title: Serine effects on collision-induced dissociation and photodissociation of peptide cation radicals of thez+•-type.
abstract: The serine residue displays specific effects on the dissociations of peptide fragment cation-radicals of thez+•type which are produced by electron transfer dissociation. Energy-resolved collision-induced dissociation (ER-CID), time-resolved infrared multiphoton dissociation (TR-IRMPD), and single-photon UV photodissociation at 355 nm revealed several competitive dissociation pathways consisting of loss of OH radical, water, and backbone cleavages occurring atN-terminal andC-terminal positions relative to the serine residue. The activation modes using slow-heating and UV photon absorption resulted in different relative intensities of fragment ions. This indicated that the dissociations proceeded through several channels with different energy-dependent kinetics. The experimental data were interpreted with the help of electron structure calculations that provided fully optimized structures and relative energies forcisandtransamide isomers of thez4+•ions as well as isomerization, dissociation, and transition state energies. UV photon absorption by thez4+•ions was due to Cα-radical amide groups created by ETD that provided a new chromophore absorbing at 355 nm.
authors.affiliation: Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, WA, 98195-1700.
authors.forename: Huong T H
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, WA, 98195-1700.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Shaffer
authors.affiliation: Department of Chemistry, University of Wisconsin, Madison, WI, USA.
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Ledvina
authors.affiliation: Department of Chemistry, University of Wisconsin, Madison, WI, USA ; Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI, USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Coon
authors.affiliation: Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, WA, 98195-1700.
authors.forename: František
authors.initials: F
authors.lastname: Tureček
keywords: UV photodissociation; collision-induced dissociation; electron transfer dissociation; infrared multiphoton dissociation; peptide ions of the z type