PROTEIN ADSORPTION CHARACTERISTICS OF POROUS AND TENTACLE ANION-EXCHANGE MEMBRANE PREPARED BY RADIATION-INDUCED GRAFT-POLYMERIZATION

A polymer chain containing a diethylamino group was grafted onto the p ore surface of a porous hollow-fiber membrane by radiation-induced gra ft polymerization. Dependence of the protein binding capacity of the m embrane on environmental parameters such as salt concentration, pH and temperature was investigated. Saturation capacity of protein bound on to the graft chain containing ion-exchange group was governed by the c onformation of the graft chain and the intensity of ion-exchange inter action. The conformation of the graft chain was investigated based on the pore radius of the membrane estimated from the permeation flux of a buffer solution through the membrane. By sufficiently permeating a b ovine serum albumin (BSA) solution within the concentration range of 0 .2-10 mg-BSA/ml through the membrane, the BSA binding capacity was det ermined. With increasing salt concentration or pH of the protein buffe r solution, the graft chain shrank and BSA binding capacity decreased. On the other hand, the BSA binding capacity slightly increased with i ncreasing temperature, and the conformation of the graft chain was ins ensitive to temperature in the range from 278 to 303 K. The bound BSA could be quantitatively eluted by permeating a buffer solution contain ing 0.5 M NaCl, and no deterioration in the BSA binding capacity was o bserved during five cycles of adsorption, elution and conditioning.