Pérez-Victoria Ignacio, Zafra Alberto, Morales Juan Carlos
Departamento de Química, Puleva Biotech SA, Granada, Spain.
J Mass Spectrom. 2008 May;43(5):633-8. doi: 10.1002/jms.1363.
Structural characterization and differentiation of a novel group of regioisomeric monolaurate esters of the nonreducing trisaccharides raffinose and melezitose, and the nonreducing tetrasaccharide stachyose has been obtained using positive electrospray ionization (ESI) mass spectrometry with in-source fragmentation. The surfactant nature and high polarity of these compounds make them appropriate analytes for being studied by conventional ESI-MS. The position of the acyl chain in each particular regioisomer has been used as a reporter group that allows unambiguous rationalization of the fragmentation routes of the corresponding natriated molecular ions M + Na. In all cases, the main fragment ions were produced through cleavage of the glycosidic bond involving two anomeric carbons, the C-1' and C-2'' of the alpha-D-Glcp-(1-2)-beta-D-Fruf bond, and it was observed that sodium cation retention occurred on the heavier mass fragment of the two formed fragments, (e.g. di- or trisaccharide type vs monosaccharide type). Our results may help to better understand the fragmentation behavior of nonreducing oligosaccharides (as sodium adducts) in positive ESI mass spectrometry.
利用带源内裂解的正电喷雾电离（ESI）质谱法，已获得了一组新型区域异构体单月桂酸酯的结构表征和分化情况，这些区域异构体单月桂酸酯由非还原性三糖棉子糖和松三糖，以及非还原性四糖水苏糖构成。这些化合物的表面活性剂性质和高极性使其成为适合用传统ESI-MS进行研究的分析物。每个特定区域异构体中酰基链的位置已被用作报告基团，这使得能够明确合理地解释相应钠化分子离子M + Na的裂解途径。在所有情况下，主要碎片离子是通过涉及两个异头碳的糖苷键裂解产生的，即α-D-葡萄糖-(1-2)-β-D-呋喃果糖键的C-1'和C-2''，并且观察到钠阳离子保留在形成的两个碎片中质量较大的碎片上，（例如二糖或三糖类型与单糖类型）。我们的结果可能有助于更好地理解非还原性寡糖（作为钠加合物）在正ESI质谱法中的裂解行为。
