Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 10617, Taiwan.
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
Analyst. 2023 Apr 11;148(8):1712-1731. doi: 10.1039/d3an00068k.
Differentiation of stereoisomers that are only dissimilar in the orientation of chemical bonds in space by mass spectrometry remains challenging. Structural determination of carbohydrates by mass spectrometry is difficult, mainly due to the large number of stereoisomers in carbohydrates. Arabinose and xylose are pentose stereoisomers typically present in plant polysaccharides and exist in α- and β-anomeric configurations of furanose and pyranose forms. Conventional methods used to determine the structures of polysaccharides include hydrolysis of polysaccharides into oligosaccharides followed by identification of these oligosaccharides' structures individually through nuclear magnetic resonance spectroscopy (NMR). Although the sensitivity of mass spectrometry is much higher than that of NMR, conventional mass spectrometry provides only limited useful information on oligosaccharide structure determination, only the linkage positions of glycosidic bonds. In this study, we demonstrated a mass spectrometry method for the identification of linkage positions, anomeric configurations, and monosaccharide stereoisomers of intact oligosaccharides consisting of arabinose and xylose. We separated arabinose and xylose monosaccharides into α-furanose, β-furanose, α-pyranose, and β-pyranose forms through high-performance liquid chromatography and obtained the corresponding collision-induced dissociation mass spectra. Using these monosaccharide spectra and a flow chart consisting of the proper CID sequences derived from the dissociation mechanisms of pentose, a simple multi-stage tandem mass spectrometry method for structural identification of intact oligosaccharides consisting of arabinose and xylose was developed. The new mass spectrometry method provides a simple method for determining the structure of polysaccharides consisting of arabinose and xylose. The flow chart can be used in computer coding for automation, an ultimate goal for oligosaccharide structure determination.
通过质谱法区分在空间中仅化学键取向不同的立体异构体仍然具有挑战性。通过质谱法对碳水化合物进行结构测定具有一定难度，这主要是由于碳水化合物的立体异构体数量众多。阿拉伯糖和木糖是戊糖立体异构体，通常存在于植物多糖中，以呋喃糖和吡喃糖形式的α-和β-端基异构体形式存在。用于确定多糖结构的常规方法包括将多糖水解成寡糖，然后通过核磁共振波谱（NMR）分别鉴定这些寡糖的结构。尽管质谱法的灵敏度远高于 NMR，但常规质谱法仅提供关于寡糖结构确定的有限有用信息，仅提供糖苷键的连接位置。在这项研究中，我们展示了一种质谱法，用于鉴定由阿拉伯糖和木糖组成的完整寡糖的糖苷键连接位置、端基异构体和单糖立体异构体。我们通过高效液相色谱将阿拉伯糖和木糖单糖分离成α-呋喃糖、β-呋喃糖、α-吡喃糖和β-吡喃糖形式，并获得相应的碰撞诱导解离质谱。使用这些单糖谱和一个由戊糖的解离机制衍生的适当 CID 序列组成的流程图，我们开发了一种用于鉴定由阿拉伯糖和木糖组成的完整寡糖结构的简单多级串联质谱法。这种新的质谱方法为确定由阿拉伯糖和木糖组成的多糖结构提供了一种简单的方法。该流程图可用于计算机编码自动化，这是寡糖结构确定的最终目标。
