Susanne C. Moyer

Fragmentation of phosphopeptides by atmospheric pressure MALDI and ESI/ion trap mass spectrometry

An investigation of phosphate loss from phosphopeptide ions was conducted, using both atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) and electrospray ionization (ESI) coupled to an ion trap mass spectrometer (ITMS). These experiments were carried out on a number of phosphorylated peptides in order to investigate gas phase dephosphorylation patterns associated with phosphoserine, phosphothreonine, and phosphotyrosine residues. In particular, we explored the fragmentation patterns of phosphotyrosine containing peptides, which experience a loss of 98 Da under collision induced dissociation (CID) conditions in the ITMS. The loss of 98 Da is unexpected for phosphotyrosine, given the structure of its side chain. The fragmentation of phosphoserine and phosphothreonine containing peptides was also investigated. While phosphoserine and phosphothreonine residues undergo a loss of 98 Da under CID conditions regardless of peptide amino acid composition, phosphate loss from phosphotyrosine residues seems to be dependent on the presence of arginine or lysine residues in the peptide sequence.

Peer Reviewed: Atmospheric Pressure MALDI

A new method for proteomics and other biological studies requiring high-throughput analyses.

Atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) on a quadrupole ion trap mass spectrometer

Abstract A new atmospheric pressure ionization technique, atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI), was recently introduced by Laiko et al. [U.S. Patent 5,965,884; Abstracts of the 4th International Symposium on Mass Spectrometry in the Health and Life Sciences, San Francisco, CA, 25–29 August 1998; Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry, Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, TX, 1999; Anal. Chem. 72 (2000) 652]. This source has been coupled to an orthogonal time-of-flight mass spectrometer [U.S. Patent 5,965,884; Abstracts of the 4th International Symposium on Mass Spectrometry in the Health and Life Sciences, San Francisco, CA, 25–29 August 1998; Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry, Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, TX, 1999; Anal. Chem. 72 (2000) 652] and to an ion trap mass spectrometer (ITMS) [Anal. Chem. 72 (2000) 5239; Atmospheric Pressure MALDI/Ion Trap Mass Spectrometry, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, June 2000; An Atmospheric Pressure MALDI Probe for Use with ESI Source Interfaces, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, June 2000; Atmospheric Pressure Matrix-Assisted Laser Desorption Ionization, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, June 2000]. Here, we present the current status of the work involving the development of an AP MALDI source for an ITMS. In addition, we present recent work from our own laboratory to demonstrate the utility of this novel configuration.