Thesis (Ph. D.)--California Institute of Technology, 2010. UM #9912874. / Title from home page. Viewed 12/02/2009. Includes bibliographical references.

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Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

The prosthetic groups of cytochrome o, the terminal ubiquinol:dioxygen oxido-reductase of Escherichia coli, were investigated in the purified and in situ enzyme. The interactions between the redox-active centres, of which there are three, were characterised using optical, magnetic resonance and X-ray absorption spectroscopy techniques. The copper complement of this enzyme was investigated and the available data suggested a single copper centre associated with the ligand binding haem centre (haem o) forming a binuclear oxygen binding and reduction site. Two redox-active copper atoms are known to exist in the mammalian cytochrome c oxidase complex and the consequences of the different copper stoicheiometries, in these enzymes, are discussed. Spatial and organisational investigations are described and a model for the binuclear reaction site presented. The location of the haem centres was determined using low-temperature EPR spectroscopy by observing the effects on the relaxation behaviour of these centres in the presence of an extrinsic paramagnetic probe.

An in situ study was conducted of the cytochrome bd ubiquinol:oxygen oxidoreductase (cytochrome b558-b595-d) of Escherichia coli grown anaerobically on glycerol with fumarate as respiratory oxidant. Nitrite reacts with and is reduced by the oxidase, resulting in the formation of NO adducts to haems b595 and d. The kinetics of formation of these species indicate that the affinity of haem d for nitrite is higher than that of haem b595. CO also binds to the oxidase, resulting in the formation of CO adducts to haems d and b595. Binding titrations indicate that the affinity of haem d for CO is higher than that of haem b595. The steady state kinetics of the oxidase reaction in the presence of nitrite or CO are cooperative with respect to oxygen binding, suggesting that both haems d and b595 are involved in the reduction of oxygen. E.p.r. studies of the ferric oxidase indicate the presence of two high spin haem signals, one rhombic and one axial, which are assigned to haems b595 and d, respectively. These signals titrate potentiometrically with midpoint potentials similar to those published on the basis of optically followed titrations for haems b595 and d. The high spin ferric haem spectra are affected by oxygen, CO, cyanide, and pH. A low spin ferric haem signal is observed at g=3.3 and is assigned to haem b558. The sidedness with respect to the cytoplasmic membrane of ligand binding haems of the oxidase was determined by investigating the effect of the exogenous paramagnetic probe DyEDTA on the e.p.r. properties of the ferrous haems d-NO and b595-NO. These haems are located towards the inner aspect of the cytoplasmic membrane at around 8 and 12A° below the surface, respectively. Overall, the data supports a functional model for cytochrome bd with two oxygen binding sites, haems d and b595, forming the binuclear centre of the oxidase reaction. Possible mechanisms of this reaction are discussed.

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Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 70-82). Also available for download via the World Wide Web; free to University of Oregon users.

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Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 154-167). Available also in a digital version from Dissertation Abstracts.