title: In-Source Decay Characterization of Isoaspartate and β-Peptides.
abstract: Deamidation and the subsequent formation of isoaspartic acid (isoAsp) are common modifications of asparagine (Asn) residues in proteins. Differentiation of isoAsp and Asp residues is a challenging task owing to their similar chemical properties and identical molecular mass. Recent studies showed that they can be differentiated using electron capture dissociation (ECD) which generates diagnostic fragmentsc'+57 andz•-57 specific to the isoAsp residue. However, the ECD approach is only applicable towards multiply charged precursor ions and generally does not work for β-amino acids other than isoAsp. In this study, the potential of in-source decay (ISD) in characterization of isoAsp and other β-amino acids was explored. For isoAsp-containing peptides, ISD with a conventional hydrogen-donating matrix produced ECD-like,c'+57 and z•-57 diagnostic ions, even for singly charged precursor ions. For other β-amino acids, a hydrogen-accepting matrix was used to induce formation of site-specifica-14 ions from a synthetic β-analogue of substance P. These results indicated that ISD can be broadly applied for β-peptide characterization.
authors.affiliation: Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, 670 Albany Street, Suite 504, Boston, MA 02118.
authors.forename: Xiang
authors.initials: X
authors.lastname: Yu
authors.affiliation: Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, 670 Albany Street, Suite 504, Boston, MA 02118.
authors.forename: Nadezda P
authors.initials: NP
authors.lastname: Sargaeva
authors.affiliation: Bruker Daltonics, Inc., 40 Manning Road, Billerica, MA 01821.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Thompson
authors.affiliation: Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, 670 Albany Street, Suite 504, Boston, MA 02118.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Costello
authors.affiliation: Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, 670 Albany Street, Suite 504, Boston, MA 02118.
authors.forename: Cheng
authors.initials: C
authors.lastname: Lin
keywords: FTICR-MS; Isoaspartate; MALDI-ISD; TOF-MS; β-peptide