Surface-modified TiO2 nanoparticles as affinity probes and as matrices for the rapid analysis of phosphopeptides and proteins in MALDI-TOF-MS

Abstract

We utilized three different types of TiO2 nanoparticles (NPs) namely TiO2-dopamine, TiO2-CdS and bare TiO2 NPs as multifunctional nanoprobes for the rapid enrichment of phosphopeptides from tryptic digests of α- and β-casein, milk and egg white using a simplified procedure in MALDI-TOF-MS. Surface-modified TiO2 NPs serve as effective matrices for the analysis of peptides (gramicidin D, HW6, leucine-enkephalin and methionine-enkephalin) and proteins (cytochrome c and myoglobin) in MALDI-TOF-MS. In the surface-modified TiO2 NPs-based MALDI mass spectra of these analytes (phosphopetides, peptides and proteins), we found that TiO2-dopamine and bare TiO2 NPs provided an efficient platform for the selective and rapid enrichment of phosphopeptides and TiO2-CdS NPs efficiently acted as the matrix for background-free detection of peptides and proteins with improved resolution in MALDI-MS. We found that the upper detectable mass range is 17 000 Da using TiO 2-CdS NPs as the matrix. The approach is simple and straightforward for the rapid analysis of phosphopeptides, peptides and proteins by MALDI-MS in proteome research. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.