Interaction of immunoglobulin G with immobilized histidine: mechanistic and kinetic aspects.

A systematic investigation of coupling methods for and the chemistry and chromatographic parameters of immunoglobulin gamma (IgG) adsorption to histidine- and imidazole-coupled Sepharose gels was undertaken in order to elucidate the interactions involved in the mechanism of recognition between IgG and the immobilized histidine. The effects of pH, salt and temperature effects indicated an ion-pairing mechanism, rather than a mechanism based on the net charge of the protein (IgG), but with some localized complementary charges recognizing the unprotonated imidazole nitrogen. The effects of the addition of ethylene glycol and urea indicated the involvement of hydrogen bonding between the ligand and the protein. The immobilized histidine binds to the Fc fragment of IgG with a fairly low affinity, in a way similar to the N-terminum of protein A binding to the Fc fragment of IgG. The kinetic parameters of the chromatographic system indicated a good capacity but a low adsorption rate constant.