PHTHALOCYANINE AND NAPHTHALOCYANINE PHOTOSENSITIZED OXIDATION OF 2'-DEOXYGUANOSINE: DISTINCT TYPE I AND TYPE II PRODUCTS |
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| Authors: | J.-L. Ravanat M. Berger F. Benard R. Langlois R. Ouellet J. E. van Lier J. Cadet |
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| Affiliation: | Laboratoire des Lesions des Acides Nucleiques, DRFMC/SESM/C.E.N. Grenoble, 85X, F-38041 Grenoble Cedex, France;MRC Group in the Radiation Sciences, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4 |
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| Abstract: | Abstract
The photodynamic properties of the di-and tetrasulfonated zinc and aluminium phthalocyanines and a tetrasulfonated aluminium napththalocyanine were studied using 2'-deoxyguanosine as a DNA model compound. The major photooxidation products of this nucleoside were identified and classified according to their formation through a radical mechanism (type I) or a singlet oxygen mediated mechanism (type II). The major type I product was obtained and identified as 2,2-diamino [(2-deoxy-β- d - erythro pentofuranosyl)-4-amino]-5( 2H )-oxazolone. Two major type II products were characterized as the 4R* and 4S* diastereomers of 9-(2-deoxy-β- d - erythro pentofuranosyl)-7,8-dihydro-4-hydroxy-8-oxoguanine. In addition a third product, also resulting from a type II photooxidation, was identified as 8-oxo-7,8-dihydro-2'-deoxyguanosine. Quantification of these products provided a means to estimate the contribution of type I and type II pathways during the phthalocyanine and naphthalocyanine mediated photooxidation of 2'-deoxyguanosine, confirming the major role of singlet oxygen in these processes. |
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