The preparation and properties of purified 125-I-labelled antibodies to insulin.

1. A procedure is described for the preparation of an insulin-immunoadsorbent containing 105-185mg. of insulin/g. of matrix, and with an antibody-binding capacity of 660mg./g. of insulin-immunoadsorbent. 2. Purified non-precipitating (125)I-labelled antibodies were prepared by iodination of the antibodies while they were isolated on the insulin-immunoadsorbent in order to protect at least one antigen-binding site. 3. The radioactive antibody was simply and rapidly separated from other radioactive material and damaging reagents, and found to be up to 94% pure as judged by its reaction with insulin-immunoadsorbent and unfixed insulin. 4. The (125)I-labelled antibody preparations had iodine contents of 0.5-64atoms/mol. of protein and specific radioactivities of 0.3-125mc/mg. of protein. 5. It is suggested that this is a simple method of producing a useful reagent.