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A neutral loss activation method for improved phosphopeptide sequence analysis by quadrupole ion trap mass
Melanie J Schroeder1, Jeffrey Shabanowitz, Jae C Schwartz
1Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22901, USA.
Analytical Chemistry
|July 2, 2004
Summary
A new Pseudo MS(n) method improves phosphopeptide analysis by enhancing ion dissociation in mass spectrometry. This technique converts neutral loss ions into informative fragments, aiding in the identification of phosphoproteomes.
Area of Science:
- Proteomics
- Analytical Chemistry
- Biochemistry
Background:
- Phosphoproteome characterization is crucial for understanding cellular signaling.
- Conventional tandem mass spectrometry (MS/MS) using collision-activated dissociation (CAD) faces challenges with phosphopeptide analysis due to dominant neutral loss of phosphoric acid.
- Effective enrichment of phosphopeptides is essential for accurate mass spectrometric analysis.
Purpose of the Study:
- To introduce and evaluate a novel phosphopeptide ion dissociation method, Pseudo MS(n), for quadrupole ion trap mass spectrometers.
- To enhance the structural information obtained from phosphopeptide analysis compared to conventional CAD.
- To improve the identification of phosphopeptides in complex mixtures.
Main Methods:
- Development of the Pseudo MS(n) method, which involves collisional activation of product ions resulting from neutral loss of phosphoric acid.
- Simultaneous storage of precursor and subsequent neutral loss product ions to generate composite spectra.
- Application of Pseudo MS(n) to synthetic phosphopeptides, enzymatically digested phosphoproteins, and complex phosphopeptide mixtures.
- Comparison of Pseudo MS(n) results with conventional MS/MS (CAD) using the TurboSEQUEST algorithm.
Main Results:
- Pseudo MS(n) demonstrated improved phosphopeptide ion dissociation for 7 out of 10 synthetic phosphopeptides.
- A similar improvement in dissociation was observed when analyzing peptides from a single phosphoprotein.
- The method successfully identified phosphopeptides that were mis-assigned by conventional CAD in complex mixtures.
- Pseudo MS(n) converts dominant neutral loss product ions into structurally informative fragments.
Conclusions:
- Pseudo MS(n) offers a significant advancement in phosphopeptide analysis by improving ion dissociation and spectral quality.
- The method enhances the identification capabilities for phosphopeptides, particularly in complex biological samples.
- Pseudo MS(n) is a valuable tool for detailed phosphoproteome characterization.