Effect of glycerol and propanediol on Cu2+ ions interactions with DNA in solutions at different temperatures

The Cu2+ ions interaction with DNA in aqueous solutions containing 4 v % of glycerol or propanediol at 29 and 45 degrees C was studied by IR-spectroscopy. It was found that DNA condenses into compact structure under Cu2+ ions influence both at 29 and at 45 degrees C in aqueous and in mixed solutions. This process is of high positive cooperativity. Propanediol addition increases cooperativity of DNA compactisation and decreases Cu2+ ions concentration which is necessary to induce DNA compactisation both at 29 and at 45 degrees C. In contrast to propanediol, influence of glycerol (in concentration up to 10 v %) on Cu2+ ions interaction with DNA is of non-monotonous character, small glycerol addition to DNA aqueous solution significantly decreases the cooperativity of DNA compactisation. As at nonelectrolyte concentration studied (4 v %) the decreases of solution dielectric constant at glycerol or propanediol addition in comparison with pure water are practically the same, we can conclude that DNA interaction with Cu2+ ions in solutions with lowered water activity depends not only on solution dielectric constant but on kind of nonelectrolyte added.