Protein Sequencing

Protein sequencing is the determination of the exact order of amino acids making up a protein's polypeptide chain or chains. Frederick Sanger accomplished it for the first time between 1945 and 1955, working out the complete sequence of both chains of bovine insulin and the three disulfide bonds linking them, using his own reagent, 1-fluoro-2,4-dinitrobenzene, now called Sanger's reagent, to label and identify each chain's terminal amino acid before breaking the chain down for analysis. Published across several papers in the Biochemical Journal and completed in Ryle, Sanger, Smith and Kitai's 1955 paper The Disulphide Bonds of Insulin, the work proved that a protein has one exact, genetically determined sequence rather than a loose or variable composition, a foundational fact for molecular biology, and won Sanger the 1958 Nobel Prize in Chemistry. He later adapted the same reagent based approach into the dideoxy chain-termination method for sequencing DNA, for which he won a second Nobel Prize in Chemistry in 1980.