A ^3H/^(14)C-labelled reagent that reacts specifically with tryptophan residues, was used to monitor the reactivity of tryptophans in the Fc and Fab portions of IgG upon binding DNP-gly, (DNP)_1-cytochrome c, and (DNP)_8-cytochrome c. Binding of monovalent antigen caused a decrease in the reactivity of tryptophan residues in the Fc by 18%; binding of multivalent antigen caused decreases in the reactivity of tryptophan residues in Fc by 21% and Fab by 12%. Experiments to elucidate the interaction between IgG and complement component C4 were attempted.
Future studies include further characterization of (DNP)_1-cytochrome c and-the complement fixation capability of IgM-ABPC22 with monovalent antigen. Also planned is an investigation of the interaction of C4 with IgM in soluble antibody-antigen complexes
