日本結晶学会誌
Online ISSN : 1884-5576
Print ISSN : 0369-4585
ISSN-L : 0369-4585
56 巻 , 4 号
選択された号の論文の21件中1~21を表示しています
特集
4.生物研究における結晶学-生命現象の可視化への挑戦-
連載企画 産業界で活躍する結晶学
最近の研究から
  • 白澤 徹郎, 高橋 敏男
    2014 年 56 巻 4 号 p. 263-269
    発行日: 2014/08/31
    公開日: 2014/09/03
    ジャーナル フリー
    We report our recent approach to the direct structure analysis of X-ray crystal truncation rod scattering data for thinfilm interface structures. Our approach is a combination use of a holographic method and the iterative phase-retrieval methods, which are respectively used for the direct construction of the initial structure model and the final refinement of the model. Results of the direct structure analysis for a Bi thinfilm and Bi/Bi2Te3 topological insulator thinfilm are presented. The holographic method successfully imaged out interfacial wetting layers for both the systems. Structural parameters were derived quantitatively by using the phaseretrieval methods, which are relevant to understanding electronic properties and film growth mechanisms at the interfaces.
  • 海野 昌喜, 齋藤 正男
    2014 年 56 巻 4 号 p. 270-276
    発行日: 2014/08/31
    公開日: 2014/09/03
    ジャーナル フリー
    Heme oxygenase(HO)is a unique enzyme that catalyzes the conversion of heme to biliverdin,carbon monoxide and free iron. The enzyme is present in not only mammal but also plant, algae and pathogenic bacteria. In order to understand mechanisms of the substrate binding and the product release of bacterial HO, we have determined the crystal structures of the substratefree, Fe3+-biliverdin-bound, biliverdin-bound forms and reaction intermediates between the latter two states of HmuO, a heme oxygenase from Corynebacterium diphtheriae. In addition to these high resolution structures, we have conducted molecular dynamics simulation for the hemebinding and bilivedin-release. The substrate-free HmuO shows a widely open active site which is formed by a partially unwounded α-helix. The water molecule cluster is rearranged when the substrate is bound to HmuO. Upon reduction of Fe3+ to Fe2+, the axial histidine dissociates from Fe2+, followed by the relase of Fe2+ from the biliverdin group. The water molecule comes into the resulted space and forms hydrogen bonds between the axial histidine and the substrate biliverdin. From these results, we can discuss the molecular mechanism of HmuO at atomic level.
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