ACCURATE X-RAY-DIFFRACTION ANALYSIS OF FIBROUS POLYSACCHARIDES CONTAINING PYRANOSE RINGS .1. LINKED-ATOM APPROACH
ACCURATE X-RAY-DIFFRACTION ANALYSIS OF FIBROUS POLYSACCHARIDES CONTAINING PYRANOSE RINGS .1. LINKED-ATOM APPROACH
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DOI：
10.1039/p29720000324
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发表时间：
1972-01-01
期刊：
影响因子：
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通讯作者：
SCOTT, WE
中科院分区：
文献类型：
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作者：
ARNOTT, S;SCOTT, WE
聚合物的X-射线衍射数据本身很少足以确定原子位置在十分之几埃恩斯特罗姆以内。当需要这种准确性时，聚合物衍射数据必须得到相关单体准确分析的立体化学数据的补充。连接原子最小二乘法是实现不同类型数据的必要综合的一种逻辑和方便的程序。该程序已被广泛用于分析多核苷酸和多肽，但到目前为止还不是多糖。由于多糖的精确结构的确定既依赖于聚合物本身的衍射数据，也取决于额外的数据，如键长和键角，我们概述了由适当小分子单晶的X射线衍射分析确定的这些量的值。作为连接原子最小二乘法应用的例子，我们提出并讨论了标准的α-和β-D-葡萄糖环的制备以及甲壳素和ι-卡拉胶的初步分子模型。
X-Ray diffraction data from polymers are, by themselves, rarely sufficient to allow determination of atomic positions within a few tenths of an Ångstrom. When this accuracy is required, the polymer diffraction data have to be supplemented by stereochemical data from accurate analyses of relevant monomers. The linked-atom least-squares approach is a logical and convenient procedure for achieving the necessary synthesis of different types of data. The procedure has been used extensively in analysing polynucleotides and polypeptides but not, so far, polysaccharides. Its adaptation for these is described, with particular attention being paid to the precise conformations of rings that dominate the geometry of these polymers.Since the determination of accurate structures of polysaccharides depends both on diffraction data from the polymers themselves and on additional data such as bond-lengths and bond-angles, we present a survey of the values of these latter quantities as determined by X-ray diffraction analysis of single crystals of appropriate small molecules.As examples of the application of linked-atom least-squares methods we present and discuss the preparation of standard α- and β-D-glucose rings and preliminary molecular models of chitin and ι-carrageenan.