INDUCED ELECTROSTATIC POTENTIALS ON ANTIGEN-ANTIBODY COMPLEXES FOR BIOANALYTICAL APPLICATIONS

A concept for directly sensing the antigen-antibody binding event is presented. This direct sensing mechanism was studied with the use of protein A-IgG complex as the model system. IgG carries a net charge except at its isoelectric point (pI). The binding of IgG to protein A would contribute to an additional electric field around protein A. The presence of this additional electric field will therefore change the local pH near the protein A-IgG complex. This change in the local pH can then be readily observed by measuring the fluorescence property of fluorescein molecules conjugated with protein A before and after the introduction of IgG. The preliminary theoretical analyses and experimental results of protein A, fluorescein conjugate, and IgG complex are discussed.