47—A STUDY OF SOME PROBLEMS IN PROTEIN CHEMISTRY USING NEW (NON-HYDROLYTIC) METHODS FOR THE DETERMINATION OF THIOL AND DISULPHIDE

Abstract

Present methods for estimating SS and SH groups in insoluble proteins are unsatisfactory, errors arising especially during preliminary hydrolysis. New (non-hydrolytic) methods have been devised for estimating SH groups by treating the protein with MeHgl, and for SS + SH by treating with MeHgl or HgCI3 in the presence of sulphite. The uptake of the reagent is measured polarographically, and a simple stoichiometry is found for the reaction of these mercury compounds with the SS and SH groups in the protein. These analytical techniques have been applied to the analysis of keratins, irradiated wool and oxidized wool. In the last case, relatively large amounts of partially oxidized disulphide residues have been detected. The principles underlying these new methods have been applied to the study of disulphide-splitting reactions, to the preparation of wools in which the SH and SS groups have been specifically and completely removed, and to the labelling of proteins with heavy atoms at the SH and SS residues.