A new calibrant for matrix-assisted laser desorption/ionization time-of-flight-time-of-flight post-source decay tandem mass spectrometry of non-digested proteins for top-down proteomic analysis
Article first published online: 13 APR 2012
Published 2012. This article is a US Government work and is in the public domain in the USA.
Rapid Communications in Mass Spectrometry
Volume 26, Issue 10, pages 1241–1248, 30 May 2012
How to Cite
Fagerquist, C. K. and Sultan, O. (2012), A new calibrant for matrix-assisted laser desorption/ionization time-of-flight-time-of-flight post-source decay tandem mass spectrometry of non-digested proteins for top-down proteomic analysis. Rapid Commun. Mass Spectrom., 26: 1241–1248. doi: 10.1002/rcm.6220
- Issue published online: 2 APR 2012
- Article first published online: 13 APR 2012
- Manuscript Accepted: 6 MAR 2012
- Manuscript Revised: 21 FEB 2012
- Manuscript Received: 3 NOV 2011
Matrix-assisted laser desorption/ionization (MALDI) time-of-flight-time-of-flight (TOF-TOF) post-source decay (PSD) tandem mass spectrometry (MS/MS) has seen increasing use for analysis of non-digested protein ions for top-down proteomic identification. However, there is no commonly accepted calibrant for this purpose beyond the use of peptide calibrants whose fragment ions span a lower mass-to-charge (m/z) range.
We have used the PSD-generated fragment ions of disulfide-reduced/alkylated thioredoxin (AlkTrx) for TOF-TOF calibration in reflectron mode for the purpose of PSD-MS/MS analysis. The average m/z values of AlkTrx fragment ions were used for calibration. The quality of the calibration was assessed from the observed fragment ion mass error of MS/MS of the YahO protein from an unfractionated bacterial cell lysate of Escherichia coli O157:H7 as well as from MS/MS of bovine ubiquitin. The fragment ion mass errors of these two analytes were also used to assess instrument calibration using the monoisotopic fragment ions of [Glu1]-fibrinopeptide B (GluFib).
A general improvement in fragment ion mass accuracy was observed using the AlkTrx calibration compared to the GluFib calibration which resulted in a more significant top-down proteomic identification of these analyte proteins.
Our results suggest that AlkTrx may be useful as a calibrant for MALDI-TOF-TOF-PSD-MS/MS of small and modest-sized protein ions. The uniform fragmentation efficiency of YahO across its sequence suggests that it may be useful as a post-calibration standard to assess PSD-MS/MS instrument performance as well as establishing appropriate top-down proteomic fragment ion tolerances. Published 2012. This article is a US Government work and is in the public domain in the USA.