Volume 08, No.6
November issue 2003
1. SPring-8の現状／PRESENT STATUS OF SPring-8
日本原子力研究所 関西研究所 放射光科学研究センター Synchrotron Radiation Research Center, Kansai Research Establishment, JAERI、（財）高輝度光科学研究センター ビームライン・技術部門 Beamline Division, JASRI、理化学研究所 播磨研究所 Harima Institute, RIKEN
- The performance of sagittal focusing for hard X-rays with a cylindrical bent crystal at the SPring-8 is described. The bending mechanism is designed for the SPring-8 standard bending-magnet beamlines. Two-dimensional focusing is achievable by combining sagittal horizontal focusing and vertical focusing mirror. The results underline that the two-dimensional focusing was achieved in the wide energy range by using an adjustable-inclined double crystal monochromator.
3. 最近の研究から／FROM LATEST RESEARCH
X-ray structure analysis of photo-induced reaction intermediates of proteins
– Direct observation of photo-induced tertiary structural changes in human hemoglobin –
高エネルギー加速器研究機構 物質構造科学研究所 Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK)、理化学研究所 播磨研究所 Harima Institute, RIKEN、横浜市立大学大学院 総合理学研究科 Graduate School of Integrated Science, Yokohama City University、自治医科大学 生理学講座 Department of Physiology, Jichi Medical School
- Proteins are encoded in genes and play a wide variety of functions in life. Three dimensional (3-D) protein structures, determined by conventional X-ray crystallographic technique and also by multidimensional nuclear magnetic resonance (NMR) spectroscopy, have provided a solid base for understanding their 3-D architecture. However, relatively little information has been extracted from these studies about how the proteins do their tasks, because the 3-D structural information is essentially static. To understand the mechanistic details of how proteins function, it is crucial to know the dynamic features of the events that give rise to their designed functions. We have been working on cryogenic trapping technique of photoactive intermediates of proteins at the BL44B2, SPring-8, and here we present our experimental setup and direct observation of photo-induced tertiary structural changes in human hemoglobin.
（財）高輝度光科学研究センター 利用研究促進部門Ⅰ Material Science Division, JASRI、京都大学大学院 工学研究科 Graduate School of Engineering, Kyoto University、大阪女子大学 理学部 Faculty of Science, Osaka Women's University、岡山大学 理学部 Faculty of Science, Okayama University、大阪大学 極限科学研究センター Research Center for Materials Science at Extreme Conditions, Osaka University、名古屋大学大学院 工学研究科 Graduate School of Engineering, Nagoya University
- We report the direct observation of dioxygen molecules physisorbed in the nanochannels of a microporous copper coordination polymer by the MEM (maximum entropy method)/Rietveld method, using in situ high-resolution synchrotron x-ray powder diffraction measurements. The obtained MEM electron density revealed that van der Waals dimers of physisorbed O2 locate in the middle of nanochannels and form a one-dimensional ladder structure aligned to the host channel structure. The observed magnetic susceptibilities is characteristic of the confined O2 molecules in one-dimensional nanochannels of CPL-1 (coordination polymer 1 with pillared layer structure).
Alter native Tertiary Structure of tRNA for Recognition by a Post – Transcriptional Modification Enzyme
東京大学大学院 理学系研究科 Graduate School of Science, The University of Tokyo
- Transfer RNA (tRNA) canonically has the clover-leaf secondary structure with the acceptor, D, anticodon, and T arms, which are folded into the L-shaped tertiary structure. To strengthen the L form, post-transcriptional modifications occur on nucleotides buried within the core, but the modification enzymes are paradoxically inaccessible to them in the L form. In this study, we determined the crystal structure of tRNA bound with archaeosine tRNA-guanine transglycosylase, which modifies G15 of the D arm in the core, by using the X-ray diffraction data set collected at BL41XU, SPring-8. The bound tRNA assumes an alternative conformation (“λform”) drastically different from the L form. All of the D arm secondary base pairs and the canonical tertiary interactions are disrupted. Furthermore, a helical structure is reorganized, while the rest of the D arm is single-stranded and protruded. Consequently, the enzyme precisely locates the exposed G15 in the active site, by counting the nucleotide number from G1 to G15 in the λform.
4. 研究会等報告／WORKSHOP AND COMMITTEE REPORT
Joint Workshop by SPring-8 Beamline and Reseach Subgroups ; “X-ray Inelastic Scattering and Materials Science II”