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Vasilieva LG, Kaminskaya OP, Yakovlev AG, Shkuropatov AY, Semenov AY, Nadtochenko VA, Krasnovsky AA, Parson WW, Allakhverdiev SI, Govindjee G. In memory of Vladimir Anatolievich Shuvalov (1943-2022): an outstanding biophysicist. PHOTOSYNTHESIS RESEARCH 2022; 154:207-223. [PMID: 36070062 DOI: 10.1007/s11120-022-00932-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
We present here a tribute to one of the foremost biophysicists of our time, Vladimir Anatolievich Shuvalov, who made important contributions in bioenergetics, especially on the primary steps of conversion of light energy into charge-separated states in both anoxygenic and oxygenic photosynthesis. For this, he and his research team exploited pico- and femtosecond transient absorption spectroscopy, photodichroism & circular dichroism spectroscopy, light-induced FTIR (Fourier-transform infrared) spectroscopy, and hole-burning spectroscopy. We remember him for his outstanding leadership and for being a wonderful mentor to many scientists in this area. Reminiscences by many [Suleyman Allakhverdiev (Russia); Robert Blankenship (USA); Richard Cogdell (UK); Arvi Freiberg (Estonia); Govindjee Govindjee (USA); Alexander Krasnovsky, jr, (Russia); William Parson (USA); Andrei Razjivin (Russia); Jian- Ren Shen (Japan); Sergei Shuvalov (Russia); Lyudmilla Vasilieva (Russia); and Andrei Yakovlev (Russia)] have included not only his wonderful personal character, but his outstanding scientific research.
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Affiliation(s)
- Lyudmila G Vasilieva
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Pushchino Moscow Region, Pushchino, Russian Federation
| | - Olga P Kaminskaya
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Pushchino Moscow Region, Pushchino, Russian Federation
| | - Andrei G Yakovlev
- A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 1, Moscow, 119992, Russian Federation
| | - Anatoliy Ya Shkuropatov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Pushchino Moscow Region, Pushchino, Russian Federation
| | - Alexey Yu Semenov
- A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 1, Moscow, 119992, Russian Federation
| | - Victor A Nadtochenko
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Kosygina St. 4, Moscow, 117977, Russian Federation
| | - Alexander A Krasnovsky
- Bach Institute of Biochemistry, Federal Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russian Federation
| | - William W Parson
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA.
| | - Suleyman I Allakhverdiev
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Pushchino Moscow Region, Pushchino, Russian Federation.
- K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russian Federation.
| | - Govindjee Govindjee
- Department of Biochemistry, Department of Plant Biology and Center of Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, 289 Morrill Hall, 505 South Goodwin Avenue, Urbana, IL, 61801, USA.
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Sipka G, Müller P, Brettel K, Magyar M, Kovács L, Zhu Q, Xiao Y, Han G, Lambrev PH, Shen JR, Garab G. Redox transients of P680 associated with the incremental chlorophyll-a fluorescence yield rises elicited by a series of saturating flashes in diuron-treated photosystem II core complex of Thermosynechococcus vulcanus. PHYSIOLOGIA PLANTARUM 2019; 166:22-32. [PMID: 30790299 DOI: 10.1111/ppl.12945] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 02/14/2019] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
Recent chlorophyll-a fluorescence yield measurements, using single-turnover saturating flashes (STSFs), have revealed the involvement of a rate-limiting step in the reactions following the charge separation induced by the first flash. As also shown here, in diuron-inhibited PSII core complexes isolated from Thermosynechococcus vulcanus the fluorescence maximum could only be reached by a train of STSFs. In order to elucidate the origin of the fluorescence yield increments in STSF series, we performed transient absorption measurements at 819 nm, reflecting the photooxidation and re-reduction kinetics of the primary electron donor P680. Upon single flash excitation of the dark-adapted sample, the decay kinetics could be described with lifetimes of 17 ns (∼50%) and 167 ns (∼30%), and a longer-lived component (∼20%). This kinetics are attributed to re-reduction of P680•+ by the donor side of PSII. In contrast, upon second-flash (with Δt between 5 μs and 100 ms) or repetitive excitation, the 819 nm absorption changes decayed with lifetimes of about 2 ns (∼60%) and 10 ns (∼30%), attributed to recombination of the primary radical pair P680•+ Pheo•- , and a small longer-lived component (∼10%). These data confirm that only the first STSF is capable of generating stable charge separation - leading to the reduction of QA ; and thus, the fluorescence yield increments elicited by the consecutive flashes must have a different physical origin. Our double-flash experiments indicate that the rate-limiting steps, detected by chlorophyll-a fluorescence, are not correlated with the turnover of P680.
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Affiliation(s)
- Gábor Sipka
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Pavel Müller
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Klaus Brettel
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Melinda Magyar
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Kovács
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Qingjun Zhu
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Yanan Xiao
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Guangye Han
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Petar H Lambrev
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jian-Ren Shen
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- Photosynthesis Research Center, Okayama University, Okayama, Japan
| | - Győző Garab
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
- Faculty of Science, University of Ostrava, Ostrava, Czech Republic
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Klevanik AV. On the Sum of Exponentials that Form Molecular Fluorescence Decay Kinetics. Biophysics (Nagoya-shi) 2018. [DOI: 10.1134/s0006350918060167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Yanykin DV, Khorobrykh AA, Zastrizhnaya OM, Klimov VV. Interaction of molecular oxygen with the donor side of photosystem II after destruction of the water-oxidizing complex. BIOCHEMISTRY (MOSCOW) 2014; 79:205-12. [PMID: 24821446 DOI: 10.1134/s0006297914030055] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Photosystem II (PSII) is a pigment-protein complex of thylakoid membrane of higher plants, algae, and cyanobacteria where light energy is used for oxidation of water and reduction of plastoquinone. Light-dependent reactions (generation of excited states of pigments, electron transfer, water oxidation) taking place in PSII can lead to the formation of reactive oxygen species. In this review attention is focused on the problem of interaction of molecular oxygen with the donor site of PSII, where after the removal of manganese from the water-oxidizing complex illumination induces formation of long-lived states (P680(+•) and TyrZ(•)) capable of oxidizing surrounding organic molecules to form radicals.
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Affiliation(s)
- D V Yanykin
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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Ke B. The Reaction-Center Complex of Photosystem II: Early Electron-Transfer Components and Reactions. Isr J Chem 2013. [DOI: 10.1002/ijch.198100052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Stirbet A. Chlorophyll a fluorescence induction: a personal perspective of the thermal phase, the J-I-P rise. PHOTOSYNTHESIS RESEARCH 2012; 113:15-61. [PMID: 22810945 DOI: 10.1007/s11120-012-9754-5] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 05/29/2012] [Indexed: 05/03/2023]
Abstract
The fast (up to 1 s) chlorophyll (Chl) a fluorescence induction (FI) curve, measured under saturating continuous light, has a photochemical phase, the O-J rise, related mainly to the reduction of Q(A), the primary electron acceptor plastoquinone of Photosystem II (PSII); here, the fluorescence rise depends strongly on the number of photons absorbed. This is followed by a thermal phase, the J-I-P rise, which disappears at subfreezing temperatures. According to the mainstream interpretation of the fast FI, the variable fluorescence originates from PSII antenna, and the oxidized Q(A) is the most important quencher influencing the O-J-I-P curve. As the reaction centers of PSII are gradually closed by the photochemical reduction of Q(A), Chl fluorescence, F, rises from the O level (the minimal level) to the P level (the peak); yet, the relationship between F and [Q(A) (-)] is not linear, due to the presence of other quenchers and modifiers. Several alternative theories have been proposed, which give different interpretations of the O-J-I-P transient. The main idea in these alternative theories is that in saturating light, Q(A) is almost completely reduced already at the end of the photochemical phase O-J, but the fluorescence yield is lower than its maximum value due to the presence of either a second quencher besides Q(A), or there is an another process quenching the fluorescence; in the second quencher hypothesis, this quencher is consumed (or the process of quenching the fluorescence is reversed) during the thermal phase J-I-P. In this review, we discuss these theories. Based on our critical examination, that includes pros and cons of each theory, as well mathematical modeling, we conclude that the mainstream interpretation of the O-J-I-P transient is the most credible one, as none of the alternative ideas provide adequate explanation or experimental proof for the almost complete reduction of Q(A) at the end of the O-J phase, and for the origin of the fluorescence rise during the thermal phase. However, we suggest that some of the factors influencing the fluorescence yield that have been proposed in these newer theories, as e.g., the membrane potential ΔΨ, as suggested by Vredenberg and his associates, can potentially contribute to modulate the O-J-I-P transient in parallel with the reduction of Q(A), through changes at the PSII antenna and/or at the reaction center, or, possibly, through the control of the oxidation-reduction of the PQ-pool, including proton transfer into the lumen, as suggested by Rubin and his associates. We present in this review our personal perspective mainly on our understanding of the thermal phase, the J-I-P rise during Chl a FI in plants and algae.
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Cardona T, Sedoud A, Cox N, Rutherford AW. Charge separation in photosystem II: a comparative and evolutionary overview. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:26-43. [PMID: 21835158 DOI: 10.1016/j.bbabio.2011.07.012] [Citation(s) in RCA: 245] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 07/22/2011] [Accepted: 07/23/2011] [Indexed: 10/17/2022]
Abstract
Our current understanding of the PSII reaction centre owes a great deal to comparisons to the simpler and better understood, purple bacterial reaction centre. Here we provide an overview of the similarities with a focus on charge separation and the electron acceptors. We go on to discuss some of the main differences between the two kinds of reaction centres that have been highlighted by the improving knowledge of PSII. We attempt to relate these differences to functional requirements of water splitting. Some are directly associated with that function, e.g. high oxidation potentials, while others are associated with regulation and protection against photodamage. The protective and regulatory functions are associated with the harsh chemistry performed during its normal function but also with requirements of the enzyme while it is undergoing assembly and repair. Key aspects of PSII reaction centre evolution are also addressed. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Tanai Cardona
- Institut de Biologie et Technologies de Saclay, URA 2096 CNRS, CEA Saclay, 91191 Gif-sur-Yvette, France
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Belyaeva NE, Schmitt FJ, Steffen R, Paschenko VZ, Riznichenko GY, Chemeris YK, Renger G, Rubin AB. PS II model-based simulations of single turnover flash-induced transients of fluorescence yield monitored within the time domain of 100 ns-10 s on dark-adapted Chlorella pyrenoidosa cells. PHOTOSYNTHESIS RESEARCH 2008; 98:105-19. [PMID: 18937044 DOI: 10.1007/s11120-008-9374-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 09/24/2008] [Indexed: 05/24/2023]
Abstract
The set up described in Steffen et al. (Biochemistry 40:173-180, 2001) was used to monitor in the time domain from 100 ns to 10 s single turnover flash-induced transients of the normalized fluorescence yield (SFITFY) on dark-adapted cells of the thermophilic algae Chlorella pyrenoidosa Chick. Perfect data fit was achieved within the framework of a previously proposed model for the PS II reaction pattern (Lebedeva et al., Biophysics 47:968-980, 2002; Belyaeva et al., Biophysics 51:860-872, 2006) after its modification by taking into account nonradiative decay processes including nonphotochemical quenching due to time-dependent populations of P680(+*) and (3)Car. On the basis of data reported in the literature, a consistent set of rate constants was obtained for electron transfer at the donor and acceptor sides of PS II, pH in lumen and stroma, the initial redox state of plastoquinone pool and the rate of plastoquinone oxidation. The evaluation of the rate constant values of dissipative processes due to quenching by carotenoid triplets in antennae and P680(+*)Q(A)(-*) recombination as well as the initial state populations after excitation with a single laser flash are close to that outlined in (Steffen et al., Biochemistry 44:3123-3133, 2005a). The simulations based on the model of the PS II reaction pattern provide information on the time courses of population probabilities of different PS II states. We analyzed the maximum (F(m)(STF)) and minimum (F(0)) of the normalized FL yield dependence on the rate of the recombination processes (radiative and dissipative nonradiative) and of P680(+*) reduction. The developed PS II model provides a basis for theoretical comparative analyses of time-dependent fluorescence signals, observed at different photosynthetic samples under various conditions (e.g. presence of herbicides, other stress conditions, excitation with actinic pulses of different intensity, and duration).
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Affiliation(s)
- N E Belyaeva
- Department of Biophysics, Biology Faculty of the M.V. Lomonosov Moscow State University, 119992 Moscow, Russia.
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Khatypov RA, Khmelnitskiy AY, Leonova MM, Vasilieva LG, Shuvalov VA. Primary light-energy conversion in tetrameric chlorophyll structure of photosystem II and bacterial reaction centers: I. A review. PHOTOSYNTHESIS RESEARCH 2008; 98:81-93. [PMID: 18853274 DOI: 10.1007/s11120-008-9370-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2008] [Accepted: 09/15/2008] [Indexed: 05/26/2023]
Abstract
The purpose of the review is to show that the tetrameric (bacterio)chlorophyll ((B)Chl) structures in reaction centers of photosystem II (PSII) of green plants and in bacterial reaction centers (BRCs) are similar and play a key role in the primary charge separation. The Stark effect measurements on PSII reaction centers have revealed an increased dipole moment for the transition at approximately 730 nm (Frese et al., Biochemistry 42:9205-9213, 2003). It was found (Heber and Shuvalov, Photosynth Res 84:84-91, 2005) that two fluorescent bands at 685 and 720 nm are observed in different organisms. These two forms are registered in the action spectrum of Q(A) photoreduction. Similar results were obtained in core complexes of PSII at low temperature (Hughes et al., Biochim Biophys Acta 1757: 841-851, 2006). In all cases the far-red absorption and emission can be interpreted as indication of the state with charge transfer character in which the chlorophyll monomer plays a role of an electron donor. The role of bacteriochlorophyll monomers (B(A) and B(B)) in BRCs can be revealed by different mutations of axial ligand for Mg central atoms. RCs with substitution of histidine L153 by tyrosine or leucine and of histidine M182 by leucine (double mutant) are not stable in isolated state. They were studied in antennaless membrane by different kinds of spectroscopy including one with femtosecond time resolution. It was found that the single mutation (L153HY) was accompanied by disappearance of B(A) molecule absorption near 802 nm and by 14-fold decrease of photochemical activity measured with ms time resolution. The lifetime of P(870)* increased up to approximately 200 ps in agreement with very low rate of the electron transfer to A-branch. In the double mutant L153HY + M182HL, the B(A) appears to be lost and B(B) is replaced by bacteriopheophytin Phi(B) with the absence of any absorption near 800 nm. Femtosecond measurements have revealed the electron transfer to B-branch with a time constant of approximately 2 ps. These results are discussed in terms of obligatory role of B(A) and Phi(B) molecules located near P for efficient electron transfer from P*.
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Affiliation(s)
- Ravil A Khatypov
- Institute of Basic Biological Problems, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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Raval MK, Biswal B, Biswal UC. The mystery of oxygen evolution: analysis of structure and function of photosystem II, the water-plastoquinone oxido-reductase. PHOTOSYNTHESIS RESEARCH 2005; 85:267-93. [PMID: 16170631 DOI: 10.1007/s11120-005-8163-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Accepted: 05/26/2005] [Indexed: 05/04/2023]
Abstract
Photosystem II (PS II) of thylakoid membrane of photosynthetic organisms has drawn attention of researchers over the years because it is the only system on Earth that provides us with oxygen that we breathe. In the recent past, structure of PS II has been the focus of research in plant science. The report of X-ray crystallographic structure of PS II complex by the research groups of James Barber and So Iwata in UK is a milestone in the area of research in photosynthesis. It follows the pioneering and elegant work from the laboratories of Horst Witt and W. Saenger in Germany, and J. Shen in Japan. It is time to analyze the historic events during the long journey made by the researchers to arrive at this point. This review makes an attempt to critically review the growth of the advancement of concepts and knowledge on the photosystem in the background of technological development. We conclude the review with perspectives on research and technology that should reveal the complete story of PS II of thylakoid in the future.
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Affiliation(s)
- M K Raval
- P.G. Department of Chemistry, Government College, Sundargarh, Orissa, India.
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Moise N, Moya I. Correlation between lifetime heterogeneity and kinetics heterogeneity during chlorophyll fluorescence induction in leaves: 2. Multi-frequency phase and modulation analysis evidences a loosely connected PSII pigment-protein complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1657:47-60. [PMID: 15238211 DOI: 10.1016/j.bbabio.2004.04.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Revised: 03/17/2004] [Accepted: 04/01/2004] [Indexed: 11/25/2022]
Abstract
We report the first direct decomposition of the fluorescence lifetime heterogeneity during multiphasic fluorescence induction in dark-adapted leaves by multi-frequency phase and modulation fluorometry (PMF). A very fast component, assigned to photosystem I (PSI), was found to be constant in lifetime and yield, whereas the two slow components, which are strongly affected by the closure of the reaction centers by light, were assigned to PSII. Based on a modified "reversible radical pair" kinetic model with three compartments, we showed that a loosely connected pigment complex, which is assumed to be the CP47 complex, plays a specific role with respect to the structure and function of the PSII: (i) it explains the heterogeneity of PSII fluorescence lifetime as a compartmentation of excitation energy in the antenna, (ii) it is the site of a conformational change in the first second of illumination, and (iii) it is involved in the mechanisms of nonphotochemical quenching (NPQ). On the basis of the multi-frequency PMF analysis, we reconciled two apparently antagonistic aspects of chlorophyll a fluorescence in vivo: it is heterogeneous with respect to the kinetic structure (several lifetime components) and homogeneous with respect to average quantities (quasi-linear mean tau-Phi relationship).
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Affiliation(s)
- Nicolae Moise
- Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, Centre Universitaire Paris-Sud, Bat. 209D, B.P. 34, 91898 Orsay Cedex, France
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Shuvalov VA, Heber U. Photochemical reactions in dehydrated photosynthetic organisms, leaves, chloroplasts and photosystem II particles: reversible reduction of pheophytin and chlorophyll and oxidation of β-carotene. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00277-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Ivanov B, Khorobrykh S. Participation of photosynthetic electron transport in production and scavenging of reactive oxygen species. Antioxid Redox Signal 2003; 5:43-53. [PMID: 12626116 DOI: 10.1089/152308603321223531] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The photosynthetic electron transport chain (PETC) is the principal place of appearance of reactive oxygen species (ROS) in plants under illumination. The peculiarities of this process in different segments of the PETC are discussed. Oxygen uptake observed under impaired electron donation to photosystem II is attributed mainly to hydroperoxide formation by reaction of oxygen with organic radicals generated after detachment of electrons by P680(+). Oxygen reduction in the plastoquinone pool is suggested to start with the reaction of O(2) with plastosemiquinone, and to be followed by reduction of superoxide to hydrogen peroxide by plastohydroquinone. The distribution of plastoquinone throughout the thylakoid membrane interior provides for the generation of ROS by this route all along the membrane surface. O(2) reduction at the acceptor side of photosystem I remains poorly understood. The regeneration of antioxidants is stated to be a priority task of photosynthetic electron transport in view of the effectiveness of monodehydroascorbate as electron acceptor. We propose that ROS generation in the plastoquinone pool and the possible formation of hydroperoxides in the vicinity of photosystem II are key processes participating in the primary stages of redox signaling.
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Affiliation(s)
- Boris Ivanov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia.
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Shuvalov V, Heber U, Schreiber U. Low temperature photochemistry and spectral properties of a photosystem 2 reaction center complex containing the proteins D1 and D2 and two hemes of Cyt b-559. FEBS Lett 2001. [DOI: 10.1016/0014-5793(89)81607-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Danielius RV, Satoh K, van Kan PJ, Plijter JJ, Nuijs AM, van Gorkom HJ. The primary reaction of photosystem II in the D1-D2-cytochromeb-559 complex. FEBS Lett 2001. [DOI: 10.1016/0014-5793(87)81498-9] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Petrouleas V, Diner BA. Investigation of the iron components in photosystem II by Mössbauer spectroscopy. FEBS Lett 2001. [DOI: 10.1016/0014-5793(82)81022-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Deligiannakis Y, Rutherford AW. One- and Two-Dimensional Electron Spin Echo Envelope Modulation Study of the Intermediate Electron Acceptor Pheophytin in 14N- and 15N-Labeled Photosystem II. J Am Chem Soc 1997. [DOI: 10.1021/ja963293y] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yiannis Deligiannakis
- Contribution from the Section de Bioénergétique (URA CNRS 2096), Département de Biologie Cellulaire et Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - A. William Rutherford
- Contribution from the Section de Bioénergétique (URA CNRS 2096), Département de Biologie Cellulaire et Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette, France
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Abstract
Upon onset of saturating continuous light only the first part of the observed polyphasic fluorescence rise follows Q(A) reduction (photochemical phase), whereas the remaining part (thermal phases) is kinetically limited by relatively slow reactions with light saturated half-times in the order of 10-50 ms. A simple hypothesis is presented for the interpretation of these fundamentally different types of variable fluorescence. The hypothesis, which is based on the reversible radical pair model of PSII, assumes stimulation of both prompt and recombination fluorescence upon Q(A) reduction, with only recombination fluorescence being in competition with nonradiative energy loss processes at the reaction centers. It is proposed that changes in the rate constants of these processes modulate the yield of recombination fluorescence in closed centers, thus causing large variations in the maximal fluorescence yield and also giving rise to the 'thermal phases'. This hypothesis can reconcile numerous experimental findings which so far have seemed difficult to interpret.
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Affiliation(s)
- U Schreiber
- Lehrstuhl Botanik I, Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Germany
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Light energy conversion with chlorophyll a and pheophytin a monolayers at the optically transparent SnO2 electrode: artificial photosynthesis. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0302-4598(95)05021-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Light energy conversion with pheophytina monolayer at the SnO2 optically transparent electrode. J SOLUTION CHEM 1994. [DOI: 10.1007/bf00973548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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De Las Rivas J, Crystall B, Booth PJ, Durrant JR, Ozer S, Porter G, Klug DR, Barber J. Long-lived primary radical pair state detected by time-resolved fluorescence and absorption spectroscopy in an isolated Photosystem two core. PHOTOSYNTHESIS RESEARCH 1992; 34:419-431. [PMID: 24408837 DOI: 10.1007/bf00029816] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/1992] [Accepted: 06/08/1992] [Indexed: 06/03/2023]
Abstract
A Photosystem two (PS II) core preparation containing the chlorophyll a binding proteins CP 47, CP 43, D1 and D2, and the non-chlorophyll binding cytochrome-b559 and 33 kDA polypeptides, has been isolated from PS II-enriched membranes of peas using the non-ionic detergent heptylthioglucopyranoside and elevated ionic strengths. The primary radical pair state, P680(+)Pheo(-), was studied by time-resolved absorption and fluorescence spectroscopy, under conditions where quinone reduction and water-splitting activities were inhibited. Charge recombination of the primary radical pair in PS II cores was found to have lifetimes of 17.5 ns measured by fluorescence and 21 ns measured by transient decay kinetics under anaerobic conditions. Transient absorption spectroscopy demonstrated that the activity of the particles, based on primary radical pair formation, was in excess of 70% (depending on the choice of kinetic model), while time-resolved fluorescence spectroscopy indicated that the particles were 91% active. These estimates of activity were further supported by steady-state measurements which quantified the amount of photoreducible pheophytin. It is concluded that the PS II core preparation we have isolated is ideal for studying primary radical pair formation and recombination as demonstrated by the correlation of our absorption and fluorescence transient data, which is the first of its kind to be reported in the literature for isolated PS II core complexes from higher plants.
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26
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Energy-dependent quenching of chlorophyll a fluorescence: effect of pH on stationary fluorescence and picosecond-relaxation kinetics in thylakoid membranes and Photosystem II preparations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1992. [DOI: 10.1016/0005-2728(92)90097-l] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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Holzwarth AR. Applications of ultrafast laser spectroscopy for the study of biological systems. Q Rev Biophys 1989; 22:239-326. [PMID: 2695961 DOI: 10.1017/s0033583500002985] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The discovery of mode-locked laser operation now nearly two decades ago has started a development which enables researchers to probe the dynamics of ultrafast physical and chemical processes at the molecular level on shorter and shorter time scales. Naturally the first applications were in the fields of photophysics and photochemistry where it was then possible for the first time to probe electronic and vibrational relaxation processes on a sub-nanosecond timescale. The development went from lasers producing pulses of many picoseconds to the shortest pulses which are at present just a few femtoseconds long. Soon after their discovery ultrashort pulses were applied also to biological systems which has revealed a wealth of information contributing to our understanding of a broadrange of biological processes on the molecular level.It is the aim of this review to discuss the recent advances and point out some future trends in the study of ultrafast processes in biological systems using laser techniques. The emphasis will be mainly on new results obtained during the last 5 or 6 years. The term ultrafast means that I shall restrict myself to sub-nanosecond processes with a few exceptions.
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Affiliation(s)
- A R Holzwarth
- Max-Planck-Institut für Strahlenchemie, Mülheim/Ruhr, FRG
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28
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Boussac A, Hodges M, Briantais JM, Moya I. The quenching characteristics of potassium iridic chloride and their meaning for the origin of chlorophyll fluorescence components. PHOTOSYNTHESIS RESEARCH 1989; 20:173-189. [PMID: 24425535 DOI: 10.1007/bf00034125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/1988] [Accepted: 08/24/1988] [Indexed: 06/03/2023]
Abstract
To understand the origins of the different lifetime components of photosystem 2 (PS2) chlorophyll (Chl) fluorescence we have studied their susceptibility to potassium iridic chloride (K2IrCl6) which has been shown to bleach antenna pigments of photosynthetic bacteria (Loach et al. 1963). The addition of K2IrCl6 to PS2 particles gives rise to a preferential quenching of the variable Chl fluorescence (Fv). At concentrations lower than 20 μM, this is brought about mainly by a decrease in the yield, but not in the lifetime, of the slowest component when all the PS2 reaction centres are closed (FM). The yield of the middle and fast decays are not significantly altered. This type of quenching is not seen with DNB. The iridate-induced quenching of the initial fluorescence level (F0) is due to a proportional decrease in the yield and lifetime of the three components and correlates with the observed modification in the relative quantum yield of oxygen evolution. In this concentration range a bleaching of Chl a is seen. At higher iridate levels, greater than 20 μM, a proportional decrease in the lifetimes and yields of the three kinetic components is seen at FM. These changes are associated with a carotenoid bleaching. In isolated light harvesting Chl a/b complexes of PS2 (LHC2), iridate addition converts a 4 ns decay into a 200 ps emission and both types of bleaching are observed. By also measuring the rate of PS2 trap closure versus iridate concentration, we have discussed the results in terms of excitation energy transfer.
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Affiliation(s)
- A Boussac
- Service de Biophysique, Départment de Biologie, CEN de Saclay, 91191, Gif sur Yvette, France
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29
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Eckert HJ, Wiese N, Bernarding J, Eichler HJ, Renger G. Analysis of the electron transfer from Pheo- to QA in PS II membrane fragments from spinach by time resolved 325 nm absorption changes in the picosecond domain. FEBS Lett 1988; 240:153-8. [PMID: 3056745 DOI: 10.1016/0014-5793(88)80358-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Absorption changes at 325 nm (delta A325) induced by 15 ps laser flashes (lambda = 650 nm) in PS II membrane fragments were measured with picosecond time-resolution. In samples with the reaction centers (RCs) kept in the open state (P I QA) the signals are characterized by a very fast rise (not resolvable by our equipment) followed by only small changes within our time window of 1.6 ns. In the closed state (PI QA-) of the reaction center the signal decays with an average half-life time of about 250 ps. It is shown that under our excitation conditions (E = 2 x 10(14) photons/cm2 per pulse) subtraction of the absorption changes in closed RCs (delta A closed 325) from those in open RCs (delta A open 325) leads to a difference signal which is dominated by the reduction kinetics of QA. From the rise kinetics of this signal and by comparison with data in the literature it is inferred that QA becomes reduced by direct electron transfer from Pheo- with a time constant of about 350 +/- 100 ps.
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Affiliation(s)
- H J Eckert
- Max-Volmer-Institut für Biophysikalische und Physikalische Chemie, Berlin, Germany
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30
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Jursinic P, Dennenberg R. Thylakoid photosystem II activity supported by the non-quinone acceptor Q400 and an ancillary quinone acceptor Aq. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90219-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Schlodder E, Brettel K. Primary charge separation in closed Photosystem II with a lifetime of 11 ns. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90052-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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32
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Hansson Ö, Duranton J, Mathis P. Yield and lifetime of the primary radical pair in preparations of Photosystem II with different antenna size. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90142-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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33
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Renger G, Kayed A. Fluorescence decline as a function of redox potential and actinic light intensity in spinach thylakoids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90195-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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34
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Trissl HW, Breton J, Deprez J, Leibl W. Primary electrogenic reactions of Photosystem II as probed by the light-gradient method. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90052-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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35
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Examination of fluorescence lifetime and radical-pair decay in Photosystem II membrane fragments from spinach. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90041-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Takahashi Y, Hansson Ö, Mathis P, Satoh K. Primary radical pair in the Photosystem II reaction centre. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90147-2] [Citation(s) in RCA: 113] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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37
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Mathis P, Rutherford A. Chapter 4 The primary reactions of photosystems I and II of algae and higher plants. NEW COMPREHENSIVE BIOCHEMISTRY 1987. [DOI: 10.1016/s0167-7306(08)60135-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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38
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Senoner M. The nanosecond decay of variable chlorophyll fluorescence in leaves of higher plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1986. [DOI: 10.1016/0005-2728(86)90149-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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39
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Nuijs AM, van Gorkom HJ, Plijter JJ, Duysens LN. Primary-charge separation and excitation of chlorophyll a in photosystem II particles from spinach as studied by picosecond absorbance-difference spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1986. [DOI: 10.1016/0005-2728(86)90038-1] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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40
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Schatz GH, Holzwarth AR. Mechanisms of chlorophyll fluorescence revisited: Prompt or delayed emission from photosystem II with closed reaction centers? PHOTOSYNTHESIS RESEARCH 1986; 10:309-318. [PMID: 24435378 DOI: 10.1007/bf00118296] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
This paper proposes a model which correlates the exciton decay kinetics observed in picosecond fluorescence studies with the primary processes of charge separation in the reaction center of photosystem II. We conclude that the experimental results from green algae and chloroplasts from higher plants are inconsistent with the concept that delayed luminescence after charge recombination should account for the long-lived (approx. 2 ns) fluorescence decay component of closed photosystem II centers. Instead, we show that the experimental data are in agreement with a model in which the long-lived fluorescence is also prompt fluorescence. The model suggests furthermore that the rate constant of primary charge separation is regulated by the oxidation state of the quinone acceptor QA.
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Affiliation(s)
- G H Schatz
- Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-4330, Mülheim a.d. Ruhr, West Germany
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41
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Golbeck JH, Warden JT. Site of salicylaldoxime interaction with photosystem II. PHOTOSYNTHESIS RESEARCH 1985; 6:371-380. [PMID: 24442956 DOI: 10.1007/bf00054110] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/1984] [Accepted: 10/10/1984] [Indexed: 06/03/2023]
Abstract
The reversible inhibition of Photosystem II by salicylaldoxime was studied in spinach D-10 particles by fluorescence, optical absorption, and electron spin resonance spectroscopy. In the presence of 15 mM salicylaldoxime, the initial fluorescence yield was raised to the level of the maximum fluorescence, indicating efficient charge recombination between reduced pheophytin (Ph) and P680(+). In agreement with the rapid (ns) backreaction expected between Ph(-) and P680(+), the optical absorption transient at 820 mm was not observed. When the particles were washed free of salicylaldoxime, the optical absorption transient resulting from the rereduction of P680(+) was restored to the µs timescale. These results, along with the previously observed inhibition of electron transport reactions and diminution of the 515-nm absorption change in chloroplasts [Golbeck, J.H. (1980) Arch Biochem Biophys 202, 458-466], are consistent with a site of inhibition between Ph and QA in Photosystem II. ESR Signal IIf and Signal Its were abolished in the presence of 25 mM salicylaldoxime, but both signals could be recovered by washing the D-10 particles free of the inhibitor. The loss of Signal Ilf is most likely a consequence of the inhibition between Ph and QA; the rapid charge recombination between Ph(-) and P680(+) would preclude electron transfer from an electron donor on the oxidizing side of Photosystem II. The loss of Signal Its may be due to a change in the environment of the donor complex such that the semiquinone radical giving rise to Signal Its interacts with a nearby reductant.
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Affiliation(s)
- J H Golbeck
- Martin Marietta Laboratories, 1450 South Rolling Road, 21227, Baltimore, MD, USA
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42
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Photoreduction of pheophytin as a result of electron donation from the water-splitting system to Photosystem-II reaction centers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1985. [DOI: 10.1016/0005-2728(85)90184-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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43
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van Grondelle R. Excitation energy transfer, trapping and annihilation in photosynthetic systems. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0304-4173(85)90017-5] [Citation(s) in RCA: 228] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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44
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Dennenberg R, Jursinic P. A comparison of the absorption changes near 325 nm and chlorophyll a fluorescence characteristics of the Photosystem II acceptors Qa and Q400. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1985. [DOI: 10.1016/0005-2728(85)90043-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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45
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Electron transfer to P-680+ in active and inhibited Photosystem II fractions from higher plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1985. [DOI: 10.1016/0005-2728(85)90047-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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46
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Seely GR, Senthilathipan V. A REACTION BETWEEN PHEOPHYTIN and CHLOROPHYLL ADSORBED TO POLYETHYLENE-TETRADECANE PARTICLES. Photochem Photobiol 1985. [DOI: 10.1111/j.1751-1097.1985.tb03500.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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47
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Evans M, Atkinson Y, Ford R. Redox characterisation of the Photosystem II electron acceptors. Evidence for two electron carriers between pheophytin and Q. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1985. [DOI: 10.1016/0005-2728(85)90102-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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48
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Trissl HW, Kunze U. II. Primary electrogenic reactions in chloroplasts probed by picosecond flash-induced dielectric polarization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1985. [DOI: 10.1016/0005-2728(85)90089-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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49
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Van Gorkom HJ. Electron transfer in photosystem II. PHOTOSYNTHESIS RESEARCH 1985; 6:97-112. [PMID: 24442870 DOI: 10.1007/bf00032785] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/1984] [Accepted: 11/07/1984] [Indexed: 06/03/2023]
Abstract
The picture presently emerging from studies on the mechanism of photosystem II electron transport is discussed. The reactions involved in excitation trapping, charge separation and stabilization of the charge pair in the reaction center, followed by the reactions with the substrates, plastoquinone reduction and water oxidation, are described successively. Finally, a brief discussion on photosystem II heterogeneity is presented.
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Affiliation(s)
- H J Van Gorkom
- Department of Biophysics, Huygens Laboratory of the State University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
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50
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Golbeck JH, Warden JT. Interaction of linolenic acid with bound quinone molecules in Photosystem II. Time-resolved optical and electron spin resonance studies. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 767:263-71. [PMID: 6093871 DOI: 10.1016/0005-2728(84)90196-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Time-resolved spectroscopic techniques, including optical flash photolysis and electron spin resonance spectroscopy, have been utilized to monitor electron-transport activity in Photosystem II subchloroplast particles. These studies have indicated that in the presence of 100 microM linolenic acid (1) a high initial fluorescence yield (Fi) is observed upon steady-state illumination of the dark-adapted sample; (2) flash-induced absorption transients (t greater than 10 mus) in the region of 820 nm, attributed to P-680+, are first slowed, then abolished; and (3) electron spin resonance Signal IIs and Signal IIf (Z+) are not detectable. Upon reversal of linolenic acid inhibition by washing with bovine serum albumin, optical and electron spin resonance transients originating from the photooxidation of P-680 are restored. Similarly, the variable component of fluorescence is recovered with an accompanying restoration of Signal IIs and Signal IIf. The data indicate that linolenic acid affects two inhibition sites in Photosystem II: one located between pheophytin and QA on the reducing side, and the other between electron donor Z and P-680 on the oxidizing side. Since both sites are associated with bound quinone molecules, we suggest that linolenic acid interacts at the level of quinone binding proteins in Photosystem II.
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