Comparative investigation of interaction of the dirhenium(III) cluster compound with different nucleotide content DNAs

Comparative investigation of interaction of bis-dimethylsulfoxide-cis-tetrachlorodi--pivalatodirhenium(III) (I) with two eukaryotic DNAs with different nucleotide content was performed by the method of UV-titration. Eukariotic deoxyribonucleic acids from calf thymus (CT DNA, 40% GC) and from herring sperm (HS DNA, 44% GC) were the matter of investigation. We observed an increase in the absorption of both DNAs with increasing the concentration of added solutions of I. Electronic absorption spectra traces of both examples of DNA exhibited pronounced hyperchromism in the presence of increasing amounts of I. The calculated binding constants were KbCT DNA=2221 l/mol and KbHS DNA=3238 l/mol. Hyperchromicity of the complexes DNA-I was different for the investigated DNAs (14.413% and 81.943% for CT DNA and HS DNA, respectively). The conclusions was made that addition of I in low concentrations to DNA led to formation of complexes DNA-I with following unwinding or unfolding of the helix that did not reach 50% of unfolding. At high concentrations of I, the preferable interaction took place with guanine; interaction of I with guanine nucleotides led to significant (more than 50%) of unfolding of guanine rich sequences. I was sensitive to the nucleotide content of DNA in high concentrations and strongly reacted with guanine reach sequences with selective and mighty unfolding abilities.