MECHANISMS OF REACTIONS OF OXYGEN WITH HEME PROTEINS

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Detailed studies of structure-reactivity in the binding of dioxygen, carbon monoxide, isocyanides, nitric oxide and nitrogen and oxygen bases to heme protein model compounds will be made. Special attention will be given to the picosecond kinetics in these systems. These studies will provide the mechanisms of the fundamental binding processes with iron(II) porphyrins in the absence of proteins. In this way the protein effects can be separated from the basic chemical effects in the dynamic processes occurring in oxygen transport. Secondly, these systems provide new approaches to the study of details of solvent-geminate pair dynamics of broader significance. To complete the study of geminate processes the picosecond relaxation after photolysis of free radical cage precursors such as porphyrin metal-alkyl complexes and ketenimines, R2C=C=N-R' will also be examined. To understand the biological effects of nitric oxide interactions, detailed equilibrium and second to picosecond kinetic studies of model heme-NO complexes will be studied. Structural and environmental effects on NO binding kinetics and equilibria and on the formation of Heme-NO from Base-Heme-NO will be studied in detail. The effect of pH on NO binding, proximal base dissociation and picosecond NO kinetics will be studied with myoglobin and other heme proteins. New model systems designed to mimic the proteins ascaris hemoglobin and peroxidases which have highly polar pockets will be prepared. These models will provide basic structural effects needed in the current discussions of the effects of polarity in protein behavior.