Gas-phase ion /ion reactions in linear ion trap instruments: Instrumentation and application to protein analysis
Abstract
Ion/ion reactions in a linear ion trap (LIT) are of great interest because LITs provide significantly higher trapping efficiency and trapping capacity for externally injected ions than three-dimensional (3D) ion traps. However, the DC trapping potential well normally used for LITs does not allow simultaneous trapping of oppositely charged ions, which is essential for ion/ion reactions in electrondynamic ion traps. During the thesis study, new instrumentation and methods to implement ion/ion reactions in LITs have been developed to improve the capabilities of ion/ion reaction studies in protein analysis. The first part of the dissertation is focused on the development of mutual storage ion/ion reactions on a triple quadrupole/linear ion trap instrument. Parameters that affect ion/ion reactions in an LIT were investigated. All key ion/ion reactions established to be useful in protein analysis studies using 3D traps were demonstrated here with the hybrid instrument. In the second part, new ionization sources for ion/ion reaction studies were developed for facile implementation of ion/ion reactions on commercial ion trap mass spectrometers. A commercial quadrupole time-of-flight (QqTOF) tandem mass spectrometer was modified for ion/ion reaction studies, where an LIT was employed as ion/ion reaction vessel and an orthogonal TOF was used for mass analysis of the ion/ion reaction products. Compared to the conventional ion/ion studies in ion traps, the QqTOF instrument with ion/ion reaction capabilities offers advanced analysis power in protein characterizations. The fragmentation patterns of a model protein under different collision-induced fragmentation (CID) condition, e.g. ion-trap CID vs. beam-type CID, were studied using ion/ion proton transfer reactions to gain more insights on the unimolecular dissociation behavior of gas-phase protein ions. Finally, the ion/molecule reactions of cation radicals formed from electron transfer dissociation (ETD) of polypeptides in a linear ion trap were investigated.
Degree
Ph.D.
Advisors
McLuckey, Purdue University.
Subject Area
Analytical chemistry
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