Protection of methionine in peptides during iodination by sulfonium salt formation.
A method for the prevention of methionine oxidation during iodination of tyrosine containing peptides is reported. The methionine containing peptide is converted into the corresponding S-tert.-butylsulfonium derivative, which is iodinated using iodine monochloride. After removal of the S-tert.-butyl group and purification, sulfoxide-free 3,5 diiodotyrosine (Dit) peptides were obtained. Dit8-substance P, Dit8-physalaemin 6-11 and Dit1, Met5-enkephalin were synthesized by this route. Tritium labeling of Dit1, Met5-enkephalin yielded 3H-enkephalin with a specific radioactivity of 38 Ci/mmol.
D004744:Enkephalin, Methionine; D007202:Indicators and Reagents; D007454:Iodides; D008715:Methionine; D009842:Oligopeptides; D010084:Oxidation-Reduction; D013329:Structure-Activity Relationship; D013452:Sulfonium Compounds
D007202:Indicators and Reagents; D007454:Iodides; D009842:Oligopeptides; D013452:Sulfonium Compounds; D004744:Enkephalin, Methionine; D008715:Methionine