Molecular mechanism for metal-independent production of hydroxyl radicals by hydrogen peroxide and halogenated quinones. Proc Natl Acad Sci U S A 2007 Nov 06;104(45):17575-8
Date
10/31/2007Pubmed ID
17968010Pubmed Central ID
PMC2077033DOI
10.1073/pnas.0704030104Scopus ID
2-s2.0-36749041417 (requires institutional sign-in at Scopus site) 167 CitationsAbstract
We have shown previously that hydroxyl radicals (HO*) can be produced by H2O2 and halogenated quinones, independent of transition metal ions; however, the underlying molecular mechanism is still unclear. In the present study, using the electron spin resonance secondary radical spin-trapping method, we found that tetrachloro-1,4-benzoquinone (TCBQ), but not its corresponding semiquinone anion radical, the tetrachlorosemiquinone anion radical (TCSQ*-), is essential for HO* production. The major reaction product between TCBQ and H2O2 was identified by electrospray ionization quadrupole time-of-flight mass spectrometry to be the ionic form of trichlorohydroxy-1,4-benzoquinone (TrCBQ-OH), and H2O2 was found to be the source and origin of the oxygen atom inserted into the reaction product TrCBQ-OH. On the basis of these data, we propose that HO* production by H2O2 and TCBQ is not through a semiquinone-dependent organic Fenton reaction but rather through the following mechanism: a nucleophilic attack of H2O2 to TCBQ, forming a trichlorohydroperoxyl-1,4-benzoquinone (TrCBQ-OOH) intermediate, which decomposes homolytically to produce HO*. This represents a mechanism of HO* production that does not require redox-active transition metal ions.
Author List
Zhu BZ, Kalyanaraman B, Jiang GBAuthor
Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
HalogensHydrogen Peroxide
Hydroxyl Radical
Metals
Quinones