Potassium cyanide (KCN) is an inhibitor that reduces the activity of terminal oxidases in electron transport system of Klebsiella oxytoca. Previous research verified that K. oxytoca could induce cyanide-resistant respiration pathway when cells were grown in KCN condition. To address the role of cyanide-resistant pathway in regulating the respiration of bacterium in KCN incubation, 8-hydroxyquinoline (8-HQ), an inhibitor of cyanide-resistant pathway, was added to the bacterial suspension pretreated with KCN. This experiment was devised into 4 groups as below: (1). TSB (without KCN or 8-HQ), (2). TSB + 1 mM KCN, (3). TSB + 100 £gM 8-HQ, and (4). TSB + 1 mM KCN+ 100 £gM 8-HQ. Our results show 100 £gM 8-HQ exerted it slight toxicity to bacterial growth. However, the bacterial growth was severely impaired when the cells treated with KCN and 8-HQ concurrently as evidenced by the lower oxygen uptake rate of cells in comparison with the control group (without addition of 8-HQ). Furthermore, K. oxytoca grown in growth medium containing 100 £gM 8-HQ produced more significant H2O2. Thus we suggested that cyanide-resistant respiration of K. oxytoca could protect the cells from H2O2 damage. Since cytochrome d has been implicated in having an important role in KCN degradation in the K. oxytoca, we constructed cyd- mutant to explore the possible role in KCN degradation. In this study the sequence of the genes encoding this terminal oxidase (cydAB) of K. oxytoca mutant were deduced. Results showed that cytochrome d oxidase of K. oxytoca is not a cyanide-insensitive oxidase, but playing an important role in KCN degradation.

Because of its potential application for flat panel displays, solid-state lighting and 1.5 µm emitter for fiber optical communications, organic light-emitting diodes (OLEDs) have been intensively researched. One of the major problems with current OLED technology relates to inefficient electron injection at the cathode interface, which causes high driving voltage and poor device stability. Making a low resistance cathode contact for electron injection is critical to device performance. This work mainly focuses on cathode interface design and engineering. The Ohmic contact using a structure of C60/LiF/Al has been developed in electron only devices. It is found that application of the C60/LiF/Al contact to Alq based OLEDs leads to a dramatic reduction in driving voltages, a significant improvement in power efficiency, and a much slower aging process. A new cathode structure based on metal-organic-metal (MOM) tri-layer films has been developed. It is found that MOM cathodes reduce reflection by deconstructive optical interference from two metal films. The absolute reflectance from the MOM tri-layer films can be reduced to as low as 7% in the visible light spectrum. In actual working devices, the reflectance can be reduced from ~80% to ~ 20%. MOM cathodes provide a potential low-cost solution for high contrast full-color OLED displays. Low voltage Erq based OLEDs at 1.5 µm emission have been developed. The Erq/Ag cathode interface has been found to be efficient for electron injection. Dramatic improvement in driving voltage and power efficiency has been realized by implementing Bphen and C60 into Erq devices as an electron transport layer. Integration of Erq devices on Si wafers has also been demonstrated.

Thesis (M.S.)--Missouri State University, 2008. / "May 2008." Includes bibliographical references (leaves 83-87). Also available online.

Man has had an intense interest in the role of enzymes in biological reactions for many years. The basic question--how enzymes are able to function so efficiently--remains as yet largely unanswered. Only in recent years has it been discovered that molybdenum is essential for certain biological processes. For example, traces of molybdenum added to certain soils have resulted in spectacular plant growth (1). Four enzymes are known to contain molybdenum: nitrate reductase (2), hydrogenase (3), xanthine oxidase (4), and aldehyde oxidase (5). In each of these enzymes riboflavin is also present as the coenzyme FAD (flavin adeninedinucleotide). Tocatlian, in 1960, showed that a strong complex containing two molybdenum atoms per riboflavin molecule is formed in solution. However, he was unable to determine the formation constants (6).

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

A prospecção e síntese de novos derivados de 8-hidroxiquinolina está em ascensão devido às suas diversas atividades biológicas. Neste trabalho é relatada a síntese e avaliação da atividade antimicrobiana de novos derivados contendo uma sulfonamida substituída na posição 5 da 8-hidroxiquinolina ou um grupamento aminossubstituído na posição 7 da 5-cloro-8-hidroxiquinolina ou 5-cloro-8-metoxiquinolina. Os derivados 5-sulfonamidas foram preparados por clorossulfonação seguida da reação com a amina apropriada. Os derivados 7-aminossubstituído foram sintetizados através da metilação da hidroxila da posição 8, seguida da reação de cross-coupling catalisada por paládio e desmetilação. A avaliação da atividade antimicrobiana foi realizada através do método de microdiluição em caldo. Dentre os compostos sintetizados, 5a (da série 5-sulfonamidas) foi o mais potente, sendo ativo contra todas as espécies fúngicas testadas, além de apresentar importante atividade contra cepas de Staphylococcus aureus, e baixa toxicidade contra células VERO. Isso sugere que a introdução de um grupamento retirador de elétrons em para no substituinte arila da posição 5 é importante para a atividade antimicrobiana. Ainda, a nanoemulsão preparada contendo 5a manteve a atividade antifúngica da substância contra espécies de Candida spp. A série 7-aminossubstituído também apresentou resultados muito interessantes. Desta série, o composto 5i foi o mais potente. Isso sugere que grupamentos heterocíclicos hidrofílicos na posição 7 podem favorecer a atividade antifúngica. A presença da hidroxila livre na posição 8 parece ser essencial para a atividade antifúngica, pois os derivados protegidos por uma metila foram pouco ativos. Os derivados de 8-hidroxiquinolina 5a e 5i podem ser considerados para estudos posteriores na busca de novos agentes antimicrobianos. / The synthesis and screening of new 8-hydroxyquinoline derivatives is growing, due to their various biological activities. In this work, the synthesis and antimicrobial evaluation of new derivatives containing a substituted 5-sulfonamide in the 8-hydroxyquinoline or a substituted amino group at the 7-position of the 5-chloro-8-hydroxyquinoline or 5-chloro-8-methoxyquinoline is reported. The 5-sulfonamide derivatives were prepared by chlorosulfonation followed by the reaction with the appropriate amine. The 7-amino derivatives were synthesized by methylation of the 8-hydroxyquinoline, followed by palladium-catalyzed cross-coupling reaction and demethylation. The antimicrobial evaluation was tested by the broth microdilution method. Among all the prepared compounds, 5a (from the 5-sulfonamide series) was the most potent, being active against all the fungal species tested, while also showing important activity against Staphylococcus aureus strains, and low toxicity against VERO cells. This suggests that the introduction of an electron-withdrawing group at para-position of the N-aryl substituent is important for the activity. In addition, the prepared 5a nanoemulsion maintained the antifungal activity of the compound against Candida spp. The 7-amino series has also presented interesting results. In this series, 5i was the most potent compound. This suggests that the hydrophilic heterocyclic substituent at the 7-position was favorable to antifungal activity. The presence of the free hydroxyl at the 8-position is important for the antifungal activity, since the methyl-protected derivatives were poorly active. The 8-hydroxyquinoline derivatives 5a and 5i may be considered for further studies in the search for novel antimicrobial agents.

A prospecção e síntese de novos derivados de 8-hidroxiquinolina está em ascensão devido às suas diversas atividades biológicas. Neste trabalho é relatada a síntese e avaliação da atividade antimicrobiana de novos derivados contendo uma sulfonamida substituída na posição 5 da 8-hidroxiquinolina ou um grupamento aminossubstituído na posição 7 da 5-cloro-8-hidroxiquinolina ou 5-cloro-8-metoxiquinolina. Os derivados 5-sulfonamidas foram preparados por clorossulfonação seguida da reação com a amina apropriada. Os derivados 7-aminossubstituído foram sintetizados através da metilação da hidroxila da posição 8, seguida da reação de cross-coupling catalisada por paládio e desmetilação. A avaliação da atividade antimicrobiana foi realizada através do método de microdiluição em caldo. Dentre os compostos sintetizados, 5a (da série 5-sulfonamidas) foi o mais potente, sendo ativo contra todas as espécies fúngicas testadas, além de apresentar importante atividade contra cepas de Staphylococcus aureus, e baixa toxicidade contra células VERO. Isso sugere que a introdução de um grupamento retirador de elétrons em para no substituinte arila da posição 5 é importante para a atividade antimicrobiana. Ainda, a nanoemulsão preparada contendo 5a manteve a atividade antifúngica da substância contra espécies de Candida spp. A série 7-aminossubstituído também apresentou resultados muito interessantes. Desta série, o composto 5i foi o mais potente. Isso sugere que grupamentos heterocíclicos hidrofílicos na posição 7 podem favorecer a atividade antifúngica. A presença da hidroxila livre na posição 8 parece ser essencial para a atividade antifúngica, pois os derivados protegidos por uma metila foram pouco ativos. Os derivados de 8-hidroxiquinolina 5a e 5i podem ser considerados para estudos posteriores na busca de novos agentes antimicrobianos. / The synthesis and screening of new 8-hydroxyquinoline derivatives is growing, due to their various biological activities. In this work, the synthesis and antimicrobial evaluation of new derivatives containing a substituted 5-sulfonamide in the 8-hydroxyquinoline or a substituted amino group at the 7-position of the 5-chloro-8-hydroxyquinoline or 5-chloro-8-methoxyquinoline is reported. The 5-sulfonamide derivatives were prepared by chlorosulfonation followed by the reaction with the appropriate amine. The 7-amino derivatives were synthesized by methylation of the 8-hydroxyquinoline, followed by palladium-catalyzed cross-coupling reaction and demethylation. The antimicrobial evaluation was tested by the broth microdilution method. Among all the prepared compounds, 5a (from the 5-sulfonamide series) was the most potent, being active against all the fungal species tested, while also showing important activity against Staphylococcus aureus strains, and low toxicity against VERO cells. This suggests that the introduction of an electron-withdrawing group at para-position of the N-aryl substituent is important for the activity. In addition, the prepared 5a nanoemulsion maintained the antifungal activity of the compound against Candida spp. The 7-amino series has also presented interesting results. In this series, 5i was the most potent compound. This suggests that the hydrophilic heterocyclic substituent at the 7-position was favorable to antifungal activity. The presence of the free hydroxyl at the 8-position is important for the antifungal activity, since the methyl-protected derivatives were poorly active. The 8-hydroxyquinoline derivatives 5a and 5i may be considered for further studies in the search for novel antimicrobial agents.

A prospecção e síntese de novos derivados de 8-hidroxiquinolina está em ascensão devido às suas diversas atividades biológicas. Neste trabalho é relatada a síntese e avaliação da atividade antimicrobiana de novos derivados contendo uma sulfonamida substituída na posição 5 da 8-hidroxiquinolina ou um grupamento aminossubstituído na posição 7 da 5-cloro-8-hidroxiquinolina ou 5-cloro-8-metoxiquinolina. Os derivados 5-sulfonamidas foram preparados por clorossulfonação seguida da reação com a amina apropriada. Os derivados 7-aminossubstituído foram sintetizados através da metilação da hidroxila da posição 8, seguida da reação de cross-coupling catalisada por paládio e desmetilação. A avaliação da atividade antimicrobiana foi realizada através do método de microdiluição em caldo. Dentre os compostos sintetizados, 5a (da série 5-sulfonamidas) foi o mais potente, sendo ativo contra todas as espécies fúngicas testadas, além de apresentar importante atividade contra cepas de Staphylococcus aureus, e baixa toxicidade contra células VERO. Isso sugere que a introdução de um grupamento retirador de elétrons em para no substituinte arila da posição 5 é importante para a atividade antimicrobiana. Ainda, a nanoemulsão preparada contendo 5a manteve a atividade antifúngica da substância contra espécies de Candida spp. A série 7-aminossubstituído também apresentou resultados muito interessantes. Desta série, o composto 5i foi o mais potente. Isso sugere que grupamentos heterocíclicos hidrofílicos na posição 7 podem favorecer a atividade antifúngica. A presença da hidroxila livre na posição 8 parece ser essencial para a atividade antifúngica, pois os derivados protegidos por uma metila foram pouco ativos. Os derivados de 8-hidroxiquinolina 5a e 5i podem ser considerados para estudos posteriores na busca de novos agentes antimicrobianos. / The synthesis and screening of new 8-hydroxyquinoline derivatives is growing, due to their various biological activities. In this work, the synthesis and antimicrobial evaluation of new derivatives containing a substituted 5-sulfonamide in the 8-hydroxyquinoline or a substituted amino group at the 7-position of the 5-chloro-8-hydroxyquinoline or 5-chloro-8-methoxyquinoline is reported. The 5-sulfonamide derivatives were prepared by chlorosulfonation followed by the reaction with the appropriate amine. The 7-amino derivatives were synthesized by methylation of the 8-hydroxyquinoline, followed by palladium-catalyzed cross-coupling reaction and demethylation. The antimicrobial evaluation was tested by the broth microdilution method. Among all the prepared compounds, 5a (from the 5-sulfonamide series) was the most potent, being active against all the fungal species tested, while also showing important activity against Staphylococcus aureus strains, and low toxicity against VERO cells. This suggests that the introduction of an electron-withdrawing group at para-position of the N-aryl substituent is important for the activity. In addition, the prepared 5a nanoemulsion maintained the antifungal activity of the compound against Candida spp. The 7-amino series has also presented interesting results. In this series, 5i was the most potent compound. This suggests that the hydrophilic heterocyclic substituent at the 7-position was favorable to antifungal activity. The presence of the free hydroxyl at the 8-position is important for the antifungal activity, since the methyl-protected derivatives were poorly active. The 8-hydroxyquinoline derivatives 5a and 5i may be considered for further studies in the search for novel antimicrobial agents.

The photochemistry of several novel photoacids was addressed experimentally and theorectically. Initial studies focused on the excited-state proton transfer (ESPT) of several chiral phtoacids and explored the effects of chirality on ESPT; subsequent studies examined photochemistry and photophysics of "super" photoacid N-methyl-6-hydroxyquinolinium (MHQ). In the initial studies, no enantioselectivity was observed from the chiral photoacids to various chiral proton acceptors. In the later studies examining ESPT in MHQ both experimentally and theoretically, the excited-state acidity constant of the photoacid was determined to be an unprecedented -7, making it the strongest photoacid reported in the literature to-date. Consideration was then given to applications of the novel photoacid including its properties as a photoinitiator in cationic polymerizations and as a photochemical probe in gas-expanded liquids and in the Nafion membrane. In the course of these studies, an interesting fluorescence quenching effect was observed that became the subject of some exploratory studies that suggest a nucleophilic quenching mechanism.

Diffusive gradient in thin film technique (DGT) represents a relatively new approach for in situ determinations of labile metal-species in aquatic systems. The DGT device passively accumulates labile species from the solution while deployed in situ, and therefore contamination problems associated with conventional collection and filtration procedures are eliminated. This study deals with a possible modification of DGT technique. The key of using DGT technique for speciation analysis of metals is to find out suitable binding phase and diffusion layer. The new resin gel based on Spheron Oxin (5 sulphophenyl-azo-8-hydroxyquinoline) ion exchanger with a higher selectivity to trace metals than Chelex 100 could potentially provide more information on metals speciation in aquatic systems. The performance of this new binding phase was tested for the determination of Cd, Cu, Ni, Pb and U under laboratory conditions. The hydrogel layer based on poly(2-hydroxyethyl methacrylate) was synthesized and tested as a new diffusion gel for application in DGT technique.