title: Factors Affecting the Production of Aromatic Immonium Ions in MALDI 157 nm Photodissociation Studies.
abstract: Immonium ions are commonly observed in the high energy fragmentation of peptide ions. In a MALDI-TOF/TOF mass spectrometer, singly charged peptides photofragmented with 157 nm VUV light yield a copious abundance of immonium ions, especially those from aromatic residues. However, their intensities may vary from one peptide to another. In this work, the effect of varying amino acid position, peptide length, and peptide composition on immonium ion yield is investigated. Internal immonium ions are found to have the strongest intensity, whereas immonium ions arising from C-terminal residues are the weakest. Peptide length and competition among residues also strongly influence the immonium ion production. Quantum calculations provide insights about immonium ion structures and the fragment ion conformations that promote or inhibit immonium ion formation.
authors.affiliation: Department of Chemistry, Indiana University, 800 East Kirkwood Ave., Bloomington, IN, 47405, USA.
authors.forename: Nick
authors.initials: N
authors.lastname: DeGraan-Weber
authors.affiliation: Department of Chemistry, Indiana University, 800 East Kirkwood Ave., Bloomington, IN, 47405, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Ashley
authors.affiliation: Department of Chemistry, Indiana University, 800 East Kirkwood Ave., Bloomington, IN, 47405, USA.
authors.forename: Karlijn
authors.initials: K
authors.lastname: Keijzer
authors.affiliation: Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 339-701, South Korea. mbaik2805@kaist.ac.kr.|Institute for Basic Science (IBS), Center for Catalytic Hydrocarbon Functionalizations, Daejeon, 339-701, South Korea. mbaik2805@kaist.ac.kr.
authors.forename: Mu-Hyun
authors.initials: MH
authors.lastname: Baik
authors.affiliation: Department of Chemistry, Indiana University, 800 East Kirkwood Ave., Bloomington, IN, 47405, USA. reilly@indiana.edu.
authors.forename: James P
authors.initials: JP
authors.lastname: Reilly
mesh_terms: D024322:Amino Acids, Aromatic / Q000737:chemistry; D001120:Arginine / Q000737:chemistry; D010455:Peptides / Q000032:analysis* / Q000737:chemistry*; D010782:Photolysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry
chemical_list: D024322:Amino Acids, Aromatic; D010455:Peptides; D001120:Arginine
keywords: Aromatic residues; Immonium ions; Peptide ion fragmentation; Photodissociation