Biopolymers and cell. 2008; 24 (2): 158 - 170

Ni²⁺ ion effect on conformational equilibrium of polynucleotides: polyA×polyU, polyA and polyU under conditions close to physiological ones

V. A. Sorokin, V. A. Valeev, E. L. Usenko

Ni²⁺ ion interactions with single-stranded polyA and polyU and double-stranded polynucleotide polyA×polyU (AU) were studied in aqueous solutions containing 0.1 M Na⁺ using the methods of differential UV-spectroscopy and thermal denaturation. The formation of innerspheric coordination bonds of nickel ions with N7 and N1 of polyA adenine was revealed in the range of high nickel concentrations. The sections, corresponding to 2®1, 2®3, and 3®1 transitions, were observed in the phase diagram of (AU + Ni2+) complex. Unlike Mg2+ ions decreasing (Tm)2®3, Ni2+ ions increase it. It is supposed that under these conditions the difference between binding constants of Ni2+ ions with AU and polyA and/or the decrease in the number of ion-binding centers at A2U contribute to the increase of (Tm)2®3.

Keywords: metal complexes of nucleic acids, polynucleotides, conformational transitions.