Date of Award
Doctor of Philosophy (PhD)
Fiedler, Adam T.
Mononuclear non-heme iron dioxygenases (MNIDs) are a class of enzymes that catalyzea variety of reactions, from amino acid catabolism to bioremediation using molecular oxygen.This work focuses on three types of MNIDs: thiol dioxygenaes (TDOs), aminophenoldioxygenases (APDOs), and sulfoxide synthases (SOSs). TDOs, found in mammals, regulate thelevels of cysteine along with other thiol-containing molecules, using molecular oxygen toconvert them into their corresponding sulfinic acids. APDOs catalyze the oxidative ringcleavage in the biodegradation of nitroaromatics. SOSs are involved in the biosynthesis of largebiologically relevant molecules in humans. Although this class of enzymes has gained moreattention in recent years, their catalytic mechanism is still not well understood. In order to gainmore insight into these procedures, synthetic models have been prepared and studied. This is acommon strategy used to learn more about the structural and electronic properties of enzymes aswell as their reactivities because small-molecule metal complexes are generally easier to prepare,handle, and characterize. Also, it is possible to trap reactive species and catalytic intermediatesin synthetic systems due to greater flexibility in structure and reaction conditions. There havebeen previously published synthetic models of TDOs and APDOs, but they lack the correctcoordination, charge, or reactivity to mimic the active sites of the enzymes. There have been noreports of synthetic models of SOSs in literature to date.Series of iron-containing biomimetic complexes were made to mimic the active sitestructures of these enzymes. A variety of spectroscopic techniques were used to characterizethese complexes – these techniques include 1H NMR, UV-Vis, infrared, electron paramagneticresonance, and resonance Raman spectroscopies. Computational studies, elemental analyses,and electrochemical studies were also performed. The reactions of these complexes with O2were studied extensively, using the techniques mentioned above. Other small molecules thatmimic the binding of O2 were also used to probe the metal center – including nitric oxide,cyanide, and azide. Additionally, cobalt was substituted for the iron center because it is morespectroscopically accessible, giving even more insight into the active site structre.
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