Abstract
This chapter discusses radioimmunoassay for chick intestinal calcium-binding protein (CaBP). The most widely used methods for quantitating chick CaBP have been the relatively insensitive Chelex binding assay and the radial immunodiffusion assay, which uses antisera produced in the rabbit against highly purified chick intestinal CaBP. This chapter discusses about a radioimmunoassay that has been developed for chick intestinal CaBP. The assay system is based on the quantitative measurement of the displacement of radioactive antigen CaBP from its binding antibodies by the unlabeled antigen— that is, there is competitive binding of radioactive and unlabeled CaBP to the specific antiserum. Because there is a fixed, limited amount of labeled CaBP, antibody and varying amounts of unlabeled CaBP, the percentage of label that is bound is inversely related to the concentration of unlabeled CaBP. The chick intestinal CaBP radioimmunoassay utilizes the double-antibody technique, which reduces background to a minimum and maximizes sensitivity. Sensitivity, precision, and accuracy of the radioimmunoassay for chick intestinal CaBP is discussed in detail.