On the contribution of tryptophan to the affinity and specificity of anti-dinitrophenyl antibodies

The importance of tryptophan in the combining sites of anti-dinitrophenyl antibodies is evaluated from a series of model studies, and from experiments with a Dnp-binding monoclonal antibody protein A3. The thermodynamic parameters characterising the formation of a Dnp/tryptophan complex are determined. It is concluded that a Dnp/tryptophan interaction could provide about a third of the binding energy of Dnp ligands in such proteins as the mouse IgA myeloma 315.