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Katayama, Yoshinori; Ikeda, Takashi; Hattori, Takanori; Saito, Hiroyuki; Aoki, Katsutoshi; Fukui, Hiroshi*; Tange, Yoshinori*; Funakoshi, Kenichi*
no journal, ,
Liquid water shows unique properties and they are related to the network structure formed by hydrogen bonds between water molecules. To study pressure dependence of structure of water, we measured X-ray diffraction of water up to 20 GPa using multi-anvil type presses in SPring-8. The coordination number of water molecules increased rapidly up to 4 GPa while maintaining the intermolecular distance. First-principles molecular dynamics simulations were also performed for high-density water. The obtained oxygen-oxygen radial distribution functions were in excellent agreement with the experimental results. Results of the simulations revealed that temperature was more important factor for the structural change. We have performed additional measurements at high temperatures. The calculated oxygen-oxygen radial distribution functions were again consistent with our experimental results. These studies clarified a pressure-temperature region where the significant structural change occurred.
structure of copper nitrite reductase from thermophilic denitriferFukuda, Yota*; Tamada, Taro; Takami, Hideto*; Inoue, Tsuyoshi*; Nojiri, Masaki
no journal, ,
Denitrification is known as anaerobic respiration in which nitrogenous compounds (NO
or NO
) are used as terminal electron acceptors. Copper-containing nitrite reductase (CuNIR) catalyzes the one electron reduction of nitrite to nitric oxide (NO), which is the key step in the denitrification pathway. Here, we report the structure analysis of CuNIR from thermophilic 
HTA426(
NIR) at 1.3 resolution. NIR folds a homo-trimeric structure, having two copper binding sites per a monomeric unit as well as other CuNIRs. There are main characteristics of NIR in two loops (tower loop and extra loop regions) and the N-terminal region. The additional N-terminal 
-helix is positioned in the vicinity of the tower loop. These characteristic structures found in NIR structure suggest evolutionary diversity of CuNIR and play a key role in functioning in the particular environment where 
inhabits.
Asaoka, Hidehito; Yamazaki, Tatsuya; Shamoto, Shinichi
no journal, ,
no abstracts in English
Kiyanagi, Ryoji; Oikawa, Kenichi; Tamura, Itaru; Ohara, Takashi; Kawasaki, Takuro; Kaneko, Koji; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*; Kimura, Hiroyuki*; et al.
no journal, ,
Honda, Mitsunori; Hattori, Takanori; Machida, Akihiko; Sano, Asami; Katayama, Yoshinori; Aoki, Katsutoshi; Arima, Hiroshi; Komatsu, Kazuki*; Oshita, Hidetoshi*; Otomo, Toshiya*
no journal, ,
High-pressure neutron diffraction experiments were performed for LaD2 with a total scattering spectrometer NOVA at J-PARC. Rietveld analysis of an ambient pressure profile of a powder sample yielded a lattice constant a=5.652(2) and hydrogen occupancies 0.94(4) at T-site and 0.09(6) at O-site. We obtained diffraction profiles at ten pressure conditions from 0.1 to 17 GPa. The peak splitting arising from the tetragonal distortion increased in magnitude on further compression to the phase separation pressure of 11 GPa. A similar lattice distortion has been reported for superstoichiometric LaH2+ in which excess H atoms occupy the O-sites to make the cubic lattice distorted. Partial transfer of the T-site D atoms into the O-sites in LaD2 is one possible cause for the distortion. The microscopic mechanism of the cubic-tetragonal structural transition and the following phase separation will be discussed on the basis of the refined structural parameters.
H
ONH-PbBr by neutron and X-ray diffraction experimentsKawasaki, Takuro; Takahashi, Miwako; Ohara, Takashi*; Oshima, Kenichi*; Kusaka, Katsuhiro*; Tanaka, Ichiro*; Hosoya, Takaaki*; Yamada, Taro*; Kurihara, Kazuo; Niimura, Nobuo*
no journal, ,