Some regularities of immunochemical analysis. A sequential saturation method

: The behaviour of an immunochemical analytical system based on the sequential binding of determined and labeled antigens to the specific antibodies (saturation analysis) was investigated by means of computer modelling. Using the mathematical model, optimal ratios of reagent concentrations and duration of immunochemical reactions were determined. To get satisfactory calibration curves the incubation time of the reaction with labelled antigen should be approximately equal to 0.1 k-1, where k-1 is a kinetic constant of dissociation of the antigen-antibody complex. Changes in the shape of the calibration curves caused by the presence of two populations of antibodies with different affinities for antigen and by positive cooperativity in the antigen binding to two binding sites of a single antibody were analysed. A satisfactory correlation between experimental and calculated results was illustrated by the ELISA of insulin.