Gadolinium oxide: Exclusive selectivity and sensitivity in the enrichment of phosphorylated biomolecules

Selectivity and sensitivity define the dynamic applicability of separation and enrichment techniques. Owing to proteome complexity, numbers of separation media have been introduced in phosphoproteomics. Complex samples are pretreated to make the low‐abundance molecules detectable by mass spectrometry. Gadolinium oxide nanoparticles, offering mono‐ and bi‐dentate interactions, are optimized to capture the phosphopeptides. Selectivity of 1:11 000 is achieved for digested β‐casein phosphopeptides in bovine serum albumin digest background using gadolinium oxide nanoparticles. The limit of detection goes down to 1 attomole. With the optimized sample preparation protocol, gadolinium oxide nanoparticles enrich phosphopeptides of κ‐casein (Ser¹⁴⁸ and Ser¹⁷⁰) from digested milk sample, fibrinogen alpha chain phosphopeptide (Ser⁶⁰⁹) along with four hydrolytic products of Ser²²‐modified phosphopeptides from serum.