Gas-phase ion/ion reactions in a triple quadrupole linear ion trap mass spectrometer: The roles of ion type and dissociation methods in biomolecule analysis
Abstract
The advent of soft ionization methods that can generate multiply charged gaseous biomolecular ions has enabled the development of gas-phase ion/ion reactions in analytical mass spectrometry. Gas-phase ion/ion reactions have proven to be particularly effective in transforming one gaseous ion type to another. Coupled with tandem mass spectrometry, ion transformation reactions, such as proton transfer, electron transfer, metal cationization, and complex formation have shown to be useful in the identification and characterization of biomolecules. The thesis work described below surveys a variety of ion/ion reactions implemented in a triple-quadrupole linear ion trap mass spectrometer, demonstrating ion manipulation in the gas phase and evaluation of different structural characterization methods for biomolecules. Cations of disulfide bond-containing polypeptide hormones, such as oxytocin, somatostatin, and insulin, were involved in gold-cationization ion/ion reactions followed by supplemental collision-induced dissociation (CID) of the peptide-gold complexes. The incorporation of Au(I) or Au(III) cations into the biomolecule demonstrated a specific and efficient method for cleaving disulfide bonds and enabled sequencing of intact peptides and proteins. Furthermore, gaseous polypeptide cations and anions were covalently modified and cross-linked in the gas phase via ion/ion reactions using N-hydroxysuccinimide (NHS) or N-hydroxysulfosuccinimide (sulfo-NHS) based reagents. The ability to covalently modify primary amine groups in the gas phase with NHS (or sulfo-NHS) reagents opens up the possibility of attaching a wide range of chemical groups to gaseous peptides and proteins and also for selectively modifying other analytes containing free primary amine groups. This project was further extended by comparing solution vs. gas phase modification of biomolecules and evaluating the different factors influencing the modification chemistry. Lastly, the effect of cation recombination energy/coulomb repulsion on product ion channel partitioning in electron transfer dissociation (ETD) and electron capture dissociation (ECD) was examined. The goal of this project was to better understand the mechanisms governing the ETD/ECD phenomena.
Degree
Ph.D.
Advisors
McLuckey, Purdue University.
Subject Area
Analytical chemistry
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