Gas -phase charge permutation using ion /ion reactions and applications on the identification and characterization of macro-molecules
The advent of electrospray ionization capable of producing multiply charged ions from macromolecules has opened a new avenue to study the high-mass species. Gas phase charge permutation methodologies have been explored to manipulate the ion charge states and identities which may shed the light on the investigation of the properties of macromolecular species. In this thesis, macromolecule analysis has been performed using gas phase ion/ion reactions in a quadrupole ion trap mass spectrometer.
The first part of this thesis focused on the application of ion/ion reactions between multiply charged protein/polymer cations/anions with singly charged reagent anions/cations to manipulate the charge states of the species of interest and to obtain structural information via their collision-induced dissociation (CID) in the gas phase. The results obtained in the systematic studies of charge state dependent dissociation behavior of the Bacteriophage MS2 coat protein ions are consistent with what has been reported for other proteins (Chapter 2). The identification and characterization of the human cancer biomarker, thymosin β4, provided a good demonstration of a study of a real sample by using ion/ion reactions (Chapter 3). The investigation of the fragmentation patterns of negatively charged polyamidomine (PAMAM) with carboxylate functional groups helped to identify the structures of the impurities present in the sample, presumably due to a synthetic failure (Chapter 4).
The second half of this thesis focuses on the methods development to manipulate ion polarities and to increase charge states in the gas phase by using ion/ion reactions. Relatively high charge increasing efficiency has been observed for macroions derived from peptides and oligonucleotides (Chapter 5). The properties of the charge inversion reagents played an important role in the process. The carboxylate functionalized PAMAM dendrimer ions have demonstrated the highest charge inversion efficiency when inverting positive ions to the negative polarity (Chapter 6).