ABSTRACT
In connective tissue research, radioimmunoassays have been first applied to analyze the antigenic structure of Type I collagen. Labeling of proteins can be performed with any suitable radioactive isotope, but a high specific activity is most conveniently achieved by the incorporation of iodine. Radioimmunoassays detect primary antigen-antibody complexes, and it is sufficient that the labeled antigen combines with a single antibody binding site. Radioimmunoassays have been applied for studying a variety of connective tissue proteins. Immunochemical studies on large proteins are faced with the complexity of binding sites on the antigen and as a consequence with an enormous heterogeneity in affinity constants of the antibodies. Radioimmunoassays which are quite sufficient for analyzing the antigenic structure of a given protein usually have to be adjusted to the particular requirements of a sensitive and quantitative assay. The disadvantages of radioimmunoassays are the low stability of labeled products and general problems arising from the work with radioactive substances.
