Molecular oxygen is crucial for the survival of most forms of life. Living organisms absorb molecular oxygen by way of metal containing proteins. Higher organisms use iron coordinated to a heme (hemoglobin, myoglobin) to absorb and transport molecular oxygen. Other organisms use proximal copper ions to serve the same function. Biological studies on the proteins as well as chemical studies on analogues of the metal binding sites of these two classes of dioxygen carriers have provided a detailed understanding of how molecular oxygen is bound and released from the metals. The third major dioxygen transporting protein is hemerythrin which contains two non-heme iron atoms which serve to bind molecular oxygen. The molecular structures of a variety of hemerythrins have been known for some time and the dioxygen binding has been established but many important, subtle details of the process remain to be answered. As has been shown for the other proteins, one of the most effective ways of addressing these questions is to synthesize small analogues of the dioxygen binding site. So far no such analogues of hemerythrin have been prepared although excellent models which reproduce many of the physical properties of hemerythrin have been characterized. The mechanism by which hemerythrin binds dioxygen is extraordinarily subtle and has no synthetic precedent. Many poorly understood elements are present in the oxidation process. This proposal is directed at synthesizing analogues of the metal binding site of hemerythrin. These analogues incorporate many of the features found in the protein. The design is sufficiently flexible so as to allow for the identification of the factors which control molecular oxygen binding in the protein. The project will, therefore, provide detailed understanding of the mechanism at the molecular level. Such information is important not only in the short term understanding of the action of the protein but also has wide general implications in the harnessing of molecular oxygen as a fuel in the long term.
