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Acta Cryst. (2014). A70, C406
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Conformational mobility is essential to many protein functions and design of therapies for a broad spectrum of human diseases depends on a deep understanding the linkage between protein structure, intramolecular motions and function. Methods for screening small molecules and mutations that alter fluctuations are essential for improved understanding of this linkage. To what extent do changes in intramolecular motions lead to changes in function? To address this question, we are using a combination of wide-angle x-ray solution scattering (WAXS) and molecular dynamics (MD) to generate novel insights into the magnitude, form and functional consequences of intramolecular motions of proteins in solution. WAXS has proven unexpectedly sensitive to the intramolecular motions of proteins in solution and can detect changes in flexibility generated by single amino acid replacements or binding of small molecule ligands. Here we formulate the effect of structural fluctuations on WAXS data in such a way as to make possible direct experimental assessment of the range of motion that proteins explore in solution. The approach differs from other strategies by treating it as an inverse source problem, deriving flexibility parameters directly from data rather than from an ensemble of structures generated to predict the data.

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Acta Cryst. (2014). A70, C1556
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LixMn2O4 is attracting much interest as a positive electrode material for Li-ion rechargeable batteries. Redox orbitals of LixMn2O4 under the charge or discharge process are not fully understood yet. Some band calculations have pointed out that intercalated Li 2s electrons occupy Mn sites or down-spin Mn 3d bands [1,2]. On the other hand molecular orbital calculation has reported the Li 2s electrons occupy O sites [3]. To clarify the redox orbital is important to understand the electrochemical reaction in the electrodes. In this study we have investigated the redox orbitals in LixMn2O4 by X-ray Compton scattering. Compton profiles were measured at BL08W of SPring-8, Japan. The energy of incident X-rays were 115keV and the scattering angle was 165 degrees. Energy spectra of Compton scattered X-rays were measured using a two-dimensional position sensitive detector. The measurements were performed under room temperature and vacuum conditions. Samples are polycrystalline of LixMn2O4 (x=0.5, 1.1, 1.2, 1.8 and 2.0). In order to clarify the redox orbitals of LixMn2O4, we obtained difference Compton profiles which represent the incremental electronic states on Li intercalation. Comparing the results with KKR-CPA and DFT calculations, we found that the O 2p bands play an important role for the redox process in LixMn2O4 with 0
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