Cherniak R, Jones R G, Slodki M E
Department of Chemistry, Georgia State University, Atlanta 30303.
Carbohydr Res. 1988 Nov 1;182(2):227-39. doi: 10.1016/0008-6215(88)84005-9.
A glucuronomannan (GM) was derived by removal, through Smith degradation, of xylose from the native (3-O-acetylglucurono)xylomannan exopolysaccharide isolated from Tremella mesenterica. 13C-N.m.r. chemical shifts measured at various pD values were compared for p-nitrophenyl beta-D-glucopyranosiduronic acid (1) and two GMs (2 and 3) differing in GlcA content (Man:GlcA; 2, 10:1; and 3, 5:1). Also measured and compared were pKa values for 1 and 2. One-dimensional and two-dimensional (COSY and HETCOR) n.m.r. data allowed unambiguous assignments of pD-sensitive chemical shifts due to 2-O-beta-D-GlcpA substituents attached to a (1----3)-linked alpha-D-Manp backbone. The pKa and n.m.r. data indicated that the CO2H groups in either GM are independent of each other, and are similar in behavior to those of p-nitrophenyl beta-D-glucopyranosiduronic acid molecules. The n.m.r. data confirmed the previous, chemically deduced, structural role of GlcpA in the native polysaccharide from T. mesenterica, and indicated that significant pD-induced changes occur in the stabilities of the glycosidic orientations in the GM. Previous 13C-n.m.r. assignments for 2-O-beta-D-GlcpA in polysaccharides derived from Cryptococcus neoformans serotype A-variant were confirmed, except for the signal due to the anomeric carbon atom. This signal is now known to be pD-sensitive. In acidic solutions, it is coincident with the signal (104.5 p.p.m.) due to the anomeric carbon atoms of the unsubstituted alpha-D-Manp backbone residues. In basic solutions, the 2-O-beta-D-GlcpA anomeric carbon resonance is shifted upfield by approximately 0.2 p.p.m., and is observed as a separate signal.
通过史密斯降解法从分离自银耳的天然（3 - O - 乙酰葡萄糖醛酸）木糖甘露聚糖胞外多糖中去除木糖，得到一种葡糖醛酸甘露聚糖（GM）。比较了在不同pD值下测得的对硝基苯基β - D - 吡喃葡萄糖醛酸（1）以及两种葡糖醛酸含量不同（甘露糖：葡糖醛酸；2，10:1；3，5:1）的GM（2和3）的13C - N.m.r.化学位移。还测量并比较了1和2的pKa值。一维和二维（COSY和HETCOR）n.m.r.数据使得能够明确归属与连接在（1→3）连接的α - D - 甘露糖骨架上的2 - O - β - D - 葡糖醛酸残基相关的对pD敏感的化学位移。pKa和n.m.r.数据表明，两种GM中的羧基彼此独立，其行为与对硝基苯基β - D - 吡喃葡萄糖醛酸分子的羧基相似。n.m.r.数据证实了先前通过化学推导得出的葡糖醛酸在银耳天然多糖中的结构作用，并表明在GM中糖苷取向的稳定性会发生显著的pD诱导变化。先前对新型隐球菌A血清型变种来源的多糖中2 - O - β - D - 葡糖醛酸的13C - N.m.r.归属得到了确认，但异头碳原子的信号除外。现在已知该信号对pD敏感。在酸性溶液中，它与未取代的α - D - 甘露糖骨架残基的异头碳原子的信号（104.5 ppm）重合。在碱性溶液中，2 - O - β - D - 葡糖醛酸异头碳的共振向高场移动约0.2 ppm，并作为一个单独的信号被观察到。
