Made available in DSpace on 2015-03-26T13:42:28Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2717003 bytes, checksum: 430ed9ce97311b4450b054a78245fcf2 (MD5) Previous issue date: 2013-02-01 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Cobalamin-independent methionine synthase (MetE) is a key enzyme for de novo synthesis of methionine in plants and it is also responsible for the regeneration of S-adenosylmethionine, which is a metabolite associated with the process of interaction with pathogens, plant growth and stresses response. In this study, 95 complete sequences of the gene for methionine synthase were obtained from 26 specimens of Carapichea ipecacuanha (species of Rubiaceae family, which is popularly known as ipecac) with aims to understand and model evolutionary events that occurred on MetE locus and on the specimens from three disjuncts ranges of occurrence of this species (Atlantic, Amazon and Central America ranges). Sequences of ITS and 5.8S from nrDNA and trnT-trnL spacers from cpDNA were also used for a multiloci population analysis. The sequenced region of MetE covered 3,890pb, where 2,298pb correspond to the coding region (composed of 11 exons) and 1,592pb to the noncoding region (comprising 10 introns and a portion of 3'UTR). In the entire sample were obtained 75 haplotypes and a nucleotide diversity of 0.00899. FST and AMOVA analyzes of MetE indicated no structure in three regions, opposite to detected for other loci analyzed here and in previous studies in which high divergence among the specimens from three ranges was observed. However, in the network haplotype was possible to observe the sympatric distribution of the haplotypes. Possibly, excess of tip haplotypes and the small number of mutational steps among neighboring haplotypes from the three ranges do not allow that the differentiation among these was significant. The Bayesian phylogenetic tree rooted by Carapichea lucida (outgroup) using the coding region sequences showed the formation of clades by geographic regions and provided evidence that sequences from "Atlantic" range is closer to the ancestral state of the gene MetE than sequences from others ranges. The heterogeneity of results for neutrality tests and for values of haplotype and nucleotide diversity at different loci suggests that these are evolving independently and also suggests that demographic events do not explain the pattern found. Thereby, tests for the presence of selection site-by-site were performed for the coding region of the gene MetE and protein alignment against others MetE from diferents plant species available in the Genbank was develop too. Four sites under positive selection were found, but the results show that negative selection (purifying selection) is the main force acting on the locus, favoring the conservation of protein structure and function in all gene copies from C. ipecacuanha. / Metionina sintase independente de cobalamina (MetE) é uma enzima chave na via de síntese de novo de metionina em plantas e também é responsável pela regeneração de S-adenosilmetionina, metabólito associado à vias de interação com patógenos, crescimento vegetal e resposta à estresses. Neste estudo, 95 sequências do gene para metionina sintase foram obtidas a partir de 26 indivíduos de Carapichea ipecacuanha (espécie da família Rubiaceae, popularmente conhecida com ipeca) com objetivo de entender e modelar os eventos evolutivos que ocorreram sobre o locus MetE e sobre os indivíduos de três regiões disjuntas de ocorrência desta espécie (Mata Atlântica, Amazônia e América Central). Sequências de ITS do nrDNA e dos espaçadores trnT-trnL do cpDNA também foram utilizadas para uma análise populacional multiloci. A região sequenciada de MetE abrangeu 3.890pb, sendo 2.298pb correspondentes à região codificante (composta por 11 exons) e 1.592pb à região não codificante (composta por 10 introns e uma parte da região 3 UTR). No total, foram obtidos 75 haplótipos e uma diversidade nucleotídica de 0,00899. As análises FST e AMOVA de MetE indicaram ausência de estruturação em relação às três regiões, diferentemente do observado para os demais loci aqui analisados e em estudos prévios em que elevada divergência entre as três regiões foi observada. Por meio rede de haplótipos foi possível observar a distribuição simpátrica destes; no entanto, o excesso de haplótipos de ponta e o pequeno número de passos mutacionais entre haplótipos vizinhos das três regiões não permitem que a diferenciação destes seja significativa. A árvore filogenética Bayesiana enraizada por Carapichea lucida (grupo externo) utilizando a região codificante também mostrou a formação de clados por regiões geográficas e forneceu evidências de que sequências da Mata Atlântica sejam mais próximas do estado ancestral do gene MetE que as sequências das demais regiões. A heterogeneidade dos resultados encontrados para os testes de neutralidade e para os valores de diversidade nucleotídica e haplotípica nos diferentes loci sugerem que estes estão evoluindo independentemente e que eventos demográficos não explicam o padrão obtido. Assim, análises para a presença de seleção foram conduzidas para a região codificante do gene MetE e também foi realizado alinhamento de proteínas preditas para esta espécie contra proteínas MetE de outras espécies vegetais disponíveis no GenBank. Em quatro sítios houve evidência de seleção positiva, mas os resultados sugerem que a seleção negativa (purificadora) é a principal força atuando sobre o locus, favorecendo a conservação da estrutura e função proteica em todas as cópias gênicas de C. ipecacuanha.

Les travaux s'inscrivent dans le développement de catalyseurs conducteurs ioniques à base de zircone stabilisée à l'oxyde d'yttrium (YSZ) pour l'oxydation des suies dans les filtres à particules (FAP) qui équipent les véhicules Diesel. L'oxydation de la suie sur YSZ a été observée à l'échelle nanométrique par microscopie électronique en transmission environnementale. La réaction d'oxydation se déroule à l'interface (20-40 nm) entre le catalyseur et la suie, l'activité étant liée au nombre de points de contact. Nous avons associé un vecteur d'oxygène mobile, l'argent, à YSZ. Les résultats montrent une synergie entre YSZ et les nanoparticules d'argent qui promeut l'activité notamment en cas de contact grossier avec la suie. Des expériences isotopiques d'échanges et d'oxydation ont démontré que l'argent active l'intégration de l'oxygène gazeux dans le réseau de YSZ. La caractérisation des propriétés physicochimiques des nanoparticules d'argent dispersées sur différents oxydes (une autre zircone yttriée aux propriétés différentes : YSZb, ZrO2, CeZrO2, SiO2) a permis de relier les performances catalytiques avec la teneur d'argent métallique en surface. Des tests de vieillissement hydrothermal ont montré que la formulation supportée sur YSZb présente une activité maintenue en contact médiocre avec la suie et une faible perte en argent. Des mini-FAPs imprégnés de catalyseur ont ensuite été testés sur un banc de gaz synthétiques capable de produire des particules de suie en suspension. L'activité des formulations catalytiques une fois mises en forme ainsi que leur capacité de filtration ont été évaluées. Un mini-FAP contenant la formulation Ag/YSZb oxyde les suies dès 350°C et s'auto-régénère (oxydation des suies plus rapide que leur collecte) dès 450°C / This study deals with the development of ionic conductive catalysts based on yttria-stabilized zirconia for soot oxidation in Diesel Particle Filter (DPF). Soot oxidation was observed at the nanoscale using Environmental Transmission Electron Microscopy. Reaction was shown to occur at the interface between YSZ and soot, ranging from 20 to 40 nm, and activity was related to the number of contact points between soot and catalyst. In order to promote activity, we associated to YSZ an oxygen carrier: silver, under the form of silver nanoparticles (AgNPs) scattered over YSZ surface. Results display a synergy between YSZ and AgNPs, allowing for the promotion of soot oxidation under poor contact conditions. Isotopic exchange and oxidation experiments demonstrated AgNPs promote oxygen integration into YSZ lattice. Characterizations of supported AgNPs over different oxides such as YSZb (displaying different properties than YSZ), ZrO2, SiO2, CeZrO2, indicate that the soot oxidation activity is related to the amount of metallic silver species on the oxide surface. Hydrothermal ageing tests indicate that Ag/YSZb formulation displays a stable activity in poor contact conditions and a low silver loss. Baby-DPF (1 inch diameter, 3 inches length) were impregnated with silver-supported catalysts and tested on a synthetic gas bench producing a gas stream containing suspended soot particles. Soot oxidation activity and filtration efficiency were measured. A baby-FAP containing the Ag/YSZb formulation was shown to oxide soot at a temperature as low as 350°C and to induce self-regeneration (soot oxidation overcoming the collection) at 450°C