Polyacrylamide Gels Copolymerized with Active Esters. A New Medium for Affinity Systems

A new and versatile method for linking biologically active ligands to a polyacrylamide matrix is reported. Active esters of acrylic acid (N-succinimidyl acrylate and N-phthalimidyl acrylate) were synthesized, then copolymerized with acrylamide and N.N′-methylenebisacrylamide. Displacement of the active ester in the gel thus formed by various ligands containing aliphatic amino groups resulted in the formation of stable amide bonds between the ligands and the polyacrylamide gel. The affinity gel thus prepared has the following advantages: (i) resistance to chemical and microbiological degradation, (ii) ease of control of ligand level and higher levels of ligand possible, (iii) ease of control of porosity, and (iv) total displacement of the active ester under suitable conditions. Efficacy of this system was tested by preparation of 6-aminohexyl 2-acetamido-2-deoxy-β-Dglucopyranoside derivative of polyacrylamide gel by the described method. It was found to be more effective for purification of wheat germ agglutinin than the previously published affinity chromatography systems and the wheat germ hemagglutinin was obtained in crystalline form. In addition, partial resolution of isolectins was obtained by elution from the affinity gel with a pH gradient.