Crystal Structure of A-amylose: A Revisit from Synchrotron Microdiffraction Analysis of Single Crystals
Crystal Structure of A-amylose: A Revisit from Synchrotron Microdiffraction Analysis of Single Crystals
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DOI：
10.1021/ma801789j
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发表时间：
2009-02-24
期刊：
影响因子：
5.5
通讯作者：
Riekel, C.
中科院分区：
文献类型：
--
作者：
Popov, D.;Buleon, A.;Riekel, C.
利用微米级单晶的同步辐射显微衍射数据，对A-直链淀粉晶体的三维结构进行了修正，得到了A-淀粉颗粒的晶区模型。由此产生的数据集允许使用通常用于小分子而不是聚合物的常规X射线结构确定技术来确定结构。虽然这种改进的结构的总体特征与以前的结构测定没有太大的不同，但高分辨率的衍射图(这在结晶聚合物中是不常见的)允许解析重要的新的精细细节，这些细节包括由于两个晶体内水分子的出现而导致的直链淀粉双螺旋的扭曲，以及涉及葡萄糖部分的每个一级和二级羟基的紧密氢键网络。水分子位于不连续的口袋中，彼此互不干扰。此外，新结构的改进表明了单位细胞内直链淀粉分子的“平行向下”组织，而不是以前的“平行向上”模型。这一新特征表明，在晶体中，直链淀粉分子的非还原末端朝向单位晶胞的c轴方向。对这一几何结构的描述对于将A-淀粉颗粒的结晶学与其超微结构及其生物合成方式相关联是重要的。在这里，我们首次介绍了利用同步辐射显微衍射技术在微米级聚合物单晶上收集的完整X射线数据集对聚合物晶体结构的分辨。这一成就是一个实质性的进步，它为更多的研究开辟了道路，因为生长聚合物和生物聚合物单晶的技术已经很成熟。
The three-dimensional structure of A-amylose crystals, as a model of the crystal domains of A-starch granule was revised using synchrotron radiation microdiffraction data collected from individual micron-sited single crystals. The resulting data sets allowed a determination of the structure with conventional X-ray structure determination techniques normally used for small molecules and not for polymers. Whereas the gross features of this improved structure do not differ extensively from previous structure determination, the high resolution of the diffraction diagrams, which is unusual for a crystalline polymer, allowed the resolution of important new fine details, These include a distortion of the amylose double helices resulting from the occurrence of two intracrystalline molecules of water and a tight network of hydrogen bonds involving each of the primary and secondary hydroxyl groups of the glucosyl moieties. Water Molecules are located in discrete pockets that do not interfere with one another. In addition, the refinement of the new structure indicates a "parallel-down" organization of the amylose molecules Within the unit cell as opposed to the previous "parallel-up" model. This new feature indicates that within the crystals the nonreducing ends of the amylose molecules are oriented toward the c-axis direction of the unit cell. The description of this geometry is important to correlate the crystallography of the granules of A-starch with their ultrastructure and their mode of biosynthesis. Here, we present for the first time the resolution of the structure of a polymer crystal front a full X-ray data set collected on micron-sized polymer single crystals using synchrotron radiation microdiffraction. This achievement is a substantial advance, which opens the way to many more Studies since the technique Of growing polymer and biopolymer single crystals is well established.