : 1 cytosinium-zinc chloride complex.