Primary radical pair in the Photosystem II reaction centre

Takahashi, Yuichiro; Hansson, Örjan; Mathis, Paul; Satoh, Kimiyuki

doi:10.1016/0005-2728(87)90147-2

Cited by 194 publications

(157 citation statements)

References 32 publications

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“…These absorption changes can be attributed to the triplet state of P680, since lifetime, spectrum (not shown) and temperature dependence of the relative quantum yield agree very well with previous results [26]. We thus conclude that the triplet formation and decay parameters in our preparation are similar to those measured for other PS II RC preparations obtained by different methods.…”

Section: Resultssupporting

confidence: 90%

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Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO₄

et al. 1994

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A Dl-D2cyt b-559 complex containing 4 chlorophyll a, 1 p-carotene and 1 cytochrome b-559 per 2 pheophytin a has been isolated from spinach with 30% yield using a Q-Sepharose Fast-Flow anion-exchange column equilibrated with 0.1% Triton X-100, 10 mM MgSO, and 50 mM Tris-HCl (pH 7.2). The preparation was then stabilized with 0.1% dodecyl-p-n-maltoside. This method gave a yield 10 times higher than that using a Fractogel TSK-DEAE 650(S) column equilibrated with 0.1% Triton X-100, 30 mM NaCl and 50 mM Tris-HCl @H 7.2). The PS II RC complex was characterized using absorption and fluorescence spectroscopy at 277 and 77 K. A selective reversible bleaching under reducing conditions with maximum at 682 nm, associated with pheophytin a reduction, and light-induced absorption differences with a lifetime of 1.0 ms, ascribed to the triplet state of P680 were measured and indicated that the isolated Dl-D2-cyt b-559 complex is active in charge separation. The results are compared with the data obtained for a PS II RC preparation containing 6 chlorophyll a, 2 B-carotene and 1 cyt b-559 per 2 pheophytin a.

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Section: Resultssupporting

confidence: 90%

“…A selective bleaching around 680 nm has been observed upon oxidation of the primary electron donor P680 [24,25], 3P680 formation [26] and reaction center inactivation [3,6].…”

Section: Discussionmentioning

confidence: 99%

Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO₄

et al. 1994

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“…As discussed below, the faster component can be ascribed to the decay of excited Chls uncoupled from electron transfer and for the fit of the second time constant is fixed to 6 ns, while the slower component mirrors the recombination of P68O'Pheo-. The residual bleaching indicates the formation of 3P680* (according to the radical pair mechanism, see below), since it decays with a time constant of 1.61 ms, which is characteristic for this state [8]. An external magnetic field of 700G slows the radical pair recombination to 175 ns and decreases the yield of 3P680*, but has no effect on the fast decay of the uncoupled Chls or on the decay time of 3P680*.…”

Section: Methodsmentioning

confidence: 99%

“…which probably arises from a carotenoid triplet state formed with a yield of 2-3% [8,18,20]. The recovery of the absorbance at 681 nm was measured at different temperatures between 90K and 3 1 OK. At all temperatures the fast component with approx.…”

Section: Febs Letters December 1993mentioning

confidence: 99%

Similarity of primary radical pair recombination in photosystem II and bacterial reaction centers

et al. 1993

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We report temperature and magnetic field dependent measurements of the recombination dynamics of the radical pair P680+Pheo-in D,D,cytbSSg reaction centers of photosystem II and compare the results to those obtained in bacterial reaction centers. In photosystem II the rate of recombination to the groundstate is found to be slower than in the bacterial reaction centers by a factor of at least 50. This difference arises from the different redox potentials of the pigments of plant and bacterial reaction centers. In contrast, the rate of recombination to the triplet state is similar in all reaction centers, indicating a similar electronic coupling which allows us to conclude upon the structural similarity.

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“…(2) The exciton coupling attributed to P (∼140 cm -1 ; 13-16) is far weaker than that associated with the bacterial primary donor (500-1000 cm -1 ; 1), most likely because of the greater separation (10 Å center to center) of P A and P B (17,18). (3) The P triplet, formed through charge recombination, at liquid helium temperature, between the primary donor-acceptor pair, is localized on a monomeric chlorophyll (19)(20)(21)(22)(23) with an orientation more like that of the bacterial reaction center monomeric accessory Bchlorophylls, B A or B B (15,24), while in bacterial reaction centers the triplet orientation is consistent with its localization on one or both of P A and P B (25,26). It has been suggested that the triplet and possibly the cation radical itself may be localized either on the PSII homologue of B A or B B (24,27) or that P A or P B or both in PSII have an orientation more like that of an accessory BChl than that of the special pair BChls of the bacterial reaction centers (24,28,29).…”

Section: Introductionmentioning

confidence: 99%

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

et al. 2001

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Site-directed mutations were introduced to replace D1-His198 and D2-His197 of the D1 and D2 polypeptides, respectively, of the photosystem II (PSII) reaction center of Synechocystis PCC 6803. These residues coordinate chlorophylls P A and P B which are homologous to the special pair Bchlorophylls of the bacterial reaction centers that are coordinated respectively by histidines L-173 and M-200 (202). P A and P B together serve as the primary electron donor, P, in purple bacterial reaction centers. In PS II, the site-directed mutations at D1 His198 affect the P + -P-absorbance difference spectrum. The bleaching maximum in the Soret region (in WT at 433 nm) is blue-shifted by as much as 3 nm. In the D1 His198Gln mutant, a similar displacement to the blue is observed for the bleaching maximum in the Q y region (672.5 nm in WT at 80 K), whereas features attributed to a band shift centered at 681 nm are not altered. In the Y Z •-Y Z -difference spectrum, the band shift of a reaction center chlorophyll centered in WT at 433-434 nm is shifted by 2-3 nm to the blue in the D1-His198Gln mutant. The D1-His198Gln mutation has little effect on the optical difference spectrum, 3 P-1 P, of the reaction center triplet formed by P + Pheo -charge recombination (bleaching at 681-684 nm), measured at 5-80 K, but becomes visible as a pronounced shoulder at 669 nm at temperatures g150 K. Measurements of the kinetics of oxidized donor-Q A -charge recombination and of the reduction of P + by redox active tyrosine, Y Z , indicate that the reduction potential of the redox couple P + /P can be appreciably modulated both positively and negatively by ligand replacement at D1-198 but somewhat less so at D2-197. On the basis of these observations and others in the literature, we propose that the monomeric accessory chlorophyll, B A , is a long-wavelength trap located at 684 nm at 5 K. B A * initiates primary charge separation at low temperature, a function that is increasingly shared with P A * in an activated process as the temperature rises. Charge separation from B A * would be potentially very fast and form P A + B A -and/or B A + Pheo -as observed in bacterial reaction centers upon direct excitation of B A ) Proc. Natl. Acad Sci. 96, 2054-2059. The cation, generated upon primary charge separation in PSII, is stabilized at all temperatures primarily on P A , the absorbance spectrum of which is displaced to the blue by the mutations. In WT, the cation is proposed to be shared to a minor extent (∼20%) with P B , the contribution of which can be modulated up or down by mutation. The band shift at 681 nm, observed in the P + -P difference spectrum, is attributed to an electrochromic effect of P A + on neighboring B A . Because of its low-energy singlet and therefore triplet state, the reaction center triplet state is stabilized on B A at e80 K but can be shared with P A at >80 K in a thermally activated process.

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Primary radical pair in the Photosystem II reaction centre

Cited by 194 publications

References 32 publications

Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO₄

Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO₄

Similarity of primary radical pair recombination in photosystem II and bacterial reaction centers

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

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Primary radical pair in the Photosystem II reaction centre

Cited by 194 publications

References 32 publications

Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO4

Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO4

Similarity of primary radical pair recombination in photosystem II and bacterial reaction centers

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

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Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO₄

Characterization of a D1‐D2‐cyt b‐559 complex containing 4 chlorophyll a/2 pheophytin a isolated with the use of MgSO₄