title: [M + Fe - 5H]2- peptide ion composition verified by Fourier transform mass spectrometry accurate mass and tandem mass spectrometry analyses.
abstract: Previously, the unusual ion composition [M + Fe - 5H]2- had been proposed as the major species observed when a gamma-carboxy glutamate-containing glyco-peptide was analyzed with electrospray ionization in the negative ionization mode. The sequence assignment of this highly post-translationally modified peptide was based on the mass analysis using a quadrupole ion trap together with information from both Edman and DNA sequencing. Because there was little precedent for the loss of five protons from a ferric cationized peptide, we utilized Fourier transform mass spectrometry accurate mass and tandem mass spectrometry analyses to verify the peptide ion composition.
authors.affiliation: Clayton Foundation Laboratories for Peptide Biology, Salk Institute, La Jolla, California 92186-5800, USA. craig@salk.edu
authors.forename: A G
authors.initials: AG
authors.lastname: Craig
authors.forename: J P
authors.initials: JP
authors.lastname: Speir
authors.forename: S
authors.initials: S
authors.lastname: Rosamilia
authors.forename: V
authors.initials: V
authors.lastname: Fursey
authors.forename: M B
authors.initials: MB
authors.lastname: Lirazan
mesh_terms: D000478:Alkylation; D000596:Amino Acids / Q000032:analysis; D005290:Ferric Compounds; D005583:Fourier Analysis; D008401:Gas Chromatography-Mass Spectrometry; D010084:Oxidation-Reduction; D010455:Peptides / Q000737:chemistry*; D011522:Protons
chemical_list: D000596:Amino Acids; D005290:Ferric Compounds; D010455:Peptides; D011522:Protons