Examples of side-chain conformational changes upon binding . (A) Immunoglobulin and (B) alpha-chymotrypsin in the unbound (blue) and bound (magenta) states. The core residues are shown as surface. The interface residues are shown in bold colors. The bound structure of the immunoglobulin is 1a2y , the unbound structure is 1vfa . The bound structure of the alpha-chymotrypsin is 1acb , and the unbound structure is 1gct .