Electrons initiate efficient formation of hydroperoxides from cysteine

Janusz M. Gebicki*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    4 Citations (Scopus)


    Amino acid and protein hydroperoxides can constitute a significant hazard if formed in vivo. It has been suggested that cysteine can form hydroperoxides after intramolecular hydrogen transfer to the commonly produced cysteine sulfur-centered radical. The resultant cysteine-derived carbon-centered radicals can react with oxygen at almost diffusion-controlled rate, forming peroxyl radicals which can oxidize other molecules and be reduced to hydroperoxides in the process. No cysteine hydroperoxides have been found so far. In this study, dilute air-saturated cysteine solutions were exposed to radicals generated by ionizing radiation and the hydroperoxides measured by an iodide assay. Of the three primary radicals present, the hydroxyl, hydrogen atoms and hydrated electrons, the first two were ineffective. However, electrons did initiate the generation of hydroperoxides by removing the –SH group and forming cysteine-derived carbon radicals. Under optimal conditions, 100% of the electrons reacting with cysteine produced the hydroperoxides with a 1:1 stoichiometry. Maximum hydroperoxide yields were at pH 5.5, with fairly rapid decline under more acid or alkaline conditions. The hydroperoxides were stable between pH 3 and 7.5, and decomposed in alkaline solutions. The results suggest that formation of cysteine hydroperoxides initiated by electrons is an unlikely event under physiological conditions.

    Original languageEnglish
    Pages (from-to)987-996
    Number of pages10
    JournalFree Radical Research
    Issue number9
    Publication statusPublished - 1 Sept 2016


    • radiation
    • oxygen
    • peroxide assay
    • carbon radicals
    • sulfur radicals


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