This dissertation expounds on the investigations of the structure and chemistry of peptides and supramolecular host-guest systems in the gas phase. These investigations used two different kinds of analytical instrument: Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and ion mobility mass spectrometry (IM-MS, IMS). These investigations were complemented by chemical modeling. The FTICR was used to radially trap ions with its 4.7 T magnet, which allowed the ions to undergo sustained off-resonance irradiation collision-induced dissociation (SORI-CID). A subsequent event then measured the collision cross sections (σ) of the targeted precursor ion and one of the selected product ions. These experiments were repeated multiple times to measure σ for as many precursor/product pairs as possible. A similar kind of experiment was performed in the IM-MS instrument, through in-source collision-induced dissociation and size-based ion separation in the instrument’s mobility region. When the precursor/product σ ratios were compared, the values obtained by both methods were in good agreement with each other. Application of the FTICR-based technique to [2.2.2]-cryptand+Cs+ caused the externally bound Cs+ to migrate into the cryptand’s cavity. Further development of the FTICR-based technique allowed me to perform the post-SORI σ measurements in a time-resolved fashion. Data collected in this manner revealed that collisionally activated peptides refold over a 5 – 10 second timescale, as determined by their σ shrinking with time. These experiments allowed for observation of a peptide refolding. The IM-MS instrument was applied to a supramolecular chemistry problem surrounding cucurbituril (CB7), and its ability to bind two identical guests within its cavity. Literature precedent and conventional wisdom suggested that only one guest would bind within CB7’s cavity while the other guest would be bound externally. When ion mobility cross sections (Ω) were obtained for [CB7 + Guest2]2+ systems, it was discovered that both guests could be bound within CB7’s cavity. This was possible because the guests possessed the correct shape and chemistry to favor dispersive interactions between CB7’s cavity and the adjacent guest, and ion-dipole interactions with CB7’s carbonyl-lined portal.
College and Department
Physical and Mathematical Sciences; Chemistry and Biochemistry
BYU ScholarsArchive Citation
Arslanian, Andrew J., "Gas Phase Techniques for the Study of Biomolecular and Supramolecular Structures and Chemistry" (2022). Theses and Dissertations. 9564.
FTICR, SORI, CID, CA, refolding, IM-MS, cucurbiturils, CRAFTI