Barr R, Crane F L
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Plant Physiol. 1977 Mar;59(3):433-6. doi: 10.1104/pp.59.3.433.
The effect of three different stable radicals-2,2-diphenyl-1-picrylhydrazyl, 1,3,5-triphenyl-verdazyl, and galvinoxyl-was studied in photosystem II of spinach (Spinacia oleracea) chloroplasts. Inhibition by the three was noted on dimethylbenzoquinone reduction in presence of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and on silicomolybdate reduction in presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) in photosystem II and on the H(2)O --> methylviologen reaction encompassing both photosystems. Inhibition of all photosystem II reactions except silicomolybdate reduction could be partially restored by alpha-tocopherol or by 9-ethoxy-alpha-tocopherone but not by other quinones or radical chasers. On this basis, a functional role for alpha-tocopherol in the electron transport chain of spinach chloroplasts between the DCMU and DBMIB inhibition sites is postulated.
研究了三种不同的稳定自由基——2,2-二苯基-1-苦基肼、1,3,5-三苯基-氮杂茂和加尔文oxyl——对菠菜（Spinacia oleracea）叶绿体光系统II的影响。在光系统II中，观察到这三种自由基在2,5-二溴-3-甲基-6-异丙基对苯醌（DBMIB）存在下对二甲基苯醌还原的抑制作用，以及在3-(3,4-二氯苯基)-1,1-二甲基脲（DCMU）存在下对硅钼酸盐还原的抑制作用，以及对涉及两个光系统的H(2)O --> 甲基紫精反应的抑制作用。除硅钼酸盐还原外，所有光系统II反应的抑制作用都可以通过α-生育酚或9-乙氧基-α-生育醌部分恢复，但不能通过其他醌类或自由基捕捉剂恢复。在此基础上，推测α-生育酚在菠菜叶绿体电子传递链中位于DCMU和DBMIB抑制位点之间具有功能作用。
