Thesis--University of Chicago. / Bibliography: p. 22-24.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 37-38). Also available via the Internet.

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Nov. 11, 2008). Includes bibliographical references.

Pyruvate:ferredoxin oxidoreductase activity was demonstrated in microaerophilic members of Campylobacter, Wolinella, and Helicobacter. Arcobacter cryaerophila (sic) and Arcobacter nitrofigilis, two aerobic species, lacked any detectable activity. Under anaerobic conditions crude extracts of Campylobacter, Helicobacter and Wolinella were capable of reducing the electron carriers benzyl viologen and metronidazole in the presence of pyruvate. Addition of Clostridium pasteurianum ferredoxin to the metronidazole-linked reaction enhanced metronidazole-reducing activity, suggesting that electron transport to artificial electron carriers is facilitated by ferredoxin. All species exhibited varying degrees of sensitivity to metronidazole (MIC = <0.8 to 25 µg/ml) except Arcobacter cryaerophila, which was resistant to > 100 µg/ml. This further supports the theory that these organisms possess ferredoxin-linked reactions. The presence of the oxygen-labile enzyme pyruvate:ferredoxin oxidoreductase may be related to the inability of these microaerophilic bacteria to grow in normal atmospheric levels of oxygen. Under aerobic conditions crude extracts of the organisms were also capable of reducing NAD in the presence of pyruvate. This might be accounted for by an NAD-linked pyruvate dehydrogenase; alternatively, it might be due to an enzymatic reduction of NAD by electrons from the reduced ferredoxin generated during the ferredoxin-linked pyruvate oxidoreductase reaction. / Master of Science

No description available.

Interest in recovery of carboxylic acids from their aqueous solutions and production media has been growing with the improvements in the production techniques. Reactive extraction is proposed as a promising method to achieve high distribution coefficients with good selectivity. In the present study, equilibrium and kinetic studies, needed for the design of a recovery unit were carried out. Reactive extraction of pyruvic, acetic and lactic acids from their single and mixed acid solutions were carried out with tertiary amines, Alamine 336 and trioctylamine, dissolved in diluents, 1-octanol and oleyl alcohol. The kinetic parameters such as reaction order and rate constant were calculated by using the aqueous solution of pyruvic acid with 1-octanol solution of trioctylamine. The distribution coefficient of pyruvic acid was obtained as 0.30 and 0.07 with 1-octanol and oleyl alcohol respectively. The trend did not change after the addition of the extractants to the diluents. As expected, the more polar diluent extracted more acid than the less polar one. The extractant was observed to be the limiting reagent of the reversible complexation reaction in the organic phase. It was seen that loading ratio was not affected by the concentration of the extractant in the organic phase but increased with the equilibrium concentration of the acid in the aqueous phase. The results showed that mainly (1-1) acid-amine reaction occurred in the organic phase. Because tertiary amines can react with only undissociated acids, the increase in the initial pH of the aqueous phase caused a decrease in the distribution coefficients of the carboxylic acids studied. The effect of the concentration of the organic phase disappeared when the initial pH of the aqueous phase was 4.0 and a distribution coefficient value of 0.1 was achieved for all concentration levels of organic phase. Similar results were obtained for acetic and lactic acids and this behavior was used to propose a selective recovery of the acids from their mixed acid solutions. The presence of acetic acid prevented the extraction of pyruvic acid. The increase in the concentration of the extractant in the organic phase caused an increase in the distribution coefficient of pyruvic acid. During the extraction process, lactic acid could not be recovered from ternary acid solutions because of its high hydrophilicity. The results of reactive extraction of lactic and pyruvic acids from their binary acid solutions showed that at higher concentration of lactic acid, the distribution of pyruvic acid was negatively affected. On the other hand, the presence of lactic acid at a low concentration level did not affect the distribution of pyruvic acid. It was found that the reaction between pyruvic acid and trioctylamine in 1-octanol was first order with respect to the reactants with a second order rate constant of 0.94 L mol-1 s-1. The enhancement factor of the system was obtained as 25.

Atmospheric aerosols affect climate change by altering the energy balance of the atmosphere, and public health due to their variable chemical composition, size, and shape. While the formation of secondary organic aerosol (SOA) from gas phase precursors is relatively well understood, it does not account for the abundance of SOA observed during field measurements. Recently it has become apparent that in-aerosol aqueous chemical reactions likely provide some of the missing sources of SOA production, and many studies of aqueous phase processes are underway. This work explores the fates of the simplest 2-oxocarboxylic acids, glyoxylic acid (GA) and pyruvic acid (PA), under simulated solar irradiation in the aqueous phase. Field measurements have revealed that mono-, di-, and oxocarboxylic acids are abundant species present in atmospheric waters. Of particular interest are 2-oxocarboxylic acids because their conjugated carbonyl moieties result in significant UV-visible absorption above 300 nm, allowing absorption of sunlight in the lower troposphere, thereby initiating radical photochemistry and leading to formation of SOA. In Chapter 2 of this work, GA is demonstrated to primarily undergo α-cleavage, producing CO, CO2, formic acid, and the key SOA precursor glyoxal. Trace amounts of oxalic acid and tartaric acid are also quantified. Additionally, the dark thermal aging of glyoxylic acid photoproducts, studied by UV-visible and fluorescence spectroscopies, reveals that the optical properties of the solutions are altered radically by the glyoxal produced. The optical properties display periodicity during photolytic-dark cycles, reflecting behavior expected for aerosols during nighttime and daytime cycles. In contrast, Chapter 3 shows that PA photoreacts via a proton-coupled electron transfer (PCET) mechanism that produces CO2 and organic acids of increased complexity with 6 to 8 carbons. A combination of analytical techniques including 1H and 13C NMR; 13C gCOSY NMR; mass spectrometry; chromatography; and isotope substitutions allows the organic products to be identified as: 2,3-dimethyltartaric acid; 2-hydroxy-2-((3-oxobutan-2-yl)oxy)propanoic acid; and the quasi-intermediate 2-(1-carboxy-1-hydroxyethoxy)-2-methyl-3-oxobutanoic acid. In Chapter 4, PA irradiation is also shown to consume dissolved oxygen so fast that solutions become depleted within a few minutes depending on reaction conditions. This fast process directly produces the atmospheric oxidant singlet oxygen, which enhances the oxidizing capacity of the atmosphere. Additionally, PA photochemistry only proceeds under very acidic conditions (pH ≤ 3.5), like those in most atmospheric aerosols. Finally, we require a thorough understanding of the behavior of 2-oxocarboxylic acids at the air-water interface of aerosols because much of the GA and PA present in the atmosphere is produced in the gas phase and needs to partition into the aqueous phase to undergo photoreaction. Therefore, Chapter 5 uses surface sensitive online electrospray ionization mass spectrometry (OESI-MS) to demonstrate that carboxylic acids delivered from the gas phase onto the surface of aqueous microdroplets display enhanced acidities relative to bulk water solutions. This work demonstrates that aqueous photolysis is a very competitive atmospheric fate for both GA and PA. It also shows that these photoreactions are capable of contributing substantially to SOA formation by building chemical complexity and forming oxidants directly.

Ces travaux de thèse portent sur l’étude chimique d’espèces marines échantillonnées en Méditerranée. Dans le cadre du projet VALBIM, co-financé par la région PACA et en étroite collaboration avec la société BioPreserv à Grasse mais également avec la Mycoteca Universitatis Taurinensis (MUT) de l’Université de Turin, nous avons isolé et caractérisé 21 molécules dont 14 se sont avérées nouvelles. L’étude de l’algue Caulerpa taxifolia a conduit à la caulerpényne et à quatre nouveaux dérivés de l’acide pyruvique sulfatés. Les travaux sur l’ascidie Polysyncraton sp. ont conduit aux bolascidines A-D, quatre nouveaux métabolites de type bolaamphiphiles dont il n’existe pas à notre connaissance d’équivalent naturel ou synthétique. La première étude chimique de l’éponge Hexadella racovitzai a conduit à deux dérivés de la bromotyrosine, la psammapline A et une nouvelle molécule, la 4-Osulfatocyclobispsammapline A. Par ailleurs, trois nouvelles crambescines C1, conjointement avec une crambescine A2 déjà répertoriée, ont été isolées de Crambe crambe. L’étude du champignon marin Stachybotrys chartarum, isolé de l’éponge Aplysina cavernicola, a conduit à la satratoxine H et à deux nouveau dérivé, la 2,3-dihydrosatratoxine H et l’épi-chartarutine G, ainsi qu’à trois dérivés stachybotrylactame déjà répertoriés dans la bibliographie. Les différents métabolites ont été évalués pour leurs propriétés antibactériennes et cytotoxiques. Ces travaux ont bénéficié de nouvelles approches analytiques (calculs des spectres de dichroïsme circulaire électroniques par TDDFT, réseaux moléculaires) permettant de renforcer l’intérêt des études liées à l’écologie chimique et à la recherche de nouvelles molécules bioactives potentiellement valorisables dans différents domaines. / This PhD work focuses on the chemical study of marine species sampled in the Mediterranean Sea. As part of the VALBIM project, cofinanced by the region PACA and in close collaboration with the SME BioPreserv in Grasse but also with the Mycoteca Universitatis Taurinensis (MUT) of the University of Turin, we have isolated and characterized 21 molecules in total.14 of them were never reported before. The study of the seaweed Caulerpa taxifolia led to caulerpenyne and four new sulphated pyruvic acid derivatives. The work on the ascidian Polysyncraton sp. led to bolascidins A-D, four new metabolites which belong to the bolaamphiphile family, which, to the best of our knowledge, have no natural or synthetic equivalent. The first chemical study of the sponge Hexadella racovitzai led to two bromotyrosine derivatives, psammapline A and a new molecule, 4-O-sulfatocyclobispsammapline A. In addition, three new C1 crambescins, together with one crambescine A2 already reported, have been isolated from Crambe crambe. For all isolated marine invertebrate metabolites, the producer(s) remain(s) to be explored. The study of the marine fungus Stachybotrys chartarum, isolated from the sponge Aplysina cavernicola, led to satratoxin H and three stachybotrylactam derivatives already reported in the literature, and to 2,3-dihydrosatratoxin H and epi-chartarutine G, two new natural products. The different metabolites were evaluated for their antibacterial and cytotoxic properties. This work benefited from new analytical approaches (calculations of electronic circular dichroïsm spectra by TDDFT, molecular networking) and reinforced the interest of studies related to chemical ecology and search for new bioactive molecules to be valorized in different areas.

Thesis (Ph. D.)--Uniformed Services University of the Health Sciences, 2005. / Typescript (photocopy).