Phosphopeptide enrichment using MALDI plates modified with high-capacity polymer brushes.

Matrix-assisted laser desorption/ionization plates coated with poly(2-hydroxyethyl methacrylate) (PHEMA) brushes that are derivatized with Fe(III)-nitrilotriacetate (NTA) complexes allow selective, efficient phosphopeptide enrichment prior to analysis by mass spectrometry (MS). Fe(III)-NTA-PHEMA brushes (60 nm thick) have a phosphopeptide binding capacity of 0.6 microg/cm(2) and exhibit phosphopeptide recoveries of over 70%, whereas much thinner polymer films containing Fe(III)-NTA afford a recovery of only 20%, and a monolayer of Fe(III)-NTA shows a recovery of just 10%.