Temperature-Resolved Proton Transfer Reactions of Biomolecular Ions

Abstract

Temperature-resolved proton transfer reactions of multiply-protonated angiotensin I, disulfide-intact and -reduced lysozyme, and ubiquitin ions to primary, secondary and aromatic amines were examined in the gas phase. Absolute reaction rate constants for proton transfer were determined from intensities of parent and product ions in the mass spectra. Remarkable change was observed for distribution of product ions and reaction rate constants. In particular, the rate constants for disulfide-intact lysozyme ions changed more drastically with change of charge states and temperature than those for disulfide-reduced ions. Proton transfer reaction was enhanced or suppressed by complex formation of the ions with gaseous molecules, which relates to their conformation changes of with change of temperature.