Phosphoprotein/Phosphopeptide Enrichment and Analysis Based on Nanostructured Materials

Protein phosphorylation is one of the most ubiquitous post-translational modifications. Many low-abundance endogenous phosphoproteins and phosphopeptides in the body fluids or tissues are biomarkers with higher clinical sensitivity and specificity, which could provide valuable information for the detection of many diseases and elucidation of pathology. It is still a great challenge to detect the phosphoproteins and phosphopeptides from complex biological samples directly due to reversibility of protein phosphorylation and the extremely low concentrations of phosphoproteins. Nanostructured materials have attracted particular attentions in enrichment, separation, and purification of phosphoproteins/phosphopeptides due to their larger surface area, numerous affinity sites and unique structures. The research subject has become one of research hotspots in phosphoproteomics presently. Various multifunctional nanostructured materials such as core-shell particles with mesoporous affinity shell and magnetic core, hybrids of multiple components and composite affinity materials have been synthesized for selective enrichment and fast purification of phosphoproteins/phosphopeptides. In this review, we are focusing on recent advancements of nanostructured materials for phosphoprotein/phosphopeptide enrichment and purification prior to MS analysis. Definition, structure characteristic, unique physicochemical properties and potential in bioseparation of the nanostructured materials are first introduced. Subsequently, the related research background on phosphoproteomic studies in proteomics using mass spectrometric strategies in combination with phosphospecific enrichment techniques is briefly presented. After that, two types of affinity enrichment mechanisms to phosphoproteins/phosphopeptides are compactly discussed. Next, mesoporous, hybrid, and composite nanostructured materials for enrichment of phosphoproteins/phosphopeptides as well as application of multifunctional nanostructured materials in phosphoproteomics are summarized in detail. Finally, some unsolved problems and a brief perspective and outlook on phosphopeptide enrichment are proposed