Dr. Wittebort is pursuing three areas of investigation under the general heading of structure and dynamics in bimolecular systems. They include the study of local magnetic interactions in transition metal clusters related to electron transport proteins, torsional dynamics in crystalline and fibrous proteins and the properties of water in solid proteins and related compounds. In each case, the experimental method employed is nuclear magnetic resonance spectroscopy. The feature of magnetic resonance that makes it useful is that in a solid, such as a crystalline molecule or a fibrous protein, interactions between nuclear spins and spatially anisotropic local fields can be directly observed and simply related to molecular structure. Furthermore, the effect of time dependent processes such as atomic reorientation is to average and reduce the anisotropic local fields in an understandable way. Thus the experiment is a good way to study simultaneously molecular structure and dynamics. The results over the past three years, which are the basis for this proposal, show that the onset of rapid electron transfer among three chemically and magnetically coupled Fe or Mn ions is coincident with the onset of rotational motion of a nearby solvate molecule, that water molecules in hexagonal ice readily explore the four tetrahedral orientations surrounding the oxygen atoms in a time of 100 microseconds, and that most of the water of hydration surrounding a crystalline protein is dynamically disordered and distinguished from liquid water primarily in its higher viscosity.*** //
