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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >The structures of T 6, T 3R 3 and R 6 bovine insulin: Combining X-ray diffraction and absorption spectroscopy
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The structures of T 6, T 3R 3 and R 6 bovine insulin: Combining X-ray diffraction and absorption spectroscopy

机译：6 T, T的结构3 R 3和6的牛胰岛素:结合x射线衍射和吸收光谱

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摘要

The crystal structures of three conformations, T 6, T 3R 3 and R 6, of bovine insulin were solved at 1.40, 1.30 and 1.80 ? resolution, respectively. All conformations crystallized in space group R 3. In contrast to the T 6 and T 3R 3 structures, different conformations of the N-terminal B-chain residue PheB1 were observed in the R 6 insulin structure, resulting in an eightfold doubling of the unit-cell volume upon cooling. The zinc coordination in each conformation was studied by X-ray absorption spectroscopy (XAS), including both EXAFS and XANES. Zinc adopts a tetrahedral coordination in all R 3 sites and an octahedral coordination in T3 sites. The coordination distances were refined from XAS with a standard deviation of 0.01 ?. In contrast to the distances determined from the medium-resolution crystal structures, the XAS results were in good agreement with similar coordination geometries found in small molecules, as well as in other high-resolution insulin structures. As the radiation dose for XRD experiments is two orders of magnitude higher compared with that of XAS experiments, the single crystals were exposed to a higher degree of radiation damage that affected the zinc coordination in the T3 sites in particular. Furthermore, XANES spectra for the zinc sites in T 6 and R 6 insulin were successfully calculated using finite difference methods and the bond distances and angles were optimized from a quantitative XANES analysis.
机译：三个构象的晶体结构,T6 T 3 R 3和6的牛胰岛素被解决为1.40,1.30和1.80吗?分别。空间群R 3。3结构,不同的构象氨基端B-chain残渣PheB1被观察到6 R胰岛素结构,导致一个8倍翻单胞的体积冷却。构象研究了x射线吸收光谱学(xa),包括EXAFS和黄嘌呤。所有R 3网站和一个八面体协调T3网站。从标准差的xa & 0.01 ?。与的距离决定的中分辨率晶体结构,xa结果是在良好的协议与相似协调几何图形中发现小分子,以及其他高分辨率胰岛素结构。实验要高两个数量级与xa实验相比,单身晶体暴露在更高程度的辐射损伤,影响锌特别是在T3网站的协调。此外,锌黄嘌呤光谱的网站T 6 R 6胰岛素被成功计算使用有限差分方法和债券距离和角度进行了优化定量分析黄嘌呤。

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