Immunoaffinity for IgG antibodies of protein A labelled with 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid

Summary Protein A was covalently labelled with 4,7-bis-(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid in several molar ratios. The binding affinity for IgG and the delayed fluorescence of the corresponding complexes with Eu(III) were determined for each labelled compound. The immunoaffinity decreased slowly with increase in ratio of the label. A better immunoaffinity/labelling ratio was obtained by coupling protein A to the chelate via bovine serum albumin. A suitable ratio of chelating agent to protein A for producing a universal marker to be used in time-resolved fluoroimmunoassays can be determined.