Highly selective enrichment of phosphorylated proteins by using Spore@Fe3+ microspheres.

The advantages of spore-based microspheres include high monodispersity, presence of different functional groups (carboxylic, amino, and hydroxyl groups), facile industrial-scale preparation by using cell cultures via fermentation in a potentially cost effective and environment friendly manner, and high uniformity. We developed a novel spore@Fe3+ microsphere for specific capture of phosphoproteins. Caseins (α-casein and β-casein) as phosphoproteins were used to evaluate binding capacity and enrichment factor. The spore@Fe3+ microspheres demonstrate high binding capacity and selectivity for phosphoproteins (1983 and 1818 mg g-1 for α-casein and β-casein, respectively). A mixture of bovine serum albumin and β-casein at 100:1 ratio displayed an enrichment factor higher than 173-fold, which can nearly be considered "purification" of phosphoproteins. The proposed method is a promising technique in developing more selective, rapid, low cost, and high-throughput platforms for phosphoprotein enrichment, and it presents potential application in investigation of protein functions and in personalized diagnostic tests.