The reaction center of photosystem II studied with polarized fluorescence spectroscopy

Kwa, Stefan L.S.; Newell, William R.; Grondelle, Rienk van; Dekker, Jan

doi:10.1016/0005-2728(92)90027-y

Cited by 91 publications

(65 citation statements)

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“…4) indicates that unconnected pigments do not contribute to the steady-state emission. Also, there is no indication of CP47 contamination, since no emission component around 690 nm could be observed [25]. A fluorescence excitation spectrum at 77 K was recorded in the range 500-720 nm for the emission at 740 nm.…”

Section: Resultsmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

“…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: 98%

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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“…[104]) and mutational analysis [92] it could be concluded that the ps spectral equilibration leads to a situation in which the excitations are very rapidly to a large extent located on the Chl a pigments on the stromal part of the protein and preferably at the periphery [105], namely on Chls 610-612, from where they can be transferred to other complexes in the thylakoid membrane. Spatial equilibration within the trimers might occur on a slower time scale (tens of ps) as was concluded from a singlet-singlet annihiliation study [106] and a pressure-induced quenching study [107], whereas (polarized) pump-probe measurements also revealed such ''slow'' kinetics [100,108,109].…”

Section: Energy Transfer In the Antenna Complexes Of Photosystem IImentioning

confidence: 90%

Light-harvesting and structural organization of Photosystem II: From individual complexes to thylakoid membrane

Croce

Amerongen

2011

Journal of Photochemistry and Photobiology B: Biology

165

114

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a b s t r a c tPhotosystem II (PSII) is responsible for the water oxidation in photosynthesis and it consists of many proteins and pigment-protein complexes in a variable composition, depending on environmental conditions. Sunlight-induced charge separation lies at the basis of the photochemical reactions and it occurs in the reaction center (RC). The RC is located in the PSII core which also contains light-harvesting complexes CP43 and CP47. The PSII core of plants is surrounded by external light-harvesting complexes (lhcs) forming supercomplexes, which together with additional external lhcs, are located in the thylakoid membrane where they perform their functions.In this paper we provide an overview of the available information on the structure and organization of pigment-protein complexes in PSII and relate this to experimental and theoretical results on excitation energy transfer (EET) and charge separation (CS). This is done for different subcomplexes, supercomplexes, PSII membranes and thylakoid membranes. Differences in experimental and theoretical results are discussed and the question is addressed how results and models for individual complexes relate to the results on larger systems. It is shown that it is still very difficult to combine all available results into one comprehensive picture.

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“…The PSII RC (D1-D2-cyt b 559 ) complexes were isolated from spinach as described in ref 21. The sample was diluted in a buffer containing 60% glycerol (v/v), 20 mM BisTris (pH 6.5), 200 mM sucrose, and 0.06% β-DM.…”

Section: Methodsmentioning

confidence: 99%

Two Different Charge Separation Pathways in Photosystem II

et al. 2010

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Charge separation is an essential step in the conversion of solar energy into chemical energy in photosynthesis. To investigate this process, we performed transient absorption experiments at 77 K with various excitation conditions on the isolated Photosystem II reaction center preparations from spinach. The results have been analyzed by global and target analysis and demonstrate that at least two different excited states, (Chl D1 Phe D1 )* and (P D1 P D2 Chl D1 )*, give rise to two different pathways for ultrafast charge separation. We propose that the disorder produced by slow protein motions causes energetic differentiation among reaction center complexes, leading to different charge separation pathways. Because of the low temperature, two excitation energy trap states are also present, generating charge-separated states on long time scales. We conclude that these slow trap states are the same as the excited states that lead to ultrafast charge separation, indicating that at 77 K charge separation can be either activation-less and fast or activated and slow.Charge separation is one of the key processes in photosynthetic energy conversion. After absorption of a photon by the photochemically active reaction center, an electronically excited state is transformed into a short-lived charge-separated state. Subsequent electron transfer results in a stable charge-separated state which ultimately powers the photosynthetic organism.Type II reaction centers found in purple bacteria and in oxygenevolving organisms (cyanobacteria, algae, and higher plants) are membrane proteins that contain four (bacterio)chlorophyll [(B)Chl] 1 and two (bacterio)pheophytin [(B)Phe] molecules arranged in two symmetric branches spanning the membrane in the center of the complex. It is established that only one branch is active in charge separation (1-4).The best understanding of the kinetics and energetics of charge separation has been obtained for the reaction center (RC) of photosynthetic purple bacteria (5). The central excitonically coupled special pair, P, of BChl molecules [P A and P B , ∼8 Å apart, center to center (6)], absorbing at ∼875 nm in Rhodobacter sphaeroides, are electronically excited after the energy transfer from the LH1 core antenna (absorbing at approximately equal energy). Then, an electron is transferred to the BChl molecule on the active branch (B A ) in 3 ps, and from B A to the BPhe (H A ) in 1 ps, resulting in the final charge-separated state, P þ H A -. However, in isolated reaction centers, excitation of the accessory BChl absorbing at ∼800 nm (B A ) resulted in an even faster charge separation, either via B A þ H A -or via P þ B A -(7-9). In vivo, this second route does not occur to a significant extent, because B A is too high in energy to receive excitation energy from the antenna.In the photosystem II reaction center (PSII RC) of oxygenevolving organisms, there is no special pair, and the similar distance of ∼10-11 Å between neighboring pigments in the center of the complex (10-13) gives rise to a...

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The reaction center of photosystem II studied with polarized fluorescence spectroscopy

Cited by 91 publications

References 30 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

Light-harvesting and structural organization of Photosystem II: From individual complexes to thylakoid membrane

Two Different Charge Separation Pathways in Photosystem II

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The reaction center of photosystem II studied with polarized fluorescence spectroscopy

Cited by 91 publications

References 30 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

Light-harvesting and structural organization of Photosystem II: From individual complexes to thylakoid membrane

Two Different Charge Separation Pathways in Photosystem II

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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