Monoiodoinsulin labelled in tyrosine residue 16 or 26 of the insulin B-chain. Preparation and characterization of some binding properties.

By the combination of polyacrylamide gel electrophoresis and QAE-Sephadex ion exchange chromatography it was possible to isolate the four isomers of porcine [125I]monoiodoinsulin to a purity of more than 97%. The yield of the two B-chain-labelled isomers was increased by iodinating in buffer containing 6M urea. The apparent binding affinity to isolated rat adipocytes was 0.65 for the A19 isomer, 1.0 for the B16 isomer, and 2.0 for the B26 isomer, respectively, relative to the A14 isomer. In contrast, the B26 isomer had only an apparent binding affinity of 1.2 relative to the A14 isomer in isolated hepatocytes.