GAS PHASE CHEMISTRY OF IONS PRODUCED BY ELECTROSPRAY

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The gas-phase chemistry of multiply charged protein ions generated by electrospray ionization mass spectrometry will be investigated. Ion/molecule reactions ad dissociation techniques will be used to obtain structural information on high mass biological ions. Fundamental kinetic, thermodynamic, and mechanistic aspects of these processes will also be considered. The development of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR or FTMS) as a tool for studies of ions generated by electrospray is an additional goal of this research. Reactivity studies will center on proton transfer and hydrogen/deuterium exchange. The effect of the gas-phase basicity of the neutral reaction partner on product formation and kinetics will be investigated. Proton transfer reactions will also include anionic partners. The impact of a protein's structure on its reactivity will be explored by varying the molecular weight of the protein, the number of protons in the ion, the basicities of the amino acid residues present, the sequence of residues, and the conformation of the ions. Multiply protonated protein ions will be subjected to low-energy collision-induced dissociation (CID) experiments. These studies will provide knowledge of the effects of protein structure on dissociation patterns. A goal is to determine which charge states, or combinations of charge states, provide the most informative fragmentation. A wide range of charge states will be investigated. Proton transfer reactions will be used to lower the degree of protonation for some proteins. Where possible, comparisons will be made between the CID pathways of multiply charged ions and those of singly charged ions produced by fast atom bombardment (FAB). The effect of experimental parameters on the spectra will be considered, with single and multiple collision conditions and sustained off-resonance irradiation being explored. Studies of both native and denaturized proteins will be performed to establish the influence of conformational features on the CID spectra. In addition, electron-induced dissociation (EID) will be evaluated as an alternative to CID for obtaining structural information on multiply charged protein ions.