Highly specific capture and direct MALDI MS analysis of phosphopeptides by zirconium phosphonate on self-assembled monolayers.

The dynamic range and low stoichiometry of protein phosphorylation frequently demands the enrichment of phosphorylated peptides from protein digests prior to mass spectrometry. Several techniques have been reported in literature for phosphopeptide enrichment, including metal oxides such as TiO(2) and ion metal affinity chromatography (IMAC). While the metal oxides have been used with reasonable success, IMAC has suffered from reduced selectivity and poor reproducibility.