par Lecomte, Jean-Paul 
;Kirsch-De Mesmaeker, Andrée ;Kelly, John M;Tossi, Alessandro;Görner, Helmut
Référence Photochemistry and photobiology, 55, 5, page (681-689)
Publication Publié, 1992-05
;Kirsch-De Mesmaeker, Andrée ;Kelly, John M;Tossi, Alessandro;Görner, HelmutRéférence Photochemistry and photobiology, 55, 5, page (681-689)
Publication Publié, 1992-05
Article révisé par les pairs
| Résumé : | The luminescence quenching of ruthenium-tris-1,4,5,8-tetraazaphenanthrene [Ru(tap)3(2+)] by nucleotides approaches the diffusion rate only with guanosine-5'-monophosphate (GMP), the most reducing nucleotide, and leads to an electron transfer with the production of the monoreduced complex and the oxidized base. The resulting deprotonated GMP(-H).radical recombines with the monoreduced complex according to a bimolecular equimolar process. The pH dependence of the decay of the transient reduced complex, in the presence of an oxidant (oxygen or benzoquinone) indicates the formation of Ru(tap)2(tapH)2+, i.e. the reduced protonated species, subsequent to the electron transfer, with a pKa of 7.6 as confirmed from pulse radiolysis experiments. As the non-protonated reduced complex, Ru(tap)2(tap-.)+, has a higher reducing power than the protonated one, oxygen is able to reoxidize only the non-protonated species, whereas benzoquinone reoxidizes both species but with different rate constants. The flash photolysis of Ru(tap)3(2+) in the presence of DNA and the effect of Mg2+ ions and GMP as supplementary additives also show the existence of a photo-induced electron transfer with the nucleic acid, which can be correlated to the photosensitized cleavage of DNA by this complex. |
