Structural analysis of underivatized neutral human milk oligosaccharides in the negative ion mode by nano-electrospray MSn (Part 1:: Methodology)
Structural analysis of underivatized neutral human milk oligosaccharides in the negative ion mode by nano-electrospray MSn (Part 1:: Methodology)
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DOI：
10.1016/s1044-0305(02)00645-1
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发表时间：
2002-11-01
影响因子：
3.2
通讯作者：
Stahl, B
中科院分区：
文献类型：
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作者：
Pfenninger, A;Karas, M;Stahl, B
采用负离子模式下的四极杆离子阱质谱仪（QIT - MS），通过纳升电喷雾电离（ESI）对人乳中未衍生化的中性低聚糖进行了分析。在这些条件下，中性低聚糖以高强度的去质子化分子[M - H](-)形式被观测到。对这些电荷定位于还原端的物质进行碰撞诱导解离（CID）实验，产生了C型碎片离子，形成了一个“新的”还原端。碎片化过程伴随着环间断裂，从而提供了内部单糖连接方式的信息。对几种具有不同结构特征的同分异构体化合物进行了研究，例如不同的糖苷键、岩藻糖基化和分支位点。阐明了这类低聚糖的碎片化行为规则，并利用QIT的MS/MS和MSⁿ功能，对一定数量具有代表性的某些同分异构糖型进行了测试。基于去质子化分子的特定碎片化行为，可以确定岩藻糖的位置以及连接类型（Gal β1→3 GlcNAc或Gal β1→4 GlcNAc），并且可以区分线性和分支结构。可以建立一些规则，这些规则可应用于对这类低聚糖（甚至是来自异质混合物的低聚糖）的进一步研究。（C）2002美国质谱学会
Underivatized neutral oligosaccharides from human milk were analyzed by nano-electrospray ionization (ESI) using a quadrupole ion trap mass spectrometer (QIT-MS) in the negative-ion mode. Under these conditions neutral oligosaccharides are observed as deprotonated molecules [M - H](-) with high intensity. CID-experiments of these species with the charge localized at the reducing end lead to C-type fragment ions forming a "new" reducing end. Fragmentations are accompanied by cross-ring cleavages that yield information about linkages of internal monosaccharides. Several isomeric compounds with distinct structural features, such as different glycosidic linkages, fucosylation and branching sites were investigated. The rules governing the fragmentation behavior of this class of oligosaccharides were elucidated and tested for a representative number of certain isomeric glycoforms using the MS/MS and MSn capabilities of the QIT. On the basis of the specific fragmentation behavior of deprotonated molecules, the position of fucoses and the linkage type (Gal beta1-->3 GlcNAc or Gal beta1-->4 GlcNAc) could be determined and linear and branched could be differentiated. Rules could be established which can be applied in further investigations of these types of oligosaccharides even from heterogenous mixtures. (C) 2002 American Society for Mass Spectrometry.