Andrus O. Metal ions influence on stability and conformational equilibrium of multistranded homopolynucleotides: polyA·polyU, polyA·2polyU and polyA·2polyI.

Experimental study of (Na+, Mg2+, Ni2+and Cd2+) metal ions complexes with three-stranded A2I and its components (polyI, polyA, AMP, IMP) and Cd2+ metal ions complexes with multistranded homopolynucleotides AU and A2U and its components (polyA and polyU) in aqueous solutions has been performed. Differential UV spectra of metalocomplexes were measured, that gave possibility to define influence of ions on polynucleotides conformation, establish ions binding sites, and suggest the structure of formed complexes and mechanisms of helices AU, A2U and A2I destruction caused by metal ions. Conformational equilibrium diagrams were obtained in the wide region of temperatures and ions concentrations. Calculations of Mg2+ and Ni2+ ions binding constants with polyI and A2I are performed. Linear density of negative charge on one-stranded polyI value is calculated. Analytical equation which shows that ratio of Mg2+ ions binding constants with three-stranded and one-stranded polynucleotides is determined by differencesin linear density of charge values in their surfaces is obtained.