Adam O, Riviére M, Vercellone A, Monsan P F, Puzo G
Institut de Pharmacologie et de Biologie Structurale du CNRS, Toulouse, France.
Eur J Biochem. 1996 Oct 15;241(2):602-10. doi: 10.1111/j.1432-1033.1996.00602.x.
The capsular polysaccharide (CPS) produced by the non-pathogenic Klebsiella strain I-714, selected for its immunomodulating activity, has been purified and almost completely detoxified in a previous study [Adam, O., Vercellone, A., Paul, F., Monsan, P. F. & Puzo, G. (1995) Anal. Biochem. 225, 321-327]. The present report concerns the structural elucidation of this CPS by several one-dimensional and two-dimensional 1H-NMR and 13C-NMR experiments performed on the native molecule. It was found to be a high molecular-mass branched polymer constituted by a hexasaccharide repeating unit of following structure: 4)-alpha-L-Rhap-(1-->3)-beta-D-Galp-(1-->2)-alpha-L-Rhap-(1- ->4)-beta-D- GlcpA-(1-->3)-¿alpha-L-Rhap-(1-->2)-¿-alpha-D-Galp-(1. The presence of two glycosidic substitutions on the Galp residue resulted in a strong overlapping of its proton signals, preventing direct assignment of both proton and carbon resonances. However, assignment could be achieved using the two-bond and three-bond 1H-13C heteronuclear coupling observed in the 1H-13C heteronuclear multiple-bond correlation (HMBC) spectrum.
非致病性克雷伯菌菌株I-714产生的荚膜多糖（CPS）因其免疫调节活性而被选用，在先前的一项研究中已被纯化并几乎完全解毒[亚当，O.，韦尔切洛内，A.，保罗，F.，蒙桑，P.F.和普佐，G.（1995年）《分析生物化学》225卷，321 - 327页]。本报告涉及通过对天然分子进行的几项一维和二维1H-NMR及13C-NMR实验对该CPS的结构解析。结果发现它是一种高分子量的支链聚合物，由具有以下结构的六糖重复单元构成：4)-α-L-鼠李糖基-(1→3)-β-D-半乳糖基-(1→2)-α-L-鼠李糖基-(1→4)-β-D-葡萄糖醛酸基-(1→3)-[α-L-鼠李糖基-(1→2)]-[α-D-半乳糖基-(1。半乳糖残基上两个糖苷取代基的存在导致其质子信号强烈重叠，阻碍了质子和碳共振的直接归属。然而，使用在1H-13C异核多键相关（HMBC）谱中观察到的双键和三键1H-13C异核耦合可以实现归属。
