The two polypeptides of human insulin are linked together by

The two polypeptides of human insulin are linked together by disulphide bridges. In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin, and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted, and combined by creating disulphide bonds to form human insulin.