Upon his arrival at the NIH, Anfinsen wanted to expand his study of the amino acid structure of proteins. Why, Anfinsen wondered, does a protein fold into its distinctive three-dimensional shape? Was it helped by other enzymes? Why do they take this particular form? He chose as his model bovine pancreatic ribonuclease (RNase), an enzyme that facilitates the DNA-RNA interaction in the pancreas cells of cows. Partly, Anfinsen's choice of this enzyme was practical: the Armour meat packing company of Chicago could provide Anfinsen's laboratory with a ready supply of raw material. Anfinsen and postdoctoral students Michael Sela and Fred White observed in laboratory experiments that amino acid chains in the active RNase enzyme fold spontaneously into what Anfinsen later called the enzyme's "native conformation." In an important article in the Journal of Biological Chemistry in 1954, Anfinsen showed that the sequence of amino acids in a peptide chain determines the folding pattern. The mysteriously complex process of protein folding could be explained entirely simply by the physical and chemical interactions among the amino acid side groups.

ANFINSEN CB, REDFIELD RR, CHOATE WL, PAGE J, CARROLL WR.Studies on the Gross Structure, Cross-Linkages, and Terminal Sequences in Ribonuclease. J Biol Chem. 1954 ,207(1):201-210.