Azurmendi Hugo F, Martin-Pastor Manuel, Bush C Allen
Department of Chemistry and Biochemistry, University of Maryland-Baltimore County, Baltimore, MD 21250, USA.
Biopolymers. 2002 Feb;63(2):89-98. doi: 10.1002/bip.10015.
The conformations of the histo-blood group carbohydrate antigens Lewis X (Le(x)) and Lewis A (Le(a)) were studied by NMR measurements of one-bond C-H residual dipolar couplings in partially oriented liquid crystal solutions. A strategy for rapid calculation of the difference between theoretical and experimental dipolar couplings of a large number of model structures generated by computer simulations was developed, resulting in an accurate model structure for the compounds. Monte Carlo simulations were used to generate models for the trisaccharides, and orientations of each model were sought that could reproduce the experimental residual dipolar coupling values. For both, Le(a) and Le(x), single low energy models giving excellent agreement with experiment were found, implying a compact rigidly folded conformation for both trisaccharides. The new approach was also applied to the pentasaccharides lacto-N-fucopentaose 2 (LNF-2) and lacto-N-fucopentaose 3 (LNF-3) proving its consistency and robustness. For describing the conformation of tightly folded oligosaccharides, a definition for characterization of ring planes in pyranoside chairs is proposed and applied to the analysis of the relation between the fucose and galactose residues in the epitopes, revealing the structural similarity between them.
通过对部分取向液晶溶液中一键C-H剩余偶极耦合进行核磁共振测量，研究了组织血型碳水化合物抗原Lewis X（Le(x)）和Lewis A（Le(a)）的构象。开发了一种快速计算计算机模拟生成的大量模型结构的理论和实验偶极耦合差异的策略，从而得到了化合物的精确模型结构。使用蒙特卡罗模拟生成三糖模型，并寻找能够重现实验剩余偶极耦合值的每个模型的取向。对于Le(a)和Le(x)，均发现了与实验结果高度吻合的单一低能量模型，这意味着两种三糖均具有紧密刚性折叠的构象。新方法还应用于五糖乳糖-N-岩藻五糖2（LNF-2）和乳糖-N-岩藻五糖3（LNF-3），证明了其一致性和稳健性。为了描述紧密折叠寡糖的构象，提出了一种用于表征吡喃糖苷椅中环平面的定义，并将其应用于分析表位中岩藻糖和半乳糖残基之间的关系，揭示了它们之间的结构相似性。
