A LASER FLASH KINETIC SPECTROPHOTOMETRIC EXAMINATION OF THE DYNAMICS OF SINGLET OXYGEN IN UNILAMMELLAR VESICLES |
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| Authors: | Michael A J Rodgers Anne L Bates |
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| Institution: | Center for Fast Kinetics Research, The University of Texas at Austin, Austin, TX 78712, USA |
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| Abstract: | Abstract— The kinetic properties of O2(1Δg) have been examined in unilamellar vesicle dispersions composed of didodecyldimethylammonium bromide, di- n -octadecyl phosphate and egg lecithin. Light absorbing sensitizers 2-acetonaphthone, methylene blue and a methylene blue derivative of enhanced water-solubility were used. The rate parameters for singlet oxygen were monitored by observing the time profile of the bleaching of the reactive substrates diphenylisobenzofuran and anthracene dipropionate. The natural lifetime of O2(1Δg) in D2O-based suspensions was shown to be 46/JS in good agreement with that found earlier for D2O alone and D2O-based micelle systems. The bimolecular rate constants for reaction with diphenylisobenzofuran and dimethylindole (both lipid-bound) and histidine (water-bound) were also in close conformity with the values found earlier in micellar media. Kinetic spectrophotometry has been shown to be a useful technique for examining rate parameters in these heterogeneous media. |
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