[A study of the molecular mechanism of DNA interaction with divalent metal ions]

The interaction of DNA with divalent metal ions: Ba2+, Mg2+, Mn2+, Ni2+, Cu2+ in solutions at different ionic strengths mu was investigated. The combination of following methods: flow birefringence, viscometry, UV-spectroscopy and circular dichroism made possible to follow the state of the secondary and tertiary structure of the DNA molecule during its interaction with ions. The presence of divalent ions in solution affects the hydrodynamic properties of DNA only at low mu. At high mu the difference in the action of mono- and divalent ions disappears. The persistence length of DNA does not change during the experiment. It is shown that the Mg2+ and Ba2+ ions interact only with phosphate groups of DNA but Mn2+, Ni2+, Cu2+ ions interact also with the nitrogen bases of the macromolecule.