Document Type
Dissertation
Degree
Doctor of Philosophy
Major
Chemistry
Date of Defense
7-3-2019
Graduate Advisor
Dr. Benjamin Bythell
Committee
Dr. Benjamin J. Bythell, Ph.D.
Dr. Keith J. Stine, Ph.D.
Dr. Alexei V. Demchenko, Ph.D.
Dr. Chung Wong, Ph.D.
Abstract
The fragmentation chemistries of small ions are characterized in the gas-phase using mass spectrometry. I utilized experimental data and computational methods to rationalize the mechanisms of fragmentation. Density functional calculations of minima, transition states, product ions, and neutrals were performed for most of the studied systems. These systems are varied widely: Protonated peptides systems (Chapters 2 and 3), lithiated monosaccharides (Chapters 4), and protonated imine, anthracene derivatives (Chapter 5). From the experimental and theoretical data of protonated histidine-containing peptides (Chapters 2), we found that altering the position of the histidine residue had a noticeable effect on the identity of b2 ion structure and its subsequent reactivity. We provide a computational study of a series of analogous protonated peptides containing proline or pipecolic acid (Chapters 3) characterizing and explaining their distinctly different dissociation chemistry. We studied the fragmentation chemistry of isomeric lithiated monosaccharide cations (glucose, mannose, and galactose) in Chapter 4, characterizing the gas-phase chemistry of the alpha, beta, and ring-open forms. All produce similar fragmentation pathways but to differing extents; water loss, 0,2A1 and 0,3A1 ion formation In Chapter 5, characterization of model protonated imine, anthracene-derivative compounds utilizing tandem mass spectrometry, deuterium labelling, and theoretical methods is illustrated.
Recommended Citation
Abutokaikah, Maha, "Gas-Phase Fragmentation Chemistry of Small Ions" (2019). Dissertations. 839.
https://irl.umsl.edu/dissertation/839