Alkaline Degradation of Oligosaccharides Coupled with Matrix-Assisted Laser Desorption/Ionization Fourier Transform Mass Spectrometry: A Method for Sequencing Oligosaccharides

A new technique for determining sequence and linkage
information of underivatized oligosaccharides is developed using alkaline degradation and matrix-assisted laser
desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS). Alkaline degradation (also known
as the “peeling” reaction) is a chemical degradation
technique that only cleaves the glycosidic bond at the
reducing end by β-elimination to yield a new reducing
end.
The reaction products are sampled directly with
minimal
cleanup and monitored by MALDI-FTMS to elucidate the
oligosaccharide sequence. Linkage information is provided by cross-ring cleavage fragmentation of the new
reducing ends, created by either MALDI source fragmentation or sustained off-resonance irradiation collision-induced dissociation. This method is illustrated by
the
successful sequence and linkage determination of neutral,
branched, fucosylated, and sialylated oligosaccharides.
Experiments on differently linked disaccharides are
also
performed to determine the specificity of the cross-ring
cleavage reactions. The power of this technique is enhanced by the Fourier transform mass analyzer, which
provides high-resolution, exact mass, and facile tandem
mass spectrometry experiments of MALDI-produced ions.

本研究开发了一种基于碱性降解和基质辅助激光解吸/电离傅里叶变换质谱法（MALDI-FTMS）的新技术，以确定未衍生寡糖的序列和连接信息。碱性降解（亦称“剥落”反应）是一种化学降解技术，仅通过β消除在还原端切割糖苷键，从而产生新的还原端。反应产物经最小化净化后直接取样，并由MALDI-FTMS进行监测，以阐明寡糖序列。连接信息由新还原端产生的交叉环裂解碎片提供，这些碎片可通过MALDI源碎片化或持续非共振照射碰撞诱导解离生成。该方法通过成功确定中性、分支、岩藻糖基化和唾液酸化寡糖的序列和连接信息得到验证。此外，还进行了不同连接的二糖实验，以确定交叉环裂解反应的特异性。该技术的强大功能得益于傅里叶变换质谱分析仪，它提供了高分辨率、精确质量和简便的MALDI产生离子的串联质谱实验。