Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 82-83.

Thesis (Ph. D.)--McMaster University, 2003. / Advisor: M. McGlinchey. Includes bibliographical references (leaves 182-195). Also available via World Wide Web.

Thesis (Ph.D.) - University of Queensland, 2005. / Title reads superscript Ar/superscript Ar. Includes bibliography.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2006. / Includes bibliographical references (leaves 70-71).

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015 / The free radical theory of aging postulates that accumulation of oxidative damage in major cellular components is the predominant underlying cause of the aging phenotype. This damage is caused most commonly by reactive oxygen species (ROS) and antioxidant enzymes such as the superoxide dismutases (SOD) that neutralize ROS, are therefore vital. Manganese superoxide dismutase (MnSOD) is particularly critical as it is functional in the mitochondria, a major site for ROS generation. Numerous studies have demonstrated a tissue-specific decrease in the activity and mRNA levels of major antioxidants, including MnSOD, with aging, however the exact mechanism of this regulation is unclear. It was hypothesized that a general down-regulation of various antioxidant enzymes such as this may occur at the transcriptional level. In order to investigate SOD2 regulation, a comprehensively annotated rat SOD2 promoter region was established using the appropriate bioinformatics tools. Following this, SOD2 mRNA levels in tissues from young and old rat tissue were compared using quantitative PCR. The results showed increased and decreased SOD2 mRNA levels in old compared to young liver tissue and brain tissue, respectively, however these trends were not statistically significant. As MnSOD has been shown to be epigenetically downregulated in various age-related diseases it was hypothesized that the decrease in MnSOD mRNA levels seen in aging brain tissue may be a result of epigenetic regulation at the SOD2 (MnSOD gene) promoter, specifically, through DNA methylation. A methylation assay assessing the SOD2 gene promoter revealed no significant evidence of hypermethylation. Although this suggests that promoter methylation is an unlikely mechanism of SOD2 regulation in aging, further work would need to be implemented in order to prove this conclusively.

No description available.

N-heterocyclic carbenes are essential for the synthesis and stabilization of various metal complexes due to the tendency to act as sigma-donor of sp2 hybridized lone pair in carbene into sigma-accepting orbital of metals. Meanwhile, the electronic and steric properties of pincer complexes can be fine-tuned by modifying three sites bonded to the metals. Utilizing advantages of both NHCs and the pincer structures, NHCs-based pincer complexes have become increasingly developed in recent years. After the discovery of zirconium and rhodium complexes with CCC-NHC backbones reported in 2005, Hollis’s group has been interested in applying the CCC-NHC pincer precursor for other transition metals. Manganese, the third most abundant transition metal in the earth’s crust, has lower cost and less toxic features compared to most of the others. Herein, the CCC-NHCs manganese pincer complex is synthesized and characterized and its catalytic activity in alpha- alkylation reaction of ketones using alcohols was studied.

Soil organic matter decomposition is a critical process that affects nutrient cycling, CO2 emissions, and carbon storage in terrestrial environments. Recent evidence suggests reactive manganese (Mn) phases, potent oxidants that depolymerize compounds like lignocellulose in soil organic matter, act as critical drivers of organic matter decomposition in soil and sediment environments. Furthermore, oxic-anoxic interfaces (OAIs) have been shown to be crucial hotspots for the formation of reactive Mn(III) species and associated organic matter degradation. However, the extent to which microbially mediated Mn(III) formation and subsequently Mn(III)-driven organic matter oxidation depends on Mn availability remains largely unknown. Additionally, the relative contributions between abiotic and biotic Mn-mediated organic matter oxidation pathways have been poorly quantified. In this study, we quantified the impact of Mn availability on Mn-mediated particulate organic carbon (POC) oxidation across the redox gradient and the specific contributions of abiotic and biotic reactions. To accomplish this, we established soil redox gradients in diffusion reactors and varied Mn(IV) oxide concentrations in the anoxic zone. The ensuing reductive mobilization of Mn(IV) oxides in the anoxic zone was meant to manipulate Mn(II) supply towards the OAI. The addition or exclusion of microbial inoculum allowed us to examine the abiotic contributions to Mn translocation and POC oxidation. Mn(II) translocation, Mn(III) formation, and C transformations across the redox gradient were quantified over a 12-week incubation period. Wet-chemical extractions combined with Mn XANES indicated that reactive Mn(III) formation at OAIs increased with enhanced Mn availability. Comparison of inoculated and uninoculated treatments revealed microbial Mn oxide reduction to be the critical driver of Mn translocation to oxic-anoxic interfaces. Subsequent enhanced Mn availability at the OAI enhanced POC oxidation and increased CO2 production rates due to enhanced microbial translocation and primarily attributed to microbially mediated Mn(III) formation. Our study emphasizes the importance of Mn(III)-mediated C oxidation across OAIs and its dependence on the provision of Mn(II) through microbial Mn reduction. Combined, our results show Mn–C coupled cycling across redox gradients as a critical biogeochemical process that has profound impacts on ecosystem scale soil C storage and CO2 fluxes.

No description available.

No description available.