Hafnia and Zirconia Chromatographic Materials for the Enrichment of Phosphorylated Peptides
Metal oxide materials from the Group IV of the Periodic Table have shown unique affinity for the isolation of phosphorylated peptides in proteomic research. This chapter provides an evaluation of the adsorptive properties of hafnia and zirconia metal oxides for the enrichment of phosphorylated peptides. Using β-casein as a model phosphorylated protein, it is shown that the enrichment of phophopeptides is influenced by the conditions used in the synthesis/processing of the metal oxides. The use of zirconia and hafnia materials processed at 300°C do not provide for discrimination for isolation between mono- or tetra- phosphorylated peptides. Hafnia processed at 1100°C showed an almost exclusive enrichment/isolation characteristic towards monophosphorylated peptides, making it more selective than the commercially available enrichment materials tested. On the other hand, zirconia material processed at 500°C showed to a large extent preferential enrichment towards tetraphosphorylated peptides. Not only the zirconia and hafnia materials complement each other, the data also suggest that using specific processing of the material during synthesis can provide for tunable adsorptive/enrichment characteristics.