Conformational energy calculations and proton nuclear Overhauser enhancements reveal a unique conformation for blood group A oligosaccharides
Conformational energy calculations and proton nuclear Overhauser enhancements reveal a unique conformation for blood group A oligosaccharides
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构象能计算和质子核 Overhauser 增强揭示了 A 型血寡糖的独特构象
DOI：
10.1021/ja00280a010
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发表时间：
1986
影响因子：
15
通讯作者：
B. Rao
中科院分区：
文献类型：
--
作者：
C. Bush;Zhenning Yan;B. Rao
一系列的血液A型活性低聚糖含有从4到10个糖残基的H NMR谱已被完全分配，和定量的核Overhauser增强（NOE）已被测量之间的质子分离的已知距离内的吡喃糖苷环。异头质子和糖苷配基糖的质子之间的NOE的观察以及远环质子之间的小影响表明寡糖具有明确的构象。对三糖Fuc（-12）（GalNAc（-13））-GalUS-O-me进行构象能计算，其模拟血型A寡糖的非还原性末端片段。用肽和碳水化合物中常用的三种不同势能函数进行计算，得到了几种最低能量构象。在构象模型的NOE计算中，调整旋转相关时间以拟合T1和环内NOE。NOE作为糖苷二面角的函数的计算的地图的比较表明，只有一个小区域的构象空间是一致的实验数据的血型A四糖alditol。这种构象发生在所有三个能量计算的能量最小值。NOE的温度依赖性意味着寡糖采用不随温度变化的单一刚性构象。«少
The H NMR spectra of a series of blood group A active oligosaccharides containing from four to ten sugar residues have been completely assigned, and quantitative nuclear Overhauser enhancements (NOE) have been measured between protons separated by known distances within the pyranoside ring. The observation of NOE between anomeric protons and those of the aglycon sugar as well as small effects between protons of distant rings suggests that the oligosaccharides have well-defined conformations. Conformational energy calculations were carried out on a trisaccharide, Fuc( -1 2)(GalNAc( -1 3))-GalUS -O-me, which models the nonreducing terminal fragments of the blood group A oligosaccharides. The results of calculations with three different potential energy functions which have been widely used in peptides and carbohydrates gave several minimum energy conformations. In NOE calculations from conformational models, the rotational correlation time was adjusted to fit T1's and intra-ring NOE. Comparison of calculated maps of NOE as a function of glycosidic dihedral angles showed that only a small region of conformational space was consistent with experimental data on a blood group A tetrasaccharide alditol. This conformation occurs at an energy minimum in all three energy calculations. Temperature dependence of the NOE implies that the oligosaccharides adopt single rigidmore » conformations which do not change with temperature.« less