Selective enrichment of phosphopeptides by porous SnO2 (#24)
As one of the most important post-translational modifications, protein phosphorylation regulates various biological functions and involves in several diseases including cancer. While phosphoproteomics attracts increasing interest, the detection of phosphorylated proteins/peptides by mass spectrometry (MS) is still challenging due to their low abundance, high dynamic range and poor ionization efficiency. Currently metal oxide affinity chromatography (MOAC) is considered more applicable compared to other pre-treatment strategies. Various metal oxides have been proposed as affinity probes (APs), and among them SnO2 is considered as a selective and effective material.
Recently we applied porous SnO2 spheres with large surface area and high activity on phosphopeptide enrichment, and compared their performance with non-porous SnO2 and commercial TiO2. In a typical enrichment process the protein digests were incubated with the MOAC materials in a batch mode, and then the eluted peptides were analyzed by MALDI-TOF MS (matrix-assisted laser desorption/ionization-time of flight mass spectrometry). The mass spectra showed that better results could be obtained using porous SnO2 in both sensitivity and real sample analysis. For tryptic digests of β-casein, when the concentration was as low as 4×10-10 M, three phosphopeptides can still be detected after enrichment by porous SnO2.
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 Leitner, A. Phosphopeptide enrichment using metal oxide affinity chromatography. Trac-Trends in Analytical Chemistry, 2010, 29 (2), 177-185.