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[求助]
多糖的甲基化结果有好多t-Glc，和NMR不一致
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把多糖送到第三方检测公司进行分析后，将结果汇总投稿，结果被编辑质疑。小白刚接触多糖分析，不知道是哪里出了问题求大佬帮忙解释。。。 审稿意见原文： The characterization of the polysaccharide shows several errors that preclude considering the current manuscript for publication in Carbohydrate Polymers. First of all, the methylation data does not yield coherent information: the number of non-reducing terminal units amounts to ca. 35% (summing up Fuc, Glc, and Man), but only less than 9% of branching points were encountered (2,4- and 3,4-di-O-methylgalactose). This large discrepancy does not allow to determine any possible structure for the polysaccharide. In the further analysis the authors refer to 2,6-linked mannose, but there is no 3,4-di-O-methylmannose appearing among the methylated monosaccharides. The methylated derivative for arabinose appears to be deuterated. How do the authors explain this issue? Have they used NaBD4? If so, all of the monosaccharides should have appeared deuterated. If they did not, there is no explanation for the appearance of one of the alditols deuterated. The 13C NMR spectrum observed in the figure appears actually to be too noisy as to make safe assignments. Some of the assignments of the Table appear to be dubious or wrong. I do not recall finding in literature a beta-D-galactopyranose C-1 around 108 ppm, in this place it is more likely to find furanoses. A C4 signal at 83.4 ppm for a terminal galactopyranose unit is very unlikely. I can see two signals around 5.2 ppm, only one of them is assigned, to 2-linked mannose units. However, the corresponding methylated sugar does not appear in the methylation analysis. In the FTIR, the authors identify one signal to a carbonyl group, but I cannot see any carbonyl group being part of this polysaccharide. 好像是说甲基化结果和NMR不一致，多糖无法存在这种结构。那我是应该找检测公司核对数据吗？    @鸭绿江畔 @superyeast @klicking 发自小木虫Android客户端 |
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非常感谢您的回答。但是我有些地方没有完全明白。 首先我单糖组成的结果里提及了糖醛酸的存在，审稿人的意思是我的糖链结构里应该是有糖醛酸的是吗？ 然后nabd4确实是加了，这个能说明什么问题呢？ 最后就是审稿人的核心观点是什么呢？是甲基化分析结果错误，于nmr不一致，还是整个糖的结构不对啊？我能否不看甲基化的结果直接放nmr分析结构呢？ 发自小木虫Android客户端 |
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2楼2021-02-25 17:35:56
4楼2021-03-07 23:08:55
