title: Flash photolysis-electron spin resonance studies of photosystem I. A fast reduction of component of P-700+.
abstract: A 300 mus decay component of ESR Signal I (P-700+) in chloroplasts is observed following a 10 mus actinic xenon flash. This transient is inhibited by treatments which block electron transfer from Photosystem II to Photosystem I (e.g. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), KCN and HgCl2). The fast transient reduction of P-700+ can be restored in the case of DCMU or DBMIB inhibition by addition of an electron donor couple (2,6-dichlorophenol indophenol (Cl2Ind)/ascorbate) which supplies electrons to cytochrome f. However, this donor couple is inefficient in restoring electron transport in chloroplasts which have been inhibited with the plastocyanin inactivators, KCN and HgCl2. Oxidation-reduction measurements reveal that the fast P-700+ reduction component reflects electron transfer from a component with Em = 375 +/- 10 mV (pH = 7.5). These data suggest the assignment of the 300-mus decay kinetics to electron transfer from cytochrome f (Fe2+) to P-700+, thus confirming the recent observations of Haehnel et al. (Z. Naturforsch. 26b, 1171-1174 (1971)).
mesh_terms: D015086:2,6-Dichloroindophenol / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003486:Cyanides / Q000494:pharmacology; D003580:Cytochromes / Q000378:metabolism*; D004237:Diuron / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D008628:Mercury / Q000494:pharmacology; D010084:Oxidation-Reduction; D010782:Photolysis; D010788:Photosynthesis; D010944:Plants; D011809:Quinones / Q000494:pharmacology
chemical_list: D003486:Cyanides; D003580:Cytochromes; D011809:Quinones; D004237:Diuron; D015086:2,6-Dichloroindophenol; D008628:Mercury; D001205:Ascorbic Acid