Preparation of radiolabeled peptides via an iodine exchange reaction

Peptides labeled with radioactive I-125 can be detected at the extremely low concentrations necessary for receptor binding studies and medical applications. Traditional methods of iodination often lead to inactive peptides due to excessive iodination, nonspecific iodination, or oxidative damage to the peptide. In this work these disadvantages are circumvented by labeling I-127 containing peptides of a predetermined biological activity using a radioactive I-125 exchange reaction with (NaI)-I-125. Specific radioactivity up to 9.8 Ci/mmol was reached in a simple and efficient procedure. (C) 1996 Academic Press, Inc.