SUPEROXIDE DISMUTASE AS AN AMPLIFIER OF THE CHEMICAL REACTIVITY OF PORPHYRIN RADICAL-CATIONS |
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| Authors: | M Bazin L K Patterson J C Ronfard-Haret R Santus |
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| Institution: | Muséum National d'Histoire Naturelle, Laboratoire de Physico-Chimie de l'Adaptation Biologique, INSERM U312, 43 rue Cuvier, 75231 Paris Cedex 05, France;Radiation Laboratory, University of Notre-Dame, Notre Dame, IN 46556. USA;Muséum National d'Histoire Naturelle, Laboratoire de Biophysique, INSERM U201, CNRS UA 481, 61 rue Buffon, 75005 Paris, France |
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| Abstract: | Abstract— Porphyrin radical-cations have been produced using laser flash photolysis via oxidation of the porphyrin triplets by metronidazole. This radical-cation reacts with OJ as shown by its increased half-life in the presence of native superoxide dismutase. Comparable results are obtained when porphyrin radical-cations are formed by Br2-O2-oxidation of porphyrins produced in pulse radiolysis of oxygen-saturated aqueous solutions containing 20 mM Br-O-. These results provide an explanation for the enhancement by superoxide dismutase of the photosensitizing capacity of porphyrins in the presence of electrophilic nitroimidazoles (Bazin and Santus, 1986). They may also apply to porphyrin radical-cations formed by monophotonic or biphotonic photoionization processes. |
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