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1.
The dynamics of energy and charge transfer in the Photosystem II reaction center complex is an area of great interest today.
These processes occur on a time scale ranging from femtoseconds to tens of picoseconds or longer. Steady-state and ultrafast
spectroscopy techniques have provided a great deal of quantitative and qualitative data that have led to varied interpretations
and phenomenological models. More recently, microscopic models that identify specific charge separated states have been introduced,
and offer more insight into the charge transfer mechanism. The structure and energetics of PS II reaction centers are reviewed,
emphasizing the effects on the dynamics of the initial charge transfer.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
The shape of the EPR spectrum of the triplet state of photosystem II reaction centers with a singly reduced primary acceptor complex QAFe2+ was studied. It was shown that the spectroscopic properties do not significantly change when the relaxation of the primary acceptor is accelerated and when the magnetic interaction between the reduced quinone molecule QA and the nonheme iron ion Fe2+ is disrupted. This observation confirmed the earlier conclusion that the anisotropy of the quantum yield of the triplet state is the main cause of the anomalous shape of the EPR spectrum. A scheme of primary processes in photosystem II that is consistent with the observed properties of the EPR spectrum of the triplet state is discussed. 相似文献
3.
Extraction of PS II particles with 50 mM cholate and 1 M NaCl releases several proteins (33-, 23-, 17- and 13 kDa) and lipids from the thylakoid membrane which are essential for O2 evolution, dichlorophenolindophenol (DCIP) reduction and for stable charge separation between P680+ and QA
-. This work correlates the results on the loss of steady-state rates for O2 evolution and PS II mediated DCIP photo-reduction with flash absorption changes directly monitoring the reaction center charge separation at 830 nm due to P680+, the chlorophyll a donor. Reconstitution of the extracted lipids to the depleted membrane restores the ability to photo-oxidize P680 reversibly and to reduce DCIP, while stimulating O2 evolution minimally. Addition of the extracted proteins of masses 33-, 23- and 17- kDa produces no further stimulation of DCIP reduction in the presence of an exogenous donor like DPC, but does enhance this rate in the absence of exogenous donors while also stimulating O2 evolution. The proteins alone in the absence of lipids have little influence on charge separation in the reaction center. Thus lipids are essential for stable charge separation within the reaction center, involving formation of P680+ and QA
-.Abbreviations A830
Absorption change at 830 nm
- Chl
Chlorophyll
- D1
primary electron donor to P680
- DCIP
2,6-dichlorophenolindophenol
- DPC
1,5-diphenylcarbazide
- MOPS
3-(N-morpholino)propanesulfonic acid
- P680
reaction center chlorophyll a molecule of photosystem II
- PPBQ
Phenyl-p-benzoquinone
- PS II
Photosystem II
- QA, QB
first and second quinone acceptors in PS II
- V-DCIP
rate of DCIP reduction
- V-O2
rate of oxygen evolution
- Y
water-oxidizing enzyme system
- CHAPS
3-Cyclohexylamino-propanesulfonic acid 相似文献
4.
Michael R. Wasielewski Douglas G. Johnson Govindjee Christopher Preston Michael Seibert 《Photosynthesis research》1989,22(1):89-99
We have measured the rate constant for the formation of the oxidized chlorophyll a electron donor (P680+) and the reduced electron acceptor pheophytin a
– (Pheo a
–) following excitation of isolated Photosystem II reaction centers (PS II RC) at 15 K. This PS II RC complex consists of D1, D2, and cytochrome b-559 proteins and was prepared by a procedure which stabilizes the protein complex. Transient absorption difference spectra were measured from 450–840 nm as a function of time with 500fs resolution following 610 nm laser excitation. The formation of P680+-Pheo a
– is indicated by the appearance of a band due to P680+ at 820 nm and corresponding absorbance changes at 490, 515 and 546 nm due to the formation of Pheo a
–. The appearance of the 490 nm and 820 nm bands is monoexponenital with =1.4±0.2 ps. Treatment of the PS II RC with sodium dithionite and methyl viologen followed by exposure to laser excitation results in accumulation of Pheo a
–. Laser excitation of these prereduced RCs at 15 K results in formation of a transient absorption spectrum assigned to 1*P680. We observe wavelength-dependent kinetics for the recovery of the transient bleach of the Qy absorption bands of the pigments in both untreated and pre-reduced PS II RCs at 15K. This result is attributed to an energy transfer process within the PS II RC at low temperature that is not connected with charge separation.Abbreviations PS I
Photosystem I
- PS II
Photosystem II
- RC
reaction center
- P680
primary electron donor in Photosystem II
- Chl a
chlorophyll a
- Pheo a
pheophytin a 相似文献
5.
Jakub P >sen >cík Martin Vácha Franti >sek Adamec Milan Ambro >z Juraj Dian Jan Bo >cek Jan Hála 《Photosynthesis research》1994,42(1):1-8
Results of low temperature fluorescence and spectral hole burning experiments with whole cells and isolated chlorosomes of the green sulfur bacterium Chlorobium limicola containing BChl c are reported. At least two spectral forms of BChl c (short-wavelength and long-wavelength absorbing BChl c) were identified in the second derivative fluorescence spectra. The widths of persistent holes burned in the fluorescence spectrum of BChl c are determined by excited state lifetimes due to fast energy transfer. Different excited state lifetimes for both BChl c forms were observed. A site distribution function of the lowest excited state of chlorosomal BChl c was revealed. The excited state lifetimes are strongly influenced by redox conditions of the solution. At anaerobic conditions the lifetime of 5.3 ps corresponds to the rate of energy transfer between BChl c clusters. This time shortens to 2.6 ps at aerobic conditions. The shortening may be caused by introducing a quencher. Spectral bands observed in the fluorescence of isolated chlorosomes were attributed to monomeric and lower state aggregates of BChl c. These forms are not functionally connected with the chlorosome.Abbreviations BChl
bacteriochlorophyll
- EET
electronic energy transfer
- FWHM
full width at half maximum
- SDF
site distribution function
- RC
reaction centre 相似文献
6.
J. Kevin Gillie Paul A. Lyle Gerald J. Small John H. Golbeck 《Photosynthesis research》1989,22(3):233-246
Persistent photochemical hole burned profiles are reported for the primary electron donor state P700 of the reaction center of PS I. The hole profiles at 1.6 K for a wide range of burn wavelengths (B) are broad (FWHM310 cm-1) and for the 45:1 enriched particles studied exhibit no sharp zero-phonon hole feature coincident with B. The B hole profiles are analyzed using the theory of Hayes et al. [J Phys Chem 1986, 90: 4928] for hole burning in the presence of arbitrarily strong linear electron-phonon coupling. A Huang-Rhys factor S in the range 4–6 and a corresponding mean phonon frequency in the range 35–50 cm-1 together with an inhomogeneous line broadening of100 cm-1 are found to provide good agreement with experiment. The zero-point level of P700* is predicted to lie at710 nm at 1.6K with an absorption maximum at702 nm. The hole spectra are discussed in the context of the hole spectra for the primary electron donor states of PS II and purple bacteria.Abbreviations NPHB
nonphotochemical hole burning
- O.D.
optical density
- PSBH
phonon sideband hole
- PS I
Photosystem I P680
- P700, P870, P960
the primary electron donors of Photosystem II, Photosystem I, Rhodobacter sphaeroides, Rhodopseudomonas viridis
- PED
primary electron donor
- RC
reaction center
- ZPH
zero-phonon holes 相似文献
7.
Rapid and simple isolation of pure photosystem II core and reaction center particles from spinach 总被引:2,自引:2,他引:0
Peter J. van Leeuwen Maaike C. Nieveen Erik Jan van de Meent Jan P. Dekker Hans J. van Gorkom 《Photosynthesis research》1991,28(3):149-153
Pure and active oxygen-evolving PS II core particles containing 35 Chl per reaction center were isolated with 75% yield from spinach PS II membrane fragments by incubation with n-dodecyl--D-maltoside and a rapid one step anion-exchange separation. By Triton X-100 treatment on the column these particles could be converted with 55% yield to pure and active PS II reaction center particles, which contained 6 Chl per reaction center.Abbreviations Bis-Tris
bis[2-hydroxyethyl]imino-tris[hydroxymethyl]methane
- Chl
chlorophyll
- CP29
Chl a/b protein of 29 kDa
- Cyt b
559
cytochrome b
559
- DCBQ
2,5-dichloro-p-benzo-quinone
- LHC II
light-harvesting complex II, predominant Chl a/b protein
- MES
2-[N-Morpholino]ethanesulfonic acid
- Pheo
pheophytin
- PS H
photosystem II
- QA
bound plastoquinone, serving as the secondary electron acceptor in PS II (after Pheo)
- SDS
sodiumdodecylsulfate 相似文献
8.
Electron paramagnetic resonance (EPR) and absorption spectroscopy have been used to study the low temperature photochemical behavior of the Photosystem II D-1/D-2/ cytochrome b559 reaction center complex. The reaction center displays large triplet state EPR signals which are attenuated after actinic illumination at low temperatures in the presence of sodium dithionite. Concomitant with the triplet attenuation is the buildup of a structured radical signal with an effective g value of 2.0046 and a peak-to-peak width of 11.9 G. The structure in the signal is suggestive of it being comprised in part of the anion radical of pheophytin a. This assignment is corroborated by low temperature optical absorbance measurements carried out after actinic illumination at the low temperatures which show absorption bleachings at 681 nm, 544 nm and 422 nm and an absorbance buildup at 446 nm indicating the formation of reduced pheophytin.Abbreviations EPR
electron paramagnetic resonance 相似文献
9.
The underlying principles of spectral hole burning spectroscopies and the theory for hole profiles are reviewed and illustrated with calculated spectra. The methodology by which the dependence of the overall hole profile on burn wavelength can be used to reveal the contributions from site inhomogeneous broadening and various homogeneous broadening contributions to the broad Qy-absorption bands of cofactors is emphasized. Applications to the primary electron donor states of the reaction centers of purple bacteria and Photosystems I and II of green plants are discussed. The antenna (light harvesting) complexes considered include B800–B850 and B875 of Rhodobacter sphaeroides and the base-plate complex of Prosthecochloris aestuarii with particular attention being given to excitonic interactions and level structure. The data presented show that spectral hole burning is a generally applicable low temperature approach for the study of excited state electronic and vibrational (intramolecular, phonon) structures, structural heterogeneity and excited state lifetimes.William E. Catron Fellow. 相似文献
10.
Peter Palencar Tatyana Prudnikova Frantisek Vacha Michal Kuty 《Journal of molecular modeling》2009,15(8):923-933
Accumulation of reduced pheophytin a (Pheo-D1) in photosystem II reaction center (PSII RC) under illumination at low redox potential is accompanied by changes
in absorbance and circular dichroism spectra. The temperature dependences of these spectral changes have the potential to
distinguish between changes caused by the excitonic interaction and temperature-dependent processes. We observed a conformational
change in the PSII RC protein part and changes in the spatial positions of the PSII RC pigments of the active D1 branch upon
reduction of Pheo-D1 only in the case of high temperature (298 K) dynamics. The resulting absorption difference spectra of
PSII RC models equilibrated at temperatures of 77 K and 298 K were highly consistent with our previous experiments in which
light-induced bleaching of the PSII RC absorbance spectrum was observable only at 298 K. These results support our previous
hypothesis that Pheo-D1 does not interact excitonically with the other chlorins of the PSII RC, since the reduced form of
Pheo-D1 causes absorption spectra bleaching only due to temperature-dependent processes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Michal KutyEmail: |
11.
Don Devault 《Photosynthesis research》1986,10(1-2):125-137
This paper points out that the orientations of the porphyrins, bacteriochlorophyll and bacteriopheophytin, in the reaction centers of Rhodopseudomonas viridis, as shown by the new X-ray determined structure, have a peculiar orientation towards each other: electron donors are broadside toward the acceptors and acceptors are edgeon toward donors. Vibronic coupling which is the mechanism of converting free-energy loss in electron transport to vibrational energy is examined as a possible explanation. Preliminary calculations do not support this as an explanation of the orientations but suggest strongly that the non-heme iron atom has the function of promoting vibronic coupling in the electron transfer from bacteriopheophytin to menaquinone. It is further suggested that the system of electron transport from the special pair of bacteriochlorophyll to the bacteriopheophytin is arranged to keep virbonic coupling to a minimum to match the very small electronic free-energy loss in this region.Abbreviations BC
Bacteriochlorophyll
- BP
Bacteriopheophytin
- BC2
Bacteriochlorophyll special pair, primary electron donor
- Fe
Non-heme iron atom
- MQ
Menaquinone, first quinone acceptor
- UQ
Ubiquinone, second quinone acceptor 相似文献
12.
The properties of Photosystem II electron donation were investigated by EPR spectrometry at cryogenic temperatures. Using preparations from mutants which lacked Photosystem I, the main electron donor through the Photosystem II reaction centre to the quinone-iron acceptor was shown to be the component termed Signal II. A radical of 10 G line width observed as an electron donor at cryogenic temperatures under some conditions probably arises through modification of the normal pathway of electron donation. High-potential cytochrome b-559 was not observed on the main pathway of electron donation. Two types of PS II centres with identical EPR components but different electron-transport kinetics were identified, together with anomalies between preparations in the amount of Signal II compared to the quinone-iron acceptor. Results of experiments using cells from mutants of Scenedesmus obliquus confirm the involvement of the Signal II component, manganese and high-potential cytochrome b-559 in the physiological process leading to oxygen evolution. 相似文献
13.
Neerken S Ma YZ Aschenbrücker J Schmidt KA Nowak FR Permentier HP Aartsma TJ Gillbro T Amesz J 《Photosynthesis research》2000,65(3):261-268
Properties of the excited states in reaction center core (RCC) complexes of the green sulfur bacterium Prosthecochloris aestuarii were studied by means of femtosecond time-resolved isotropic and anisotropic absorption difference spectroscopy at 275 K.
Selective excitation of the different transitions of the complex resulted in the rapid establishment of a thermal equilibrium.
At about 1 ps after excitation, the energy was located at the lowest energy transition, BChl a 835. Time constants varying between 0.26 and 0.46 ps were observed for the energy transfer steps leading to this equilibrium.
These transfer steps were also reflected in changes in polarization. Our measurements indicate that downhill energy transfer
towards excited BChl a 835 occurs via the energetically higher spectral forms BChl a 809 and BChl a 820. Low values of the anisotropy of about 0.07 were found in the ‘two-color’ measurements at 820 and 835 nm upon excitation
at 800 nm, whereas the ‘one-color’ kinetics showed much higher anisotropies. Charge separation occurred with a time constant
varying between 20 and 30 ps.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
G�bor Sipka Melinda Magyar Alberto Mezzetti Parveen Akhtar Qingjun Zhu Yanan Xiao Guangye Han Stefano Santabarbara Jian-Ren Shen Petar H Lambrev Gyz Garab 《The Plant cell》2021,33(4):1286
Photosystem II (PSII) uses solar energy to oxidize water and delivers electrons for life on Earth. The photochemical reaction center of PSII is known to possess two stationary states. In the open state (PSIIO), the absorption of a single photon triggers electron-transfer steps, which convert PSII into the charge-separated closed state (PSIIC). Here, by using steady-state and time-resolved spectroscopic techniques on Spinacia oleracea and Thermosynechococcus vulcanus preparations, we show that additional illumination gradually transforms PSIIC into a light-adapted charge-separated state (PSIIL). The PSIIC-to-PSIIL transition, observed at all temperatures between 80 and 308 K, is responsible for a large part of the variable chlorophyll-a fluorescence (Fv) and is associated with subtle, dark-reversible reorganizations in the core complexes, protein conformational changes at noncryogenic temperatures, and marked variations in the rates of photochemical and photophysical reactions. The build-up of PSIIL requires a series of light-induced events generating rapidly recombining primary radical pairs, spaced by sufficient waiting times between these events—pointing to the roles of local electric-field transients and dielectric relaxation processes. We show that the maximum fluorescence level, Fm, is associated with PSIIL rather than with PSIIC, and thus the Fv/Fm parameter cannot be equated with the quantum efficiency of PSII photochemistry. Our findings resolve the controversies and explain the peculiar features of chlorophyll-a fluorescence kinetics, a tool to monitor the functional activity and the structural-functional plasticity of PSII in different wild-types and mutant organisms and under stress conditions.The closed-state of photosystem II possesses a hitherto unrecognized structural and functional plasticity and upon illumination assumes a light-adapted charge-separated state. 相似文献
15.
A protein dynamics study of photosystem II: the effects of protein conformation on reaction center function 总被引:2,自引:0,他引:2
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Molecular dynamics simulations have been performed to study photosystem II structure and function. Structural information obtained from simulations was combined with ab initio computations of chromophore excited states. In contrast to calculations based on the x-ray structure, the molecular-dynamics-based calculations accurately predicted the experimental absorbance spectrum. In addition, our calculations correctly assigned the energy levels of reaction-center (RC) chromophores, as well as the lowest-energy antenna chlorophyll. The primary and secondary quinone electron acceptors, QA and QB, exhibited independent changes in position over the duration of the simulation. QB fluctuated between two binding sites similar to the proximal and distal sites previously observed in light- and dark-adapted RC from purple bacteria. Kinetic models were used to characterize the relative influence of chromophore geometry, site energies, and electron transport rates on RC efficiency. The fluctuating energy levels of antenna chromophores had a larger impact on quantum yield than did their relative positions. Variations in electron transport rates had the most significant effect and were sufficient to explain the experimentally observed multi-component decay of excitation in photosystem II. The implications of our results are discussed in the context of competing evolutionary selection pressures for RC structure and function. 相似文献
16.
Masayuki Komura 《BBA》2006,1757(12):1657-1668
We performed picosecond time-resolved fluorescence spectroscopy in spinach photosystem II (PS II) particles at 4, 40, and 77 K and identified a new fluorescence band, F689. F689 was identified in addition to the well-known F685 and F695 bands in both analyses of decay-associated spectra and global Gaussian deconvolution of time-resolved spectra. Its fast decay suggests the energy transfer directly from F689 to the reaction center chlorophyll P680. The contribution of F689, which increases only at low temperature, explains the unusually broad and variable bandwidth of F695 at low temperature. Global analysis revealed the three types of excitation energy transfer/dissipation processes: (1) energy transfer from the peripheral antenna to the three core antenna bands F685, F689, and F695 with time constants of 29 and 171 ps at 77 and 4 K, respectively; (2) between the three core bands (0.18 and 0.82 ns); and (3) the decays of F689 (0.69 and 3.02 ns) and F695 (2.18 and 4.37 ns). The retardations of these energy transfer rates and the slow F689 decay rate produced the strong blue shift of the PS II fluorescence upon the cooling below 77 K. 相似文献
17.
Gall Bernhard Ellervee Aleksandr Tars Märt Scheer Hugo Freiberg Arvi 《Photosynthesis research》1997,52(3):225-231
Absorption spectra of the D1-D2-cytochrom b559 complex at 4°C were investigated at pressures up to 300 MPa. Pressure effects were mostly reversible and independent of the detergent used (CHAPS or dodecyl--D-maltoside). Red-shifts were observed under pressure for the chlorophyll Qy- and the -carotene S0 S2 bands. The relatively small Qy-shift of approximately 0.15 cm-1/MPa is an indication for the absence of strongly coupled chlorophyll dimers within the reaction center and supports earlier reports from low-temperature measurements (Chang HC, Jankowiak R, Reddy NRS and Small GJ (1995) Chem Phys 197: 307–321). The carotene red-shift (seen in CHAPS) is much larger (0.5 – 0.6 cm-1/MPa) and within the range observed for excitonically coupled chlorophylls. However, since carotenes are more sensitive to changes of refractive index, we do not consider this evidence for excitonically coupled carotenes. Varying the pH and the detergent induced only small effects. Pigment exchange using high pressure instead of elevated temperature was not possible under the conditions tested. 相似文献
18.
Long term fumigation of 4-year-old spruce trees with ozone concentrations up to 200 nl l−1 has only minor effects on the photosynthetic activities measured as chlorophyll a fluorescence. Nevertheless, it drastically changes the turnover of the D-1 reaction center polypeptide of photosystem II. During summer, fumigation with ozone for 2 weeks resulted in an almost 4-fold stimulation of the light dependent incorporation of [14 C] leucine into the D-1 protein in the exposed trees. The amount of immunodetectable D-1 protein remained constant when based on chlorophyll. This indicates that exposure to ozone stimulates both the synthesis and the degradation of the D-1 protein. When spruce trees were exposed during winter for 4 weeks to 100 and 200 nl l−1 ozone, respectively, an almost 3-fold increase of the amount of immunodetectable D-1 protein per chlorophyll in the exposed trees was observed. This can be explained by a varying stimulation of D-1 protein synthesis and degradation depending on the different physiological conditions. Since so far the D-1 protein has been found only as a component of photosystem II reaction centers, one has to assume that the relative content of photosystem II reaction centers also increases under certain stress conditions. The increased turnover of the D-1 protein in trees exposed to ozone explains the synergistic effects of stress conditions and high light intensities often observed in the field. 相似文献
19.
Yuan Fang Dongyang Liu Jingjing Jiang Axin He Rui Zhu Lijin Tian 《The Journal of biological chemistry》2022,298(4)
Photosynthetic organisms have evolved light-harvesting antennae over time. In cyanobacteria, external phycobilisomes (PBSs) are the dominant antennae, whereas in green algae and higher plants, PBSs have been replaced by proteins of the Lhc family that are integrated in the membrane. Red algae represent an evolutionary intermediate between these two systems, as they employ both PBSs and membrane LHCR proteins as light-harvesting units. Understanding how red algae cope with light is not only interesting for biotechnological applications, but is also of evolutionary interest. For example, energy-dependent quenching (qE) is an essential photoprotective mechanism widely used by species from cyanobacteria to higher plants to avoid light damage; however, the quenching mechanism in red algae remains largely unexplored. Here, we used both pulse amplitude-modulated (PAM) and time-resolved chlorophyll fluorescence to characterize qE kinetics in the red alga Porphyridium purpureum. PAM traces confirmed that qE in P. purpureum is activated by a decrease in the thylakoid lumen pH, whereas time-resolved fluorescence results further revealed the quenching site and ultrafast quenching kinetics. We found that quenching exclusively takes place in the photosystem II (PSII) complexes and preferentially occurs at PSII’s core antenna rather than at its reaction center, with an overall quenching rate of 17.6 ± 3.0 ns−1. In conclusion, we propose that qE in red algae is not a reaction center type of quenching, and that there might be a membrane-bound protein that resembles PsbS of higher plants or LHCSR of green algae that senses low luminal pH and triggers qE in red algae. 相似文献
20.
Flash-induced optical kinetics at room temperature of cytochrome (Cyt) c
551 and an Fe-S center (CFA/CFB) bound to a purified reaction center (RC) complex from the green sulfur photosynthetic bacterium Chlorobium tepidum were studied. At 551 nm, the flash-induced absorbance change decayed with a t
1/2 of several hundred ms, and the decay was accelerated by 1-methoxy-5-methylphenazinium methyl sulfate (mPMS). In the blue region, the absorbance change was composed of mPMS-dependent (Cyt) and mPMS-independent component (CFA/CFB) which decayed with a t
1/2 of 400–650 ms. Decay of the latter was effectively accelerated by benzyl viologen (Em –360 mV) and methyl viologen (–440 mV), and less effectively by triquat (–540 mV). The difference spectrum of Cyt c had negative peaks at 551, 520 and 420 nm, with a positive rise at 440 to 500 nm. The difference spectrum of CFA/CFB resembled P430 of PSI, and had a broad negative peak at 430435 nm.Abbreviations (B)Chl
(bacterio)chlorophyll
- Cyt
cytochrome
- FA, FB and FX
iron-sulfur center A, B and X of Photosystem I
- CFA, CFB and CFX
FA-,FB- and FX-like Fe-S center of Chlorobium
- mPMS
1-methoxy-5-methylphenazinium methyl sulfate
- PSI
Photosystem I
- RC
reaction center 相似文献