title: Infrared multiphoton dissociation for enhanced de novo sequence interpretation of N-terminal sulfonated peptides in a quadrupole ion trap.
abstract: Infrared multiphoton dissociation (IRMPD) of N-terminal sulfonated peptides improves de novo sequencing capabilities in a quadrupole ion trap mass spectrometer. Not only does IRMPD promote highly efficient dissociation of the N-terminal sulfonated peptides but also the entire series of y ions down to the y(1) fragment may be detected due to alleviation of the low-mass cutoff problem associated with conventional collisional activated dissociation (CAD) methods in a quadrupole ion trap. Commercial de novo sequencing software was applied for the interpretation of CAD and IRMPD MS/MS spectra collected for seven unmodified peptides and the corresponding N-terminal sulfonated species. In most cases, the additional information obtained by N-terminal sulfonation in combination with IRMPD provided significant improvements in sequence identification. The software sequence tag results were combined with a commercial database searching algorithm to interpret sequence information of a tryptic digest on alpha-casein s1. Energy-variable CAD studies confirmed a 30-40% reduction in the critical energies of the N-terminal sulfonated peptides relative to unmodified peptides. This reduction in dissociation energy facilitates IRMPD in a quadrupole ion trap.
authors.affiliation: Department of Chemistry and Biochemistry, 1 University Station A5300, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Wilson
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Brodbelt
mesh_terms: D000595:Amino Acid Sequence; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D013450:Sulfones / Q000737:chemistry*
chemical_list: D010455:Peptides; D013450:Sulfones