Time-resolved resonance Raman spectroscopy is a recently developed technique which is to be used as a unique probe to obtain information about the dynamics of a number of porphyrin containing enzymes and compound. Since many bio-inorganic compounds have visible absorptions which originate from the active site, resonance Raman spectroscopy has arisen as a powerful method for the study of these compounds, as it allows enhancement of Raman active vibrations at the protein active site relative to the other vibrations of the molecule which can be great in number in the case of large proteins. Since resonance Raman spectroscopy uses lasers as excitation sources, resonance Raman spectroscopy is capable of the same time-resolution as the various time-resolved absorption techniques, such as flash photolysis, temperature jump, or stopped flow kinetics, but with the added advantage of being able to provide a resonantly enhanced high resolution vibrational spectra in place of transient absorptions which tend to be broad and featureless with little fine structure. Several topics are to be investigated. It is proposed to use resonance Raman and time-resolved resonance Raman spectroscopies to study the structures of intermediates and derivatives of a number of peroxidases and catalases. These enzymes catalyze the reactions of peroxides and involve oxidation of the heme to high oxidation states in common with other enzymes such as cytochrome P-450. Cytochrome P-450 has been implicated in carcinogenesis upon interaction with polyaromatic hydrocarbons, and it is desirable to learn more about this mechanism, in the hope that a defense against this process can be devised. Metals are well known to be involved in biological oxidation-reduction reactions. Time-resolved resonance Raman spectroscopy will be used to study catalytic intermediates and excited states in metalloporphyrin oxidation-reduction reactions in order to better understand the mechanisms of these processes. Photoradiation therapy has recently begun to be used for treatment of advanced malignancies. At present this treatment has deliterious side effects and the mechanism of operation is not well understood. Time-resolved resonance Raman spectroscopy should be able to provide some information on this mechanism.
