ECD AND EDD OF NATIVE AND PERMETHYLATED GLYCANS

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 寡糖是由多个单糖单元通过糖苷键连接而成的生物聚合物。寡糖的结构表征不仅需要确定每个单糖单元的身份和序列，而且还需要区分可能的分支，连接，差向异构体和异头异构体。先前在我们的实验室和其他地方已经表明，电子捕获解离（ECD）和热ECD（hECD）通常比传统的碰撞活化解离（CAD）和红外多光子解离（IRMPD）方法提供更广泛的交叉环裂解。这些交叉环片段有助于确定分支和连接位点。本研究以全甲基化直链和支链寡糖离子为对象，采用电子捕获技术（ECD）研究了金属离子和电子能量对其裂解行为的影响，以及ECD在异构体鉴别中的普遍适用性。 2010-2011年最新情况： 寡糖的电子捕获解离（ECD）行为取决于电子能量和电荷载体的类型。锂化和碱土金属加合物寡糖在低能量和高能量条件下有效地片段化，而其他碱金属加合物寡糖仅在热ECD条件下片段化。在此，我们对模型寡糖进行了系统的半定量研究，以进一步研究改变电子能量和电荷载体对寡糖ECD行为的影响。 能量依赖的ECD实验结果表明，随着电子能量的增加，金属加合寡糖离子可以经历三种不同的碎裂过程：ECD，当电子能量在0.5 ~ 6 eV之间时占主导地位;热ECD，当电子能量在6 ~ 16 eV之间时，以形成一定的交叉环劈裂为特征;和EID，其特征在于双电荷碎片离子的存在，当电子能量高于9 eV时发生。尽管热ECD和EID过程的起始与电荷载流子的类型无关，但较小的电荷载流子通常导致较高程度的EID，而较大的电荷载流子倾向于提供更多样化的交叉环裂解，覆盖热ECD条件下更宽范围的残留物。 通过在各种电子能量下对寡糖键合异构体的结构表征进行ECD，正在进一步研究ECD用于异构体区分的潜力。例如，尽管使用低能ECD不能实现LNT和LNnT之间的异构体区分，但热ECD能够为每种异构体产生诊断离子：MS/MS谱中1，3A 2和2，5A 2片段的存在证实了LNT中N-乙酰葡糖胺残基上的1 <$3键，2，4A 2和3，5A 2片段证实了1 <$3键。4连接。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Oligosaccharides are biopolymers composed of multiple monosaccharide units connected through glycosidic bonds. Structural characterization of oligosaccharides requires not only determination of the identity and sequence of each monosaccharide unit, but also differentiation of possible branching, linkage, epimeric and anomeric isomers. It has been shown previously, in our lab and elsewhere, that electron capture dissociation (ECD) and hotECD (hECD) generally provide more extensive cross-ring cleavages than the conventional collisionally activated dissociation (CAD) and infrared multiphoton dissociation (IRMPD) methods. These cross-ring fragments are instrumental in determining the branching and linkage sites. In this study, metal-adducted permethylated linear and branched oligosaccharide ions were subject to ECD at several energies to investigate the effect of metal ion and electron energy on their fragmentation behaviors as well as the general applicability of ECD to isomer differentiation. Update for 2010-2011: Electron capture dissociation (ECD) behavior of oligosaccharides depends on both the electron energy and the type of charge carriers. Lithiated and alkali-earth metal adducted oligosaccharides fragmented effectively under both low and high energy conditions, whereas other alkali metal adducted oligosaccharides fragmented only under the hot-ECD conditions. Here, we carried out a systematic semi-quantitative study on model oligosaccharides to further investigate the effects of varying the electron energy and the charge carriers on the ECD behavior of oligosaccharides. The results of the energy-dependent ECD experiments indicate that, as the electron energy increases, the metal-adducted oligosaccharide ions can undergo three different fragmentation processes: ECD, which dominates when the electron energy is between 0.5 and 6 eV; hot-ECD, as characterized by formation of certain cross-ring cleavages, which occurs when the electron energy is between 6 and 16 eV; and EID, as characterized by the presence of doubly-charged fragment ions, which occurs when the electron energy is above 9 eV. Although the onsets of both the hot-ECD and EID processes were independent of the type of the charge carriers, smaller charge carriers frequently led to a higher degree of EID, whereas larger charge carriers tend to provide more diverse cross-ring cleavages covering a broader range of residues under hot-ECD condition. The potential of ECD for isomer differentiation is being further investigated by performing ECD at various electron energies towards the structural characterization of oligosaccharide linkage isomers. For example, although isomer differentiation between LNT and LNnT could not be achieved using low-energy ECD, hot ECD was able to generate diagnostic ions for each isomer: the presence of 1,3A2 and 2,5A2 fragments in the MS/MS spectra confirmed the 1¿3 linkage on the N-acetylglucosamine residue in LNT, and the 2,4A2 and 3,5A2 fragments confirmed the 1¿4 linkage on this residue in LNnT.