We plan to continue work in progress on the dynamics of proteins and the relationship between structure and function. Spatial and temporal fluctuations appear to be essential ingredients in biomolecular action. By using flash photolysis over extended ranges in time (ns to ks), temperature (2-350 degrees K), pressure (0.1-600 MPa), and solvent conditions (viscosity, pH) on a wide variety of systems (heme proteins, bacteriorhodopsin) we will obtain detailed information on the multiple steps involved in the binding and in the photocycle of bacteriorhodopsin, on the distribution of conformational substates and on conformational relaxation. Monitoring in the infrared as well as in the visible spectrum will provide additional information on the motion of the ligand through the heme protein and on the conformational changes in the protein in the course of the reactions. Experiments will be performed on modified proteins in order to determine the influence of structure on function. The nature of the photodissociated state will be explored using optical and infrared spectroscopy and EXAFS. X-ray diffraction over the temperature range from about 50-300 degrees K will be used to determine the spatial fluctuations of each atom, and in particular, the shape of the potential in which each atom moves. The total information we plan to gather from the wide range of techniques will do much to elucidate the dynamic aspects of protein function.
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