Abstract

In studies designed to determine the distribution of the disulphide bridges, insulin was hydrolysed with cold concentrated hydrochloric acid and many more cystine peptides were obtained than could be accounted for by a unique structure for insulin. Thin result led to the suspicion that an interchange reaction took place at the disulphide bonds, and this suspicion was confirmned by experiments with model disulphides (Sanger, 1953). This paper reports the results of some further studies on the disulphide interchange reaction in acid, neutral and slightly alkaline solutions, which were made with the aim of finding how, and under what conditions, the interchange occurred, and particularly how it might be prevented during studies on the arrange- ment of the disulphide bonds of proteins.