Vibrational spectroscopy is an important physical tool for studying structure. However, in order to realize its full potential, such spectroscopic studies must progress beyond the band correlation stage to the use of the rigorous methods of normal mode analysis, which permit detailed predictions to be made of spectral frequencies and intensities associated with a given three-dimensional structure. Dr. Krimm has laid a strong foundation for such approaches by refining an empirical vibrational force field for the polypeptide chain and applying it to normal mode calculations and the analyses of structure in some simple polypeptide systems. He will now extend this approach to a number of new systems, including more complex globular proteins, as well as develop a more detailed and theoretically-based force field from quantum mechanical studies. The determination of the three-dimensional structure of peptides, polypeptides and proteins continues to be a necessary goal in achieving a molecular understanding of their biological functioning. While X-ray diffraction is clearly the most powerful technique for obtaining the structure of a large molecule at the atomic level, it is not satisfactory for studying conformations in non-crystalline systems or under a variety of environmental conditions. The application of spectroscopic methods to the study of protein conformation is of particular importance, since they can provide equally effective ways of probing molecular structure. Vibrational spectroscopy has a long history of application to structural studies on polypeptides and proteins. In recent years it has become possible to do meaningful normal vibration analyses on such molecules and make specific predictions of the vibrational frequencies associated with a proposed structure. As a result, much stronger structural conclusions can be reached.
