Energy Capture in Photosynthesis: Photosystem II

Radmer, Richard; Kok, Bessel

doi:10.1146/annurev.bi.44.070175.002205

Cited by 55 publications

(13 citation statements)

References 124 publications

(195 reference statements)

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“…In conclusion, on S-states where deactivations can occur, misses are caused by deactivations (Radmer and Kok 1975) controlled by the redox state of plastoquinone (Diner and Mauzerall 1973, Radmer and Kok 1973, Diner 1977. Deactivations occur preferentially in the $2 state (Diner 1977), resulting in apparent misses on the Sl state.…”

mentioning

confidence: 91%

“…The effect of a single-hit followed by a deactivation from $2 is therefore the same as that of a "true" miss on the state S~. Thus, in an oxygen evolution sequence, single-hits followed by deactivations cannot be distinguished from "true" misses (Radmer and Kok, 1975). Even at a high flash frequency (5 Hz), $2 deactivation was shown to contribute to the number of apparent misses (Packham et al 1988).…”

Section: Introductionmentioning

confidence: 96%

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Control of misses in oxygen evolution by the oxido-reduction state of plastoquinone in Dunaliella tertiolecta

Meunier

Popovic

1990

Photosynth Res

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The way misses happen in oxygen evolution is subject to debate (Govindjee et al. 1985). We recently observed a linear lowering of the miss probability with the flash number (Meunier and Popovic 1989). Therefore, we investigated in Dunaliella tertiolecta the link between the average miss probability and the redox state of plastoquinone after n flashes. The effect of flashes was to oxidize the plastoquinone pool; we found that the oxidation of plastoquinone highly correlated (linear regression: R (2)=0.996) with the lowering of the miss probability. The flash frequency was found to affect both the miss probability and the redox state of plastoquinone. When pre-flashes were given using a high flash frequency (10 Hz), the plastoquinone pool was oxidized and misses were low; however, if long dark intervals between flashes were used, the oxidizing effect of flashes was lost and the misses were high. We could not explain our results by assuming equal misses over all S-states; but unequal misses, caused by deactivations, were coherent with our results. We deduced that chlororespiration was responsible for the reduction of plastoquinone in the dark interval between flashes. We compared oxygen evolution with and without benzoquinone, using a low flash frequency (0.5 Hz) for maximum misses. Benzoquinone lowered the misses from 34% to 3%, and raised the amplitude of oxygen evolution by more than a factor of two (2). From this we deduced that the charge carrier "C" postulated to explain misses (Lavorel and Maison-Peteri 1983) did not account for more than 3% of miss probability in Dunaliella tertiolecta. These results indicate that the misses in oxygen evolution are controlled by the redox state of plastoquinone, through deactivations.

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confidence: 91%

Section: Introductionmentioning

confidence: 96%

Control of misses in oxygen evolution by the oxido-reduction state of plastoquinone in Dunaliella tertiolecta

Meunier

Popovic

1990

Photosynth Res

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“…In our initial communication on the generation of 2, we noted that a Mn(II)-phenylamido dimer, Mn2(µ-NHPh)2(NR2)2(THF)2 (1b) was isolated under conditions of excess hydrazine and low temperature. A simple protocol for the synthesis of 1b was also provided 26 via the reaction of two equivalents of aniline with two equivalents of Mn(NR2)2: (9) We proposed at this time that 1b could be an intermediate in the assembly of 2. The intermediate could form from the Mn II -NHPh product of HAT by reaction with an equivalent of Mn(NR2)2:…”

Section: Scheme 1 Activation Of Oligomeric 1a (Hypothetical Geometrymentioning

confidence: 99%

Mechanistic Elucidation of the Stepwise Formation of a Tetranuclear Manganese Pinned Butterfly Cluster via N–N Bond Cleavage, Hydrogen Atom Transfer, and Cluster Rearrangement

et al. 2014

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A mechanistic pathway for the formation of the structurally characterized manganese-amide-hydrazide pinned butterfly complex, Mn4(μ3-PhN-NPh-κ(3)N,N')2(μ-PhN-NPh-κ(2)-N,N')(μ-NHPh)2L4 (L = THF, py), is proposed and supported by the use of labeling studies, kinetic measurements, kinetic competition experiments, kinetic isotope effects, and hydrogen atom transfer reagent substitution, and via the isolation and characterization of intermediates using X-ray diffraction and electron paramagnetic resonance spectroscopy. The data support a formation mechanism whereby bis[bis(trimethylsilyl)amido]manganese(II) (Mn(NR2)2, where R = SiMe3) reacts with N,N'-diphenylhydrazine (PhNHNHPh) via initial proton transfer, followed by reductive N-N bond cleavage to form a long-lived Mn(IV) imido multinuclear complex. Coordinating solvents activate this cluster for abstraction of hydrogen atoms from an additional equivalent of PhNHNHPh resulting in a Mn(II)phenylamido dimer, Mn2(μ-NHPh)2(NR2)2L2. This dimeric complex further assembles in fast steps with two additional equivalents of PhNHNHPh replacing the terminal silylamido ligands with η(1)-hydrazine ligands to give a dimeric Mn2(μ-NHPh)2(PhN-NHPh)2L4 intermediate, and finally, the addition of two additional equivalents of Mn(NR2)2 and PhNHNHPh gives the pinned butterfly cluster.

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“…The mediator for oxygen evolution in higher plants and algae, PS 2 is believed localized in the grana of the thylakoid membranes of the chloroplast. Photosystem 2 under the influence of illumination of A < 680 accumulates a strong oxidant which is ultimately discharged by the splitting of water (Cheniae, 1970;Radmer and Kok, 1975). The composition of the electron transfer pathway in PS 2 is not known in great detail as very few spectroscopically detectable intermediates have been observed.…”

Section: Green Plants and Algaementioning

confidence: 99%

Biological Magnetic Resonance

1978

Biological Magnetic Resonance

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Energy Capture in Photosynthesis: Photosystem II

Cited by 55 publications

References 124 publications

Control of misses in oxygen evolution by the oxido-reduction state of plastoquinone in Dunaliella tertiolecta

Control of misses in oxygen evolution by the oxido-reduction state of plastoquinone in Dunaliella tertiolecta

Mechanistic Elucidation of the Stepwise Formation of a Tetranuclear Manganese Pinned Butterfly Cluster via N–N Bond Cleavage, Hydrogen Atom Transfer, and Cluster Rearrangement

Biological Magnetic Resonance

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