Influence of surface hydrophobic groups on the adsorption of proteins ontononporous polymeric particles with immobilized metal ions

Iminodiacetic acid (IDA) and octyl moieties were covalently bound on nonpor ous particles, which were prepared from dispersion polymerization of methyl methacrylate and glycidyl methacrylate. After being charged with copper io ns, the IDA-bound particles could specifically adsorb deoxyribonuclease I ( DNase I) through the affinity interaction between protein and immobilized m etal ion. A mixed-ligand (metal-chelate and octyl-bound) support was obtain ed after hydrophobic (octyl) groups were also introduced to the particle su rface. The affinity adsorption of DNase I on the copper-IDA chelate was inf luenced by interaction between the protein and the bound octyl group. Both the affinity and the hydrophobic interactions could be well described by th e Langmuir isotherms. The equilibrium adsorption constants were estimated s eparately to be 0.96 and 0.50 liter g(-1) for affinity and hydrophobic bind ings, respectively. For binding on mixed-ligand support, the adsorption con stant was 0.45 liter g(-1). It was evident that both affinity and hydrophob ic interactions are involved in the adsorption of proteins onto mixed-ligan d particles. Desorption of the inactive proteins from the support was possi ble by increasing the hydrophobicity of the solution. (C) 2001 Academic Pre ss.