The free energy of angular position of the fab arms of IgG antibody

From the observed distribution of ring-shaped complexes formed with bivalent antibody and bivalent hapten, we have calculated the free energies of angular position of the Fab arms at different angles about the hinge region. These positional energies are found to be small, less than RT, except for the case of complete closure of the hinge angle. When complete closure occurs with the formation of a dimeric complex, we calculate that the strain energy is approximately 700 cal/dimer.