Antigenic determinants of proteins apparently involve considerable lengths of the amino acid chain (1). Because of molecular folding, chemical groups on the surface of the molecule which might constitute an antibody binding site could be widely separated in the amino acid sequence. Changes in the three dimensional configuration of a protein, by altering the topography of such binding sites, should interfere with its immunologic specificity. The availability of a method for altering the spacial configuration of a purified protein, ribonuclease, to new and reasonably stable three dimensional structures without chemically changing the amino acid residues, offered an opportunity for testing this hypothesis.
Procedures which grossly denature proteins are known to result in a loss of antigenic specificity (2, 3), but the molecular changes caused by such methods are ill-defined. They probably involve covalent changes in a number of amino acid residues.