Development of a hybrid tandem mass spectrometer for ultraviolet photodissociation of biomolecules

Mass spectrometry has become a standard platform for the analysis of biomolecules since the advent of matrix-assisted laser desorption/ionization and electrospray ionization. The structural information needed for the identification and characterization of biomolecules is obtained typically from tandem mass spectrometry. Ultraviolet (UV) photodissociation deposits a well-defined high energy into ions of interest in a very short timescale and results in tandem mass spectra that are dissimilar to those observed with other fragmentation methods. This dissertation focused on the development of a hybrid linear ion trap/orthogonal time-of-flight tandem mass spectrometer with an electrospray source for UV photodissociation of biomolecules, particularly peptide ions. This instrument enabled energy- and time-dependent observations of product ions generated by 157 nm photodissociation of peptide ions. Precursor ions having low internal energies allowed more radical ions to be detectable for some time after photodissociation. Time-resolved observation of product ions generated by 157 nm photodissociation showed different proton mobilization timescales for arginine- and lysine-terminated tryptic peptides. Time-resolved detection of vacuum UV photodissociation fragment ions of singly charged phosphopeptides also made it possible to measure the timescale on which the phosphate group is lost from either precursor or product ions. Finally, this instrumentation also allowed us to detect fragment ions specific to the gas phase conformations of proline-containing peptide ions.