TIME RESOLVED AND LOW TEMPERATURE RAMAN INVESTIGATION OF HEME PROTEINS

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This study will combine the resources of two established laboratories to produce a complete study of the dynamics of interaction between globin, heme, and ligand in a complex bimolecule, hemoglobin. Metastable heme transient species will be generated via ligand (02, NO, CO) photolysis by picosecond and nanosecond pulsed laser sources. The dynamics of these species will be probed on timescales, from picosecs to millisecs using both Raman and absorption techniques already established in our laboratories. The effects of various globins and solution conditions on geminate recombination kinetics will be determined with picosecond transient absorption spectroscopy. The structural specificity of resonance Raman spectroscopy will allow us to examine individual molecular coordinates in this complex system and cryogenic techniques will allow us to determine the energetics involved in the relaxation of the proximal and distal heme pockets subsequent to ligand photolysis and rebinding respectively. The large body of data concerning the equilibrium structures of the hemoglobin molecules, coupled with the large number of globins with known perturbations, provides for the expectation that it will be possible to interpret complex time and temperature resolved data on a molecular, "chemical dynamics" levels. This is a unique opportunity in biophysics and the technology and demonstrated expertise in time-resolved Raman and absorption spectroscopies now available in our laboratories makes such an undertaking eminently feasible.