An octamolybdate-metal organic framework hybrid for the efficient adsorption of histidine-rich proteins

The incorporation of a polyoxometalate, octamolybdate (TBA₄Mo₈O₂₆), into a metal-organic framework, mesoporous chromium terephthalate MIL-101(Cr), produces a novel hybrid Mo₈O₂₆@MIL-101(Cr). The covalent interactions of the Mo₈O₂₆ moiety in the hybrid with the N-terminal site and the multi-metal binding site of proteins offer Mo₈O₂₆@MIL-101(Cr) favorable adsorption performance towards histidine-rich proteins, giving rise to adsorption capacities of 785.6 mg g^-1 for HSA and 420.1 mg g^-1 for IgG at pH 5.0. Thus, a protocol for the depletion of high abundance proteins from human plasma is proposed. The percentages of serum albumin and IgG are reduced from 50.15% and 13.18% to 7.41% and 3.42%, respectively. Meanwhile, low abundance proteins, e.g., Ig heavy chains, rheumatoid factors, protein IGKV3-11, anti-H1N1 influenza HA, and cDNA FLJ53691, are enriched to a certain extent by ultra-filtration. After the depletion of high abundance proteins, 335 protein species are identified in human plasma, with respect to 265 identified from the raw plasma. This illustrates well the potential of Mo₈O₂₆@MIL-101(Cr) in the application of proteomic studies.