Conditions for binding bovine IgG1 to protein A-Sepharose

Conditions were established so that both subclasses of bovine IgG were bound to Protein A-Sepharose. Increasing the pH of the starting buffer to pH 8.0 from pH 7.0 and increasing the starting phosphate concentration of the buffer to 0.5 M from 0.2 M enhanced the separation. Using these modifications in the buffer system, IgG1 was eluted from pH 7.0 to 7.8 and IgG2 at pH 5.0. Two major peaks were associated with IgG1 activity indicating heterogeneity of binding to protein A-Sepharose. One peak was found for IgG2. The molecular weights of the fractions were determined to be that of IgG by sodium dodecyl sulfate polyacrylamide gel electrophoresis.