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首页> 外文期刊>Chemistry: A European journal >Synthesis and Conformational Analysis of a Conformationally Constrained Trisaccharide, adn Complexation Properties with Concanavalin A
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Synthesis and Conformational Analysis of a Conformationally Constrained Trisaccharide, adn Complexation Properties with Concanavalin A

机译：伴刀豆球蛋白A的构象约束三糖的合成及构象分析

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摘要

The trisaccharide #beta#-D-GlcNAc(1->2)-#alpha#-D-Man(1->3)D-Man is a fragmetn fo a biantennary glycan that is recognized by #alpha#-D-Man-specific lectins such as concanavalin A (ConA), Lathyrus ochrus lectin, lentil lectin, and can badopt several conformations upon binding. To probe the importance of loss of flexibility of a saccharide during binding with ConA this trisaccharide has been synthesized in a conformationally constrained form where a methylene acetal bridge mimics a GlcNAc-O-6”…Man-O-4 intramolecualr hydrogen bond. Microcalorimetry measurements revealed that the conformationally constrained compound has a more favorable entropy term but this term is offset by a smaller enthalpy term. NMR spectroscopic studies have shown that the cyclic compound is indeed considerably less flexible than the linear compound and both compounds adopt mainly one conformation. SYBYL software together with energy parameters appropriate for carbohydrates was used for a systematic conformational search. Teh linear compound is very flexible. A clustering method determined seven main conformational families. Six possible conformational families were identified for the cyclic compound when considering the orientations of the #beta#GlcNAc(1 -> 2)Man and #alpha##beta#Man-(1 -> 3)Man glycosidic bonds. The central mannose residue was docked in the binding site of ConA and the complex was refined. The results are compared with crystal structures of legume lectin - oligosaccharide complexes and with the NMR and thermodynamic data.
机译：三糖＃beta＃-D-GlcNAc（1-> 2）-＃alpha＃-D-Man（1-> 3）D-Man是被＃alpha＃-D-Man识别的双天线聚糖的芳香剂特异性凝集素，例如伴刀豆球蛋白A（ConA），山thy豆och凝集素，小扁豆凝集素，在结合时会选择几种构象。为了探究在与ConA结合过程中糖失去柔韧性的重要性，该三糖以构象约束形式合成，其中亚甲基缩醛桥模拟GlcNAc-O-6”…Man-O-4分子内氢键。微量量热法测量显示，构象受约束的化合物具有更有利的熵项，但是该项被较小的焓项所抵消。 NMR光谱研究表明，环状化合物的柔韧性确实比线性化合物差得多，并且两种化合物主要采用一种构象。 SYBYL软件与适合碳水化合物的能量参数一起用于系统的构象搜索。线性化合物非常灵活。聚类方法确定了七个主要构象家族。当考虑＃beta＃GlcNAc（1-> 2）Man和＃alpha ## beta＃Man-（1-> 3）Man糖苷键的方向时，为环状化合物确定了六个可能的构象家族。将中央甘露糖残基对接在ConA的结合位点，并纯化复合物。将结果与豆科植物凝集素-寡糖复合物的晶体结构以及NMR和热力学数据进行了比较。

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