Metal-organic framework incorporated monolithic capillary for selective enrichment of phosphopeptides

Protein phosphorylation is a major post-translational modification, which plays a central role in the cellular signaling of numerous biological processes. Mass spectrometry (MS) has been an essential tool for the analysis of protein phosphorylation, for which it is a key step to selectively enrich phosphopeptides from complex biological samples. In this study, a metal-organic framework (MOF) incorporated monolithic capillary has been successfully prepared as an effective sorbent for the selective enrichment of phosphopeptides and has been off-line coupled with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) for efficient analysis of phosphopeptides. Using beta-casein as a representative phosphoprotein, efficient phosphorylation analysis by this off-line platform was verified. Phosphorylation analysis of a nonfat milk sample was also well demonstrated. Due to the combination of MOFs with large surface areas and highly ordered pores and the monolithic column, the MOF incorporated monolithic capillary exhibited several significant advantages, such as excellent selectivity toward phosphopeptides, superb tolerance to interference and a simple operation procedure, making the MOF-based monolithic capillary an ideal sorbent for the selective enrichment of phosphopeptides. Because of these highly desirable properties, the MOF-based monolithic capillary could be a useful tool for protein phosphorylation analysis.