Resonance Raman Studies of Electron-Nuclear Coupling, Time Resolved Dynamics, and Magnetic Perturbations of Biomolecules

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9405979 Champion The proposed research will utilize resonance Raman scattering and its time domain analog, coherent impulsive scattering, to probe the electronic and nuclear structure/function relationships of biological molecules such as heme proteins (myoglobin, hemoglobin and cytochrome c) and photosynthetic systems (light harvesting antennae and reaction centers). Related techniques, such as electronic absorption and infrared spectroscopy, will also be utilized, and theoretical models that link a variety of experimental measurements will be developed. Absolute cross- section measurements will be used to directly extract the electron-nuclear coupling strengths while the temperature dependence of the optical absorption lineshape yields the coupling of low frequency motion and its role in damping. The studies of low frequency protein motion will be complemented with ultrafast impulsive scattering techniques, which allow real time measurement of such motion. Further experimental and theoretical studies involving the spectroscopic and kinetic effects of protein distributions are also proposed. Dynamic studies will include the measurement and analysis of ligand binding and electron transfer under a wide variety of sample conditions, as well as pump/probe experiments designed to monitor protein folding and conformational relaxations. Laser mediated thermal perturbations will be followed using Stokes/anti-Stokes Raman scattering. Studies of dynamic processes induced by photoreduction and kinetic studies of biological single crystals will also be extended. %%% The general scientific objectives are to achieve a better understanding of the dynamics of motion of large biologically important molecules and their absorption and resonant light scattering properties. The aim is to apply this knowledge to elucidate their mechanism of action. These studies are significant not only in their relationship to the biological sciences, but also in their connection to our u nderstanding of the interaction of light with complex material systems in the condensed phase. ***