Use of n-Bromosuccinimide for the Iodination of Proteins for Radioimmunoassay

A new method, employing the mild oxidant N-bromosuccinimide, for the iodination of proteins for radioimmunoassay is described. Human prolactin, follicle-stimulating, luteinising, thyroid-stimulating, and growth hormones were iodinated with 125I by this method to specific activities up to 136 muCi/microgram. Incorporation of iodine ranged from 67% to 83% using 2 microgram hormone, 200 muCi Na125I, 0.5 nmol oxidant, and a reaction time of 15s. In comparative studies in immunological activity after iodination by this method was equal to, or greater than that by the chlorine gas, Iodo-Gen, or chloramine-T methods. The reagent is cheap and stable, and the method permits efficient use of antigen and iodide.