Rapid enrichment of phosphopeptides by BaTiO3 nanoparticles after microwave-assisted tryptic digest of phosphoproteins, and their identification by MALDI-MS

We show that BaTiO3 nanoparticles (NPs) can be used as a novel substrate for the rapid enrichment of phosphopeptides from microwave tryptic digests of alpha-casein and non-fat milk prior to their identification by MALDI-MS. Protein digestion is achieved by microwave tryptic digest for 50 s, and the resulting phosphopeptides can be effectively adsorbed on the surfaces of the NPs. The phosphopeptides were selectively detected via MALDI-MS. Digestion, enrichment and detection are accomplished within similar to 60 min. The method was applied to the indentification of 24 phosphopeptides from alpha-casein and of 21 phosphopeptides (of the alpha-casein type) from nonfat milk.