Halogen anion formation in 5-halouracil films: X rays compared to subionization electrons |
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Authors: | DV Klyachko MA Huels L Sanche |
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Affiliation: | Département de Médecine Nucléaire et de Radiobiologie, Université de Sherbrooke, Québec, Canada. |
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Abstract: | The radiosensitization properties of 5-halouracils (5-FU, 5-BrU and 5-IU), i.e. the enhanced sensitivity of biological media containing these compounds to ionizing radiation, have been studied using surface science methods. We show that soft X rays and near 0 eV electrons both induce dissociation of 5-halouracils into a halogen anion and a uracilyl radical. The yield of anions from 5-FU is much smaller than that from the bromo- and iodo-analogs. We explain the high anion yields in 5-BrU and 5-IU with dissociative electron attachment (DEA) of near 0 eV electrons. The thermodynamic threshold for DEA to 5-FU is near 2 eV and therefore prohibits dissociation by near 0 eV electrons. |
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