Field Desorption Mass Spectra of Gastrine Peptides and Glutathione Derivatives

Abstract

<jats:p>Oligopeptides comprising the sequence of the C-terminal tetrapeptide of gastrine, Trp-Met-Asp-Phe-NH<jats:sub>2</jats:sub>, and several derivatives of glutathione, γ-Glu-Cys(SR)-Gly, were characterized by field desorption mass spectrometry. The field desorption mass spectra obtained at various field ion emitter temperatures reveal abundant molecular ions and fragmentation reactions that yield partial sequence information. In the series of glutathione derivatives investigated, characteristic ions formed by cleavage of the γ-Glu-Cys peptide bond determine the substituent at the Cys residue and can therefore be used to identify corresponding conjugation products of drug metabolites with glutathione. </jats:p>

Utility of Atmospheric-Pressure Chemical Ionization and Photoionization Mass Spectrometry in Bottom-Up Proteomics

“…One of them was extensive fragmentation in EI, which made molecular ions detection difficult [2]. Later "soft" ionization techniques such as chemical ionization or field desorption were discovered and applied for peptides [3,4]. The introduction of fast atom bombardment (FAB) in 1981 represented a significant advancement in the mass spectrometry of peptides [2].…”

“…The mobile phase contained 7% of acetone 2. In APCI, buffered mobile phases with acetonitrile were not tested because methanol phases worked better 3. In APPI, buffered mobile phases with methanol were not tested because acetonitrile phases worked better.…”