The Nobel Prize in Chemistry 1958 was awarded to Frederick Sanger "for his work on the structure of proteins, especially that of insulin".
 

The proteins are among the most complicated and enigmatic substances in Nature and appear to be particularly closely related to all that we call Life. That insulin is a physiologically important hormone which is used in the treatment of diabetes is well known to all. The start was promising. Sanger developed a method to "mark" at its free amino end the particular amino acid which sits at the end of a chain. If the chains are only partially broken down - for example by treatment with weak acids or enzymes - one obtains larger fragments of the chain, containing, 2, 3, 4, 5 or more amino acids in the very sequence in which they occur in the intact molecule. Sanger succeeded in isolating and identifying a large number of such fragments from the complicated mixtures obtained by such a treatment. Sanger managed to determine the sequence of amino acids in each bit of the chain thus isolated. In this work his "end-group" methods, already mentioned here, was of great help.