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reductase by X-ray crystallography; New insights into regulation of efficient electron transferYamada, Mitsugu*; Tamada, Taro; Takeda, Kazuki*; Matsumoto, Fumiko*; Ono, Hiraku*; Kosugi, Masayuki*; Takaba, Kiyofumi*; Shoyama, Yoshinari*; Kimura, Shigenobu*; Kuroki, Ryota; et al.
Journal of Molecular Biology, 425(22), p.4295 - 4306, 2013/11
Times Cited Count：21 Percentile：50.76(Biochemistry & Molecular Biology)NADH-Cytochrome reductase (b5R), a flavoprotein consisting of NADH and flavin adenine dinucleotide (FAD) binding domains, catalyzes electron transfer from the two-electron carrier NADH to the one-electron carrier cytochrome (Cb5). The crystal structures of both the fully reduced form and the oxidized form of porcine liver b5R were determined. In the reduced b5R structure determined at 1.68
resolution, the relative configuration of the two domains was slightly shifted in comparison with that of the oxidized form. This shift resulted in an increase in the solvent-accessible surface area of FAD and created a new hydrogen-bonding interaction between the N5 atom of the isoalloxazine ring of FAD and the hydroxyl oxygen atom of Thr66, which is considered to be a key residue in the release of a proton from the N5 atom. The isoalloxazine ring of FAD in the reduced form is flat as in the oxidized form and stacked together with the nicotinamide ring of NAD
. Determination of the oxidized b5R structure, including the hydrogen atoms, determined at 0.78 resolution revealed the details of a hydrogen-bonding network from the N5 atom of FAD to His49 via Thr66. Both of the reduced and oxidized b5R structures explain how backflow in this catalytic cycle is prevented and the transfer of electrons to one-electron acceptors such as Cb5 is accelerated. Furthermore, crystallographic analysis by the cryo-trapping method suggests that re-oxidation follows a two-step mechanism. These results provide structural insights into the catalytic cycle of b5R.
Wakasa, Arimitsu*; Fukuyama, Atsushi*; Murakami, Sadayoshi*; Miki, Masayuki*; Yokoyama, Masayuki*; Sato, Masahiko*; Toda, Shinichiro*; Funaba, Hisamichi*; Tanaka, Kenji*; Ida, Katsumi*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Miki, Masayuki*; Fukuyama, Atsushi*; Honda, Mitsuru
Plasma and Fusion Research (Internet), 5, p.S2040_1 - S2040_4, 2010/12
Wada, Atsushi*; Watanabe, Masayuki; Yamanoi, Yoshinori*; Nankawa, Takuya; Namiki, Kosuke*; Yamasaki, Mikio*; Murata, Masaki*; Nishihara, Hiroshi*
Bulletin of the Chemical Society of Japan, 80(2), p.335 - 345, 2007/02
Times Cited Count：22 Percentile：57.38(Chemistry, Multidisciplinary)Lanthanide complexes with linear and cyclic octadentate oligopyridine-amine ligands were synthesized, and their molecular structures were determined by single-crystal X-ray crystallography. All of the complexes had a distorted capped square antiprism (CSAP) geometry, and the coordination environments of lanthanide complexes were more distortedfor the complexes with the linear ligand than those with the cyclic ligand. The Eu
complexes with the linear ligand showed more intense emissions, which were attributed to the 
D
F
transition, than the complex withthe cyclic ligand in acetonitrile, which can be attributed to the distortion in the coordination environments. These results indicate that the coordination environments of lanthanide complexes, and thus the luminescence properties, can be controlled by tuning the geometrical structures of polydentate ligands.
Watanabe, Masayuki; Nankawa, Takuya*; Yamada, Teppei*; Kimura, Takaumi; Namiki, Kosuke*; Murata, Masaki*; Nishihara, Hiroshi*; Tachimori, Shoichi
Inorganic Chemistry, 42(22), p.6977 - 6979, 2003/11
Times Cited Count：34 Percentile：75.29(Chemistry, Inorganic & Nuclear)A tripodal ligand, tris(2-pyridyl)carbinol affords a novel tetradentate coordination mode in homodinuclear lanthanide complexes, which exhibit remarkably short distance between the metal ions. Strong fluorescence of Eu(III) and Tb(III) complexes with the ligand demonstrate that the ligand has a suitable excited state for energy transfer from the ligand to Eu(III) and Tb(III) center.
Watanabe, Masayuki; Nankawa, Takuya; Wada, Atsushi*; Namiki, Kosuke*; Murata, Masaki*; Nishihara, Hiroshi*; Kimura, Takaumi
no journal, ,
A tripodal ligand, tris(2-pyridyl)carbinol affords a novel tetradentate coordination mode in homodinuclear lanthanide complexes, which exhibit remarkably short distances between metal ions. Structures of dinuclear complexes synthesized from triflates exhibited the same structure other than the difference in the bond lengths which was induced by lanthanide contraction across the lanthanide series from Pr to Lu. In these complexes, the distance between two lanthanide ions was remarkably short. In this study the same type of dinuclear complexes were synthesized from nitrates. The nitrate ion can coordinate in both monodentate fand bidentate fashions. Since ionic radii are dependent upon the coordination number, nitrate could affect the metal-metal distance. In fact, dinuclear complexes exhibited longer distance between lanthanide ions than the triflates due to the increase of ionic radii of lanthanide ions. Some features of these dinuclear systems, which are induced from the difference of metal-metal distance, will be discussed in the presentation.
