The work is based on the comparative study of metal oxide nanocomposites based on alumina in combination with two transition metal oxides (zirconia and titania) and two lanthanide oxides (ceria and lanthanum oxide). The choice is based on specific aims, i.e. to improve the limitations of individual metal oxides in phosphopeptide enrichment. The nanocomposites have shown improved phosphopeptide enrichment efficiency in comparison to the individual metal oxides. Alumina-zirconia show enhanced mono-phosphorylated peptide enrichment than ZrO2 whereas alumina-titania has better recovery of mono- and multi-phosphorylated peptides in comparison to individual TiO2. Alumina-ceria and alumina-lanthanum oxide overall enrich higher number of phosphopeptides. The alumina nanocomposites show higher selectivity and sensitivity for spiked β-casein in BSA (1:1000) and diluted β-casein digest (10 femtomole), respectively. Through the transition metal oxide nanocomposites, number of phosphoproteins from human serum are identified while this number is highest in case of alumina-lanthanum oxide nanocomposite. Thus the enrichment is affected by the choice of metal oxide in the nanocomposite based enrichment strategies.
Keywords: Alumina; Ceria; Co-precipitation; Lanthanum oxide; MALDI-MS; Nanocomposites; Phosphopeptides; Titania; Zirconia.