title: Infrared multiphoton dissociation in quadrupole time-of-flight mass spectrometry: top-down characterization of proteins.
abstract: The first implementation of infrared multiphoton dissociation (IRMPD) for a hybrid quadrupole time-of-flight (QqTOF) mass spectrometer is reported. Ions were trapped in the radio frequency-only quadrupole (q2), which normally serves as a collision cell, and irradiated by a continuous CO2 IR laser. The laser beam was introduced coaxially with the quadrupoles in order to maximize overlap with the ion path. The resolution of the TOF mass analyzer allowed direct charge state determination for fragments smaller than 7 kDa. For larger fragments, the charge state could be assigned using the multiple losses of water, characteristic for IRMPD of proteins. The analytical performance is demonstrated by top-down sequencing of several representative proteins (equine myoglobin, bovine casein, and human insulin and chaperonin 10). Various post-translational modifications such as phosphorylation, acetylation, formation of disulfide bridges, and removal of N-terminal methionine followed by acetylation are detected and characterized. The utility of IRMPD for the analysis of biological samples is demonstrated in a study of a recently identified potential marker for endometrial cancer, chaperonin 10.
authors.affiliation: Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario, Canada.
authors.forename: Serguei A
authors.initials: SA
authors.lastname: Raspopov
authors.forename: Ayman
authors.initials: A
authors.lastname: El-Faramawy
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Thomson
authors.forename: K W Michael
authors.initials: KW
authors.lastname: Siu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins