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SUPRAMOLECULAR CATIONIC TETRARUTHENATED PORPHYRIN AND LIGHT INDUCE DECOMPOSITION OF 2-DEOXYGUANOSINE PREDOMINANTLY BY SINGLET MOLECULAR OXYGENJean-Luc Ravanat, Paolo Di Mascio*, Sandrine Spinelli, Marisa H.G. Medeiros*, Koiti Araki*, Henrique E.Toma and Jean CadetDépartement de Recherche Fondamentale sur la Matière Condensée,
Service de Chimie Inorganique et Biologique, Laboratoire des Lésions des Acides
Nucléiques, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9 France. Summary The ability for tetraruthenated porphyrin derivatives to induce photosensitization
reactions has been determined using 2'-deoxyguanosine as a DNA model compound. The main
photooxidation products of the nucleoside were identified and classified according to
their mechanism of formation. These involve a radical pathway (type I) and/or a singlet
oxygen mediated mechanism (type II). Quantification of the different oxidation products
provides a means to evaluate the relative contribution of type I and type II pathways
associated with the oxidative photosensitization of 2'-deoxyguanosine by tetraruthenated
porphyrin derivatives. Results indicate that singlet oxygen plays a major role in the
mechanism of photooxidation mediated by these porphyrin derivatives. For each sensitizer,
the ratio between type II and type I photoproducts have been calculated and compared to
that of other known dyes such as methylene blue and riboflavin |