Lewis blood group antigens are a prominent example of isomeric oligosaccharides with biological activity. Understanding the fragmentation mechanism in the gas phase is essential for their identification and assignment by mass spectrometric methods such as ESI-MS. In this work, the [M + H]⁺ species of Lewis A trisaccharide and Lewis A trisaccharide methyl glycoside were studied by ESI-MS with FT-ICR as mass analyzer with respect to their fragmentation mechanism. The comparison between the underivatized and the methylated species has shown that the reducing end plays a key role in this mechanism. The results of this study question the existence of Z-type fragment ions after activation of the protonated species. The main product of the fragmentation are Y-type fragment ions and a combination of Y-type fragmentation and the loss of water at the reducing end instead of Z-type fragmentation. C-type fragment ions could not be detected. MS³ measurements also reveal that each fragment ion only occurs with the participation of a mobile proton and the possibility of glycosidic bond cleavage after fragmentation has already occurred at the reducing end as B₂ fragment ion.

Lewis血型抗原是具有生物活性的异构寡糖的一个突出例子。了解气相中的碎裂机制对于通过质谱方法（如 ESI-MS）进行鉴定和分配至关重要。在这项工作中，[M + H] ⁺采用ESI-MS和FT-ICR作为质量分析仪，研究了Lewis A三糖和Lewis A三糖甲基糖苷的裂解机制。未衍生化和甲基化物种之间的比较表明，还原端在该机制中起关键作用。本研究的结果质疑质子化物质激活后 Z 型碎片离子的存在。碎裂的主要产物是 Y 型碎裂离子和 Y 型碎裂与还原端失水的组合，而不是 Z 型碎裂。无法检测到 C 型碎片离子。女士³测量结果还表明，每个碎片离子仅在移动质子的参与下发生，并且在还原端已经发生碎片化后糖苷键断裂的可能性作为 B ₂碎片离子。