Matching Items (2)
Filtering by
- All Subjects: pH
Description
Hydrothermal environments are important locales for carbon cycling on Earth and elsewhere in the Universe. Below its maximum temperature (~73 °C), microbial photosynthesis drives primary productivity in terrestrial hydrothermal ecosystems, which is thought to be performed by bacterial phototrophs in alkaline systems and eukaryotic algae in acidic systems, yet has received little attention at pH values intermediate to these extremes. Sequencing of 16S and 18S rRNA genes was performed at 12 hot springs with pH values 2.9-5.6 and revealed that cyanobacteria affiliated with the genus Chlorogloeopsis and algae of the order Cyanidiales coexisted at 10 of the sites. Cyanobacteria were present at pH values as low as 2.9, which challenges the paradigm of cyanobacteria being excluded below pH 4. Presence of the carotenoid β-cryptoxanthin in only 2 sites and quantitative PCR data suggest that algae were inactive at many of the sites when sampled. Spatial, but perhaps not temporal, overlap in the habitat ranges of bacterial and eukaryal microbial phototrophs indicates that the notion of a sharp transition between these lineages with respect to pH is untenable.
In sedimentary basins, biosphere-derived organic carbon is subjected to abiotic transformations under hydrothermal conditions. Benzaldehyde was experimentally evaluated as a model to assess the chemistry of aldehydes under these conditions. It was first demonstrated that gold, a traditional vessel material for hydrothermal experiments, caused catalysis of benzaldehyde degradation. Experiments in silica tubes were performed at 250, 300, and 350 °C yielding time-dependent data at several starting concentrations, which confirmed second-order kinetics. Therefore, disproportionation was expected as a major reaction pathway, but unequal yields of benzoic acid and benzyl alcohol were inconsistent with that mechanism. Consideration of other products led to development of a putative reaction scheme and the time dependencies of these products were subjected to kinetic modeling. The model was able to reproduce the observed yields of benzoic acid and benzyl alcohol, indicating that secondary reactions were responsible for the observed ratios of these products. Aldehyde disproportionation could be an unappreciated step in the formation of carboxylic acids, which along with hydrocarbons are the most common organic compounds present in natural systems.
In sedimentary basins, biosphere-derived organic carbon is subjected to abiotic transformations under hydrothermal conditions. Benzaldehyde was experimentally evaluated as a model to assess the chemistry of aldehydes under these conditions. It was first demonstrated that gold, a traditional vessel material for hydrothermal experiments, caused catalysis of benzaldehyde degradation. Experiments in silica tubes were performed at 250, 300, and 350 °C yielding time-dependent data at several starting concentrations, which confirmed second-order kinetics. Therefore, disproportionation was expected as a major reaction pathway, but unequal yields of benzoic acid and benzyl alcohol were inconsistent with that mechanism. Consideration of other products led to development of a putative reaction scheme and the time dependencies of these products were subjected to kinetic modeling. The model was able to reproduce the observed yields of benzoic acid and benzyl alcohol, indicating that secondary reactions were responsible for the observed ratios of these products. Aldehyde disproportionation could be an unappreciated step in the formation of carboxylic acids, which along with hydrocarbons are the most common organic compounds present in natural systems.
ContributorsFecteau, Kristopher Michael, 1986- (Author) / Shock, Everett L (Thesis advisor) / Gould, Ian R (Committee member) / Hartnett, Hilairy E (Committee member) / Arizona State University (Publisher)
Created2016
Description
Mitochondria are crucial intracellular organelles which play a pivotal role in providing energy to living organisms in the form of adenosine triphosphate (ATP). The mitochondrial electron transport chain (ETC) coupled with oxidative phosphorylation (OX-PHOS) transforms the chemical energy of amino acids, fatty acids and sugars to ATP. The mitochondrial electron transport system consumes nearly 90% of the oxygen used by the cell. Reactive oxygen species (ROS) in the form of superoxide anions (O2*-) are generated as byproduct of cellular metabolism due to leakage of electrons from complex I and complex III to oxygen. Under normal conditions, the effects of ROS are offset by a variety of antioxidants (enzymatic and non-enzymatic).
Mitochondrial dysfunction has been proposed in the etiology of various pathologies, including cardiovascular and neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, ischemia-reperfusion (IR) injury, diabetes and aging. To treat these disorders, it is imperative to target mitochondria, especially the electron transport chain. One of the methodologies currently used for the treatment of mitochondrial and neurodegenerative diseases where endogenous antioxidant defenses are inadequate for protecting against ROS involves the administration of exogenous antioxidants.
As part of our pursuit of effective neuroprotective drugs, a series of pyridinol and pyrimidinol analogues have been rationally designed and synthesized. All the analogues were evaluated for their ability to quench lipid peroxidation and reactive oxygen species (ROS), and preserve mitochondrial membrane potential (Δm) and support ATP synthesis. These studies are summarized in Chapter 2.
Drug discovery and lead identification can be reinforced by assessing the metabolic fate of orally administered drugs using simple microsomal incubation experiments. Accordingly, in vitro microsomal studies were designed and carried out using bovine liver microsomes to screen available pyridinol and pyrimidinol analogues for their metabolic lability. The data obtained was utilized for an initial assessment of potential bioavailability of the compounds screened and is summarized fully in Chapter 3.
Mitochondrial dysfunction has been proposed in the etiology of various pathologies, including cardiovascular and neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, ischemia-reperfusion (IR) injury, diabetes and aging. To treat these disorders, it is imperative to target mitochondria, especially the electron transport chain. One of the methodologies currently used for the treatment of mitochondrial and neurodegenerative diseases where endogenous antioxidant defenses are inadequate for protecting against ROS involves the administration of exogenous antioxidants.
As part of our pursuit of effective neuroprotective drugs, a series of pyridinol and pyrimidinol analogues have been rationally designed and synthesized. All the analogues were evaluated for their ability to quench lipid peroxidation and reactive oxygen species (ROS), and preserve mitochondrial membrane potential (Δm) and support ATP synthesis. These studies are summarized in Chapter 2.
Drug discovery and lead identification can be reinforced by assessing the metabolic fate of orally administered drugs using simple microsomal incubation experiments. Accordingly, in vitro microsomal studies were designed and carried out using bovine liver microsomes to screen available pyridinol and pyrimidinol analogues for their metabolic lability. The data obtained was utilized for an initial assessment of potential bioavailability of the compounds screened and is summarized fully in Chapter 3.
ContributorsAlam, Mohammad Parvez (Author) / Hecht, Sidney M. (Thesis advisor) / Gould, Ian R (Committee member) / Moore, Ana (Committee member) / Arizona State University (Publisher)
Created2014