Chiroptical Probes of Protein Structure

Abstract

Although x-ray diffraction studies of crystals is the definitive technique for the investigation of molecular structure in the solid state, it is certainly possible, even probable, that there are significant differences in the microscopic structure of protein molecules in the solid state and in solution. Even though it may be unlikely that significant deviations occur in the path of the polypeptide chain it is likely that the conformations of certain amino acid side chains, especially those on the surface, may vary significantly in the two states. Since it is the side chains that constitute the functional portions of enzyme molecules insofar as biological activity is concerned, this is a problem of considerable significance. The recent discovery that lysozyme can be crystallized in at least two different forms (l–3), and Vallee’s (4) results which indicate a conformational change of a tyrosine residue when crystalline carboxypeptidase is dissolved may be taken as evidence supportive of this point of view.