Tritiated peptides. Part 9. Synthesis of [3,5-3H2-Tyr12]- and [2,5-3H2-His20]-human calcitonin

Abstract

The syntheses are described of human calcitonin dotriacontapeptides separately labelled with tritium in the tyrosine and histidine residues at positions 12 and 20 to specific radioactivities of 50.5 and 8.2 Ci mmol^–1, respectively, by reductive de-iodination of suitable 11–32 fragments followed by rapid coupling to the 1–10 fragment and column-chromatographic purification of the reaction mixtures, using gel-filtration, and ion-exchange and high-pressure liquid chromatographic techniques. It was demonstrated that the peptide containing a disulphide bridge poisons the catalysts used for tritiation.