Monosaccharide Identification as a First Step toward de Novo Carbohydrate Sequencing: Mass Spectrometry Strategy for the Identification and Differentiation of Diastereomeric and Enantiomeric Pentose Isomers
Monosaccharide Identification as a First Step toward de Novo Carbohydrate Sequencing: Mass Spectrometry Strategy for the Identification and Differentiation of Diastereomeric and Enantiomeric Pentose Isomers
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DOI：
10.1021/acs.analchem.5b00760
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发表时间：
2015-04-21
影响因子：
7.4
通讯作者：
Pohl, Nicola L. B.
中科院分区：
文献类型：
--
作者：
Nagy, Gabe;Pohl, Nicola L. B.
从头碳水化合物测序，包括单糖鉴定，在很大程度上仍然是一个巨大的分析挑战。任何大型多糖的完整结构测定的第一步是准确和稳健的单糖组成分析方法。本文报道了第一种基于质谱的方法，用于完全鉴定和确定所有1.2戊糖异构体的绝对构型，包括阿拉伯糖、来苏糖、核糖、木糖、核酮糖和木酮糖的D和L对映异构体。与早期区分己糖异构体的工作相比，戊糖异构体的手性分离明显更具挑战性。具体而言，12种戊糖在结构上彼此更加相似，只有两个羟基的轴向或赤道取向在这些异构体之间的五元环呋喃糖结构中有所区别，并且戊糖构象之间的能量差异小于己糖构象之间的能量差异。尽管12种戊糖之间存在这种固有的最小能量差异，但发现了两种独特的固定配体动力学方法组合来实现这组异构体的手性鉴别。该测定法可容易地应用于仅使用微克量和商业仪器鉴定任何分离的戊糖单糖，并补充了区分己糖异构体的方法。一个工作流程，采用这种基于质谱的方法，从而可以实现完整的从头鉴定的所有单糖结构单元中的寡糖或多糖的建议。
De novo carbohydrate sequencing, including monosaccharide identification, largely remains a tremendous analytical challenge. A first step in the complete structural determination of any large polysaccharide is an accurate and robust method for analysis of the constituent monosaccharides. Herein, the first mass spectrometry-based method for the complete identification and absolute configuration determination of all 1.2 pentose isomers, including the D and L enantiomers for arabinose, lyxose, ribose, xylose, ribulose, and xylulose, is reported. As compared to earlier work to distinguish hexose isomers, the chiral separation of the pentose isomers was significantly more challenging. Specifically, the 12 pentoses are much more structurally similar to one another, with only the axial or equatorial orientation of two hydroxyl groups differentiating among these isomers in their five-membered ring furanose structure and smaller energetic differences between pentose conformations than between hexose conformations. Despite such inherently minimal energetic differences between the 12 pentoses, two unique fixed ligand kinetic method combinations were discovered to achieve chiral discrimination for this set of isomers. This assay can be readily applied to the identification of any isolated pentose monosaccharide using only microgram quantities and a commercial instrument and complements the method to distinguish hexose isomers. A workflow that incorporates this mass spectrometry-based method and thereby could achieve complete de novo identification of all monosaccharide building blocks in an oligo- or polysaccharide is proposed.