Conformational distribution function of a disaccharide in a liquid crystalline phase determined using NMR spectroscopy.
Conformational distribution function of a disaccharide in a liquid crystalline phase determined using NMR spectroscopy.
复制标题
使用核磁共振波谱测定液晶相中二糖的构象分布函数。
DOI：
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发表时间：
2002
影响因子：
15
通讯作者：
A. Maliniak
中科院分区：
文献类型：
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作者：
Baltzar Stevensson;C. Landersjö;G. Widmalm;A. Maliniak
提出了一种新的方法来分析一般的NMR参数，特别是残余偶极耦合。该方法，使建设的构象分布函数，被施加到溶解在稀液晶中的二糖。我们的方法依赖于两个模型，已被频繁用于解释偶极耦合液晶：（i）添加剂势模型（AP）和（ii）最大熵方法（ME）。然而，这些模型受到严重的限制：AP模型需要扭转势的函数形式的先验知识，而ME方法给出了最平坦的可能分布，这导致对低取向阶系统的不正确描述。本文提出的程序（APME）是有效的低阶限制。的intraresidue偶极耦合被用来确定的取向顺序，而构象分布函数是从interresidue偶极和J耦合，连同NOE。实验和计算的NMR参数之间的非常好的协议进行了观察。尝试使用单个分子构象分析实验数据导致了显著更大的误差。本研究表明，APME方法可以作为一种工具，在柔性分子的结构测定在稀液晶。
A new approach is proposed for analysis of NMR parameters in general, and residual dipolar couplings in particular. The method, which enables construction of the conformational distribution function, is applied to a disaccharide dissolved in a dilute liquid crystal. Our approach rests on two models that have been frequently used for interpretations of dipolar couplings in liquid crystals: (i) the additive potential model (AP) and (ii) the maximum entropy method (ME). These models suffer, however, from serious limitations: the AP model requires an a priori knowledge of the functional form of the torsional potential, while the ME approach gives the flattest possible distribution, which results in an incorrect description of systems with low orientational order. The procedure presented herein (APME) is valid in the low-order limit. The intraresidue dipolar couplings were used to determine the orientational order, while the conformational distribution function is constructed from the interresidue dipolar- and J couplings, together with NOEs. Very good agreement between experimental and calculated NMR parameters was observed. An attempt to analyze the experimental data using a single molecular conformation resulted in significantly larger errors. This study demonstrates that the APME method can be used as a tool in structure determination of flexible molecules in dilute liquid crystals.