ANTIBODY-BINDING EFFICIENCY OF DIFFERENTLY LABELED STEROID-HORMONES

The binding of estradiol labelled with H-3 or with external labels (isoluminol and horseradish peroxidase) to anti-estradiol-6-carboxymethyloxime-bovine serum albumin antibodies was compared. The external labels were coupled covalently to the steroid via homologous 6-carboxymethyloxime or heterologous 3- and 17-hemisuccinate bridges. Different factors and conditions influencing this binding and the slope and shape of the calibration graph were studied, including the type of label, the liquid- and solid-phase antibody system, the matrix effect and general incubation conditions, e.g., time and temperature. External homologous labels yielded the most sensitive calibration graphs and the lowest detection limits. Large differences in the binding of the label and in the shape of the calibration graph between the different antibodies were observed.