title: Hydrogen atom scrambling in selectively labeled anionic peptides upon collisional activation by MALDI tandem time-of-flight mass spectrometry.
abstract: We have previously shown that peptide amide hydrogens undergo extensive intramolecular migration (i.e., complete hydrogen scrambling) upon collisional activation of protonated peptides (Jørgensen et al. J. Am. Chem. Soc. 2005, 127, 2785-2793). The occurrence of hydrogen scrambling enforces severe limitations on the application of gas-phase fragmentation as a convenient method to obtain information about the site-specific deuterium uptake for proteins and peptides in solution. To investigate whether deprotonated peptides exhibit a lower level of scrambling relative to their protonated counterparts, we have now measured the level of hydrogen scrambling in a deprotonated, selectively labeled peptide using MALDI tandem time-of-flight mass spectrometry. Our results conclusively show that hydrogen scrambling is prevalent in the deprotonated peptide upon collisional activation. The amide hydrogens ((1)H/(2)H) have migrated extensively in the anionic peptide, thereby erasing the original regioselective deuteration pattern obtained in solution.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
authors.forename: Nicolai
authors.initials: N
authors.lastname: Bache
authors.forename: Kasper D
authors.initials: KD
authors.lastname: Rand
authors.forename: Peter
authors.initials: P
authors.lastname: Roepstorff
authors.forename: Michael
authors.initials: M
authors.lastname: Ploug
authors.forename: Thomas J D
authors.initials: TJ
authors.lastname: Jørgensen
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions; D018360:Crystallography, X-Ray; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D066298:In Vitro Techniques; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D055293:Receptors, Urokinase Plasminogen Activator / Q000037:antagonists & inhibitors / Q000737:chemistry; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000838:Anions; D009842:Oligopeptides; D010455:Peptides; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; D006859:Hydrogen