Primary light induced processes in hemoproteins and bacteriorhodopsin will be explored using novel femtosecond laser methods particularly infrared spectroscopy. The goal is to elucidate mechanisms of energy relaxation and transport including energy flowing within proteins, from proteins to the surrounding medium and within the medium. Information will be obtained about protein conformational changes and motions within nucleic acids based on bond reorientation amplitudes and frequencies. Specifically, the ligand dissociation and rebinding in CO and NO myoglobin and hemoglobin will be studied to discover whether there are electronic barriers to recombination and if the ligand kinetics is controlled by equilibrium fluctuations or by the relaxation of the protein structure. Direct observations of ligands CO and NO with transient IR spectroscopy will allow these ligands to be seen commuting in and out of the protein. Polarized infrared pump experiments are aimed at establishing the structural details and timescales of molecular reorientations occurring within the hemepockets of Hb and Mb, and of the energy flow within the protein following ligand reactions. Studies of bacteriorhodopsin will use IR methods to further characterize the early steps in the photocycle but an important goal is the determination of isomerization induced changes in protein structure, not previously possible. Vibrational excitations of specific bonds of ions, protein constituents and nucleic acids will be used to obtain new information on orientational dynamics in these systems. All the proposed work can be brought into relationship with theoretical simulations of the dynamcis.
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