Association and dissociation kinetics of bobwhite quail lysozyme with monoclonal antibody HyHEL-5

The anti-hen egg lysozyme monoclonal antibody HyHEL-5 and its complexes wit h various species-variant and mutant lysozymes have been the subject of con siderable experimental and theoretical investigation, The affinity of HyHEL -5 for bobwhite quail lysozyme (BWQL) is over 1000-foId lower than its affi nity for the original antigen, hen egg lysozyme (HEL). This difference is b elieved to arise almost entirely from the replacement in BWQL of the struct ural and energetic epitope residue Arg68 by lysine, In this study, the asso ciation and dissociation kinetics of BWQL with HyHEL-5 were investigated un der a variety of conditions and compared with previous results for HEL, HyH EL-5-BWQL association follows a bimolecular mechanism and the dissociation of the antibody-antigen complex is a first-order process. Changes in ionic strength (from 27 to 500 mM) and pH (from 6.0 to 10.0) produced about a 2-f old change in the association and dissociation rates. The effect of viscosi ty modifiers on the association reaction was also studied. The large differ ence in the HEL and BWQL affinities for HyHEL-5 is essentially due to diffe rences in the dissociation rate constant.