Quinoid redox cycling

Squadrito GL, Cueto R, Dellinger B, Pryor WA (2001) Quinoid redox cycling as a mechanism for sustained free radical generation by inhaled airborne particulate matter. Free Radic Biol Med 31 1132-1138... 

Sioutas C, Koutrakis P, Burton RM (1995) A technique to expose animals to concentrated fine ambient aerosols. Environ Health Perspect 103 172-177 Sioutas C, Delfino RJ, Singh M (2005) Exposure assessment for atmospheric ultrafine particles (UFPs) and implications in epidemiologic research. Environ Health Perspect 113 947-955 Southern Ontario Centre for Atmospheric Aerosol Research (SOCAAR) (2007) FacUities-Concentrated Ambient Particle Exposure Facility (CAPEF). http //www.socaar.utoronto.ca/ fac-inst/Facilities.htm. Accessed 21 September 2009 Squadrito GL, Cueto R, Dellinger B et al (2001) Quinoid redox cycling as a mechanism for sustained fiee radical generation by inhaled airborne particulate matter. Free Radic Biol Med 31 1132-1138... 

A simplified scheme of the redox cycle of plastoquinone is shown in Figure 3.8. The quinoid structure and the isoprene side chain make it possible for plastoquinone to take up one electron at a time, producing rather stable semiquinone radicals (which is not shown in the figure), and there are probably at least two plastoquinones involved. 

The previous investigation showed that HO can be generated in suspensions of PM without H2O2 through the redox cycling of quinoids and subsequent reactions, but the addition of hydrogen peroxide (0.02-0.1 M) in the PM suspension enhanced... 

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