Robust, Reproducible, and Economical Phosphopeptide Enrichment Using Calcium Titanate

Mass-spectrometry-based phosphoproteomics has revolutionized phosphoprotein analysis and enhanced our understanding of diverse and fundamental cellular processes important for human health and disease. Because of their relative scarcity, phosphopeptides must be enriched before analysis. Many different enrichment methods and materials have been described, and many reports have made claims about the advantages of particular materials and methodological variations. We demonstrate an effective and highly reproducible single-step enrichment method using an off-the-shelf preparation of calcium titanate. Using two different cell lines and replicate analysis, we show that our method achieves a purity and depth of analysis comparable or superior to a widely used TiO2-based method at a reduced cost and effort. This method provides a new and immediately available tool for expanding the reach of phosphoproteomic inquiry.