Berlin, Freie Universiẗat, Diss., 2005. / Dateiformat: zip, Dateien im PDF-Format.

Berlin, Freie Universiẗat, Diss., 2005. / Dateiformat: zip, Dateien im PDF-Format.

Berlin, Techn. Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Berlin, Techn. Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Mainz, Universiẗat, Diss., 2000.

Mainz, Universiẗat, Diss., 2004.

Köln, University, Diss., 2002.

The thesis focuses on the role of Psb28 proteins, namely the Psb28-1 and its homolog Psb28-2, in the biogenesis of the Photosystem II complex (PSII) in the cyanobacterium Synechocystis PCC 6803. The aims of this work were to localize the proteins within the cells, and to determine their function. A fraction of both Psb28 proteins was identified in the monomeric PSII core complexes but most proteins were found in the unassembled protein fraction associated with thylakoid membranes. Psb28-1 was mostly detected as a dimer while Psb28-2 as a monomer. Psb28-1 also differed from Psb28-2 by its higher affinity to the PSII core complex lacking CP43 antenna. Characterization of Psb28-less mutants suggested regulatory function of the proteins in PSII biogenesis in connection with chlorophyll biosynthetic pathway. Analysis of preparations isolated using FLAG-tagged versions of Psb28 proteins showed their association with Photosystem II - Photosystem I supercomplexes, especially under increased irradiance, and supported a role of Photosystem I in the PSII biogenesis.

Thesis advisor: William H. Armstrong / The Oxygen-Evolving Complex (OEC) of Photosystem II (PSII) utilizes a Mn4Ca cluster to catalyze the conversion of water to dioxygen within plant chloroplasts. The active site of the water oxidase is found on the lumenal side of the thylakoid membrane. For many years, the nature of this convoluted system, including the unresolved structural arrangement of the OEC manganese-oxo aggregate, stimulated on-going research projects in a diverse set of scientific fields. A tetranuclear oxo-bridged manganese complex associated with calcium [Ca] and chloride [Cl], along with a redox active tyrosine (Tyr), is thought to be the center of this remarkable and unique biological machinery. An illustrious catalytic cycle, known as the Kok cycle, progresses through a series of five intermediate states (Si, i = 0-4) to conduct water oxidation and dioxygen evolution. A tentative structural proposal based on the single crystal X-ray diffraction (XRD) crystallographic measurements introduced a CaMn3 cubane cluster and an appended fourth manganese atom. It was proposed that water binds between the “dangling” Mn atom and the Ca atom, and that is where the O-O bond formation is proposed to occur, followed by O2 release without structural rearrangement of the cubane core. The plausible manganyl (MnV=O) species was also suggested as an intermediate in the S4 state for the O-O bond formation and release O2. We have examined plausible reactive manganyl species as are proposed to exist at the OEC S4 state. The existence of manganyl in synthetic model systems will be presented in Chapter 2. In this study, we utilized stopped-flow UV-vis spectroscopy and mass spectrometry to investigate the formation and the nature of the intermediate in the reaction between mononuclear Schiff base manganese complexes and a reagent that is often used for O atom transfer reactions. Chapter 3 involves establishment of a logical synthetic method to prepare the related complexes, Mn2O2(bpy/dmb)2(ArRCOO)2 [R = 2,6-diphenyl, 2,6-ditolyl]. The dimanganese-oxo center is considered as a basic unit on the path toward the construction of higher nuclearity of Mn aggregates, preferably Mn4 clusters to be used for OEC catalytic cycle mimicry. Controlled ligand exchange synthesis of this type of carboxylate-rich/bridged {Mn2O2} dimers will provide an alternate pathway toward obtaining the Mn aggregates that are not attainable by direct ‘self-assembly’ synthetic methods. In Chapter 4, we will describe a novel mixed-ligand tetranuclear Mn cluster of the adamantane core type, [Mn4(μ-O6)(bpy)4(py)4](ClO4)4. This cluster was synthesized by using a simple reaction and its spectroscopic characterization will be discussed. We will also demonstrate chromatographic behavior of the Mn clusters that we encountered in this work (see Appendix A). / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Berlin, Humboldt-Univ., Diss., 2001. / Computerdatei im Fernzugriff.