1
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Noguchi T. Mechanism of Proton Transfer through the D1-E65/D2-E312 Gate during Photosynthetic Water Oxidation. J Phys Chem B 2024; 128:1866-1875. [PMID: 38364371 DOI: 10.1021/acs.jpcb.3c07787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2024]
Abstract
In photosystem II, the D1-E65/D2-E312 dyad in the Cl-1 channel has been proposed to play a pivotal role in proton transfer during water oxidation. However, the precise mechanism remains elusive. Here, the proton transfer mechanism within the Cl-1 channel was investigated using quantum mechanics/molecular mechanics calculations. The molecular vibration of the E65/E312 dyad and its deuteration effect revealed that the recently suggested stepwise proton transfer, i.e., initial proton release from the dyad followed by slow reprotonation, does not occur in the Cl-1 channel. Instead, proton transfer is proposed to take place via a conformational change at the E65/E312 dyad, acting as a gate. In its closed form, a proton is trapped within the dyad, preventing forward proton transfer. This closed form converts into the open form, where protonated D1-E65 provides a hydrogen bond to the water network, thereby facilitating fast Grotthuss-type proton transfer.
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Affiliation(s)
- Takumi Noguchi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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2
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Amin M, Kaur D, Brudvig GW, Brooks BR. Mapping the Oxygens in the Oxygen-Evolving Complex of Photosystem II by Their Nucleophilicity Using Quantum Descriptors. J Chem Theory Comput 2024. [PMID: 38306696 DOI: 10.1021/acs.jctc.3c00926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2024]
Abstract
The oxygen-evolving complex (OEC) of Photosystem II catalyzes the water-splitting reaction using solar energy. Thus, understanding the reaction mechanism will inspire the design of biomimetic artificial catalysts that convert solar energy to chemical energy. Conceptual Density Functional Theory (CDFT) focuses on understanding the reactivity of molecules and the atomic contribution to the overall nucleophilicity and electrophilicity of the molecule using quantum descriptors. However, this method has not been applied to the OEC before. Here, we use Fukui functions and the dual descriptor to provide quantitative measures of the nucleophilicity and electrophilicity of oxygens in the OEC for different models in different S states. Our results show that the μ-oxo bridges connected to terminal Mn4 are nucleophilic, and those in the cube formed by Mn1, Mn2, and Mn3 are mostly electrophilic. The dual descriptors of the bridging oxygens in the OEC showed a similar reactivity to that of bridging oxygens in Mn model compounds. However, the terminal water W1, which is bound to Mn4, showed very strong reactivity in some of the S3 models. Thus, our calculations support the model that proposes the formation of the O2 molecule through nucleophilic attack by a terminal water.
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Affiliation(s)
- Muhamed Amin
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
- Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
| | - Divya Kaur
- Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada L2S 3A1
| | - Gary W Brudvig
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Bernard R Brooks
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
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3
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Li H, Nakajima Y, Nango E, Owada S, Yamada D, Hashimoto K, Luo F, Tanaka R, Akita F, Kato K, Kang J, Saitoh Y, Kishi S, Yu H, Matsubara N, Fujii H, Sugahara M, Suzuki M, Masuda T, Kimura T, Thao TN, Yonekura S, Yu LJ, Tosha T, Tono K, Joti Y, Hatsui T, Yabashi M, Kubo M, Iwata S, Isobe H, Yamaguchi K, Suga M, Shen JR. Oxygen-evolving photosystem II structures during S 1-S 2-S 3 transitions. Nature 2024; 626:670-677. [PMID: 38297122 PMCID: PMC10866707 DOI: 10.1038/s41586-023-06987-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 12/15/2023] [Indexed: 02/02/2024]
Abstract
Photosystem II (PSII) catalyses the oxidation of water through a four-step cycle of Si states (i = 0-4) at the Mn4CaO5 cluster1-3, during which an extra oxygen (O6) is incorporated at the S3 state to form a possible dioxygen4-7. Structural changes of the metal cluster and its environment during the S-state transitions have been studied on the microsecond timescale. Here we use pump-probe serial femtosecond crystallography to reveal the structural dynamics of PSII from nanoseconds to milliseconds after illumination with one flash (1F) or two flashes (2F). YZ, a tyrosine residue that connects the reaction centre P680 and the Mn4CaO5 cluster, showed structural changes on a nanosecond timescale, as did its surrounding amino acid residues and water molecules, reflecting the fast transfer of electrons and protons after flash illumination. Notably, one water molecule emerged in the vicinity of Glu189 of the D1 subunit of PSII (D1-E189), and was bound to the Ca2+ ion on a sub-microsecond timescale after 2F illumination. This water molecule disappeared later with the concomitant increase of O6, suggesting that it is the origin of O6. We also observed concerted movements of water molecules in the O1, O4 and Cl-1 channels and their surrounding amino acid residues to complete the sequence of electron transfer, proton release and substrate water delivery. These results provide crucial insights into the structural dynamics of PSII during S-state transitions as well as O-O bond formation.
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Affiliation(s)
- Hongjie Li
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Yoshiki Nakajima
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Eriko Nango
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
- RIKEN SPring-8 Center, Sayo, Japan
| | - Shigeki Owada
- Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Daichi Yamada
- Department of Picobiology, Graduate School of Life Science, University of Hyogo, Kobe, Japan
| | - Kana Hashimoto
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Fangjia Luo
- Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Rie Tanaka
- RIKEN SPring-8 Center, Sayo, Japan
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Fusamichi Akita
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Koji Kato
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | | | - Yasunori Saitoh
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Shunpei Kishi
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Huaxin Yu
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Naoki Matsubara
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Hajime Fujii
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | | | - Mamoru Suzuki
- Institute for Protein Research, Osaka University, Osaka, Japan
| | - Tetsuya Masuda
- Division of Food and Nutrition, Faculty of Agriculture, Ryukoku University, Otsu, Japan
| | - Tetsunari Kimura
- Department of Chemistry, Graduate School of Science, Kobe University, Kobe, Japan
| | - Tran Nguyen Thao
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Shinichiro Yonekura
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Long-Jiang Yu
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | | | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Yasumasa Joti
- Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Takaki Hatsui
- Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Makina Yabashi
- Japan Synchrotron Radiation Research Institute, Sayo, Japan
| | - Minoru Kubo
- Department of Picobiology, Graduate School of Life Science, University of Hyogo, Kobe, Japan
| | - So Iwata
- RIKEN SPring-8 Center, Sayo, Japan
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hiroshi Isobe
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Kizashi Yamaguchi
- Center for Quantum Information and Quantum Biology, Osaka University, Osaka, Japan
| | - Michihiro Suga
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
| | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
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4
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Yamaguchi K, Miyagawa K, Shoji M, Kawakami T, Isobe H, Yamanaka S, Nakajima T. Theoretical elucidation of the structure, bonding, and reactivity of the CaMn 4O x clusters in the whole Kok cycle for water oxidation embedded in the oxygen evolving center of photosystem II. New molecular and quantum insights into the mechanism of the O-O bond formation. PHOTOSYNTHESIS RESEARCH 2023:10.1007/s11120-023-01053-7. [PMID: 37945776 DOI: 10.1007/s11120-023-01053-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 09/25/2023] [Indexed: 11/12/2023]
Abstract
This paper reviews our historical developments of broken-symmetry (BS) and beyond BS methods that are applicable for theoretical investigations of metalloenzymes such as OEC in PSII. The BS hybrid DFT (HDFT) calculations starting from high-resolution (HR) XRD structure in the most stable S1 state have been performed to elucidate structure and bonding of whole possible intermediates of the CaMn4Ox cluster (1) in the Si (i = 0 ~ 4) states of the Kok cycle. The large-scale HDFT/MM computations starting from HR XRD have been performed to elucidate biomolecular system structures which are crucial for examination of possible water inlet and proton release pathways for water oxidation in OEC of PSII. DLPNO CCSD(T0) computations have been performed for elucidation of scope and reliability of relative energies among the intermediates by HDFT. These computations combined with EXAFS, XRD, XFEL, and EPR experimental results have elucidated the structure, bonding, and reactivity of the key intermediates, which are indispensable for understanding and explanation of the mechanism of water oxidation in OEC of PSII. Interplay between theory and experiments have elucidated important roles of four degrees of freedom, spin, charge, orbital, and nuclear motion for understanding and explanation of the chemical reactivity of 1 embedded in protein matrix, indicating the participations of the Ca(H2O)n ion and tyrosine(Yz)-O radical as a one-electron acceptor for the O-O bond formation. The Ca-assisted Yz-coupled O-O bond formation mechanisms for water oxidation are consistent with recent XES and very recent time-resolved SFX XFEL and FTIR results.
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Affiliation(s)
- Kizashi Yamaguchi
- Center for Quantum Information and Quantum Biology, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
- RIKEN Center for Computational Science, Kobe, Hyogo, 650-0047, Japan.
- SANKEN, Osaka University, Ibaraki, Osaka, 567-0047, Japan.
| | - Koichi Miyagawa
- Center of Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan
| | - Mitsuo Shoji
- Center of Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan
| | - Takashi Kawakami
- RIKEN Center for Computational Science, Kobe, Hyogo, 650-0047, Japan
- Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Hiroshi Isobe
- Research Institute for Interdisciplinary Science, and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
| | - Shusuke Yamanaka
- Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Takahito Nakajima
- RIKEN Center for Computational Science, Kobe, Hyogo, 650-0047, Japan
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5
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Gates C, Williams JM, Ananyev G, Dismukes GC. How chloride functions to enable proton conduction in photosynthetic water oxidation: Time-resolved kinetics of intermediates (S-states) in vivo and bromide substitution. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148998. [PMID: 37499962 DOI: 10.1016/j.bbabio.2023.148998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 07/11/2023] [Accepted: 07/19/2023] [Indexed: 07/29/2023]
Abstract
Chloride (Cl-) is essential for O2 evolution during photosynthetic water oxidation. Two chlorides near the water-oxidizing complex (WOC) in Photosystem II (PSII) structures from Thermosynechococcus elongatus (and T. vulcanus) have been postulated to transfer protons generated from water oxidation. We monitored four criteria: primary charge separation flash yield (P* → P+QA-), rates of water oxidation steps (S-states), rate of proton evolution, and flash O2 yield oscillations by measuring chlorophyll variable fluorescence (P* quenching), pH-sensitive dye changes, and oximetry. Br-substitution slows and destabilizes cellular growth, resulting from lower light-saturated O2 evolution rate (-20 %) and proton release (-36 % ΔpH gradient). The latter implies less ATP production. In Br- cultures, protonogenic S-state transitions (S2 → S3 → S0') slow with increasing light intensity and during O2/water exchange (S0' → S0 → S1), while the non-protonogenic S1 → S2 transition is kinetically unaffected. As flash rate increases in Cl- cultures, both rate and extent of acidification of the lumen increase, while charge recombination is suppressed relative to Br-. The Cl- advantage in rapid proton escape from the WOC to lumen is attributed to correlated ion-pair movement of H3O+Cl- in dry water channels vs. separated Br- and H+ ion movement through different regions (>200-fold difference in Bronsted acidities). By contrast, at low flash rates a previously unreported reversal occurs that favors Br- cultures for both proton evolution and less PSII charge recombination. In Br- cultures, slower proton transfer rate is attributed to stronger ion-pairing of Br- with AA residues lining the water channels. Both anions charge-neutralize protons and shepherd them to the lumen using dry aqueous channels.
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Affiliation(s)
- Colin Gates
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Computational Biology and Molecular Biophysics, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Biochemistry, Loyola University Chicago, IL 60660, USA
| | - Jonah M Williams
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, NJ 08854, USA
| | - Gennady Ananyev
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, NJ 08854, USA
| | - G Charles Dismukes
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, NJ 08854, USA.
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6
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Drosou M, Comas-Vilà G, Neese F, Salvador P, Pantazis DA. Does Serial Femtosecond Crystallography Depict State-Specific Catalytic Intermediates of the Oxygen-Evolving Complex? J Am Chem Soc 2023; 145:10604-10621. [PMID: 37137865 DOI: 10.1021/jacs.3c00489] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Recent advances in serial femtosecond crystallography (SFX) of photosystem II (PSII), enabled by X-ray free electron lasers (XFEL), provided the first geometric models of distinct intermediates in the catalytic S-state cycle of the oxygen-evolving complex (OEC). These models are obtained by flash-advancing the OEC from the dark-stable state (S1) to more oxidized intermediates (S2 and S3), eventually cycling back to the most reduced S0. However, the interpretation of these models is controversial because geometric parameters within the Mn4CaO5 cluster of the OEC do not exactly match those expected from coordination chemistry for the spectroscopically verified manganese oxidation states of the distinct S-state intermediates. Here we focus on the first catalytic transition, S1 → S2, which represents a one-electron oxidation of the OEC. Combining geometric and electronic structure criteria, including a novel effective oxidation state approach, we analyze existing 1-flash (1F) SFX-XFEL crystallographic models that should depict the S2 state of the OEC. We show that the 1F/S2 equivalence is not obvious, because the Mn oxidation states and total unpaired electron counts encoded in these models are not fully consistent with those of a pure S2 state and with the nature of the S1 → S2 transition. Furthermore, the oxidation state definition in two-flashed (2F) structural models is practically impossible to elucidate. Our results advise caution in the extraction of electronic structure information solely from the literal interpretation of crystallographic models and call for re-evaluation of structural and mechanistic interpretations that presume exact correspondence of such models to specific catalytic intermediates of the OEC.
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Affiliation(s)
- Maria Drosou
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Gerard Comas-Vilà
- Institute of Computational Chemistry and Catalysis, Chemistry Department, University of Girona, Montilivi Campus, Girona, Catalonia 17003, Spain
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Pedro Salvador
- Institute of Computational Chemistry and Catalysis, Chemistry Department, University of Girona, Montilivi Campus, Girona, Catalonia 17003, Spain
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
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7
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Boussac A, Sellés J, Sugiura M. Energetics and proton release in photosystem II from Thermosynechococcus elongatus with a D1 protein encoded by either the psbA 2 or psbA 3 gene. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148979. [PMID: 37080330 DOI: 10.1016/j.bbabio.2023.148979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/05/2023] [Accepted: 04/12/2023] [Indexed: 04/22/2023]
Abstract
In the cyanobacterium Thermosynechococcus elongatus, there are three psbA genes coding for the Photosystem II (PSII) D1 subunit that interacts with most of the main cofactors involved in the electron transfers. Recently, the 3D crystal structures of both PsbA2-PSII and PsbA3-PSII have been solved [Nakajima et al., J. Biol. Chem. 298 (2022) 102668.]. It was proposed that the loss of one hydrogen bond of PheD1 due to the D1-Y147F exchange in PsbA2-PSII resulted in a more negative Em of PheD1 in PsbA2-PSII when compared to PsbA3-PSII. In addition, the loss of two water molecules in the Cl-1 channel was attributed to the D1-P173M substitution in PsbA2-PSII. This exchange, by narrowing the Cl-1 proton channel, could be at the origin of a slowing down of the proton release. Here, we have continued the characterization of PsbA2-PSII by measuring the thermoluminescence from the S2QA-/DCMU charge recombination and by measuring proton release kinetics using time-resolved absorption changes of the dye bromocresol purple. It was found that i) the Em of PheD1-•/PheD1 was decreased by ~30 mV in PsbA2-PSII when compared to PsbA3-PSII and ii) the kinetics of the proton release into the bulk was significantly slowed down in PsbA2-PSII in the S2TyrZ• to S3TyrZ and S3TyrZ• → (S3TyrZ•)' transitions. This slowing down was partially reversed by the PsbA2/M173P mutation and induced by the PsbA3/P173M mutation thus confirming a role of the D1-173 residue in the egress of protons trough the Cl-1 channel.
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Affiliation(s)
- Alain Boussac
- I2BC, UMR CNRS 9198, CEA Saclay, 91191 Gif-sur-Yvette, France.
| | - Julien Sellés
- Institut de Biologie Physico-Chimique, UMR CNRS 7141 and Sorbonne Université, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Miwa Sugiura
- Proteo-Science Research Center, and Department of Chemistry, Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
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8
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Lubitz W, Pantazis DA, Cox N. Water oxidation in oxygenic photosynthesis studied by magnetic resonance techniques. FEBS Lett 2023; 597:6-29. [PMID: 36409002 DOI: 10.1002/1873-3468.14543] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/23/2022]
Abstract
The understanding of light-induced biological water oxidation in oxygenic photosynthesis is of great importance both for biology and (bio)technological applications. The chemically difficult multistep reaction takes place at a unique protein-bound tetra-manganese/calcium cluster in photosystem II whose structure has been elucidated by X-ray crystallography (Umena et al. Nature 2011, 473, 55). The cluster moves through several intermediate states in the catalytic cycle. A detailed understanding of these intermediates requires information about the spatial and electronic structure of the Mn4 Ca complex; the latter is only available from spectroscopic techniques. Here, the important role of Electron Paramagnetic Resonance (EPR) and related double resonance techniques (ENDOR, EDNMR), complemented by quantum chemical calculations, is described. This has led to the elucidation of the cluster's redox and protonation states, the valence and spin states of the manganese ions and the interactions between them, and contributed substantially to the understanding of the role of the protein surrounding, as well as the binding and processing of the substrate water molecules, the O-O bond formation and dioxygen release. Based on these data, models for the water oxidation cycle are developed.
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Affiliation(s)
- Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Mülheim/Ruhr, Germany
| | | | - Nicholas Cox
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
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9
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Sirohiwal A, Pantazis DA. Functional Water Networks in Fully Hydrated Photosystem II. J Am Chem Soc 2022; 144:22035-22050. [PMID: 36413491 PMCID: PMC9732884 DOI: 10.1021/jacs.2c09121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Water channels and networks within photosystem II (PSII) of oxygenic photosynthesis are critical for enzyme structure and function. They control substrate delivery to the oxygen-evolving center and mediate proton transfer at both the oxidative and reductive endpoints. Current views on PSII hydration are derived from protein crystallography, but structural information may be compromised by sample dehydration and technical limitations. Here, we simulate the physiological hydration structure of a cyanobacterial PSII model following a thorough hydration procedure and large-scale unconstrained all-atom molecular dynamics enabled by massively parallel simulations. We show that crystallographic models of PSII are moderately to severely dehydrated and that this problem is particularly acute for models derived from X-ray free electron laser (XFEL) serial femtosecond crystallography. We present a fully hydrated representation of cyanobacterial PSII and map all water channels, both static and dynamic, associated with the electron donor and acceptor sides. Among them, we describe a series of transient channels and the attendant conformational gating role of protein components. On the acceptor side, we characterize a channel system that is absent from existing crystallographic models but is likely functionally important for the reduction of the terminal electron acceptor plastoquinone QB. The results of the present work build a foundation for properly (re)evaluating crystallographic models and for eliciting new insights into PSII structure and function.
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10
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Nakajima Y, Ugai-Amo N, Tone N, Nakagawa A, Iwai M, Ikeuchi M, Sugiura M, Suga M, Shen JR. Crystal structures of photosystem II from a cyanobacterium expressing psbA 2 in comparison to psbA 3 reveal differences in the D1 subunit. J Biol Chem 2022; 298:102668. [PMID: 36334624 PMCID: PMC9709244 DOI: 10.1016/j.jbc.2022.102668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/27/2022] [Accepted: 10/30/2022] [Indexed: 11/07/2022] Open
Abstract
Three psbA genes (psbA1, psbA2, and psbA3) encoding the D1 subunit of photosystem II (PSII) are present in the thermophilic cyanobacterium Thermosynechococcus elongatus and are expressed differently in response to changes in the growth environment. To clarify the functional differences of the D1 protein expressed from these psbA genes, PSII dimers from two strains, each expressing only one psbA gene (psbA2 or psbA3), were crystallized, and we analyzed their structures at resolutions comparable to previously studied PsbA1-PSII. Our results showed that the hydrogen bond between pheophytin/D1 (PheoD1) and D1-130 became stronger in PsbA2- and PsbA3-PSII due to change of Gln to Glu, which partially explains the increase in the redox potential of PheoD1 observed in PsbA3. In PsbA2, one hydrogen bond was lost in PheoD1 due to the change of D1-Y147F, which may explain the decrease in stability of PheoD1 in PsbA2. Two water molecules in the Cl-1 channel were lost in PsbA2 due to the change of D1-P173M, leading to the narrowing of the channel, which may explain the lower efficiency of the S-state transition beyond S2 in PsbA2-PSII. In PsbA3-PSII, a hydrogen bond between D1-Ser270 and a sulfoquinovosyl-diacylglycerol molecule near QB disappeared due to the change of D1-Ser270 in PsbA1 and PsbA2 to D1-Ala270. This may result in an easier exchange of bound QB with free plastoquinone, hence an enhancement of oxygen evolution in PsbA3-PSII due to its high QB exchange efficiency. These results provide a structural basis for further functional examination of the three PsbA variants.
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Affiliation(s)
- Yoshiki Nakajima
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan
| | - Natsumi Ugai-Amo
- Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Naoki Tone
- Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Akiko Nakagawa
- Proteo-Science Research Center, Ehime University, Matsuyama, Japan
| | - Masako Iwai
- Graduate School and College of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan
| | - Masahiko Ikeuchi
- Graduate School and College of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan
| | - Miwa Sugiura
- Proteo-Science Research Center, Ehime University, Matsuyama, Japan
| | - Michihiro Suga
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan,Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan,For correspondence: Michihiro Suga; Jian-Ren Shen
| | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan,Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan,For correspondence: Michihiro Suga; Jian-Ren Shen
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11
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Shimada Y, Sugiyama A, Nagao R, Noguchi T. Role of D1-Glu65 in Proton Transfer during Photosynthetic Water Oxidation in Photosystem II. J Phys Chem B 2022; 126:8202-8213. [PMID: 36199221 DOI: 10.1021/acs.jpcb.2c05869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Photosynthetic water oxidation takes place at the Mn4CaO5 cluster in photosystem II (PSII) through a light-driven cycle of five intermediates called S states (S0-S4). Although the PSII structures have shown the presence of several channels around the Mn4CaO5 cluster leading to the lumen, the pathways for proton release in the individual S-state transitions remain unidentified. Here, we studied the involvement of the so-called Cl channel in proton transfer during water oxidation by examining the effect of the mutation of D1-Glu65, a key residue in this channel, to Ala using Fourier transform infrared difference and time-resolved infrared spectroscopies together with thermoluminescence and delayed luminescence measurements. It was shown that the structure and the redox property of the catalytic site were little affected by the D1-Glu65Ala mutation. In the S2 → S3 transition, the efficiency was still high and the transition rate was only moderately retarded in the D1-Glu65Ala mutant. In contrast, the S3 → S0 transition was significantly inhibited by this mutation. These results suggest that proton transfer in the S2 → S3 transition occurs through multiple pathways including the Cl channel, whereas this channel likely serves as a single pathway for proton exit in the S3 → S0 transition.
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Affiliation(s)
- Yuichiro Shimada
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Ayane Sugiyama
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Ryo Nagao
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan.,Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Okayama700-8530, Japan
| | - Takumi Noguchi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
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12
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Imaizumi K, Ifuku K. Binding and functions of the two chloride ions in the oxygen-evolving center of photosystem II. PHOTOSYNTHESIS RESEARCH 2022; 153:135-156. [PMID: 35698013 DOI: 10.1007/s11120-022-00921-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
Light-driven water oxidation in photosynthesis occurs at the oxygen-evolving center (OEC) of photosystem II (PSII). Chloride ions (Cl-) are essential for oxygen evolution by PSII, and two Cl- ions have been found to specifically bind near the Mn4CaO5 cluster in the OEC. The retention of these Cl- ions within the OEC is critically supported by some of the membrane-extrinsic subunits of PSII. The functions of these two Cl- ions and the mechanisms of their retention both remain to be fully elucidated. However, intensive studies performed recently have advanced our understanding of the functions of these Cl- ions, and PSII structures from various species have been reported, aiding the interpretation of previous findings regarding Cl- retention by extrinsic subunits. In this review, we summarize the findings to date on the roles of the two Cl- ions bound within the OEC. Additionally, together with a short summary of the functions of PSII membrane-extrinsic subunits, we discuss the mechanisms of Cl- retention by these extrinsic subunits.
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Affiliation(s)
- Ko Imaizumi
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan
| | - Kentaro Ifuku
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan.
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13
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Boussac A, Sugiura M, Sellés J. Probing the proton release by Photosystem II in the S 1 to S 2 high-spin transition. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148546. [PMID: 35337840 DOI: 10.1016/j.bbabio.2022.148546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 02/24/2022] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
The stoichiometry and kinetics of the proton release were investigated during each transition of the S-state cycle in Photosystem II (PSII) from Thermosynechococcus elongatus containing either a Mn4CaO5 (PSII/Ca) or a Mn4SrO5 (PSII/Sr) cluster. The measurements were done at pH 6.0 and pH 7.0 knowing that, in PSII/Ca at pH 6.0 and pH 7.0 and in PSII/Sr at pH 6.0, the flash-induced S2-state is in a low-spin configuration (S2LS) whereas in PSII/Sr at pH 7.0, the S2-state is in a high-spin configuration (S2HS) in half of the centers. Two measurements were done; the time-resolved flash dependent i) absorption of either bromocresol purple at pH 6.0 or neutral red at pH 7.0 and ii) electrochromism in the Soret band of PD1 at 440 nm. The fittings of the oscillations with a period of four indicate that one proton is released in the S1 to S2HS transition in PSII/Sr at pH 7.0. It has previously been suggested that the proton released in the S2LS to S3 transition would be released in a S2LSTyrZ• → S2HSTyrZ• transition before the electron transfer from the cluster to TyrZ• occurs. The release of a proton in the S1TyrZ• → S2HSTyrZ transition would logically imply that this proton release is missing in the S2HSTyrZ• to S3TyrZ transition. Instead, the proton release in the S1 to S2HS transition in PSII/Sr at pH 7.0 was mainly done at the expense of the proton release in the S3 to S0 and S0 to S1 transitions. However, at pH 7.0, the electrochromism of PD1 seems larger in PSII/Sr when compared to PSII/Ca in the S3 state. This points to the complex link between proton movements in and immediately around the Mn4 cluster and the mechanism leading to the release of protons into the bulk.
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Affiliation(s)
- Alain Boussac
- I(2)BC, UMR CNRS 9198, CEA Saclay, 91191 Gif-sur-Yvette, France.
| | - Miwa Sugiura
- Proteo-Science Research Center, Department of Chemistry, Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Julien Sellés
- Institut de Biologie Physico-Chimique, UMR CNRS 7141 and Sorbonne Université, 13 rue Pierre et Marie Curie, 75005 Paris, France
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14
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Time-resolved infrared absorption spectroscopy applied to photoinduced reactions: how and why. Photochem Photobiol Sci 2022; 21:557-584. [DOI: 10.1007/s43630-022-00180-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 01/28/2022] [Indexed: 10/19/2022]
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15
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Hussein R, Ibrahim M, Bhowmick A, Simon PS, Chatterjee R, Lassalle L, Doyle M, Bogacz I, Kim IS, Cheah MH, Gul S, de Lichtenberg C, Chernev P, Pham CC, Young ID, Carbajo S, Fuller FD, Alonso-Mori R, Batyuk A, Sutherlin KD, Brewster AS, Bolotovsky R, Mendez D, Holton JM, Moriarty NW, Adams PD, Bergmann U, Sauter NK, Dobbek H, Messinger J, Zouni A, Kern J, Yachandra VK, Yano J. Structural dynamics in the water and proton channels of photosystem II during the S 2 to S 3 transition. Nat Commun 2021; 12:6531. [PMID: 34764256 PMCID: PMC8585918 DOI: 10.1038/s41467-021-26781-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Accepted: 10/21/2021] [Indexed: 11/30/2022] Open
Abstract
Light-driven oxidation of water to molecular oxygen is catalyzed by the oxygen-evolving complex (OEC) in Photosystem II (PS II). This multi-electron, multi-proton catalysis requires the transport of two water molecules to and four protons from the OEC. A high-resolution 1.89 Å structure obtained by averaging all the S states and refining the data of various time points during the S2 to S3 transition has provided better visualization of the potential pathways for substrate water insertion and proton release. Our results indicate that the O1 channel is the likely water intake pathway, and the Cl1 channel is the likely proton release pathway based on the structural rearrangements of water molecules and amino acid side chains along these channels. In particular in the Cl1 channel, we suggest that residue D1-E65 serves as a gate for proton transport by minimizing the back reaction. The results show that the water oxidation reaction at the OEC is well coordinated with the amino acid side chains and the H-bonding network over the entire length of the channels, which is essential in shuttling substrate waters and protons.
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Affiliation(s)
- Rana Hussein
- grid.7468.d0000 0001 2248 7639Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
| | - Mohamed Ibrahim
- grid.7468.d0000 0001 2248 7639Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
| | - Asmit Bhowmick
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Philipp S. Simon
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Ruchira Chatterjee
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Louise Lassalle
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Margaret Doyle
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Isabel Bogacz
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - In-Sik Kim
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Mun Hon Cheah
- grid.8993.b0000 0004 1936 9457Department of Chemistry - Ångström, Molecular Biomimetics, Uppsala University, SE 75120 Uppsala, Sweden
| | - Sheraz Gul
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Casper de Lichtenberg
- grid.8993.b0000 0004 1936 9457Department of Chemistry - Ångström, Molecular Biomimetics, Uppsala University, SE 75120 Uppsala, Sweden ,grid.12650.300000 0001 1034 3451Department of Chemistry, Umeå University, SE 90187 Umeå, Sweden
| | - Petko Chernev
- grid.8993.b0000 0004 1936 9457Department of Chemistry - Ångström, Molecular Biomimetics, Uppsala University, SE 75120 Uppsala, Sweden
| | - Cindy C. Pham
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Iris D. Young
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Sergio Carbajo
- grid.512023.70000 0004 6047 9447Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | - Franklin D. Fuller
- grid.512023.70000 0004 6047 9447Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | - Roberto Alonso-Mori
- grid.512023.70000 0004 6047 9447Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | - Alex Batyuk
- grid.512023.70000 0004 6047 9447Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | - Kyle D. Sutherlin
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Aaron S. Brewster
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Robert Bolotovsky
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Derek Mendez
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - James M. Holton
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Nigel W. Moriarty
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Paul D. Adams
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA ,grid.47840.3f0000 0001 2181 7878Department of Bioengineering, University of California, Berkeley, CA 94720 USA
| | - Uwe Bergmann
- grid.14003.360000 0001 2167 3675Department of Physics, University of Wisconsin–Madison, Madison, WI 53706 USA
| | - Nicholas K. Sauter
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Holger Dobbek
- grid.7468.d0000 0001 2248 7639Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
| | - Johannes Messinger
- Department of Chemistry - Ångström, Molecular Biomimetics, Uppsala University, SE 75120, Uppsala, Sweden. .,Department of Chemistry, Umeå University, SE 90187, Umeå, Sweden.
| | - Athina Zouni
- Institut für Biologie, Humboldt-Universität zu Berlin, 10115, Berlin, Germany.
| | - Jan Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Vittal K. Yachandra
- grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
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16
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de Lichtenberg C, Kim CJ, Chernev P, Debus RJ, Messinger J. The exchange of the fast substrate water in the S 2 state of photosystem II is limited by diffusion of bulk water through channels - implications for the water oxidation mechanism. Chem Sci 2021; 12:12763-12775. [PMID: 34703563 PMCID: PMC8494045 DOI: 10.1039/d1sc02265b] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/31/2021] [Indexed: 12/02/2022] Open
Abstract
The molecular oxygen we breathe is produced from water-derived oxygen species bound to the Mn4CaO5 cluster in photosystem II (PSII). Present research points to the central oxo-bridge O5 as the 'slow exchanging substrate water (Ws)', while, in the S2 state, the terminal water ligands W2 and W3 are both discussed as the 'fast exchanging substrate water (Wf)'. A critical point for the assignment of Wf is whether or not its exchange with bulk water is limited by barriers in the channels leading to the Mn4CaO5 cluster. In this study, we measured the rates of H2 16O/H2 18O substrate water exchange in the S2 and S3 states of PSII core complexes from wild-type (WT) Synechocystis sp. PCC 6803, and from two mutants, D1-D61A and D1-E189Q, that are expected to alter water access via the Cl1/O4 channels and the O1 channel, respectively. We found that the exchange rates of Wf and Ws were unaffected by the E189Q mutation (O1 channel), but strongly perturbed by the D61A mutation (Cl1/O4 channel). It is concluded that all channels have restrictions limiting the isotopic equilibration of the inner water pool near the Mn4CaO5 cluster, and that D61 participates in one such barrier. In the D61A mutant this barrier is lowered so that Wf exchange occurs more rapidly. This finding removes the main argument against Ca-bound W3 as fast substrate water in the S2 state, namely the indifference of the rate of Wf exchange towards Ca/Sr substitution.
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Affiliation(s)
- Casper de Lichtenberg
- Department of Chemistry, Umeå University Linnaeus väg 6 (KBC huset), SE-901 87 Umeå Sweden
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University POB 523 SE-75120 Uppsala Sweden
| | - Christopher J Kim
- Department of Biochemistry, University of California Riverside California 92521 USA
| | - Petko Chernev
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University POB 523 SE-75120 Uppsala Sweden
| | - Richard J Debus
- Department of Biochemistry, University of California Riverside California 92521 USA
| | - Johannes Messinger
- Department of Chemistry, Umeå University Linnaeus väg 6 (KBC huset), SE-901 87 Umeå Sweden
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University POB 523 SE-75120 Uppsala Sweden
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