Co-Authors:
Kim, H., Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, MD 20892, United States
Rosenthal, I., Department of Food Science, The Volcani Center, ARO, P.O. Box 6, Bet Dagan, 50250, Israel
Kirschenbaum, L.J., Department of Chemistry, University of Rhode Island, Kingston, RI 02881, United States
Riesz, P., Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, MD 20892, United States
Abstract:
The chloroaluminum phthalocyanine tetrasulfonate sensitized photooxidation of ascorbic acid to ascorbate radical (A·-)was followed by electron spin resonance (ESR) spectroscopy. In air saturated aqueous media, steady-state amounts of (A·-)are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished-more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of free radical production by direct reaction between ascorbate ion and sensitized phthalocyanine (a Type I mechanism) in competition with the (Type II) reaction of HA- with singlet oxygen, a reaction which does not produce ascorbate radical intermediates. © 1992.
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