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首页> 外文期刊>Biopolymers: Original Research on Biomolecules and Biomolecular Assemblies >A FLEXIBLE MODEL FOR THE CELL WALL POLYSACCHARIDE OF STREPTOCOCCUS MITIS J22 DETERMINED BY THREE-DIMENSIONAL C-13 EDITED NUCLEAR OVERHAUSER EFFECT SPECTROSCOPY AND C-13-H-1 LONG-RANGE COUPLING CONSTANTS COMBINED WITH MOLECULAR MODELING
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A FLEXIBLE MODEL FOR THE CELL WALL POLYSACCHARIDE OF STREPTOCOCCUS MITIS J22 DETERMINED BY THREE-DIMENSIONAL C-13 EDITED NUCLEAR OVERHAUSER EFFECT SPECTROSCOPY AND C-13-H-1 LONG-RANGE COUPLING CONSTANTS COMBINED WITH MOLECULAR MODELING

机译：用三维C-13编辑的核超分子谱和C-13-H-1长范围耦合常数与分子建模相结合确定米氏链球菌J22细胞壁多糖的灵活模型

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We report on the conformation of a tetrasaccharide fragment in the repeating subunit of the cell wall polysaccharide of Streptococcus mitis J22, a receptor for the lectin of Actinomyces viscosus T14V in a bacterial coaggregation that is important in the ecological interactions of oral bacteria. Although there is considerable overlap of the H-1-nmr signals, some cross peaks can be extracted from conventional two-dimensonal nuclear Overhauser effect spectroscopy (NOESY) data on the polysaccharide. These data cannot befit to a single conformation of the tetrasaccharide fragment. Therefore we have prepared a polysaccharide sample fully enriched in C-13 from which we have determined accurate NOESY cross-peak volumes in a three-dimensional heteronuclear-resolved spectrum that allows accurate determination of many more NOESY cross peaks than does conventional two-dimensional spectroscopy. We have also used the C-13 enriched polysaccharide to measure accurate values of long-range C-13-H-1 coupling constants that can be correlated with glycosidic dihedral angles. Molecular modeling calculations on the polysaccharide fragment, including molecular dynamics simulations, identify multiple low-energy conformations This result is to be contrasted with previous calculations on blood group oligosaccharides in our laboratory using similar methods that showed relatively rigid conformations with little flexibility of the glycosidic linkages. The present NOESY and (3)J(CH), data can be reconciled with a model for the antigenic tetrasaccharide in which three distinct conformations are in fast exchange. We propose that some carbohydrate epitopes such as those of the blood group oligosaccharides are relatively rigid while others such as the tetrasaccharide fragment in these studies exhibit much greater flexibility. (C) 1996 John Wiley & Sons, Inc. [References: 34]
机译：我们报道了链球菌J22细胞壁多糖的重复亚基中的四糖片段的构象，链霉菌是粘性的放线菌T14V的凝集素，在细菌聚集中对口腔细菌的生态相互作用很重要。尽管H-1-nmr信号有相当多的重叠，但可以从多糖的常规二维核核Overhauser效应光谱（NOESY）数据中提取一些交叉峰。这些数据不能适合四糖片段的单一构象。因此，我们准备了一个完全富含C-13的多糖样品，从中我们已经确定了三维异核分辨光谱中准确的NOESY交叉峰体积，与传统的二维光谱法相比，该光谱可以准确测定更多的NOESY交叉峰。 。我们还使用了富含C-13的多糖来测量可与糖苷二面角相关的远程C-13-H-1偶联常数的准确值。多糖片段的分子建模计算，包括分子动力学模拟，可识别多个低能构象。该结果与以前在我们实验室中对血型寡糖的计算结果相反，后者使用相似的方法，显示出相对刚性的构象，糖苷键的灵活性很小。当前的NOESY和（3）J（CH）数据可以与抗原性四糖模型相吻合，其中三个不同的构象正在快速交换。我们提出，在这些研究中，某些碳水化合物表位（如血型寡糖的表位）相对较硬，而其他表位（如四糖片段）表现出更大的灵活性。 （C）1996 John Wiley＆Sons，Inc. [参考：34]

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