SUPRAMOLECULAR CATIONIC TETRARUTHENATED PORPHYRIN AND LIGHT INDUCE DECOMPOSITION OF 2’-DEOXYGUANOSINE PREDOMINANTLY BY SINGLET MOLECULAR OXYGEN

D�partement de Recherche Fondamentale sur la Mati�re Condens�e, Service de Chimie Inorganique et Biologique, Laboratoire des L�sions des Acides Nucl�iques, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9 France.
e-mail : [email protected]
*Departamento de Bioqu�mica, Instituto de Qu�mica, Universidade de S�o Paulo, CP 26077, CEP 05599-970, SP, Brasil. e-mail: [email protected]

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