Stochastic searches and NMR experiments on four Lewis A analogues: NMR experiments support some flexibility around the fucosidic bond

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• 作者：France-Isabelle Auzanneau ; Trudy A. Jackson ; Liang Liao
• 关键词：Carbohydrates ; Conformation analysis ; NMR spectroscopy ; Lewis A
• 刊名：Bioorganic and Medicinal Chemistry
• 出版年：2012
• 出版时间：1 September, 2012
• 年：2012
• 卷：20
• 期：17
• 页码：5085-5093
• 全文大小：906 K

文摘

We have compared the conformational behavior of three Le^a analogues with that of Le^a using stochastic searches (MOE2005) and selective ROESY experiments. In the analogues either or both the ¦Â-d-Gal and ¦Á-l-Fuc residues were replaced by ¦Â-d-Glc and ¦Á-l-Rha units, respectively. All compounds showed similar behavior and even though four conformational families were identified, the calculations and NMR experiments support that the ¡®stacked conformation¡¯ known for Le^a is predominant for all analogues. Interestingly, ROESY showed a correlation between H-1 Fuc/Rha and H-3 GlcNAc which, although small, could be seen in all analogues. For two compounds, the corresponding distance was measured and found to be shorter (¡«3.7 ?) than that found in the global minimum (4.5 ?). While one published study suggests some motion around the fucosidic bond, this constitutes the first experimental evidence supporting such flexibility. Our MD simulation (Amber10/Glycam06) on Le^a was in full agreement with previous studies which described a rigid conformation for this branched trisaccharide. Thus, NMR seems to indicate that these dynamic studies are underestimating flexibility around the fucosidic bond.