研究者詳細 - 沈　建仁

論文 - 沈　建仁

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A manganese(ii) phthalocyanine under water-oxidation reaction: new findings 査読国際誌

Younes Mousazade, Mohammad Mahdi Najafpour, Robabeh Bagheri, Zvonko Jaglicic, Jitendra Pal Singh, Keun Hwa Chae, Zhenlun Song, Margarita V. Rodionova, Roman A. Voloshin, Jian-Ren Shen, Seeram Ramakrishna, Suleyman I. Allakhverdiev

DALTON TRANSACTIONS 48 ( 32 ) 12147 - 12158 2019年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

Phthalocyanines are a promising class of ligands for manganese because of their high binding affinity. This effect is suggested to be an important factor because phthalocyanines tightly bind manganese and stabilize it under moderate conditions. The strong donor power of phthalocyanine is also suggested as a critical factor to stabilize high-valent manganese phthalocyanine. Herein, a manganese(ii) phthalocyanine, which is stable under moderate conditions, was investigated under harsh electrochemical water oxidation. By scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, extended X-ray absorption fine structure analysis, X-ray absorption near edge structure analysis, chronoamperometry, magnetic measurements, Fourier-transform infrared spectroscopy, and electrochemical methods, it is shown that manganese phthalocyanine, a known molecular complex showing good stability under moderate conditions, could not withstand water oxidation catalysis and ultimately is altered to form catalytic oxide particles. Such nanosized Mn oxides are the true catalyst for water oxidation. Besides, we try to go a step forward to find an answer as to how Mn oxides form on the surface of the electrode.

DOI： 10.1039/c9dt01790a

The pigment-protein network of a diatom photosystem II-light-harvesting antenna supercomplex 査読国際誌

Xiong Pi, Songhao Zhao, Wenda Wang, Desheng Liu, Caizhe Xu, Guangye Han, Tingyun Kuang, Sen-Fang Sui, Jian-Ren Shen

SCIENCE 365 ( 6452 ) 463 - + 2019年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC ADVANCEMENT SCIENCE

Diatoms play important roles in global primary productivity and biogeochemical cycling of carbon, in part owing to the ability of their photosynthetic apparatus to adapt to rapidly changing light intensity. We report a cryo-electron microscopy structure of the photosystem II ( PSII)-fucoxanthin ( Fx) chlorophyll ( Chl) a/c binding protein ( FCPII) supercomplex from the centric diatom Chaetoceros gracilis. The supercomplex comprises two protomers, each with two tetrameric and three monomeric FCPIIs around a PSII core that contains five extrinsic oxygen-evolving proteins at the lumenal surface. The structure reveals the arrangement of a huge pigment network that contributes to efficient light energy harvesting, transfer, and dissipation processes in the diatoms.

DOI： 10.1126/science.aax4406

pH-Sensing Machinery of Excitation Energy Transfer in Diatom PSI-FCPI Complexes 査読国際誌

Ryo Nagao, Makio Yokono, Yoshifumi Ueno, Jian-Ren Shen, Seiji Akimoto

JOURNAL OF PHYSICAL CHEMISTRY LETTERS 10 ( 13 ) 3531 - 3535 2019年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Excitation energy-transfer processes in photosynthetic light-harvesting complexes are strongly affected by the surrounding environments of pigments. Here we report on the effects of pH changes on excitation energy dynamics in both diatom photosystem I-fucoxanthin chlorophyll a/c-binding protein (PSI-FCPI) and PSI core complexes by means of fluorescence spectroscopies. The steady-state fluorescence spectra of the PSI-FCPI showed similar features among three samples at pH 5.0, 6.5, and 8.0. However, fluorescence decay-associated spectra of the pH 5.0- and 8.0-adapted PSI-FCPI within 100 ps exhibit peak shifts to longer and shorter wavelengths, respectively, than the peaks in the pH 6.5 spectra. Because such spectral changes hardly occur in the PSI complexes, the peak shifts at pH 5.0 and 8.0 in the PSI-FCPI can be ascribed to alterations of pigment pigment and/or pigment protein interactions around/within FCPI caused by the pH changes. These findings provide novel physical insights into the pH-sensing light-harvesting strategy in diatom PSI-FCPI.

DOI： 10.1021/acs.jpclett.9b01314

Proton-Coupled Electron Transfer of Plastoquinone Redox Reactions in Photosystem II: A Pump-Probe Ultraviolet Resonance Raman Study 査読国際誌

Jun Chen, Jinfan Chen, Ying Liu, Yang Zheng, Qingjun Zhu, Guangye Han, Jian-Ren Shen

JOURNAL OF PHYSICAL CHEMISTRY LETTERS 10 ( 12 ) 3240 - 3247 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Plastoquinones (PQs) act as electron and proton mediators in photosystem II (PSII) for solar-to-chemical energy conversion. It is known that the redox potential of PQ varies in a wide range spanning hundreds of millivolts; however, its structural origin is not known yet. Here, by developing a pump-probe ultraviolet resonance Raman technique, we measured the vibrational structures of PQs including Q(A) and Q(B) in cyanobacterial PSII directly The conversion of Q(A) to Q(A)(center dot-) in the Mn-depleted PSII is verified by direct observation of the distinct Q(A)(center dot-) vibrational bands. A frequency upshift of the ring C=O/C=C stretch band at 1565 cm(-1) for Q(A)(center dot-) was observed, which suggests a pi-pi interaction between the quinone ring and Trp253. In contrast, proton-coupled reduction of Q(A) to Q(A)H upon light-driven electron transfer is demonstrated in PSII without Q(B) bound. The H-bond between Q(A) and His214 is likely the proton origin of this proton-coupled electron transfer.

DOI： 10.1021/acs.jpclett.9b00959

Biochemical characterization of photosystem I complexes having different subunit compositions of fucoxanthin chlorophyll a/c-binding proteins in the diatom Chaetoceros gracilis 査読国際誌

Ryo Nagao, Yoshifumi Ueno, Fusamichi Akita, Takehiro Suzuki, Naoshi Dohmae, Seiji Akimoto, Jian-Ren Shen

PHOTOSYNTHESIS RESEARCH 140 ( 2 ) 141 - 149 2019年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Diatoms are dominant phytoplankton in aquatic environments and have unique light-harvesting apparatus, fucoxanthin chlorophyll a/c-binding protein (FCP). Diatom photosystem I (PSI) interacts with specific FCPs (FCPI); however, it remains unclear how PSI cores receive excitation energy from FCPI. To analyze the energy transfer dynamics, it is necessary to isolate both PSI cores and PSI-FCPI complexes. In this study, we prepared three PSI complexes, which are PSI-FCPI membrane fragments, detergent-solubilized PSI-FCPI supercomplexes and PSI core-like complexes, from the marine centric diatom, Chaetoceros gracilis, and examined their biochemical properties. Both the PSI-FCPI membrane fragments and supercomplexes showed similar subunit compositions including FCPI, whereas the PSI complexes were devoid of most FCPI subunits. The purity and homogeneity of the two detergent-solubilized PSI preparations were verified by clear-native PAGE and electron microscopy. The difference of pigment contents among the three PSI samples was shown by absorption spectra at 77K. The intensity in the whole spectrum of PSI-FCPI membranes was much higher than those of the other two complexes, while the spectral shape of PSI complexes was similar to that of cyanobacterial PSI core complexes. 77-K fluorescence spectra of the three PSI preparations exhibited different spectral shapes, especially peak positions and band widths. Based on these observations, we discuss the merits of three PSI preparations for evaluating excitation energy dynamics in diatom PSI-FCPI complexes.

DOI： 10.1007/s11120-018-0576-y

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 査読国際誌

Gabor Sipka, Pavel Mueller, Klaus Brettel, Melinda Magyar, Laszlo Kovacs, Qingjun Zhu, Yanan Xiao, Guangye Han, Petar H. Lambrev, Jian-Ren Shen, Gyozo Garab

PHYSIOLOGIA PLANTARUM 166 ( 1 ) 22 - 32 2019年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY

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 819nm, 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 17ns (approximate to 50%) and 167ns (approximate to 30%), and a longer-lived component (approximate to 20%). This kinetics are attributed to re-reduction of P680(center dot+) by the donor side of PSII. In contrast, upon second-flash (with t between 5s and 100ms) or repetitive excitation, the 819nm absorption changes decayed with lifetimes of about 2ns (approximate to 60%) and 10ns (approximate to 30%), attributed to recombination of the primary radical pair P680(center dot+)Pheo(center dot-), and a small longer-lived component (approximate to 10%). These data confirm that only the first STSF is capable of generating stable charge separation-leading to the reduction of Q(A); 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.

DOI： 10.1111/ppl.12945

Blocking backward reaction on hydrogen evolution cocatalyst in a photosystem II hybrid Z-scheme water splitting system 査読

Zhen Li, Yu Qi, Wangyin Wang, Deng Li, Zheng Li, Yanan Xiao, Guangye Han, Jian-Ren Shen, Can Li

CHINESE JOURNAL OF CATALYSIS 40 ( 4 ) 486 - 494 2019年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SCIENCE PRESS

Photocatalytic Z-scheme water splitting is considered as a promising approach to produce solar hydrogen. However, the forward hydrogen production reaction is often impeded by backward reactions. In the present study, in a photosystem II-integrated hybrid Z-scheme water splitting system, the backward hydrogen oxidation reaction was significantly suppressed by loading a PtCrOx cocatalyst on a ZrO2/TaON photocatalyst. Due to the weak chemisorption and activation of molecular hydrogen on PtCrOx, where Pt is stabilized in the oxidized forms, POII and Pt-IV, hydrogen oxidation is inhibited. However, it is remarkably well-catalyzed by the metallic Pt cocatalyst, thereby rapidly consuming the produced hydrogen. This work describes an approach to inhibit the backward reaction in the photosystem II-integrated hybrid Z-scheme water splitting system using Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple as an electron shuttle. (C) 2019, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/S1872-2067(19)63311-5

Phospholipid distributions in purple phototrophic bacteria and LH1-RC core complexes 査読

S. Nagatsuma, K. Gotou, T. Yamashita, L.-J. Yu, J.-R. Shen, M.T. Madigan, Y. Kimura, Z.-Y. Wang-Otomo

Biochimica Biophysica Acta 1860 461 - 468 2019年4月

Spin, Valence, and Structural Isomerism in the S-3 State of the Oxygen-Evolving Complex of Photosystem II as a Manifestation of Multimetallic Cooperativity 査読国際誌

Hiroshi Isobe, Mitsuo Shoji, Takayoshi Suzuki, Jian-Ren Shen, Kizashi Yamaguchi

JOURNAL OF CHEMICAL THEORY AND COMPUTATION 15 ( 4 ) 2375 - 2391 2019年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Photosynthetic water oxidation is catalyzed by a Mn4CaO5-cluster in photosystem II through an S-state cycle. Understanding the roles of heterogeneity in each S-state, as identified recently by the EPR spectroscopy, is very important to gain a complete description of the catalytic mechanism. We performed herein hybrid DFT calculations within the broken-symmetry formalism and associated analyses of Heisenberg spin models to study the electronic and spin structures of various isomeric structural motifs (hydroxo-oxo, oxyl-oxo, peroxo, and superoxo species) in the S(3 )state. Our extensive study reveals several factors that affect the spin ground state: (1) (formal) Mn oxidation state; (2) metal-ligand covalency; (3) coordination geometry; and (4) structural change of the Mn cluster induced by alternations in Mn...Mn distances. Some combination of these effects could selectively stabilize/destabilize some spin states. We found that the high spin state (S-total= 6) of the oxyl-oxo species can be causative for catalytic function, which manifests through mixing of the metal-ligand character in magnetic orbitals at relatively short 05...06 distances (<2.0 angstrom) and long Mn-A center dot center dot center dot O5 distances (>2.0 angstrom). These results will serve as a basis to conceptually identify and rationalize the physicochemical synergisms that can be evoked by the unique "distorted chair" topology of the cluster through cooperative Jahn-Teller effects on multimetallic centers.

DOI： 10.1021/acs.jctc.8b01055

Cobalt/Cobalt Oxide Surface for Water Oxidation 査読

Hadi Feizi, Robabeh Bagheri, Zhenlun Song, Jian-Ren Shen, Suleyman I. Allakhverdiev, Mohammad Mahdi Najafpour

ACS SUSTAINABLE CHEMISTRY & ENGINEERING 7 ( 6 ) 6093 - 6105 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Water splitting to produce molecular hydrogen is an essential method to store sustainable energies. One of the bottlenecks for water splitting is the availability of an efficient and stable water-oxidizing catalyst. Herein, metallic cobalt foil, after the treatment under high potential (10-60.0 V), was used for water oxidation. The cobalt/ cobalt oxide surface was characterized by various spectroscopic, microscopy, X-ray diffraction, and electrochemical methods. Diffuse reflectance infrared Fourier transform spectroscopy showed peaks for Co oxide at 489 and 595 cm(-1) attributed to the stretching of Co-O and bending of O-Co-O bonds in the CoO6 octahedra. Small aggregated particles (ca. 50-100 nm) with a spherical morphology were detected by scanning electron microscopy, and high-resolution transmission electron microscopy from the mechanically separated particles indicated spacings of 2.5-2.6 angstrom corresponding to the interplanar spacings of the (011) plane for Co3O4. Selected area (electron) diffraction showed concentric rings centered on a bright central spot, indicating a polycrystalline material. Each ring is related to planes of different orientation and different interplanar spacing, attributed to metallic cobalt and cobalt oxides. X-ray diffraction resulted in patterns corresponding to Co3O4 and CoO(OH), and X-ray photoelectron spectroscopy could confirm the formation of metallic cobalt, Co(II) and Co(III) oxides on the surface of the electrode. These results suggest that the oxide on the surface of foil could be a mixture of different phases of Co oxide containing Co3O4 and CoO(OH). Under overpotentials of 460 and 780 mV, current densities of 0.144 and 0.5 A/cm(2) were observed at pH-14 without dropping of IR. To the best of our knowledge, the three-dimensional electrode obtained here is among the most efficient cobalt-based water-oxidizing electrodes under alkaline conditions reported so far and may be applied in large scale water-splitting systems.

DOI： 10.1021/acssuschemeng.8b06269

Ultrafast Excitation Energy Dynamics in a Diatom Photosystem I-Antenna Complex: A Femtosecond Fluorescence Upconversion Study 査読国際誌

Ryo Nagao, Kohei Kagatani, Yoshifumi Ueno, Jian-Ren Shen, Seiji Akimoto

JOURNAL OF PHYSICAL CHEMISTRY B 123 ( 12 ) 2673 - 2678 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Fucoxanthin chlorophyll (Chl) a/c-binding proteins (FCPs) are unique light-harvesting antennas in diatoms. Recent time-resolved fluorescence analysis of photosystem I with FCP associated (PSI-FCPI) has mainly shown excitation energy transfer among Chls a from FCPI to PSI in tens of picoseconds. However, it remains unclear how each pigment, especially carotenoids and Chl c, in the FCPI is functionally related to the energy transfer in a femtosecond time range. Here, we reveal ultrafast excitation energy transfer mechanism in the PSI-FCPI preparations isolated from a diatom, Chaetoceros gracilis, by means of femtosecond time-resolved fluorescence spectroscopy with an upconversion system. Compared with the fluorescence lifetime components of PSI core-like complexes, the energy transfer of Chl c -> Chl a in the FCPI was observed within hundreds of femtoseconds, and the energy in the FCPI was transferred to PSI in similar to 2 ps. The comparative fluorescence analyses provide physical insights into the energy transfer machinery within FCPI and from FCPI to PSI.

DOI： 10.1021/acs.jpcb.8b12086

Site-directed mutagenesis of two amino acid residues in cytochrome b₅₅₉ α subunit that interact with a phosphatidylglycerol molecule (PG772) induces quinone-dependent inhibition of photosystem II activity. 査読国際誌

Endo K, Kobayashi K, Wang HT, Chu HA, Shen JR, Wada H

Photosynthesis research 139 ( 1-3 ) 267 - 279 2019年3月

Structure of a green algal photosystem I in complex with a large number of light-harvesting complex I subunits 査読国際誌

Xiaochun Qin, Xiong Pi, Wenda Wang, Guangye Hang, Lixia Zhu, Mingmei Liu, Linpeng Cheng, Jian-Ren Shen, Tingyun Kuang, Sen-Fang Sui

NATURE PLANTS 5 ( 3 ) 263 - 272 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Photosystem I (PSI) is a highly efficient natural light-energy converter, and has diverse light-harvesting antennas associated with its core in different photosynthetic organisms. In green algae, an extremely large light-harvesting complex I (LHCI) captures and transfers energy to the PSI core. Here, we report the structure of PSI-LHCI from a green alga Bryopsis corticulans at 3.49 angstrom resolution, obtained by single-particle cryo-electron microscopy, which revealed 13 core subunits including subunits characteristic of both prokaryotes and eukaryotes, and 10 light-harvesting complex a (Lhca) antennas that form a double semi-ring and an additional Lhca dimer, including a novel four-transmembrane-helix Lhca. In total, 244 chlorophylls were identified, some of which were located at key positions for the fast energy transfer. These results provide a firm structural basis for unravelling the mechanisms of light-energy harvesting, transfer and quenching in the green algal PSI-LHCI, and important clues as to how PSI-LHCI has changed during evolution.

DOI： 10.1038/s41477-019-0379-y

Properties and structure of a low-potential, penta-heme cytochrome c(552) from a thermophilic purple sulfur photosynthetic bacterium Thermochromatium tepidum 査読国際誌

Jing-Hua Chen, Long-Jiang Yu, Alain Boussac, Zheng-Yu Wang-Otomo, Tingyun Kuang, Jian-Ren Shen

PHOTOSYNTHESIS RESEARCH 139 ( 1-3 ) 281 - 293 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

The thermophilic purple sulfur bacterium Thermochromatium tepidum possesses four main water-soluble redox proteins involved in the electron transfer behavior. Crystal structures have been reported for three of them: a high potential iron-sulfur protein, cytochrome c, and one of two low-potential cytochrome c(552) (which is a flavocytochrome c) have been determined. In this study, we purified another low-potential cytochrome c(552) (LPC), determined its N-terminal amino acid sequence and the whole gene sequence, characterized it with absorption and electron paramagnetic spectroscopy, and solved its high-resolution crystal structure. This novel cytochrome was found to contain five c-type hemes. The overall fold of LPC consists of two distinct domains, one is the five heme-containing domain and the other one is an Ig-like domain. This provides a representative example for the structures of multiheme cytochromes containing an odd number of hemes, although the structures of multiheme cytochromes with an even number of hemes are frequently seen in the PDB database. Comparison of the sequence and structure of LPC with other proteins in the databases revealed several characteristic features which may be important for its functioning. Based on the results obtained, we discuss the possible intracellular function of this LPC in Tch. tepidum.

DOI： 10.1007/s11120-018-0507-y

Structural basis for blue-green light harvesting and energy dissipation in diatoms 査読国際誌

Wenda Wang, Long-Jiang Yu, Caizhe Xu, Takashi Tomizaki, Songhao Zhao, Yasufumi Umena, Xiaobo Chen, Xiaochun Qin, Yueyong Xin, Michihiro Suga, Guangye Han, Tingyun Kuang, Jian-Ren Shen

SCIENCE 363 ( 6427 ) 598 - + 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC ADVANCEMENT SCIENCE

Diatoms are abundant photosynthetic organisms in aquatic environments and contribute 40% of its primary productivity. An important factor that contributes to the success of diatoms is their fucoxanthin chlorophyll a/c-binding proteins (FCPs), which have exceptional light-harvesting and photoprotection capabilities. Here, we report the crystal structure of an FCP from the marine diatom Phaeodactylum tricornutum, which reveals the binding of seven chlorophylls (Chls) a, two Chls c, seven fucoxanthins (Fxs), and probably one diadinoxanthin within the protein scaffold. Efficient energy transfer pathways can be found between Chl a and c, and each Fx is surrounded by Chls, enabling the energy transfer and quenching via Fx highly efficient. The structure provides a basis for elucidating the mechanisms of blue-green light harvesting, energy transfer, and dissipation in diatoms.

DOI： 10.1126/science.aav0365

Low-Energy Chlorophylls in Fucoxanthin Chlorophyll a/c-Binding Protein Conduct Excitation Energy Transfer to Photosystem I in Diatoms 査読国際誌

Ryo Nagao, Makio Yokono, Yoshifumi Ueno, Jian-Ren Shen, Seiji Akimoto

JOURNAL OF PHYSICAL CHEMISTRY B 123 ( 1 ) 66 - 70 2019年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Photosynthetic organisms handle solar energy precisely to achieve efficient photochemical reactions. Because there are a wide variety of light-harvesting antennas in oxyphototrophs, the excitation energy transfer mechanisms are thought to differ significantly. In this study, we compared excitation energy dynamics between photosystem I (PSI) cores and a complex between PSI and fucoxanthin chlorophyll (Chl) a/c-binding protein I (PSI FCPI) isolated from a diatom, Chaetoceros gracilis, by means of picosecond time-resolved fluorescence analyses. Time-resolved spectra measured at 77 K clearly show that low-energy Chls in the FCPI transfer not only most of the excitation energy to the reaction center Chls in the PSI cores but also the remaining energy to carotenoids for quenching. Under room-temperature conditions, the energy in the low-energy Chls is rapidly equilibrated on Chls in the PSI cores by uphill energy transfer within a few tens of picoseconds. These findings provide solid evidence that the low-energy Chls in the FCPI contribute to the photochemical reactions in PSI.

DOI： 10.1021/acs.jpcb.8b09253

A transparent electrode with water-oxidizing activity 査読

Gouhar Azadi, Robabeh Bagheri, Rahman Bikas, Younes Mousazade, Junfeng Cui, Zhenlun Song, Vasyl Kinzhybalo, Jian-Ren Shen, Suleyman I. Allakhverdiev, Mohammad Mahdi Najafpour

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 43 ( 51 ) 22896 - 22904 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

Hydrogen production by water splitting is a promising method to store energy. Water-oxidation reaction is a bottleneck in water-splitting systems. Herein, a mononuclear nickel(II) phosphine complex with 1,2-bis(dicyclohexylphosphino)ethane ligand, was synthesized and characterized by X-ray crystallography method. The water-oxidizing catalyst under the electrochemical condition was studied. The role of Ni compound for the water-oxidation reaction on the surface of fluorine-doped tin oxide as one of the true catalysts was investigated by the electrochemical methods and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) Spectroscopy. The big ligand around the Ni ion causes a very small size of Ni-based particles on the surface of the electrode, which are the active catalysts for the water-oxidation reaction. Such small nanosized Ni-based compounds are transparent and have no effect on the transparency of the obtained fluorine-doped tin oxide. Thus, it is a promising method to synthesize a transparent fluorine-doped tin oxide with water-oxidizing activity. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2018.10.146

Novel features of LH1-RC from Thermochromatium tepidum revealed from its atomic resolution structure 査読国際誌

Long-Jiang Yu, Michihiro Suga, Zheng-Yu Wang-Otomo, Jian-Ren Shen

FEBS JOURNAL 285 ( 23 ) 4359 - 4366 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY

Light-harvesting-1 (LH1)-reaction center (RC) super-complex is a membrane protein-pigment complex existing in purple photosynthetic bacteria, where LH1 absorbs light energy and transfers them rapidly and efficiently to RC to initiate the charge separation and electron transfer reactions. The structure of LH1-RC has been reported at relatively low resolutions from several different species of bacteria previously, but was solved at an atomic resolution recently from a thermophilic photosynthetic bacterium Thermochromatium tepidum. This high-resolution structure revealed the detailed organization of the super-complex including a number of unique features that are important for its functioning, such as a more intact RC structure, transporting routes for quinones to replace the bound Q(B) as well as for the in-and-out of the closed LH1 ring, detailed coordinating environment of the Ca2+ ions in LH1 important for the remarkable red shift of the absorption spectrum, as well as for the enhanced thermostability. These results thus greatly advance our understanding on the mechanisms of energy transfer, quinone exchange, the red shift in the LH1-Qy transition and the enhanced thermal stability, in this super-complex.

DOI： 10.1111/febs.14679

Thylakoid membrane lipid sulfoquinovosyl-diacylglycerol (SQDG) is required for full functioning of photosystem II in Thermosynechococcus elongatus 査読国際誌

Yoshiki Nakajima, Yasufumi Umena, Ryo Nagao, Kaichiro Endo, Koichi Kobayashi, Fusamichi Akita, Michihiro Suga, Hajime Wada, Takumi Noguchi, Jian-Ren Shen

JOURNAL OF BIOLOGICAL CHEMISTRY 293 ( 38 ) 14786 - 14797 2018年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Sulfoquinovosyl-diacylglycerol (SQDG) is one of the four lipids present in the thylakoid membranes. Depletion of SQDG causes different degrees of effects on photosynthetic growth and activities in different organisms. Four SQDG molecules bind to each monomer of photosystem II (PSII), but their role in PSII function has not been characterized in detail, and no PSII structure without SQDG has been reported. We analyzed the activities of PSII from an SQDG-deficient mutant of the cyanobacterium Thermosynechococcus elongatus by various spectroscopic methods, which showed that depletion of SQDG partially impaired the PSII activity by impairing secondary quinone (Q(B)) exchange at the acceptor site. We further solved the crystal structure of the PSII dimer from the SQDG deletion mutant at 2.1 angstrom resolution and found that all of the four SQDG-binding sites were occupied by other lipids, most likely PG molecules. Replacement of SQDG at a site near the head of Q(B) provides a possible explanation for the Q(B) impairment. The replacement of two SQDGs located at the monomer-monomer interface by other lipids decreased the stability of the PSII dimer, resulting in an increase in the amount of PSII monomer in the mutant. The present results thus suggest that although SQDG binding in all of the PSII-binding sites is necessary to fully maintain the activity and stability of PSII, replacement of SQDG by other lipids can partially compensate for their functions.

DOI： 10.1074/jbc.RA118.004304

Alterations of pigment composition and their interactions in response to different light conditions in the diatom Chaetoceros gracilis probed by time-resolved fluorescence spectroscopy 査読国際誌

Ryo Nagao, Yoshifumi Ueno, Makio Yokono, Jian-Ren Shen, Seiji Akimoto

BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1859 ( 7 ) 524 - 530 2018年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Maintenance of energy balance under changeable light conditions is an essential function of photosynthetic organisms to achieve efficient photochemical reactions. Among the photosynthetic organisms, diatoms possess light-harvesting fucoxanthin chlorophyll (Chl) a/c-binding protein (FCP) as peripheral antennas. However, how diatoms regulate excitation-energy distribution between FCP and the two photosystem cores during light adaptation is poorly understood. In this study, we examined spectroscopic properties of a marine diatom Chaetoceros gracilis adapted in the dark and at photosynthetic photon flux density at 30 and 300 mu mol photons m(-2)s(-1). Absorption spectra at 77 K showed significant changes in the Soret region, and 77-K steady-state fluorescence spectra showed significant differences in the spectral shape and relative fluorescence intensity originating from both PSII and PSI, among the cells grown under different light conditions. These results suggest alterations of pigment composition and their interactions under the different light conditions. These alterations affected the excitation-energy dynamics monitored by picosecond time-resolved fluorescence analyses at 77 K significantly. The contributions of Chls having lower energy levels than the reaction center Chls in the two photosystems to the energy dynamics were clearly identified in the three cells but with presumably different roles. These findings provide insights into the regulatory mechanism of excitation-energy balance in diatoms under various light conditions.

DOI： 10.1016/j.bbabio.2018.04.003

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