Study on the photo-generation of superoxide radicals in Photosystem II with EPR spin trapping techniques |
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Authors: | Zhang Suping Weng Jun Pan Jingxi Tu Tiecheng Yao Side Xu Chunhe |
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Institution: | (1) Institute of Plant Physiology, Shanghai Institutes for the Biological Sciences, Chinese Academy of Sciences, 200032 Shanghai, China;(2) Institute of Plant Physiology, Shanghai Institutes for the Biological Sciences, Chinese Academy of Sciences, 200032 Shanghai, China |
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Abstract: | Direct EPR evidence of the photo-generation of superoxide radicals (O2
–.) was obtained by using a novel spin trapping probe in spinach Photosystem II (PS II) membrane fragments. The production of O2
–. was detected by following the formation of 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) superoxide adducts (DEPMPO-OOH). The inhibition of O2
–. formation by 3-(3,4-dichlorophenyl) -1,1-dimethylurea (DCMU) and the 77 K fluorescence spectrum indicated that O2
–. were generated from PS II, not from PS I. The inhibition of O2
–. formation by DCMU also suggested that O2
–. were generated from the QBbinding site, not at a site prior to DCMU blockage. The extrinsic proteins and Mn are very important to eliminate O2
–., showing that the oxygen-evolving system is involved in O2
–. removal rather than production.This revised version was published online in October 2005 with corrections to the Cover Date. |
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Keywords: | DEPMPO EPR Photosystem II QB binding site superoxide dismutase superoxide radicals |
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