CHARACTERIZATION OF GLYCOPROTEIN PERMETHYLATED OLIGOSACCHARIDES BY FT ICR MS

结构鉴定中的一个主要困难 碳水化合物低聚物经质谱分析是数量众多的 结构异构体是由两个不同的 单体残基之间的连接位置和可能的 与单一残基有多个联系。因此，对于直链 齐聚物，结构鉴定需要测定 糖基连接类型的序列，包括连接位置 和异构体构型，以及单体序列 表征氨基或氨基所需的残基 核酸低聚物。多个链接也允许多个 连接拓扑和生物系统中的碳水化合物和 糖共轭化合物通常表现为支链和线形 结构。在过去的几十年里，基于 离子碎裂在分析中发挥了主要作用 碳水化合物结构。在某些(选择)设置中，串联质量 Spectrme尝试能够为两者提供一个彻底的拓扑 关于糖苷键的表征和广泛的信息。 在更一般的设置中，来自MS/MS的信息被泄露。这个 碳水化合物齐聚物中原子物种的相对较窄范围 导致等压离子碎片。不稳定糖苷类药物的共存 粘合和耐用的吡喃糖环结构导致 较大离子中的碎裂途径几乎只涉及 糖苷键的断裂。中使用的开环路径 链接指定被抑制。采用离子陷阱的MSN技术 质谱仪可以解决这两个限制。使用MSN、ION 片段还具有世代层次结构等特点 表征可以识别结构特征。按顺序 将分子、离子碎片与数量减少的 自由度是准备好的，它们的解离又导致 加强了非糖苷键的解离。实用的 MSN用于碳水化合物分析的能力取决于性能 离子捕获装置的各个方面，即碰撞能量 可以获得连续的离子碎片保留率 几代人的离子解离。实现碳水化合物MSN FT ICR质谱仪受到分析需求的影响 保留和解离相对较小的离子碎片 高活化能。磁控膨胀与离子动力学 典型碳水化合物MSN实验中的热量计算公式为 包含两个非线性陷阱的详细数值模拟 势和三维离子中性散射。在分析中 这些实验，既有离子运动的动力学不稳定性，也有 内部供暖被证明是严重的问题。我们主要关注的是 因此，目前在FT-ICR MS中的研究重点是离子动力学和 重点阐述了实施复测和MSN存在的问题。 最近的努力被分为理论/数值研究 离子动力学和与之相关的仪器修改 用回旋加速器实现离子的轴向旋转冷却 平移运动。数字目标是：a)发展 桥接代码，使电极电位由商业产生 程序包(SIMION)可用于弹道仿真；b)实现 弹道中的随机三维排斥散射 模拟；c)允许宽带激励；d)实施库仑 离子对之间的耦合；e)在MIDAS中输出时间域文件 兼容格式，即使模拟生成“光谱”；f) 构建一套计划以反映不同的用户目标和 操作环境。最后一个目标包括发展 与图形用户界面相结合的程序(基于CVI LabWindows，National Instruments)在Windows 95/NT和外壳下运行 将脚本控制的程序作为后台进程在Unix中运行 (Linux)环境。回旋加速器的仪器改装 轴向旋转涉及到计算机设计和数值计算 各种电池和激励几何形状的分析。

A principal difficulty in the structural identification of carbohydrate oligomers by mass spectrometry is the large number of structural isomers that arise from the existence of both different linkage positions between monomer residues and the possibility of multiple linkages to a single residue. Hence, for a straight-chain oligomer, structural identification requires determination of the sequence of glycosyl linkage types, including the linkage positions and the anomeric configurations, as well as the sequence of monomer residues that would be required for characterization of amino or nucleic acid oligomers. Multiple linkages also allow for multiple connection topologies and in biological systems carbohydrates and glycoconjugates commonly exhibit branched as well as linear structures. In the past decades, mass spectral techniques based on ion fragmentation have played a major role in the analysis of carbohydrate structures. In some (select) settings, tandem mass spectrome try is able to provide both a thorough topological characterization and extensive information about glycosidic linkages. In more general settings, information from MS/MS is compromised. The relatively narrow range of atomic species in carbohydrate oligomers leads to isobaric ion fragments. The coexistence of labile glycosidic bonds along with durable pyranose ring structures leads to fragmentation pathways in larger ions that involve almost exclusively the breaking of glycosidic bonds. Ring-opening pathways used in linkage assignments are suppressed. MSn techniques employing ion trap mass spectrometers can address both of these limits. With MSn, ion fragments are also characterized by a generational hierarchy and such characterization can identify structural features. By sequentially dissociating a molecule, ion fragments with a reduced number of degrees of freedom are prepared and their dissociation, in turn, leads to enhanced dissociation of non-glycosidic bonds. The practical potent ial of MSn for carbohydrate analysis hinges on performance aspects of the ion trapping device, i.e., the collision energies that can be obtained and the ion fragment retention in successive generations of ion dissociation. Implementing carbohydrate MSn with FT ICR mass spectrometers is compromised by the analytical need to retain and dissociate relatively small ion fragments with relatively high activation energies. Kinetics of magnetron expansion and ion heating in prototypical carbohydrate MSn experiments are calculated by detailed numerical simulations incorporating both nonlinear-trapping potentials and three-dimensional ion-neutral scattering. In analyzing these experiments, both dynamical instabilities of the ion motion and internal heating are shown to be significant problems. Our main focus of current research in FT-ICR MS is therefore ion dynamics with an emphasis on the problems of implementing remeasurement and MSn. Recent effort has been divided into theoretical/numerical studies of ion dynamics and instrumental modifications associated with implementing cyclotron to axial rotation for the cooling of the ion's translational motion. The numerical objectives are: a) develop bridge code so that electrode potentials generated by a commercial package (SIMION) could be used for trajectory simulation; b) implement stochastic, three dimensional repulsive scattering in the trajectory simulations; c) allow for broadband excitation; d) implement Coulomb coupling between ion pairs; e) output time domain files in a MIDAS compatible format, i.e., have the simulations generate 'spectra'; f) construct a suite of programs to reflect different user objectives and operating environments. The last objective includes developing programs coupled with a graphical user interfa ce (based on CVI LabWindows, National Instruments) to run under Windows 95/NT and shell script controlled programs to run as background processes in a UNIX (Linux) environment. The instrumental modifications for cyclotron to axial rotation have involved the computer design and numerical analysis of various cell and excitation geometries.