We have observed detailed and informative resonance Raman spectra from heme proteins such as cytochrome P450, cytochrome c, myoglobin and hemoglobin. Laser excitation in the deep blue and near ultraviolet resonant absorption bands leads to greatly enhanced signal intensities associated with the heme prosthetic group.
We aim to extend our understanding of the structure and function of cytochrome P450 and other heme protein systems by the use of Raman and other rapidly developing laser based spectroscopies. These studies will employ Raman excitation profile measurements that allow key electron-nuclear coupling parameters to be extracted from the combined absorption and Raman data. Careful studies of the absorption and Raman lineshapes will also be carried out as a function of temperature. Sample perturbations involving site directed mutagenesis, pH and optical pumping are also scheduled. Time resolved protein dynamics will be studied in both the nanosecond and picosecond regimes. Ligand photolysis and electron transport phenomena along with thermal relaxation and non-radiative decay processes will be investigated. Single crystal samples of myoglobin and cytochrome P450cam will also be studied as a function of orientation and excitation wavelength. Various ligands that induce z-polarized charge transfer excitations will be complexed to the crystals in order to examine the details of the polarizability tensor. Theoretical work involving ligand binding to heme proteins, electron transfer and resonant light- matter interactions will also be pursued. Collaborative experiments involving microwave conductivity, electron spin resonance and deep ultraviolet Raman scattering will be initiated. This overall project has wide range of health related implications involving cytochrome P450 in particular and heme proteins in general. Many chemotherapeutic agents as well as polycyclic carcinogens are metabolized by P450 systems. Moreover, all metabolic disorders involving a P450 protein must relate to this research. Certainly a fundamental understanding of the active site structure and function of P450 at the molecular level will result in a better insight for those concerned with treatment of these disorders at any level.
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