CONDITIONS FOR THE ADSORPTION OF PROTEINS ON ULTRASTABLE ZEOLITE-Y AND ITS USE IN PROTEIN-PURIFICATION

The adsorption of proteins on ultrastable zeolites was investigated. P rotein binding to one of these, ultrastable zeolite Y (USY), was studi ed in detail. Protein binding to USY, with a Si/Al ratio of > 240, was found to be dependent on the pH of the solution, being highest at or just below the pI of the protein. The amount of protein adsorbed on th e zeolite was found to be 10 times as much as the estimated binding to the external surface of the USY. We propose an adsorption mechanism i nvolving the formation of a protein layer strongly bound to the USY su rface, further protein layers being formed on tap of this on the basis of protein-protein interactions. The protein-protein interactions can be disrupted by changing the pH. Ultrastable zeolite Y was used as a new matrix for protein purification, Undesired proteins can be removed from a crude preparation by adsorption on USY, increasing the purity of a specific protein, or the protein can be adsorbed on the zeolite a nd subsequently eluted through changing the pH. These two means of pro tein purification are exemplified by the purification of peroxidase fr om a crude horseradish extract and by the purification of lysozyme fro m egg white. (C) 1997 Academic Press.