Effect of Ni2+ ions on conformational transitions in poly(dA)-poly(dT) system
Abstract
The effect of Ni2+ ions on conformational transitions in duplex and triplex complexes formed by poly(dA) with poly(dT) was studied. Investigations were carried out in buffer solutions (pH=6.9, 0,1 М NaCl), at polynucleotide concentration of 0.1 - 0.3 mМ and Ni2+ concentration up to 3 mМ, by the method of thermal denaturation with registration of melting profiles by absorbance change at 260 nm. Aggregation processes in the systems were traced by intensity of light scattering in the visible range at 540 nm. The diagram of conformational transitions was plotted from the data obtained for poly(dA)-poly(dT)-Ni2+ system. Nickel ions increased the temperatures of helix-to-coil transition for poly(dA)-poly(dT) and triplex-duplex one for poly(dA)-2poly(dT), the value of constant of proportionality for 3—>2 transition was essentially higher than that for 2—>1 one. An aggregation in these systems arose at [Ni2+]≥3 mМ, and a reversibility of helix-to-coil transition was broken, that is connected with a molecular condensation of poly(dA).
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