Interaction of oxo-bridged vanadium(III) phenanthroline and bipyridine dimers with DNA

Cationic mu-oxo V(III) dimers of the type [V2OL4Cl2](2+) (L = 1,10-phenanth roline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanth roline, or 2,2'-bipyridine) are shown to interact very strongly with DNA an d to lead ultimately to its degradation. Spectroscopic binding studies, ele ctrophoreses, DNA melting temperature experiments, and other tests on the p arent 1,10-phenthroline complex all yield results consistent with tight bin ding. However, the exact nature of the binding-i.e., intercalative, groove binding, electrostatic, or covalent-remains unclear. Resonance Raman spectr oscopy is found to be a powerful method for studying the interaction of the se mu-oxo V(III) dimers with DNA and shows that in frozen aqueous solution, the parent complex [V2O(phen)(4)-Cl-2](2+) undergoes initial aquation, fol lowed by the reaction of the aquated species with the DNA. Once the V(III) dimer is bound to the DNA, redox takes place, leading to the formation of a lkaline-sensitive lesions. Hydrogen peroxide is implicated as a partner in this redox event, based on the effects of the enzymes SOD and catalase.