HUMAN β‐ENDORPHIN: SYNTHESIS AND CHARACTERIZATION OF ANALOGS IODINATED AND TRITIATED AT TRYOSINE RESIDUES 1 AND 27

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Abstract
Three tritiated analogs of human .beta.-endorphin were prepared from their corresponding iondinated analogs. The iodinated analogs (diiodotyrosine at positions 1, 27 or 1 and 27) were synthesized by the solid-phase method and had biological and physical properties which were altered when compared with the native molecule. Catalytic exchange of these iodinated analogs in the presence of tritium yielded tritiated human .beta.-endorphins having full biological activity [guinea pig ileum assay] and specific activity of 50-100 Ci/mmol. Both the iodinated and tritiated .beta.-endorphin analogs were shown to be homogeneous by chromatograpy on carboxymethylcellulose, partition chromatography, paper chromatography, amino acid analysis, electrophoresis, high performance liquid chromatography and isoelectric focusing on polyacrylamide.