Iodination of [Tyr8] – Bradykinin – Comparison of Chloramine-T and Lactoperoxidase Techniques

Antigen-antibody kinetics were studied using a hapten which was iodinated by two unique procedures. Using bradykinin, a vasopressor hormone as a model peptide, radioactive iodination (125I) of its 8-tyrosyl analogue was carried out both enzymatically and chemically using modified procedures. Two distinct chemical species were obtained which were characterized on a chromatographic, chemical as well as charge basis as a mono-iodinated form of [Tyr8]-bradykinin using the lactoperoxidase procedure and a di-iodinated entity using chloramine-T technique. The addition of a second iodine atom to the antigen lowers its immunoreactivity for its antibody and thus alters the kinetics of this reaction. Further experiments on the stability (temperature, time of storage, and chemical environment) of these iodinated peptides are described.