Polymer-protein conjugates. II. Affinity precipitation separation of human immunogammaglobulin by a poly(N-isopropylacrylamide)-protein A conjugate.

The conjugate of protein A with poly(N-isopropylacrylamide) was synthesized and utilized in the separation of human immunogammaglobulin. In the separation process, poly(N-isopropylacrylamide)-protein A conjugate binds to the immunoglobulin with high specificity to form the poly(N-isopropylacrylamide)-protein A/immunoglobulin complex. The complex can be conveniently separated by precipitation upon heating above the lower critical solution temperature of the poly(N-isopropylacrylamide)-protein A/immunogammaglobulin complex. The separation capacity of poly(N-isopropylacrylamide)-protein A conjugate for human immunogammaglobulin was studied and it was demonstrated that approximately one out of every four protein A molecules binds to human immunogammaglobulin with a dissociation constant (Ks) of 3 x 10(-6) M. The affinity precipitation separation of human immunogammaglobulin is a rapid process which avoids the need for chromatographic columns. It can also be designed to run in a continuous mode.