MG2-ACTIVATED DOUBLE-STRANDED DNA CLEAVAGE BY [(BPY)(2)(OH2)RU-III-O-RU-III(H2O)(BPY)(2)](4+)()

The reaction of the title complex with DNA has been examined. Addition of [(bpy)(2)(OH2)RuORu(OH2) (bpy)(2)](4+) to DNA leads to the reducti on of the complex to Ru(bpy)(2)(OH2)(2)(2+), as indicated by absorptio n spectroscopy and cyclic voltammetry. The reaction is accelerated by Mg2+. The combined evidence points to a mechanism where the ore-bridge d dimer is hydrolyzed to a monomeric Ru(III) complex that is capable o f oxidizing DNA to effect strand scission. Gel electrophoresis demonst rates nicking of supercoiled phi X174 DNA by [(bpy)(2)(OH2)RuORu(OH2)( bpy)(2)](4+), and double-stranded cleavage is observed in the presence of Mg2+. Linearization of the plasmid prior to treatment with the com plex does not lead to further fragmentation, suggesting that supercoil ing is required to realize double-stranded cleavage.