Direct Observation of Hapten–Antibody Equilibria

IF the bivalency of antibodies, for which there is now considerable evidence, is accepted, it is to be expected that the addition of bivalent hapten to solutions of purified homologous antibody would bring about a linear association of alternating antibody and hapten molecules. The equilibrium extent of this association should be dictated solely by the value of the free energy of formation (Δ F 0 ) of a hapten–antibody bond and the concentration of the two reacting species. Hence a determination of the extent of association would provide the value of Δ F 0 , and if this were done as a function of temperature the values of the entropy (Δ S 0 ) and the heat (Δ H 0 ) of bond formation would be available as well.