MOBILE PROTONS IN NEGATIVE CID TANDEM MS OF SULFATED OLIGOSACCHARIDES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 所有种类的碳水化合物都由建立在共同核心单元上的糖状混合物组成。这种混合物的组成和结构的确定在很大程度上依赖于串联质谱学数据。对于数量很少的样品和硫化多聚糖类别，通常首选天然多聚糖。负串联MS为中性低聚糖提供了有用的产物离子图谱，并且是酸性类的首选。在本实验室以前的工作中，阐明了唾液酸化对负离子模式下产物离子分布的影响。目前的工作显示了另外两个酸性基团，糖醛酸和硫酸盐的相互作用，如何决定硫酸软骨素糖胺多糖的产物离子模式。未经硫酸盐化的软骨素低聚糖几乎完全解离形成C型离子。硫酸盐化形式只产生B型和Y型离子。这些观测用碰撞加热过程中发生的竞争质子转移反应来解释。根据天然低聚糖和甲酯化低聚糖的碰撞击穿图，提出了产物离子的形成机理。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Carbohydrates of all classes consist of glycoform mixtures built on common core units. Determination of compositions and structures of such mixtures relies heavily on tandem mass spectrometric data. Native glycans are often preferred for samples available in very low quantities and for sulfated glycan classes. Negative tandem MS provides useful product ion profiles for neutral oligosaccharides and is preferred for acidic classes. In previous work from this laboratory, the influence of sialylation on product ion profiles in the negative mode was elucidated. The present work shows how the interplay of two other acidic groups, uronic acids and sulfates, determines product ion patterns for chondroitin sulfate glycosaminoglycan oligosaccharides. Unsulfated chondroitin oligosaccharides dissociate to form C-type ions almost exclusively. Sulfated forms produce only B- and Y-type ions. These observations are explained in terms of competing proton transfer reactions that occur during the collisional heating process. Mechanisms for product ion formation are proposed based on collisional breakdown diagrams of native and methyl esterified oligosaccharides.