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飲罪千觴銅蟲 (小有名氣)
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[求助]
多糖的甲基化結(jié)果有好多t-Glc，和NMR不一致
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把多糖送到第三方檢測公司進行分析后，將結(jié)果匯總投稿，結(jié)果被編輯質(zhì)疑。小白剛接觸多糖分析，不知道是哪里出了問題求大佬幫忙解釋。。。 審稿意見原文： 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. 好像是說甲基化結(jié)果和NMR不一致，多糖無法存在這種結(jié)構(gòu)。那我是應(yīng)該找檢測公司核對數(shù)據(jù)嗎？ @鴨綠江畔 @superyeast @klicking 發(fā)自小木蟲Android客戶端 |
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非常感謝您的回答。但是我有些地方?jīng)]有完全明白。 首先我單糖組成的結(jié)果里提及了糖醛酸的存在，審稿人的意思是我的糖鏈結(jié)構(gòu)里應(yīng)該是有糖醛酸的是嗎？ 然后nabd4確實是加了，這個能說明什么問題呢？ 最后就是審稿人的核心觀點是什么呢？是甲基化分析結(jié)果錯誤，于nmr不一致，還是整個糖的結(jié)構(gòu)不對��？我能否不看甲基化的結(jié)果直接放nmr分析結(jié)構(gòu)呢？ 發(fā)自小木蟲Android客戶端 |
3樓2021-02-28 04:36:33
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4樓2021-03-07 23:08:55
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