IR-spectroscopy investigation of Cu2+ ion action on conformational state of DNA

Abstract

This work studies the Cu²⁺ ion interaction ([Cu²⁺]/[P]=0,2-0,8) with the DNA macromolecule in aqueous solutions at different temperatures (T=26-93⁰С) by the IR spectroscopy method. It is shown that Cu²⁺ ion binding to phosphate groups of the DNA molecule induce the increase of the intensity of the absorption spectrum in the region of vibrations of the sugar-phosphate chain that evidences the DNA transition into the compact state. The DNA transition into the compact state occurs in a rather narrow interval of Cu²⁺ ion concentrations ([Cu²⁺]/[P]=0,3-0,6). At the ratio [Cu²⁺]/[P]>0,6 Cu²⁺ ions disorder the DNA secondary structure at room temperature (T=26⁰C). Effect of Cu²⁺ ions on the resistance of the DNA secondary structure for temperature changes were studied too. A nonlinear dependence of the DNA melting temperature on Cu²⁺ ion concentrations was obtained: the DNA melting temperature decreases significantly at [Cu²⁺]/[P]>0,2. This effect is due to the preferential binding of Cu²⁺ ions to nitrogen bases of DNA that destabilizes its secondary structure.