Preparation and characterization of a fully iodinated insulin derivative.

In the course of a study of the thermodynamics of the ionization of the lysyl residue of insulin (l), it was found desirable to make an iodinated derivative of insulin in order to convert the four tyrosyl residues in the monomer (molecular weight 5733 (2)) to 3,5-diiodotyrosyl groups which have lower pK values (3). Numerous properties of the iodinated derivative have been studied in order to ascertain whether the iodination of insulin was specific for the tyrosyl residues or whether other changes occurred in the molecule.