Hydrogen / Deuterium Exchange and Fragmentation of Biomolecules to Probe Gas Phase Structure and Energetics

摘要: Presented in this dissertation are FT-ICR H/D exchange and fragmentation studies of protonated peptides for the purpose better understanding gas phase conformation protonation motifs, their affect on patterns. In addition, a new ion activation method is developed to enhance abundance higher energy pathways, thereby providing additional structural and/or mechanistic information.Studies probe relay mechanism small, model found that residue position, proline configuration, availability termini have measurable effect behavior reflective different / motifs.Charge remote cleavage C-terminal aspartic acid was studied with fixed charge derivative tris(2,4,6-trimethoxyphenyl) phosphonium (tTMP-P+). Ab initio calculations demonstrate tTMP-P+ cannot activate proposed nucleophile, acidic side chain hydrogen initiates cleavage. Despite absence an ionizing proton, derivatized peptide P+LDIFSDF (where P+ = tTMP-P+) exchanges three hydrogens deuterium. This supports occurs without direct involvement proton because protons able participate added proton. analogues provides insight into sites mechanisms exchange.H/D separate distinct populations differing rates subsequent motif affects spectrum observed. Studies [P+LDIFSDF + H]2+, [RPPGFSPFR 2H]2+ (bradykinin), [RVYIFPF show at least two structures exist The overall MS/MS linear combination all conformations motifs. labeled suggests complementary bn+ ym-n+ pairs being formed from doubly-charged precursor by same mechanism.SORI-RE CID based sustained off-resonance irradiation (SORI) on-resonant excitation (RE) enhancing while maintaining low processes. experiments presented serve illustrate usefulness SORI-RE diverse cases.