SELECTIVE TYPE I PHOTOOXIDATIONS IN MIXTURES OF PORPHYRINS AND ELECTROPHILIC NITROIMIDAZOLES |
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Authors: | M. Bazin R. Santus |
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Affiliation: | Museum National d'Histoire Naturelle, Laboratoire de Physico-Chimie de I'Adaptation, Biologique and U.A. 481. du CNRS., 43, rue Cuvier 75231 Paris Cédex 05, France |
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Abstract: | Abstract— Electrophilic compounds metronidazole (METRO) and misonidazole (MISO), considerably enhance the photooxidation quantum yield of Type I photodynamic substrates such as Trp, Tyr and Cys. For the latter, the quantum yield of photooxidation which can be much greater than one, suggests radical chain reactions. On the other hand, METRO and MISO inhibit 1O2 formation because they react at diffusion controlled rate (∼109 M−1 S−1) with porphyrin triplets forming, porphyrin radical cations. As a result, the porphyrins are still able to photosensitize the destruction of Type I substrates even in the absence of O2. These results are discussed with respect to the possibility of increasing the sensitivity of hypoxic cells to porphyrin photosensitization. |
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