Urea-modified metal-organic framework of type MIL-101(Cr) for the preconcentration of phosphorylated peptides

Mass spectrometry (MS) is the most powerful tool in phosphoproteomics research. However, phosphopeptides usually are present in low concentrations and their preconcentration therefore is highly desired. We describe a two-step method for the synthesis of a metal organic framework of the type MIL-101(Cr) that is modified with urea (then designated as MIL-101(Cr)-UR 2 ). It possesses large surface area, good solvent stability and high affinity for some phosphates. Due to the presence of modified urea functions, this material allows for selective and effective enrichment of phosphorylated peptides. It was successfully applied to the enrichment of phosphopeptides from non-fat-milk. The method was applied to the detection of phosphopeptides in a tryptic digest of β-casein where is showed a detection sensitivity as low as 10 −10  M. A two step method was designed to synthesis MIL-101(Cr)-UR 2 and the prepared green solid was successfully applied to recognize phosphopeptides. (Amino functionalized metal-organic framework (MOF-NH 2 ); urea modified metal-organic framework (MOF-UR 2 ); matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS))