A rapid and convenient means of immobilizing biological membranes is described. Sonication for formation of small vesicles, diffusion of the vesicles in support beads, and freeze-thawing is carried out in an immobilized multi-enzyme system. Large amounts of brush border membranes from bovine kidney were immobilized in Sepharose CL-6B, Sephacryl S-500, and Sephacryl S-1000 and increased in that order. For the latter two beads, the amounts were further increased with repetition of freeze-thawing up to a maximum of three times. Particle distribution analysis reveals that small vesicles are enlarged by the freeze-thawing repetition, suggesting an immobilization mode in which enlarged vesicles are physically entrapped in the beads. The bead-immobilized membrane vesicles were relatively stable, exhibiting constant enzyme activities for at least 6 h under packed column operation.
