The effect of pH on the conversion of superoxide to hydroxyl free radicals

Mark S. Baker, Janusz M. Gebicki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

117 Citations (Scopus)


The conversion of superoxide (O2 {minus sign, dot below}) to the hydroxyl (HO.) free radical by superoxidedriven Fenton reactions was measured by the formation of hydroxylated derivatives from benzoate. Among a range of catalysts required for the conversion, the Fe3+EDTA complex was the most effective. The effect of superoxide dismutase and catalase indicated that O2 {minus sign, dot below} and H2O2 were essential reactants, while the formation of authentic HO. was confirmed by the inhibiting capacities of formate, t-butanol, and mannitol. The conversion of O2 {minus sign, dot below} to HO. was tested over a broad pH range, and was found to be highest at pH 4.8 whether Fe3+EDTA or free Fe3+ were used as the catalysts. When Fe3+EDTA was used at the optimum pH, every HO. produced required 3.7 O2 {minus sign, dot below} radicals, close to the theoretical limit of one HO. from every three O2 {minus sign, dot below} radicals generated.

Original languageEnglish
Pages (from-to)258-264
Number of pages7
JournalArchives of Biochemistry and Biophysics
Issue number1
Publication statusPublished - 1984


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