N-methacryloyl-(l)-histidine methyl ester carrying porous magnetic beads for metal chelate adsorption of cytochrome c

A magnetic metal-chelate adsorbent utilizing N-methacryloyl-(l)-histidine methyl ester (MAH) as a metal-chelating ligand was prepared. MAH was synthesized using methacryloyl chloride and l-histidine methyl ester. Magnetic beads with an average diameter of 50–100 μm were produced by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and MAH carried out in a dispersion medium. Specific surface area of the magnetic beads was found to be 80 m2/g. Elemental analysis of the magnetic beads for nitrogen was estimated as 70 μmol MAH/g polymer. Magnetic beads were complexed with the Cu2+ ions directly via MAH for the adsorption of cytochrome c from aqueous solutions. The cytochrome c adsorption on the mag-poly(EGDMA–MAH) beads was 51 mg/g. Cu2+ complexing increased the cytochrome c adsorption significantly. The maximum cytochrome c adsorption capacity of the Cu2+-chelated beads (carrying 68 μmol Cu2+ per gram of polymer) was found to be 222 mg/g at pH 8.0 in phosphate buffer. Cytochrome c adsorption decreased with increasing temperature. Cytochrome c molecules could be reversibly adsorbed and desorbed ten times with the magnetic adsorbents without noticeable loss in their cytochrome c adsorption capacity. The resulting magnetic chelator beads posses excellent long term storage stability.