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The effect of herbicides on components of the PS II reaction centre measured by EPR
Author(s) -
Rutherford A.W.,
Zimmermann J.L.,
Mathis P.
Publication year - 1984
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(84)80161-1
Subject(s) - chemistry , dcmu , pheophytin , electron paramagnetic resonance , reagent , photochemistry , redox , photosystem ii , stereochemistry , nuclear magnetic resonance , inorganic chemistry , biochemistry , photosynthesis , physics
Incubation of PS II membranes with herbicides results in changes in EPR signals arising from reaction centre components. Dinoseb, a phenolic herbicide which binds to the reaction centre polypeptide, changes the width and form of the EPR signal arising from photoreduced Q − A Fe. o ‐Phenanthroline slightly broadens the Q − A Fe signal. These effects are attributed to changes in the interaction between the semi‐quinone and the iron. DCMU, which binds to the 32 kDa protein, has virtually no effect on the width of the Q − A Fe signal but does give rise to an increase in its amplitude. This could result from a change in redox state of an interacting component. Herbicide effects can also be seen when Q − A Fe is chemically reduced and these seen to be reflected by changes in splitting and amplitude of the split pheophytin − signal. Dinoseb also results in the loss of ‘Signal II dark’, the conversion of reduced high‐potential cytochrome b 559 to its oxidized low‐potential form and the presence of transiently photooxidized carotenoid after a flash at 25°C; these effects indicate that dinoseb may also act as an ADRY reagent.