Universiẗat, Diss., 2004--Frankfurt (Main).

Thesis (Ph.D.)--University of Tulsa, 1989. / Bibliography: leaves 124-130.

This thesis concerns the mechanism of oxidative phosphorylation, with special reference to the bacterium Paracoccus denitrificans. A new method using affinity chromatography is described for the separation of vesicles of different membrane orientation. The working hypothesis is the chemisosmotic theory of Mitchell with its emphasis on the transmembrane proton motive force made up of a membrane potential and a transmembrane pH gradient. The 3 experimental systems used ape bovine heart submitochondrial particles, chromatophores from the photosynthetic bacterium Rhodospirillum rubrum and phosphorylating vesicles from P. denitrificans. From the uncoupling obtained with various ions added to the P. denitrificans particles it is concluded that the transmembrane distribution of weak bases and permeant anions permits a determination of the protonmotive force. A flow-dialysis method has been developed to measure the steady-state transmembrane distribution of weak bases and anions in a determination of the protonmotive force. This method successfully overcomes problems which arise with the techniques previously used for these measurements. Under the experimental conditions used to determine the extent of oxidative phosphorylation (the phosphorylation potential) no transmembrane pH gradient was detectable, and the protonmotive force could be accounted for completely by the membrane potential. A method using ion-selective electrodes was developed to provide a continuous determination of this membrane potential. In all 3 systems the proton motive force determined by the above methods was found to be significantly lower than that required by the chemiosmotic hypothesis. A simple modification of the chemiosmotic hypothesis is proposed. This new concept is based on electrodic theory. It is shown to be useful in explaining results reported in the literature (from both photosynthetic and respiratory systems) which appeared to be at odds with the chemiosmotic theory in its usual form.

Two strains of Alcaligenes denitrificans, designated BRI 3010 and BRI 6011, were isolated from polychlorinated biphenyl (PCB) contaminated soil using 2,5-dichlorobenzoic acid (2,5-DCBA) and 2,4-DCBA, respectively, as sole carbon and energy sources. Both strains degraded 2-chlorobenzoic acid (2-CBA), 2,3-DCBA, and 2,5-DCBA. BRI 6011 alone degraded 2,4-DCBA. Metabolism of the chlorinated substrates resulted in the stoichiometric release of chloride, and degradation proceeded by intradiol cleavage of the aromatic ring. Growth of both strains on dichlorobenzoic acids induced pyrocatechase activities having catechol (catechol 1,2-dioxygenase) and chlorocatechols (chlorocatechol 1,2-dioxygenase) as substrates. Growth on 2-CBA and benzoic acid induced a pyrocatechase activity (catechol 1,2-dioxygenase) directed against catechol only. / The chlorocatechol 1,2-dioxygenase from BRI 6011 was purified, characterized, and compared with the chlorocatechol 1,2-dioxygenase from Pseudomonas sp. B13 and P. putida, organisms limited with respect to their CBA degradative versatility. These enzymes appear to be very similar based on biochemical and genetic data and possess sufficient broad substrate specificity to accommodate a wide range of chlorinated catechols, hence the increased versatility for chlorobenzoic acid degradation of A. denitrificans cannot be attributed to a more specialized chlorocatechol 1,2-dioxygenase. / Uptake of benzoic acid by BRI 3010 and BRI 6011 was inducible, exhibited saturation kinetics and the substrate was accumulated intracellularly against a concentration gradient by a factor of 8 and 10, respectively, indicative of active transport. Uptake of 2,4-DCBA by BRI 6011 was constitutive and saturation kinetics were not observed, suggesting passive diffusion of 2,4-DCBA and other CBAs into the cell down a concentration gradient. / Based on oxygen uptake experiments with whole cells, benzoic acid dioxygenase and chlorobenzoic acid dioxygenase activity was induced by benzoic acid and ortho-substituted chlorobenzoic acids, respectively. Since 2,4-DCBA diffuses across the membrane and the expected catecholic intermediates of 2,4-DCBA metabolism are metabolizable by BRI 3010, this suggests that the major difference between BRI 3010 and BRI 6011 might be the inability of the chlorobenzoic acid dioxygenase in BRI 3010 to recognize 2,4-DCBA as a substrate.

xxix, 283 leaves : ill. ; 25 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agricultural Biochemistry and Soil Science, 1974

Universiẗat, Diss., 2007--Frankfurt (Main). / Zsfassung in dt. und engl. Sprache.

Thesis (Ph.D.)--University of Tulsa, 1985. / Bibliography: leaves 186-192.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Agricultural Biochemistry and Soil Science, 1974.

Frankfurt (Main), Universiẗat, Diss., 2006.

Universiẗat, Diss., 2004--Frankfurt (Main).