Spectroscopic investigation of Cu2+ ions interaction with DNA

Abstract

Absorption IR-spectra of H₂O and D₂O solutions of thymus DNA with different concentrations of copper ions: [Cu²⁺]/[P]=0,05 ÷0,8 ([Na⁺] = 0,15 M) have been obtained. The increase in the band intensities in the region of the sugar-phosphate vibrations at the ratio [Cu²⁺]/[P]=0,4 ÷0,6 marks the interaction between copper ions and phosphate groups of the DNA. The sharp increase in the absorption provides evidence of the transition of the DNA into the compact state. The further increase in the copper ions concentration leads to the denaturation of the DNA molecule, which is accompanied by the decrease in the absorption band intensities of the sugar-phosphate vibrations and the hyperchromism in the region of the nitrogen base vibrations. The melting curves of the DNA with Cu²⁺ ions were obtained by the UV-spectroscopy method. From the analysis of the melting curves, we can conclude that the presence of the copper ions at the ratio [Cu²⁺]/[P]=0,05÷0,1 in solution with ion strength 0,15 does not influences the helix-coil transition. However, when [Cu²⁺]/[P] ratio reaches 0,2 the temperature of DNA melting decreases, and the melting range widens.