DNA interaction with complex ions in solution

The methods of flow birefringence, low shear viscometry, and circular dichr oism were used to investigate the DNA conformation in solution during the i nteraction with coordination compounds [Co(NH3)(6)]Cl-3 and [Co(NO2)(6)]Na- 3. It has been shown that the compound [Co(NO2)(6)]Na-3, which dissociates in an aqueous solution to produce a negative complex ion [Co(NO2)(6)](3-), binds to a DNA molecule, causing considerable changes in its parameters. Fo r the binding to occur, the complex ion must undergo a transition to its aq ueous form. Even a low cobalt content is shown to produce DNA shrinkage. It is attended by an increased DNA optical anisotropy. This effect was observ ed for both compounds used. The comparison of these data with earlier resul ts on DNA-Fe3+ interaction has revealed some features common to the DNA bin ding to trivalent metal ions. We have suggested that the mutual orientation of DNA statistical segments is changed because of the formation of intramo lecular linkages between trivalent ions and remote DNA chain segments.