Porous membranes are useful for protein purification because convective mass transport rapidly brings proteins to binding sites, which should minimize diffusion-based limitations and also decrease non-specific adsorption and increase protein purity. Unfortunately membranes have low binding capacities compared to columns, but modifying membrane pores with polymer brushes can greatly enhance protein binding. This thesis describes an aqueous method to grow polymer brushes from macroinitiators adsorbed in membranes pores. Compared to growth of brushes from silane initiators, this method leads to 4-fold increases in membrane permeability and an order of magnitude decrease in the time required for brush polymerization. The aqueous method is applicable to a wide range of polymeric membrane including nylon, polyethersulfone and polyvinylidine fluoride. Poly(2-(methacryloyloxy)ethyl succinate brushes grown from macroinitiators in nylon membranes bind as much as 120 mg lysozyme/cm3 of membrane, and when functionalized with nitrilotriacetate-Ni2+ complexes these brushes bind 85 mg/cm3 of polyhistidine-tagged (His-tagged) proteins. More importantly, these membranes isolate His-tagged proteins directly from complex cell extracts. This thesis also investigate the effect of reduction of the areal density of the polymer brushes on protein binding and purification of maltose binding protein using maltose attached to polymer brushes.
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