Step 1: Understanding the Concept: Frederick Sanger developed a groundbreaking method to determine the amino acid sequence of proteins, earning him a Nobel Prize.
His pioneering sequencing work was conducted on the protein hormone insulin.
Step 2: Key Formula or Approach: The approach relies on recalling the historical biochemical techniques and specific chemical reagents used for N-terminal amino acid sequencing.
Step 3: Detailed Explanation: Sanger utilized 1-fluoro-2,4-dinitrobenzene (FDNB), which is now commonly known as Sanger's reagent.
This chemical reacts specifically with the N-terminal amino acid of a polypeptide chain under mildly alkaline conditions to form a stable dinitrophenyl (DNP) derivative.
After acid hydrolysis of the protein, the specific DNP-amino acid remains intact and can be isolated and identified using chromatography, thereby determining the N-terminal sequence.
Edman later developed a more continuous sequencing method using Phenylisothiocyanate (PITC).
Ninhydrin is used to detect free ammonia or primary/secondary amines, and Biuret reagent tests for the presence of peptide bonds in general.
Step 4: Final Answer: Sanger used Fluorodinitrobenzene (FDNB) to sequence the structure of insulin.