On the hydroxyl radical formation in the reaction between hydrogen peroxide and biologically generated chromium(V) species

Xianglin Shi, N. S. Dalal

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207 Scopus citations


Electron spin resonance (ESR) measurements on solutions and isolated powders provide direct evidence for the involvement of Cr(V) species in the reduction of Cr(VI) by NAD(P)H. ESR analysis of an isolated Cr(V)-NAD(P)H solid yields g = 1.9831 and g = 1.9772, indicating that the unpaired electron occupies the dz2 orbital of the Cr(V) ion, with square-pyramidal geometry. Addition of hydrogen peroxide (H2O2) to the NAD(P)H-Cr(VI) reaction mixtures suppresses the Cr(V) species and generates hydroxyl (.OH) radicals. The .OH radicals were detected via ESR spin trapping, employing 5,5-dimethyl-1-pyrroline-N-oxide and α-(4-pyridyl-1-oxide)-N-tert-butylnitrone as spin traps. The dependence of Cr(V) and .OH radical formation on the H2O2 and Cr(VI) concentrations indicates that the Cr(V) species react with H2O2 to generate the .OH radicals. Similar results were obtained by using various diols (arabinose, cellobiose, FAD, fructose, glyceraldehyde, ribose, and tartaric acid), α-hydroxycarboxylic acids, and glutathione. Investigations with superoxide dismutase showed no significant participation of O2- in the generation of .OH radicals. These results thus indicate that the Cr(V) complexes, produced in the reduction of Cr(VI) by cellular reductants, react with H2O2 to generate .OH radicals, which might be the initiators of the primary events in the Cr(VI) cytotoxicity.

Original languageEnglish
Pages (from-to)342-350
Number of pages9
JournalArchives of Biochemistry and Biophysics
Issue number2
StatePublished - Mar 1990

Bibliographical note

Funding Information:
’ Part of this work has been supported by the Department of the Interior’s Mineral program administered by the Bureau of Mines through the Generic Mineral Technology Center for Respirable Dust under Grant G1135142. * To whom correspondence and requests for reprints should be addressed. 3 Abbreviations used: ESR, electron dimethyl-2-thiourea; SOD, superoxide methyl-1-pyrroline-N-oxide; 4-POBN, butylnitrone; Me2S0, dimethyl sulfoxide.

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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