[Spectroscopic investigations of the structure of DNA complexes with Mn2+ in UV and IR regions].

Based on the data of UV and IR spectroscopy, electronic and vibrational circular dichroism, the interaction of manganese ions with DNA was investigated. It was shown that the binding of ions to DNA proceeds in three stages depending on the manganese-to-DNA phosphates molar ratio [Mn]/[P]. At the first stage ([Mn]/[P] < or = 1), the interaction of manganese ions with DNA phosphates occurs, causing a partial screening of their negative charge and the stabilization of the double helix. At the second stage (1 < [Mn]/[P] < 6), the ions interact with both the phosphates and the nitrogen bases of DNA. At this stage, it is possible for the manganese ion to coordinate simultaneously to the oxygen atom of the phosphate and the neighbouring base of DNA. At a higher [Mn]/[P] ratio, the destabilization of the double helix begins, and partial breakage of the hydrogen bonds between the nitrogen bases occurs.