Thesis (Ph.D)--Mississippi State University. College of Veterinary Medicine. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references. Also available on the World Wide Web.

No description available.

The syntheses and characterisation of di(cyclohexylmethyl), di(2-cyclohexylethyl), di(2-methylcyclohexyl) and di(4-methylcyclohexyl) phosphoric acids; cyclohexylmethyl phosphonic acid monocyclohexylmethyl ester, di(cyclohexylmethyl), di(4-methylcyclohexyl), di(4-tert- butylcyclohexyl), di(3-methylcyclohexyl), di(3,5-dimethylcyclohexy) and di(2-methylcyclohexyl) phosphinic acids are reported. Problems encountered and how they were resolved during the preparation of the above organophosphorus acids are reported and discussed in detail. These acids are then evaluated as potential hydrometallurgical extractants, for the separation of cobalt from nickel in acid leach liquors, and compared with two commercially available extractants, namely di(2-ethylhexyl)phosphoric acid (D2EHPA) and di(2,4-4- trimethylpentyl)phosphinic acid (Cyanex 272). The effects of variablest such as metal feed solution concentration, extractant concentration, diluent, modifier and temperature are examined experimentally in order to determine which factors are important for optimisation of an extraction system. The extraction characteristics for each acid as a function of pH are presented graphically and the pHO 5 values, distribution coefficients and separation factors are calculated. The dialkylphosphinic acids are found to exhibit much greater selectivity, for cobalt over nickel, than the dialkylphosphoric acids. It is postulated, that steric crowding of the phosphorus atom, by the hydrocarbon groups attached to the phosphorus, increases the selectivity of an extractant. This effect is particularly apparent in the dialkylphosphinic acids with di(2-methylcyclohexyl)phosphinic acid giving the best selectivity; much better than the commercially available Cyanex 272. Several of the dialkylphosphinic acids, evaluated as extractants in this thesis, are protected by a British Patent Application.

Thesis (Ph.D.)--McMaster University (Canada), 1994. / Source: Dissertation Abstracts International, Volume: 56-01, Section: B, page: 0252. Adviser: C. J. L. Lock.

Thesis (M.S.)--University of Missouri--Columbia, 2003. / "December 2003." Typescript. Vita. Includes bibliographical references (leaves 84-96). Also issued on the Internet.

Thesis (M.S.)--University of Missouri--Columbia, 2003. / "December 2003." Typescript. Vita. Includes bibliographical references (leaves 84-96). Also issued on the Internet.

Mechanistic aspects of phosphorylation, dephosphorylation, pyrophosphorylation and depyrophosphorylation reactions that mimic phosphorylases, dephosphorylases, pyrophosphorylases and depyrophosphorylases have been studied in the biologically important middle pH region. The different systems monitored are; (a) the reactions between [{CoN4(OH)(OH2)}]2+ and [HPO4]- for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [HPO4]2- ratios. (b) the reactions between [{CoN4PO4] and [O2NC6H4O]- (abbreviated as NP-) for 1:1, 2:1 and 3:1 [{CoN4PO4] to [O2NC6H4O]- ratios. (c) the reactions between [{CoN4(OH)(OH2)}]2+ and [O2NC6H4PO4]2- (abbreviated as NPP2-) for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [O2NC6H4PO4]2- ratios. (d) the reactions between [{CoN4(OH)(OH2)}]2+ and [H2P2O7]2- for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [H2P2O7]2- ratios. (e) the reactions between [{CoN4P2O7}]- and [O2NC6H4O]- for 1:1, 2:1 and 3:1 [{CoN4P2O7}]- to [O2NC6H4O]- ratios. Significant phosphorylation was noted for systems containing 1:1 molar ratio [{CoN4PO4] and [O2NC6H4O]-. Enhanced phosphorylation was depicted for system containing 1:1 molar ratio of [{CoN4(OH)}2PO4]+ and [O2NC6H4O]-. Pyrophosphorylation was noted for reactions of 1:1 molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. The rate of pyrophosphorylation was substantially reduced for systems that were 2:1 in molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. No appreciable pyrophosphorylation was noted for systems, which has a 3:1 molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. Specific mechanistic features and the possible roles metal ions play in phosphorylase, dephosphorylase and pyrophosphorylase are highlighted from results of UV-Visible spectroscopy, 31P {1H} NMR spectroscopy and Surface Enhanced Raman Scattering (SERS) studies / Chemistry / D.Phil. (Chemistry)

Orientador: Ana Maria Lima de Azeredo-Espin / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T10:06:29Z (GMT). No. of bitstreams: 1 Carvalho_RenatoAssisde_D.pdf: 2025643 bytes, checksum: 24641039150d3a87bfa143c90c98fc64 (MD5) Previous issue date: 2010 / Resumo: A mosca-da-bicheira, Cochliomyia hominivorax, é uma das principais moscas causadoras de miíases da América do Sul, sendo responsável por severos prejuízos à pecuária através da mortalidade e redução da produtividade dos animais infestados. No Brasil, o seu controle tem sido realizado principalmente através da aplicação de inseticidas organofosforados (OF). Porém, o uso indevido e/ou prolongado desses agentes químicos pode provocar seleção de indivíduos resistentes, devido à alteração do sítio alvo ou à desintoxicação metabólica do inseticida antes de atingir o sítio alvo. Nesse sentido, o objetivo desse estudo foi investigar as bases moleculares da resistência a inseticidas OF na mosca da bicheira, através da caracterização da carboxilesterase E3, do sítio alvo acetilcolinesterase (AChE) e da expressão diferencial de enzimas metabólicas (caiboxilesterases, P450 e GST) em indivíduos resistentes. A seqüência predita da enzima carboxilesterase E3 em C. hominivorax apresentou domínios altamente conservados dentre as carboxil/colinesterases que contribuem para o mecanismo catalítico do sítio ativo. Duas mutações, já descritas em outras espécies, foram encontradas, a G137D, associada com resistência principalmente aos dietil-OPs, e a W251S, associada com resistência aos dietil-OPs e piretróides. A freqüência dessas mutações foi investigada em períodos distintos de diferentes populações do Uruguai, indicando uma correlação da freqüência de cada mutação com a classe de inseticida utilizada no controle da espécie. A região codificante da acetilcolinesterase foi sequenciada em C. hominivorax possibilitando a investigação, em populações naturais, de mutações já caracterizadas por conferir resistência a OF em outras espécies (I298V, G401A, F466Y). Apenas 2/135 indivíduos apresentaram uma das mutações (F466Y). Em contraste, a mutação G137D na carboxilesterase E3, que confere resistência metabólica aos inseticidas OF, foi encontrada em mais de 50% dos indivíduos na maioria dessas populações, indicando ser um dos principais mecanismos de resistência nessa espécie. Para a identificação de genes diferencialmente expressos em indivíduos resistentes foi gerado um banco de dados através da caracterização do transcriptoma utilizando uma das técnicas de sequenciamento de nova geração (Roche 454). Ao todo, foram obtidas 548.940 seqüências, resultando em 36.650 "contigs" e 782 "singlets" Após a anotação desses transcritos, foram selecionados genes candidatos pertencentes às famílias de enzimas de detoxificação metabólica (carboxilesterases, monooxigenases P450 e GSTs) para terem sua expressão comparada entre os indivíduos que sobreviveram ao tratamento (CL90) com o inseticida diclorvos (dimetil-OF) e um grupo controle (sem tratamento). Apenas um gene foi diferencialmente expresso, ortólogo ao CYP6GJ, e estudos futuros serão necessários para determinar a associação da expressão dessa P450 e resistência ao inseticida OF. Em ambos os grupos, o gene da AChE não se encontrou alterado. Já o gene da carboxilesterase E3 apresentou a mutação W251S em todos os indivíduos do grupo resistente (n=44), enquanto que no grupo controle (n-40) 13 indivíduos apresentaram a mutação, confirmando a associação dessa mutação com resistência aos dimetil-OP. Assim, a identificação das mutações nesse gene em populações naturais da mosca-da-bicheira pode ser uma ferramenta importante de monitoramento da resistência ao longo da atual distribuição geográfica da espécie, contribuindo para a implementação de estratégias mais efetivas de controle por meio da escolha apropriada dos produtos químicos. / Abstract: The New World Screwworm (NWS) fly Cochliomyia hominivorax is one of most important myiasis-causing flies in the Neotropics. It is responsible for severe losses to the livestock industry through both mortality and loss of productivity of infested animals. In Brazil, it has been controlled by the application of chemical insecticides, mainly the organophosphate (OP) compounds. However, the intensive use of these compounds over many years may select resistant individuals which have the potential to compromise the efficacy of current control strategies. Major mechanisms of insecticide resistance in insects involve either mutation in the target site of the insecticide, or an alteration in the rate of insecticide detoxification. Therefore, the aim of this study was to investigate the molecular basis of resistance to organophosphate insecticides in NWS throughout characterization of the carboxylesterase and acetylcholinesterase genes and expression evaluation of detoxification enzymes. The predicted amino sequence of the E3 gene showed highly conserved domains within carboxyl/cholinesterases involved in the catalytic mechanism of active site. Two mutations previously described in other dipteran species were found, G137D, associated mainly with diethyl-OP hydrolysis, and W251S, associated with dimethyl-OP and pyrethroid hydrolysis. The frequency of these mutations was analyzed in different Uruguayan regions in 2003 and 2009, indicating a correlation between each mutation and the insecticide class used for NWS control. The entire coding sequence of acetylcholinesterase was sequenced allowing surveying of mutations previously known for conferring insecticide resistance (I298V, G401A, F466Y). Only 2/135 individuals from NWS natural populations showed one of these mutations (F466Y). In contrast, G137D mutation in carboxylesterase E3. that also confers resistance to OP insecticides, was found in a high frequency in the same populations, suggesting this is one of the most important resistance mechanisms and that metabolic resistance has been preferentially selected rather altered target site in this species. Differentially expressed genes in resistant NWS individuals were analyzed throughout candidate gene expression evaluation. For this, NWS transcriptome was sampled by deep sequencing of polyadenilated transcripts using 454 sequencing technology, which generated a total of 548,940 sequences resulting in 37,432 unigenes (36,650 contigs and 782 singlets). Following functional annotation, gene expression of candidate genes belonging to detoxification enzyme families (carboxylesterases, monooxygenases P450 and GSTs) were evaluated in NWS resistant individuals surviving bioassays (1X90) with the active ingredient dichlorvos (dimethyl-OP) and from a control group (without treatment). No genes over expressed were found in the resistant group, and the ortholog to CYP6G1 was down-regulated in this group, requiring further studies to determine the association between reduced expression of a P450 gene and OP resistance. In both groups the target site was not altered. In contrast, E3 gene showed W251S mutation in all resistant individuals (44), while 13 individuals showed such mutation in the control group (40). This result corroborates the association between this mutation and the dimethyl-OP resistance in this species. Therefore, identification of mutations in carboxylesterase gene in NWS natural populations can be an important tool in monitoring insecticide resistance. The selection of appropriate chemicals for NWS control may contribute to implement more effective control strategies. / Doutorado / Genetica Animal e Evolução / Doutor em Genetica e Biologia Molecular

Orientador: Matthieu Tubino / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T09:15:46Z (GMT). No. of bitstreams: 1 Silva_MarcosPauloda_D.pdf: 2828527 bytes, checksum: ced6ec2ea662cc6579764c3b61537c2c (MD5) Previous issue date: 2011 / Resumo: O Brasil é um dos maiores consumidores mundiais de pesticidas. A agência nacional de vigilância sanitária constatou em 2008 que aproximadamente 15 % da amostras analisadas possuíam limite máximo de resíduos (LMR) acima do permitido por lei. Quando os pesticidas são utilizados de maneira adequada trazem ganhos à produção. Porém, quando mal usados podem trazer sérias conseqüências ao meio ambiente e à população, o que tem levado a sociedade civil a cobrar dos órgãos ambientais um controle mais rigoroso e aumentado a demanda por dados analíticos. Neste trabalho, foi desenvolvido um método de varredura para a determinação de pesticidas organofosforados através de procedimento FIA associado a um biossensor enzimático baseado na enzima acetilcolinesterase. O método é seletivo para inibidores desta enzima, sendo de execução muito simples, é de custo baixo e apresenta baixos limites de detecção. Para a introdução no sistema FIA a solução contendo o pesticida deve ser aquosa, não sendo, no entanto, necessário realizar a pré-concentração do analito. Para o pesticida metil paration o limite de detecção está faixa de 10 mol L, o coeficiente de correlação é de 0,9917 e o desvio padrão relativo médio é de 4,8 % (n=6). Para o pesticida clorpirifos o limite de detecção é, cerca de, 10 mol L, o coeficiente de correlação é de 0,9979, o desvio padrão relativo médio é 2,3%. Para o pesticida malation o limite de detecção apresenta-se na faixa de 10 mol L, o coeficiente de correlação é de 0,9902, o desvio padrão relativo médio de 5,8 (n=3). Para o pesticida diclorvos o limite de detecção é cerca de 10 mol L, o coeficiente de correlação é de 0,9921 e o desvio padrão relativo médio é 3,8% (n=6) / Abstract: Brazil is one of the world's largest consumers of pesticides. The national agency for health monitoring found, in 2008, that approximately 15% of samples had maximum residue limit (MRL) above the permitted by Law. When used properly pesticides help increase production. But when misused they can be extremely detrimental to the environment and to the population, which has led civil society to demand tighter control from environmental agencies and increased the demand for analytical data. In this work, we developed a scanning method for the determination of organophosphorus pesticides using a FIA procedure associated with an enzymatic biosensor based on acetylcholinesterase. The method is selective for inhibitors of this enzyme and is extremely simple, of low cost and very good. detection limits. For introduction into the FIA system, the solution containing the pesticide should be in aqueous solution but it is not necessary to perform any prior concentration of the analyte. For the pesticide methyl parathion the detection limit is the range of 10 mol L. The correlation coefficient is 0.9917 and the average relative standard deviation is 4.8% (n = 6). For the pesticide chlorpyrifos the detection limit is about 10 mol L, the correlation coefficient is 0.9979 and the average relative standard deviation is 2.3%. For the pesticide malathion the detection limit is in the range of 10 mol L, the correlation coefficient is 0.9902 and the average relative standard deviation is 5.8 (n = 3). For the pesticide dichlorvos the detection limit was about 10 mol L, the correlation coefficient was 0.9921 and the average standard deviation of 3.8 (n = 6) / Doutorado / Quimica Analitica / Doutor em Ciências