Covalent immobilization of proteins onto (Maleic anhydride-alt-methyl vinyl ether) copolymers: enhanced immobilization of recombinant proteins.

Two genetically modified HIV-1 capsid p24 proteins, RH24 and RH24K, were covalently bound to maleic anhydride-alt-methyl vinyl ether (MAMVE) copolymer, under aqueous conditions. We demonstrated that the addition of a six lysine unit tag at the COOH-terminus of RH24K greatly improved the grafting reaction which could take place under many different experimental conditions. The course of the reaction was controlled by electrostatic attractive forces between the protein and the negatively charged polymer, as the chemical binding was more efficient at low ionic strength. The maximum loading capacity of the polymer depended on whether the protein bore the lysine tag (RH24K) or not (RH24). Twenty-four molecules of RH24 could be immobilized per polymer chain and 49 for RH24K. Such a difference could be explained by a difference of orientation of the protein on the polymer, side-on for RH24 and end-on for RH24K to account for the observed high packing density.