MUTATIONS IN THE COMPLEMENTARITY-DETERMINING REGIONS DO NOT CAUSE DIFFERENCES IN FREE-ENERGY DURING THE PROCESS OF FORMATION OF THE ACTIVATED COMPLEX BETWEEN AN ANTIBODY AND THE CORRESPONDING PROTEIN ANTIGEN

Effects of mutations on antigen-antibody interactions were energetically examined using several kinds of Fv fragments, derivatives of a monoclonal antibody, D1.3, that is specific for hen egg-white lysozyme. According to the transition-state theory, the thermodynamic parameters involved in pre and post-processes of formation of the activated complex were estimated separately In the pre-process, there is a strong compensation between changes in entropy and changes in enthalpy caused by substitutions of amino acid residues. Thus, the differences in the association constant (K-A) caused by mutations are not related to the pre-process but to the post-process.