Robert Harold Bateman

Peptide sequence determination by matrix-assisted laser desorption ionization employing a tandem double focusing magnetic—Orthogonal acceleration time-of-flight mass spectrometer

This report describes the fragmentation processes for peptides induced by collisional activation of the 12C isobar of matrix-assisted laser desorption ionization (MALDI)-generated pseudomolecular ions employing an EBE orthogonal acceleration time-of-flight mass spectrometer and using xenon as the collision gas at a laboratory collision energy of 800 eV. These MALDI-collision-induced dissociation (CID) spectra are shown to provide sequence information of comparable quality to those obtained by using high energy CID conditions with liquid secondary ionization mass spectrometry on a four-sector tandem instrument. Peptide sequencing via MALDI-CID is demonstrated on three tryptic peptides obtained from a bacterial protein (P450 isozyme) of unknown sequence. Sensitivity is shown to be at the 1 pmol level for standard peptides.

A parallel approach to post source decay MALDI-TOF analysis.

We present a novel enhancement to matrix-assisted laser desorption ionization (MALDI) post-source decay (PSD) analysis whereby fragment ions from multiple precursor ions are acquired into the same spectrum without employing a timed ion gate to preselect each parent ion. Fragment ions are matched to their corresponding precursor ions by comparing spectra acquired at slightly different reflectron electric fields. By measuring the difference in time-of-flight (TOF) between the two spectra for each fragment, it is possible to calculate the mass of the fragment ion and its parent. This new “parallel PSD” technique reduces analysis time and consumes less sample than conventional PSD, which requires an ion gate for serial preselection of precursor ions.