Merged Beam MALDI TOF-TOF Using Ion-Ion Reactions to Determine Structure of

摘要本研究的最终目标是利用正离子的电子转移解离（ETD）和负离子的质子转移解离（PTD）对具有生物意义的分子进行MALDI- tof质谱分析，以确定分子结构。这项技术将提供在单一碰撞条件下研究离子-离子碰撞过程的能力，并直接测量电荷转移和碎片的结果。竞争过程的反应截面将测量几种类型的离子-离子碰撞过程。基础研究的重点是导致激发离子在碰撞后解离产生结构信息片段离子的反应。单电荷前驱体可以通过双电荷转移来分析，首先产生有效碎片化的激发中性离子，然后通过第二次碰撞使碎片电离，产生与前驱体相反电荷的碎片离子。除了基础知识之外，本研究还将为确定MALDI产生的单电荷和双电荷分子离子的分子结构提供实用技术。该方法应适用于各种分子，包括完整的蛋白质、肽、寡核苷酸、寡糖、糖缀合物、脂质和代谢物，并且可能提供比电喷雾电离和离子阱可用的更快、灵敏度和特异性的未知分子鉴定和结构阐明。该仪器的特点是在最近开发的高性能MALDI-TOF-TOF质谱联用系统上增加了第二个脉冲离子源。来自两个源的脉冲光束在碰撞单元内合并，脉冲在时间上精确同步，光束的相对速度精确确定且非常接近于零。所提出的仪器将允许对极性相反的离子之间的反应以及离子与受激中性之间的反应进行灵敏的测量，这些反应在低平动能量下是以前无法获得的。反应物的内部温度（或激发）可能很高，但平移温度很低，导致这些过程的横截面很高。碰撞质量降低为100 Da，相对速度为1 m/s，对应的平动能量为5 × 10-7 eV，平动温度为6 × 10-3 K。我们不知道在这些条件下离子-离子碰撞过程的任何先前的工作。

DESCRIPTION (provided by applicant): Merged Beam MALDI TOF-TOF Using Ion-Ion Reactions to Determine Structure of Biological Molecules Summary The ultimate goals of this research are practical techniques for MALDI-TOF MS-MS on biologically significant molecules using electron transfer dissociation (ETD) of positive ions and proton transfer dissociation (PTD) of negative ions to determine molecular structure. This technology will provide the ability to study ion-ion collision processes under single collision conditions with direct measurement of the results in terms of charge transfer and fragmentation. Reaction cross sections for competing processes will be measured for several types of ion-ion collision processes. The emphasis in the fundamental studies is on reactions that lead to excited ions that dissociate following collision to produce structurally informative fragment ions. Singly charged precursors may be analyzed by employing double charge transfer to first produce excited neutrals that fragment efficiently, and then ionize the fragments by a second collision to produce fragment ions with charge opposite that of the precursor. In addition to fundamental knowledge, this research will provide practical techniques for determining molecular structure of singly and doubly charged molecular ions produced by MALDI. The approach should be applicable to a wide variety of molecules including intact proteins, peptides, oligonucleotides, oligosaccharides, glycoconjugates, lipids, and metabolites, and may provide speed, sensitivity, and specificity for identification and structural elucidation of unknowns that surpasses that available with electrospray ionization and ion traps. The instrument features addition of a second pulsed ion source to a recently developed high- performance MALDI-TOF-TOF MS-MS system. Pulsed beams from the two sources are merged within a collision cell with the pulses accurately synchronized in time, and with the relative velocity of the beams accurately determined and very near zero. The proposed apparatus will allow sensitive measurements of reactions between ions of opposite polarity and between ions and excited neutrals at low translational energies not previously accessible. The internal temperature (or excitation) of the reactants may be quite high but the translational temperatures are very low leading to very high cross sections for these processes. Collisions with reduced mass of 100 Da and relative velocity of 1 m/s correspond to translational energy of 5x10-7 eV, and translational temperature of 6x10-3 K. We are not aware of any previous work on ion-ion collision processes under these conditions. PUBLIC HEALTH RELEVANCE (provided by applicant): The "Holy Grail" of mass spectrometry for biological applications is an instrument that provides accurate molecular weight and complete, unambiguous sequence, including unusual amino acids and post- translational modifications, on proteins present at trace levels in complex mixtures. It should also provide similar information on mass and structure of other biologically significant molecules, including metabolites, lipids, oligosaccharides, glycoconjugates, oligonucleotides, and peptides. This may be it.