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Identification of the 120 mus phase in the decay of delayed fluorescence in spinach chloroplasts and subchloroplast particles as the intrinsic back reaction. The dependence of the level of this phase on the thylakoids internal pH.
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JournalBiochim. Biophys. ActaNot FoundDate
1975-Dec-11
Publication Type
Journal Article
Volume
1975-Dec-11 / 408 : 269-38
Author
Haveman J , Lavorel J
DoiPMIDMESH
Carbonyl Cyanide m-Chlorophenyl Hydrazone
Chloroplasts
Digitonin
Diuron
Electron Spin Resonance Spectroscopy
Hydrogen-Ion Concentration
Hydroxylamines
Kinetics
Lasers
Luminescent Measurements
Nigericin
Photosynthesis
Plants
Semicarbazides
Spectrometry, Fluorescence
Valinomycin
Abstract
After a 500 mus laser flash a 120 mus phase in the decay of delayed fluorescence is visible under a variety of circumstances in spinach chloroplasts and subchloroplast particles enriched in Photosystem II prepared by means of digitonin. The level of this phase is high in the case of inhibition of oxygen evolution at the donor side of Photosystem II. Comparison with the results of Babcock and Sauer (1975) Biochim. Bio-phys. Acta 376, 329-344, indicates that their EPR signal IIf which they suppose to be due to Z+, the oxidized first secondary donor of Photosystem II, is well correlated with a large amplitude of our 120 mus phase. We explain our 120 mus phase by the intrinsic back reaction of the excited reaction center in the presence of Z+, as predicted by Van Gorkom and Donze (1973) Photochem. Photobiol. 17, 333-342. The redox state of Z+ is dependent on the internal pH of the thylakoids. The results on the effect of pH in the mus region are compared with those obtained in the ms region.
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