Zinc tetraruthenated porphyrin binding and photoinduced oxidation of calf-thymus DNA

The photooxidation of calf-thymus DNA has been investigated in the presence of a supramolecular tetraruthenated zincporphyrin (ZnTRP) sensitizer. A strong interaction of ZnTRP with DNA has been observed, exhibiting a gradual transition from a non-specific electrostatic binding mode to a more specific one at high DNA concentrations. Formation of O-2((1)Delta(g)) has been detected from its near-infrared emission, after the excitation of ZnTRP in dioxygen-containing solutions. In the presence of DNA and dioxygen, ZnTRP promotes efficient photocatalytic oxidation of the 2'-deoxyguanosine sites, via their direct reaction with O-2((1)Delta(g)), as in a previous work on the ZnTRP-photoinduced oxidation of the free nucleosides. (C) 2000 Elsevier Science Inc. All rights reserved.