Fred Sanger on Identifying Amino Groups in Insulin
  Fred Sanger     Biography    
Recorded: 16 Jun 2005

Well, that’s a long story, but I had some experience in chemistry, you see. Insulin was a protein, or rather it was a large protein then or it was thought to be, but it turned out to be smaller later on which was lucky. It had a rather large amount of free amino groups. He put me onto looking at the three amino groups; why they were. All proteins have free amino groups, but these are usually on the lysine residues, which is the one amino acid which has a free amino group. But insulin had rather more free amino groups than could be accounted for by the lysine residues.

I had some experience with chemistry and I looked for a reagent to couple with the free amino groups. I came up with the dinitrofluorobenzene, which was a lucky find because it did work well and it fit with something that I could use for labeling the free amino groups. I found that, in fact, there were four free amino groups in the insulin molecules, and I identified them using this reagent fluorodinitrobenzene.

Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice a Nobel laureate in chemistry. In 1958 he was awarded a Nobel prize in chemistry "for his work on the structure of proteins, especially that of insulin". In 1980, Walter Gilbert and Sanger shared half of the chemistry prize "for their contributions concerning the determination of base sequences in nucleic acids". The other half was awarded to Paul Berg "for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant-DNA".

He is the fourth (and only living) person to have been awarded two Nobel Prizes, either wholly or in part.

http://en.wikipedia.org/wiki/Frederick_Sanger