The reaction rate constants for <tex-math>${\rm e}{}_{aq}{}^{-}$</tex-math> and OH with nitrofurazone have been experimentally measured as <tex-math>$2.8\times 10^{10}\ M^{-1}\ {\rm s}^{-1}$</tex-math> and <tex-math>$10.6\times 10^{9}\ M^{-1}\ {\rm s}^{-1}$</tex-math> respectively by pulse radiolysis techniques. Electron transfer from various substrate radicals to nitrofurazone has been observed and rate constants determined. From steady-state yields of "destroyed nitrofurazone", G values have been determined for the destruction of this sensitizer by separate radical species. Radiation-induced binding of nitrofurazone to DNA has been measured and the importance of this reaction is discussed in relation to various radiosensitizing mechanisms. Of the various substrate radicals tested, those generated by OH reactions with pyrimidines were found to react most efficiently with nitrofurazone. These data suggest that an important part of the radiosensitizing mechanism of nitrofurazone results from irreversible binding of the sensitizer to radicals in DNA. In this respect nitrofurazone may radiosensitize hypoxic cells by a radiation chemical mechanism similar to that of molecular oxygen and other electron-affinic compounds.

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