title: The competition of charge remote and charge directed fragmentation mechanisms in quaternary ammonium salt derivatized peptides--an isotopic exchange study.
abstract: Derivatization of peptides as quaternary ammonium salts (QAS) is a promising method for sensitive detection by electrospray ionization tandem mass spectrometry (Cydzik et al. J. Pept. Sci. 2011, 17, 445-453). The peptides derivatized by QAS at their N-termini undergo fragmentation according to the two competing mechanisms - charge remote (ChR) and charge directed (ChD). The absence of mobile proton in the quaternary salt ion results in ChR dissociation of a peptide bond. However, Hofmann elimination of quaternary salt creates an ion with one mobile proton leading to the ChD fragmentation. The experiments on the quaternary ammonium salts with deuterated N-alkyl groups or amide NH bonds revealed that QAS derivatized peptides dissociate according to the mixed ChR-ChD mechanism. The isotopic labeling allows differentiation of fragments formed according to ChR and ChD mechanisms.
authors.affiliation: Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland.
authors.forename: Marzena
authors.initials: M
authors.lastname: Cydzik
authors.forename: Magdalena
authors.initials: M
authors.lastname: Rudowska
authors.forename: Piotr
authors.initials: P
authors.lastname: Stefanowicz
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Szewczuk
mesh_terms: D041961:Deuterium Exchange Measurement / Q000379:methods*; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D010455:Peptides / Q000032:analysis / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D007477:Ions; D010455:Peptides; D000644:Quaternary Ammonium Compounds