Performance information

• Effect of frequency chirp on RYDMR spectrum in AWG-RYDMR system at low magnetic field　　　　　　　　　　　　　　　
  Akihiro Tateno; Hiroki Nagashima; Kiminori Maeda
  Chemical Physics Letters, Apr. 2025, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1016/j.cplett.2025.141905
  DOI ID：10.1016/j.cplett.2025.141905, ORCID：176224456
• Anisotropic and Coherent Control of Radical Pairs by Optimized RF Fields　　　　　　　　　　　　　　　
  Akihiro Tateno; Kenta Masuzawa; Hiroki Nagashima; Kiminori Maeda
  International Journal of Molecular Sciences, Jun. 2023, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.3390/ijms24119700
  DOI ID：10.3390/ijms24119700, ORCID：136332548
• Synergetic Role of Conformational Flexibility and Electronic Coupling for Quantitative Intramolecular Singlet Fission　　　　　　　　　　　　　　　
  Shunta Nakamura; Hayato Sakai; Hiroki Nagashima; Masaaki Fuki; Kakeru Onishi; Ramsha Khan; Yasuhiro Kobori; Nikolai V. Tkachenko; Taku Hasobe
  The Journal of Physical Chemistry C, Volume：125, Number：33, First page：18287, Last page：18296, Aug. 2021, [Reviewed]
  We present a novel design concept of molecular dimers for quantitative individual triplet yield (φT) through intramolecular singlet fission. We synthesized a series of tetracene (Tc) dimers bridged by different phenylene-based linkers, focusing on the conformational flexibility in addition to the electronic coupling. In transient absorption measurements, a 4,4′-biphenyl-bridged Tc dimer with weaker electronic coupling and larger conformational flexibility exhibited the quantitative φT: 196 ± 12% at high excitation energy. Moreover, decoupled spins associated with conformational change were directly characterized by time-resolved electron paramagnetic resonance. Strong interplay of the geometry change and electronic localization was revealed on the triplet pair dissociation through magnitudes of spin-spin exchange couplings. Thus, a synergetic role of conformational flexibility and electronic coupling in quantitative φT was clarified.
  American Chemical Society ({ACS}), Scientific journal
  DOI：https://doi.org/10.1021/acs.jpcc.1c04734
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85114009615&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85114009615&origin=inward
  DOI ID：10.1021/acs.jpcc.1c04734, ISSN：1932-7447, eISSN：1932-7455, ORCID：98448849, SCOPUS ID：85114009615
• Ultra‐Narrow Depletion Layers in a Hematite Mesocrystal‐Based Photoanode for Boosting Multihole Water Oxidation　　　　　　　　　　　　　　　
  Zhujun Zhang; Hiroki Nagashima; Takashi Tachikawa
  Angewandte Chemie International Edition, Volume：59, Number：23, First page：9047, Last page：9054, Jun. 2020, [Reviewed]
  Wiley
  DOI：https://doi.org/10.1002/anie.202001919
  DOI ID：10.1002/anie.202001919, PubMed ID：32173995
• Spin Dynamics of Quintet and Triplet States Resulting from Singlet Fission in Oriented Terrylenediimide and Quaterrylenediimide Films　　　　　　　　　　　　　　　
  Youn Jue Bae; Xingang Zhao; Matthew D. Kryzaniak; Hiroki Nagashima; Joseph Strzalka; Qingteng Zhang; Michael R. Wasielewski
  The Journal of Physical Chemistry C, Volume：124, Number：18, First page：9822, Last page：9833, May 2020, [Reviewed]
  American Chemical Society ({ACS}), Scientific journal
  DOI：https://doi.org/10.1021/acs.jpcc.0c03189
  DOI ID：10.1021/acs.jpcc.0c03189, ORCID：72772604
• Orientation of Ligand Field for Dangling Manganese in Photosynthetic Oxygen-Evolving Complex of Photosystem II　　　　　　　　　　　　　　　
  Hiroyuki Mino; Hiroki Nagashima
  The Journal of Physical Chemistry B, Volume：124, Number：1, First page：128, Last page：133, Jan. 2020, [Reviewed]
  American Chemical Society ({ACS}), Scientific journal
  DOI：https://doi.org/10.1021/acs.jpcb.9b10817
  DOI ID：10.1021/acs.jpcb.9b10817, ORCID：66440085
• Interfacial oxygen vacancies yielding long-lived holes in hematite mesocrystal-based photoanodes　　　　　　　　　　　　　　　
  Zhujun Zhang; Izuru Karimata; Hiroki Nagashima; Shunsuke Muto; Koji Ohara; Kunihisa Sugimoto; Takashi Tachikawa
  NATURE COMMUNICATIONS, Volume：10, Oct. 2019, [Reviewed]
  Hematite (alpha-Fe2O3) is one of the most promising candidates as a photoanode materials for solar water splitting. Owing to the difficulty in suppressing the significant charge recombination, however, the photoelectrochemical (PEC) conversion efficiency of hematite is still far below the theoretical limit. Here we report thick hematite films (similar to 1500 nm) constructed by highly ordered and intimately attached hematite mesocrystals (MCs) for highly efficient PEC water oxidation. Due to the formation of abundant interfacial oxygen vacancies yielding a high carrier density of similar to 1020 cm(-3) and the resulting extremely large proportion of depletion regions with short depletion widths (<10 nm) in hierarchical structures, charge separation and collection efficiencies could be markedly improved. Moreover, it was found that long-lived charges are generated via excitation by shorter wavelength light (below similar to 500 nm), thus enabling long-range hole transfer through the MC network to drive high efficiency of light-to-energy conversion under back illumination.
  NATURE PUBLISHING GROUP, English, Scientific journal
  DOI：https://doi.org/10.1038/s41467-019-12581-z
  DOI ID：10.1038/s41467-019-12581-z, ISSN：2041-1723, Web of Science ID：WOS:000491858200021
• Controlled Orientations of Neighboring Tetracene Units by Mixed Self-Assembled Monolayers on Gold Nanoclusters for High-Yield and Long-Lived Triplet Excited States through Singlet Fission　　　　　　　　　　　　　　　
  Toshiyuki Saegusa; Hayato Sakai; Hiroki Nagashima; Yasuhiro Kobori; Nikolai V. Tkachenko; Taku Hasobe
  Journal of the American Chemical Society, Volume：141, Number：37, First page：14720, Last page：14727, Sep. 2019, [Reviewed]
  Copyright © 2019 American Chemical Society. Although tetracene (Tc) is well-known as a good candidate for singlet fission (SF), the number of high-yield and long-lived triplet excited states through SF is extremely limited because of the relative acceleration of the reverse triplet-triplet annihilation (TTA) considering the energy matching between a singlet and two triplet states. Systematic control of electronic interactions between two neighboring units using conventional covalent linkages and molecular assembly methods to optimize these kinetic processes is quite difficult because of the complicated synthesis and random orientations. In this study, we propose a novel supramolecular strategy utilizing mixed self-assembled monolayers (SAMs) with two different chain lengths. Specifically, mixed Tc-SAMs on gold nanoclusters, which are prepared using Tc-modified heterodisulfides with two different chain lengths, attain high-yield SF (φSF ≈ 90%) and individual triplet yields (φ? ≈ 160%). The obtained φSF is the highest value among Tc derivatives in homogeneous solution to the best of our knowledge.
  American Chemical Society ({ACS}), Scientific journal
  DOI：https://doi.org/10.1021/jacs.9b06567
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85072270985&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85072270985&origin=inward
  DOI ID：10.1021/jacs.9b06567, ISSN：0002-7863, eISSN：1520-5126, ORCID：61325979, PubMed ID：31529955, SCOPUS ID：85072270985
• Long-lived Triplet Excitons Formed by Exergonic Intramolecular Singlet Fission of an Adamantane-linked Tetracene Dyad
  Yasunori Matsui; Shuhei Kawaoka; Hiroki Nagashima; Tatsuo Nakagawa; Naoki Okamura; Takuya Ogaki; Eisuke Ohta; Seiji Akimoto; Shigeyuki Yagi; Yasuhiro Kobori; Hiroshi Ikeda
  Mar. 2019
  American Chemical Society ({ACS})
  DOI：https://doi.org/10.26434/chemrxiv.7808435.v1
  DOI ID：10.26434/chemrxiv.7808435.v1, ORCID：55047389
• Quantitative Sequential Photoenergy Conversion Process from Singlet Fission to Intermolecular Two-Electron Transfers Utilizing Tetracene Dimer
  Shunta Nakamura; Hayato Sakai; Hiroki Nagashima; Yasuhiro Kobori; Nikolai V. Tkachenko; Taku Hasobe
  ACS Energy Letters, Volume：4, Number：1, First page：26, Last page：31, Nov. 2018, [Reviewed]
  American Chemical Society ({ACS}), English, Scientific journal
  DOI：https://doi.org/10.1021/acsenergylett.8b01964
  DOI ID：10.1021/acsenergylett.8b01964, ISSN：2380-8195, eISSN：2380-8195, ORCID：51118023
• Synthesis, Structure and Electronic Properties of Graphitic Carbon Nitride Films
  Hiroki Nagashima
  The journal of physical chemistry C, Oct. 2018, [Reviewed]
  English, Scientific journal
  DOI：https://doi.org/10.1021/acs.jpcc.8b07972
  DOI ID：10.1021/acs.jpcc.8b07972, ORCID：49885004
• Identifying triplet pathways in dilute pentacene films　　　　　　　　　　　　　　　
  Daphné Lubert-Perquel; Enrico Salvadori; Matthew Dyson; Paul N. Stavrinou; Riccardo Montis; Hiroki Nagashima; Yasuhiro Kobori; Sandrine Heutz; Christopher; W.M. Kay
  Nature Communications, Volume：9, Number：1, First page：4222, Last page：4222, Oct. 2018, [Reviewed], ［International magazine］
  Building efficient triplet-harvesting layers for photovoltaic applications requires a deep understanding of the microscopic properties of the components involved and their dynamics. Singlet fission is a particularly appealing mechanism as it generates two excitons from a single photon. However, the pathways of the coupled triplets into free species, and their dependence on the intermolecular geometry, has not been fully explored. In this work, we produce highly ordered dilute pentacene films with distinct parallel and herringbone dimers and aggregates. Using electron paramagnetic resonance spectroscopy, we provide compelling evidence for the formation of distinct quintet excitons in ambient conditions, with intrinsically distinctive electronic and kinetic properties. We find that the ability of quintets to separate into free triplets is promoted in the parallel dimers and this provides molecular design rules to control the triplets, favouring either enhanced photovoltaic efficiency (parallel) or strongly bound pairs that could be exploited for logic applications (herringbone).
  English, Scientific journal
  DOI：https://doi.org/10.1038/s41467-018-06330-x
  DOI ID：10.1038/s41467-018-06330-x, ORCID：49011922, PubMed ID：30310077, PubMed Central ID：PMC6181988
• Singlet-Fission-Born Quintet State: Sublevel Selections and Trapping by Multiexciton Thermodynamics　　　　　　　　　　　　　　　
  Nagashima, Hiroki; Kawaoka, Shuhei; Akimoto, Seiji; Tachikawa, Takashi; Matsui, Yasunori; Ikeda, Hiroshi; Kobori, Yasuhiro
  The journal of physical chemistry letters, Volume：9, First page：5855, Last page：5861, Sep. 2018, [Reviewed]
  ACS Publications, English, Scientific journal
  ORCID：48687389
• Multiexciton Dynamics Depending on Intramolecular Orientations in Pentacene Dimers: Recombination and Dissociation of Correlated Triplet Pairs
  Hayato Sakai; Ryutaro Inaya; Hiroki Nagashima; Shunta Nakamura; Yasuhiro Kobori; Nikolai V. Tkachenko; Taku Hasobe
  Journal of Physical Chemistry Letters, Volume：9, Number：12, First page：3354, Last page：3360, Jun. 2018, [Reviewed]
  Pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as o-(Pc)2 and m-(Pc)2] were synthesized to examine intramolecular orientation-dependent multiexciton dynamics, especially focusing on singlet fission (SF) and recombination from correlated triplet pairs . Absorption and electrochemical measurements indicated strong intramolecular couplings of o-(Pc)2 relative to m-(Pc)2. Femtosecond and nanosecond TA measurements successfully demonstrated efficient SF in both dimers. In contrast, the dissociation process from the (TT) to the individual triplets was clearly observed in m-(Pc)2, which is in sharp contrast to a major recombination process in o-(Pc)2. Time-resolved electron spin resonance (TR-ESR) measurements demonstrated that the recombination and dissociation proceed from the quintet state of 5(TT) in m-(Pc)2. The rate constant of the SF was 2 orders of magnitude greater in o-(Pc)2 than that in m-(Pc)2 and was rationalized by enhanced electronic coupling between adjacent HOMOs of the Pc units.
  American Chemical Society, English, Scientific journal
  DOI：https://doi.org/10.1021/acs.jpclett.8b01184
  DOI ID：10.1021/acs.jpclett.8b01184, ISSN：1948-7185, ORCID：45425927, SCOPUS ID：85048051622
• Local Structural Modification of Ca2+-Depleted Photosystem II Detected by Proton Matrix ENDOR
  Hiroki Nagashima; Hiroyuki Mino
  Applied Magnetic Resonance, Volume：49, Number：8, First page：1, Last page：10, Apr. 2018, [Reviewed]
  Angular dependence of the proton matrix electron nuclear double resonance (ENDOR) spectra was investigated in the oriented Ca2+-depleted Photosystem II (PS II). Six pairs of the proton signals have been previously detected in the untreated PS II and one of the six pairs has been disappeared in the Ca2+-depleted PS II (Nagashima and Mino, J Biol Chem 290:28166–28174, 2015), where the proton signals with 4 MHz separation were lost and assigned to the proton closest to the terminal Mn, labeled as Mn4 in the Mn cluster. In the oriented Ca2+-depleted PS II, the proton signal with 4 MHz separation was disappeared when the external magnetic field is parallel to the membrane normal n (θ = 0°). A pair of broad ENDOR signals with 1.4–2.0 MHz hyperfine coupling was detected in the oriented Ca2+-depleted PS II at θ = 90°. These results indicate the Ca2+-depletion derives the rearrangement of the hydrogen bonding of the water molecule surrounded Mn cluster.
  Springer-Verlag Wien, English, Scientific journal
  DOI：https://doi.org/10.1007/s00723-018-1006-1
  DOI ID：10.1007/s00723-018-1006-1, ISSN：0937-9347, ORCID：44570356, SCOPUS ID：85046032094
• Time-Resolved EPR Study on Singlet-Fission Induced Quintet Generation and Subsequent Triplet Dissociation in TIPS-Phenyl-Tetracene Aggregates　　　　　　　　　　　　　　　
  Hiroki Nagashima; Shuhei Kawaoka; Yasunori Matsui; Takashi Tachikawa; Hiroshi Ikeda; Yasuhiro Kobori
  JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY, Volume：31, Number：2, First page：163, Last page：167, 2018, [Reviewed]
  The singlet fission (SF) is expected to be powerful tool for exceeding the theoretical limit of the power conversion efficiency on the organic solar cells. However, little is known on the intermolecular SF mechanism in the solid state. In the present study, we have investigated intermolecular SF in 2-phenyl-6,11-bis(triisopropylsilylethynyl)tetracene (TIPS-Ph-Tc) in frozen solutions using a time-resolved electron paramagnetic resonance measurement at a low temperature. SF-born quintet states (Q) and subsequent dissociations into two triplet states (T + T) were detected for a diluted solute concentration of 10(-4) M in dichloromethane. The microsecond triplet dissociation was found to occur due to the amorphous morphology in the frozen aggregate, suggesting that Q is generated as a trapped state. Furthermore, it was also suggested that the T + T dissociation follows the Q generation due to a T-T repulsion, whose energy were determined by the negative exchange couplings in the triplet pairs, (TT).
  TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN, English, Scientific journal
  DOI：https://doi.org/10.2494/photopolymer.31.163
  DOI ID：10.2494/photopolymer.31.163, ISSN：0914-9244, ORCID：48141756, Web of Science ID：WOS:000440124400004
• Multiple Quintets via Singlet Fission in Ordered Films at Room Temperature　　　　　　　　　　　　　　　
  Lubert-Perquel; Daphn{\'e; Salvadori, Enrico; Dyson, Matthew; Stavrinou; Paul N.; Montis, Riccardo; Nagashima, Hiroki; Kobori, Yasuhiro; Heutz, Sandrine; d Kay; Christopher WM
  arXiv preprint arXiv:1801.00603, 2018, [Reviewed]
  Scientific journal
  ORCID：42527264
• Magnetic structure of manganese cluster in photosystem II investigated by electron paramagnetic resonance　　　　　　　　　　　　　　　
  Nagashima, Hiroki; Asada, Mizue; Mino, Hiroyuki
  Biophysics and Physicobiology, Volume：15, First page：45, Last page：50, 2018, [Reviewed]
  The Biophysical Society of Japan, Scientific journal
  ORCID：42527056
• Dimeric Structure of the Blue Light Sensor Protein Photozipper in the Active State　　　　　　　　　　　　　　　
  Ozeki, Kohei; Tsukuno, Hiroyuki; Nagashima, Hiroki; Hisatomi, Osamu; Mino, Hiroyuki
  Biochemistry, Volume：57, Number：5, First page：494, Last page：497, Dec. 2017, [Reviewed]
  ACS Publications, English, Scientific journal
  ORCID：42527027
• Regulated Electron Tunneling of Photoinduced Primary Charge Separated State in the Photosystem II Reaction Center　　　　　　　　　　　　　　　
  Masashi Hasegawa; Hiroki Nagashima; Reina Minobe; Takashi Tachikawa; Hiroyuki Mino; Yasuhiro Kobori
  JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Volume：8, Number：6, First page：1179, Last page：1184, Mar. 2017, [Reviewed]
  In initial events of the photosynthesis by higher plants, the photosystem II (PSII) generates photoinduced primary charge-separated (CS) state composed of reduced pheophytin (Pheo(D1)(-center dot)) and oxidized special pair (P+center dot) in chlorophyll a (Chla) P-D1/P-D2 in the D-1/D-2 heterodimer, ultimately leading to the water oxidation at the oxygen-evolving Mn4CaO5 cluster by P+center dot. To understand the mechanism of the efficient generation of initially localized CS state (P-D1(+center dot) Pheo(D1)(-center dot)), we have characterized cofactor geometries and electronic coupling of the photoinduced primary CS state in quinone prereduced membrane of PSII from spinach using the time-resolved electron paramagnetic resonance method. It has been revealed that the electronic coupling between the charges is significantly weak in the CS state separated by 1.5 nm, showing the importance of regulated cofactor-cofactor electronic interaction between a vinyl substituent in Pheo(D1) and an accessory chlorophyll to inhibit the energy-wasting charge recombination after the primary electron-transfer processes.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/acs.jpclett.7b00044
  DOI ID：10.1021/acs.jpclett.7b00044, ISSN：1948-7185, ORCID：37329641, Web of Science ID：WOS:000396975600014
• Hyperfine Sublevel Correlation Spectroscopy Studies of Iron-Sulfur Cluster in Rieske Protein from Green Sulfur Bacterium Chlorobaculum tepidum　　　　　　　　　　　　　　　
  Hiroki Nagashima; Hiraku Kishimoto; Risa Mutoh; Naotaka Terashima; Hirozo Oh-oka; Genji Kurisu; Hiroyuki Mino
  JOURNAL OF PHYSICAL CHEMISTRY B, Volume：121, Number：12, First page：2543, Last page：2553, Mar. 2017, [Reviewed]
  The magnetic properties of the Rieske protein purified from Chlorobaculum tepidum were investigated using electron paramagnetic resonance and hyperfine sublevel correlation spectroscopy (HYSCORE). The g-values of the Fe2S2 center were g(x) = 1.81, g(y) = 1.90, and g(z) = 2.03. Four classes of nitrogen signals were obtained by HYSCORE. Nitrogens 1 and 2 had relatively strong magnetic hyperfine couplings and were assigned as the nitrogen directly ligated to Fe. Nitrogens 3 and 4 had relatively weak magnetic hyperfine couplings and were assigned as the other nitrogen of the His ligands and peptide nitrogen connected to the sulfur atom via hydrogen bonding, respectively. The anisotropy of nitrogen 3 reflects the different spin density distributions on the His ligands, which influences the electron transfer to quinone.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/acs.jpcb.6b12968
  DOI ID：10.1021/acs.jpcb.6b12968, ISSN：1520-6106, ORCID：37329643, Web of Science ID：WOS:000398247700003
• Location of Methanol on the S-2 State Mn Cluster in Photosystem II Studied by Proton Matrix Electron Nuclear Double Resonance　　　　　　　　　　　　　　　
  Hiroki Nagashima; Hiroyuki Mino
  JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Volume：8, Number：3, First page：621, Last page：625, Feb. 2017, [Reviewed]
  Proton matrix electron nuclear double resonance (ENDOR) spectroscopy was performed to specify the location of the methanol molecule near the manganese cluster in photosystem II. Comparison of the ENDOR spectra in the presence of CH3OH and CD3OH revealed two pairs of hyperfine couplings, 1.2 MHz for A(perpendicular to) and 2.5 MHz for A(//), arising from the methyl group in methanol. On the basis of the crystal structure, the possible location of methanol close to the manganese cluster was discussed.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/acs.jpclett.7b00110
  DOI ID：10.1021/acs.jpclett.7b00110, ISSN：1948-7185, ORCID：37329645, Web of Science ID：WOS:000393443400014
• ESR 分光法による光化学系 II の酸素発生系 Mn クラスターの構造解析　　　　　　　　　　　　　　　
  浅田瑞枝; 長嶋宏樹; 三野広幸
  生物物理, Volume：57, Number：1, First page：011, Last page：14, 2017, [Reviewed]
  

  Electronic structure of Manganese cluster in photosystem II was investigated by Electron Spin Resonance (ESR) spectroscopy. Spin projections on Mn ions in S₂ state manganese cluster were determined by Pulsed Electron-Electron Double Resonance (PELDOR). Protons surrounded manganese cluster were detected by Electron Nuclear Double Resonance (ENDOR). Based on obtained spin projections, ENDOR signals were assigned to the water molecules ligated to manganese cluster. PELDOR technique was applied to the determination of the high affinity Mn²⁺ site in apo-photosystem II, which is the key site of photo-activation process of manganese cluster.

  
  一般社団法人 日本生物物理学会, Japanese
  DOI：https://doi.org/10.2142/biophys.57.011
  DOI ID：10.2142/biophys.57.011, ISSN：0582-4052, CiNii Articles ID：130005296470, CiNii Books ID：AN00129693, ORCID：37329661
• Proton Matrix ENDOR Studies on Ca2+-depleted and Sr2+-substituted Manganese Cluster in Photosystem II　　　　　　　　　　　　　　　
  Hiroki Nagashinna; Yoshiki Nakajima; Jian-Ren Shen; Hiroyuki Mino
  JOURNAL OF BIOLOGICAL CHEMISTRY, Volume：290, Number：47, First page：28166, Last page：28174, Nov. 2015, [Reviewed]
  Proton matrix ENDOR spectra were measured for Ca2+-depleted and Sr2+-substituted photosystem II (PSII) membrane samples from spinach and core complexes from Theymosynechococcus vulcanus in the S-2 state. The ENDOR spectra obtained were similar for untreated PSII from T. vulcanus and spinach, as well as for Ca2+-containing and Sr2+-substituted PSII, indicating that the proton arrangements around the manganese cluster in cyanobacterial and higher plant PSII and Ca2+-containing and Sr2+-substituted are similar in the S-2 state, in agreement with the similarity of the crystal structure of both Ca2+-containing and Sr2+-substituted PSII in the Si state. Nevertheless, slightly different hyperfine separations were found between Ca2+-containing and Sr2+-substituted PSII because of modifications of the water protons ligating to the Sr2+ ion. Importantly, Ca2+ depletion caused the loss of ENDOR signals with a 1.36-MHz separation because of the loss of the water proton W4 connecting Ca2+ and Y, directly. With respect to the crystal structure and the functions of Ca2+ in oxygen evolution, it was concluded that the roles of Ca2+ and Sr2+ involve the maintenance of the hydrogen bond network near the Ca2+ site and electron transfer pathway to the manganese cluster.
  AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, English, Scientific journal
  DOI：https://doi.org/10.1074/jbc.M115.675496
  DOI ID：10.1074/jbc.M115.675496, ISSN：0021-9258, eISSN：1083-351X, ORCID：37329644, Web of Science ID：WOS:000365761900012
• 2P258 ENDOR studies on Ca depleted and Sr substituted Mn cluster in photosystem II(18B. Photobiology:Photosynthesis,Poster)　　　　　　　　　　　　　　　
  Nagashima Hiroki; Nakajima Yoshiki; Shen Jian-Ren; Mino Hiroyuki
  Seibutsu Butsuri, Volume：54, Number：1, First page：S237, 2014
  The Biophysical Society of Japan General Incorporated Association, English
  DOI：https://doi.org/10.2142/biophys.54.S237_6
  DOI ID：10.2142/biophys.54.S237_6, CiNii Articles ID：110009932804
• Highly resolved proton matrix ENDOR of oriented photosystem II membranes in the S-2 state　　　　　　　　　　　　　　　
  Hiroki Nagashima; Hiroyuki Mino
  BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Volume：1827, Number：10, First page：1165, Last page：1173, Oct. 2013, [Reviewed]
  Proton matrix ENDOR was performed to investigate the protons close to the manganese cluster in oriented samples of photosystem II (PS II). Eight pairs of ENDOR signals were detected in oriented PS II membranes. At an angle of theta = 0 degrees between the membrane normal vector n and the external field H-0, five pairs of ENDOR signals were exchangeable in D2O medium and three pairs were not exchangeable in D2O medium. The hyperfine splitting of 3.60 MHz at theta = 0 degrees increased to 3.80 MHz at theta = 90 degrees. The non-exchangeable signals with 1.73 MHz hyperfine splitting at theta = 0 degrees, which were assigned to a proton in an amino acid residue, were not detected at theta = 90 degrees in oriented PS II or in non-oriented PS II. Highly resolved spectra show that only limited numbers of protons were detected by CW-ENDOR spectra, although many protons were located near the CaMn4O5 cluster. The detected exchangeable protons were proposed to arise from the protons belonging to the water molecules, labeled W1-W4 in the 1.9 angstrom crystal structure, directly ligated to the CaMn4O5 cluster, and nearby amino-acid residue. (C) 2013 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.bbabio.2013.06.001
  DOI ID：10.1016/j.bbabio.2013.06.001, ISSN：0005-2728, ORCID：37329646, Web of Science ID：WOS:000323798800004
• Electronic structure of S-2 state of the oxygen-evolving complex of photosystem II studied by PELDOR　　　　　　　　　　　　　　　
  Mizue Asada; Hiroki Nagashima; Faisal Hammad Mekky Koua; Jian-Ren Shen; Asako Kawamori; Hiroyuki Mino
  BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Volume：1827, Number：3, First page：438, Last page：445, Mar. 2013, [Reviewed]
  Photosynthetic water splitting is catalyzed by a Mn4CaO5 cluster in photosystem II, whose structure was recently determined at a resolution of 1.9 angstrom [Umena, Y. et al. 2011, Nature, 473:55-60]. To determine the electronic structure of the Mn4CaO5 cluster, pulsed electron-electron double resonance (PELDOR) measurements were performed for the tyrosine residue Y-D(center dot) and S-2 state signals with non-oriented and oriented photosystem II (PS H) samples. Based on these measurements, the spin density distributions were calculated by comparing with the experimental results. The best fitting parameters were obtained with a model in which Mn1 has a large positive projection, Mn3 has a small positive projection, and Mn2 and Mn4 have negative projections (the numbering of Mni (i=1-4) is based on the crystal structure at a 1.9 angstrom resolution), which yielded spin projections of 1.97, -120, 1.19 and -0.96 for Mn1-4 ions. The results show that the Mn1 ion, which is coordinated by H332, 0342 and E189, has a valence of Mn(III) in the S-2 state. The sign of the exchange interactions J(13) is positive, and the other signs are negative. 2(C) 013 Els,evier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.bbabio.2012.12.011
  DOI ID：10.1016/j.bbabio.2012.12.011, ISSN：0005-2728, eISSN：1879-2650, ORCID：37329642, Web of Science ID：WOS:000315249000023
• 3D0900 Determine the location of protons surrounding Mn cluster of PS II by proton matrix ENDOR using oriented PS II membrane(Photobiology:Photosynthesis,Oral Presentation,The 50th Annual Meeting of the Biophysical Society of Japan)　　　　　　　　　　　　　　　
  Nagashima Hiroki; Mino Hiroyuki
  Seibutsu Butsuri, Volume：52, First page：S61, Last page：S62, 2012
  The Biophysical Society of Japan General Incorporated Association, English
  DOI：https://doi.org/10.2142/biophys.52.S61_6
  DOI ID：10.2142/biophys.52.S61_6, CiNii Articles ID：110009584815
• 3D1022 Determination of magnetic couplings of S_2 state Mn-cluster in Photosystem II studied by PELDOR measurement(Photobiology:Photosynthesis,Oral Presentation,The 50th Annual Meeting of the Biophysical Society of Japan)　　　　　　　　　　　　　　　
  Asada Mizue; Nagashima Hiroki; Koua Faisal Hammad Mekky; Shen Jian-Ren; Mino Hiroyuki
  Seibutsu Butsuri, Volume：52, First page：S63, 2012
  The Biophysical Society of Japan General Incorporated Association, English
  DOI：https://doi.org/10.2142/biophys.52.S63_1
  DOI ID：10.2142/biophys.52.S63_1, CiNii Articles ID：110009584821

• 26aXC-3 Magnetic and Molecular Structure on S_2 state Oxygen Evolving Complex studied by ENDOR　　　　　　　　　　　　　　　
  Mino Hiroyuki; Nagashima Hiroki; Asada Mizue
  Meeting abstracts of the Physical Society of Japan, Volume：68, Number：1, First page：414, Last page：414, 26 Mar. 2013
  The Physical Society of Japan (JPS), Japanese
  ISSN：1342-8349, CiNii Articles ID：110009643924, CiNii Books ID：AA11439205

• The quintet state generation process via inter- and intra-molecular singlet fission　　　　　　　　　　　　　　　
  Hiroki Nagashima; Yasui Matsunori; Shuhei Kawaoka; Seiji Akimoto; Takashi Tachikawa; Hiroshi Ikeda; Yasuhiro Kobori
  Rocky Mountain Conference 2019, Jul. 2019, [International conference]
  English, Poster presentation
• EPR and ENDOR studies on geometry of the reaction intermediates　　　　　　　　　　　　　　　
  Hiroki Nagashima
  4th Kanto Area Spin Chemistry Meeting, Nov. 2018, [Invited], [Domestic conference]
  English, Oral presentation
• Spin dynamics of the singlet-fission-born triplet pair analyzed by TREPR　　　　　　　　　　　　　　　
  Hiroki Nagashima
  Nov. 2018, [Domestic conference]
  Japanese, Oral presentation
• The mechanism of efficient charge separation reaction in photosystem II of higher plants　　　　　　　　　　　　　　　
  Hiroki Nagashima; Masashi Hasegawa; Reina Minobe; Hiroyuki Mino; Yasuhiro Kobori
  Sep. 2017, [Domestic conference]
  English, Poster presentation

• The mechanism of magnetic response generated by the structure of biomolecules　　　　　　　　　　　　　　　
  Oct. 2024 - Mar. 2028
  Saitama University, Principal investigator
  Grant number：JPMJPR24F7
• 任意波形磁気共鳴と磁場方向スイッチングによる新しいスピン操作と反応制御　　　　　　　　　　　　　　　
  30 Jun. 2023 - 31 Mar. 2026
  Grant amount(Total)：6500000, Direct funding：5000000, Indirect funding：1500000
  Grant number：23K17662
• Electron spin resonance study on the photo-induced structural change of the cryptochrome from Europian Robin.　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists, 01 Apr. 2021 - 31 Mar. 2023
  Saitama University
  Grant amount(Total)：4680000, Direct funding：3600000, Indirect funding：1080000
  Grant number：21K14581
• Artificial Photosynthesis by Sodium Tantalate Photocatalysts: Multinational Collaboration in Fundamental Science　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)), Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)), 09 Oct. 2018 - 31 Mar. 2022
  Onishi Hiroshi, Kobe University
  Grant amount(Total)：17940000, Direct funding：13800000, Indirect funding：4140000
  Metal cations, doped into semiconductor photocatalysts for artificial photosynthesis, are impurities that compromise the periodic structure of the host semiconductor. The cations curiously reduce electron-hole recombination and enhance the yield of photocatalytic reactions. To unravel this intriguing phenomenon, a multinational team was assembled to scrutinize the structure of the doped photocatalysts. Two metal-oxide semiconductors, sodium tantalate and strontium titanate, were doped with hetero-metal cations such as lanthanum, strontium, barium, iron, manganese, and others. The local structures of these infused cations were detailed using techniques such as fluorescence X-ray holography, X-ray absorption fine structure, and scanning transmission electron microscopy.
  Grant number：18KK0161
• Study for the spin conversion mechanism in the multiexciton generated by the singlet fission　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists, Grant-in-Aid for Early-Career Scientists, 01 Apr. 2019 - 31 Mar. 2021
  Nagashima Hiroki, Saitama University
  Grant amount(Total)：4290000, Direct funding：3300000, Indirect funding：990000
  Singlet fission is a unique reaction which produces two triplet excitons from one singlet exciton. In this study, we measured time-resolved electron spin resonance to understand the spin conversion mechanism in the correlated triplet-triplet pair which is important to develop efficient singlet fission materials in future. The time-resolved electron spin resonance spectra of the singlet-fission-born quintet state revealed that geometric structures of the pair of singlet fission materials are related with the spin conversion. The study revealed that the structural flexibility of the singlet fission materials are important for spin conversion.
  Grant number：19K15506
• Development and application of new structural analysis on the light-induced radical pair by time-resolved electron spin resonance spectroscopy　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows, Grant-in-Aid for JSPS Fellows, 26 Apr. 2017 - 31 Mar. 2020
  Kobe University
  Grant amount(Total)：4420000, Direct funding：3400000, Indirect funding：1020000
  Grant number：17J01125
• ＥＮＤＯＲ法による光合成酸素発生における基質水分子の同定及び反応メカニズムの解明　　　　　　　　　　　　　　　
  25 Apr. 2014 - 31 Mar. 2017
  Grant amount(Total)：3200000, Direct funding：3200000
  Grant number：14J11113