Symmetric nonaqueous redox flow batteries (RFBs) use negative and positive battery solutions of the same solution composition to operate at high cell voltages. This research effort targets these systems since they offer performance improvements derived from using nonaqueous systems and symmetric active species. Nonaqueous solutions permit significantly higher cell voltages than state-of-the-art aqueous RFBs and symmetric active species chemistries reduce the required complexity of cell reactors. Both performance advantages correspond to significant cost improvements beyond already commercially competitive aqueous RFB chemistries. This document focuses on two classes of symmetric nonaqueous RFB chemistries: coordination complexes such as vanadium acetylacetonate [V(acac)₃] or chromium acetylacetonate [Cr(acac)₃], and organic active species such as 9,10-diphenylanthracene (DPA). V(acac)₃ delivers reversible electrochemistry that supports a 2.2 V equilibrium cell potential, but there are some gaps in the understanding of its degradation mechanisms. Cr(acac)₃ supports redox reactions that suggest cell potentials above 4 V, but shows signs of irreversibility in voltammetry experiments and is not yet well understood. Finally, the DPA system could be interesting because it does not use metal active species, and its voltammetry promises cell potentials above 3 V. Yet DPA suffers from low solubility in nonaqueous solvents that limit its practicality. These three systems show promise for symmetric nonaqueous RFBs and offer avenues for further improvement. Voltammetry and spectroelectrochemical electrolysis experiments on the metal coordination complexes clarify the mechanisms behind the voltammetry on these symmetric chemistries. Ligand dissociation causes the irreversible behavior observed in voltammetry on Cr(acac)₃. The same experiments reaffirm the expected cyclability of V(acac)₃. Chemical functionalization of the DPA center is performed to investigate the solubility and reactivity of various derivatives. Functionalizing DPA with ethylene glycol chains to form 'DdPA' significantly increases solubility limits from 0.6 mM and 44 mM for DPA in acetonitrile and 1,2-dimethoxyethane, respectively, to 12 mM and 0.21 M for DdPA in the same solvents. At the same time, DdPA retains redox activity that promises 3 V cell potentials. Ultimately, a custom, nonaqueous-compatible redox flow reactor was designed and used to test the performance of V(acac)₃, DPA, and DdPA under various operating conditions. Contradicting previous reports, V(acac)₃ delivers stable cycling over the 21- cycle experimental protocol. Exploration over a range of flow rates and current densities give energy and power densities up to 1.09 WhL^-1 and 0.16 Wcm^-2, respectively, for the battery solution compositions examined. These experiments further predict values up to 28 WhL^-1 and at least 0.22 Wcm^-2 for optimized V(acac)₃ battery solutions. DPA and DdPA deliver the highest operating potential observed from organic nonaqueous RFBs, discharging at 3 V and 2.9 V, but require further work to understand degradation in the systems.

An investigation into the processes taking place at the surface interface of ferroelectric Pb(Zr1-x,Tix)O3 immersed in metal salt solution under ultraviolet illumination is presented. The semiconducting and switchable dipolar nature of this material allows the spatial separation and control of photo-induced reduction and oxidation across its surface interface. These properties can be of application in novel techniques such as the controlled growth of metallic nanoparticles across specific polar domains. 70nm thick Pb(Zr0.3,Ti0.7)O3 samples, PZT(30/70), are manufactured using the sol gel methodology, two crystallographic orientations being produced. The orientation being controlled by the substrate used; Si was used for [111] orientation and MgO for [100]. The initial work with wideband ultraviolet light shows that the reduction and growth of silver on the PZT surface is greatly influenced by the structure of the film. The crystallographic orientation of the film affects metal deposition such that on [111] films the metal deposits only on positive domains, where as the [100] films experience deposition on both positive and negative domains. This is shown to be due to the difference in width of the space charge region, Δw = 4.4nm, between the [111] and [100] samples so that the negative domain on [100] samples have 10 19 times higher chance of electron tunnelling compared to the [111]. It is also shown that grain boundaries have the greatest effect on the growth of metal, with a metal cluster growth rate 51 times faster than elsewhere on the surface. This increased rate of growth is due to the effect a grain boundary has on the surrounding area, the energy band bending at the boundary attracting charge carriers from the grains around it. The interface types ranked from greatest to lowest influence are grain boundaries, positive domains, domain boundaries and finally interphase boundaries.ii It is shown that the stern layer, strongly adsorbed charged ions of opposite sign to the surface charge, at the PZT/solution interface act as an insulating layer to metal reduction. The accumulation of photoexcited charge carriers at points along grain boundaries causes the surface potential gradient to alter and allows metal reduction and thus clusters to nucleate. The energy required to cause this variation is investigated by use of narrow band, 5nm bandwidth, ultraviolet. For energy from 4.4eV to 5 eV, it is found there is an increase in the average silver cluster cross sectional area by a ratio of ca 1.6 to 1 for both the [111] and [100] orientations of PZT. Finally it is shown that the type of metal salt used in the photochemical process affects the type of reaction that takes place at the sample surface. For a cation to reduce on positive domains its reduction potential needs to be below the bottom edge of the conduction band of PZT. Chloride salts, that sit above the conduction band, cause decomposition of the negative domains. Use is made of these effects to find the position of the bottom of the conduction band for PZT. It is found that across similar [111] PZT samples FeCl2 can both reduce on positive domains and decompose negative domains, this puts the bottom of the conduction band for PZT(30/70) between 4.06 and 4.36 eV from vacuum. It is also discovered that the type of anion affects the decomposition of the negative domains. Nitrate salts with cations above the conduction band cause no decomposition whereas chlorides do. The decomposition is shown to be the loss of Pb from the negative surface.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-03-03T19:55:15Z No. of bitstreams: 1 ErikaCristinaPinheiroDeCastro_DISSERT.pdf: 2706231 bytes, checksum: fd12403d1b13d2a828b00af3b56d6cc1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-03-07T21:59:52Z (GMT) No. of bitstreams: 1 ErikaCristinaPinheiroDeCastro_DISSERT.pdf: 2706231 bytes, checksum: fd12403d1b13d2a828b00af3b56d6cc1 (MD5) / Made available in DSpace on 2016-03-07T21:59:52Z (GMT). No. of bitstreams: 1 ErikaCristinaPinheiroDeCastro_DISSERT.pdf: 2706231 bytes, checksum: fd12403d1b13d2a828b00af3b56d6cc1 (MD5) Previous issue date: 2013-12-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / O consumo mundial de ?leos vegetais aumentou nos ?ltimos anos devido sua aplica??o na ind?stria aliment?cia, qu?mica, farmac?utica e, recentemente energ?tica. Todavia, as sementes oleaginosas das quais esses ?leos s?o extra?dos envelhecem rapidamente, comprometendo o cultivo e a produtividade destas. O objetivo deste trabalho foi avaliar o efeito do envelhecimento sobre a coordena??o dos sistemas antioxidantes da catalase (CAT) e da ascorbato peroxidase (APX) em c?rtamo e girassol. Para tanto, sementes foram submetidas a envelhecimento acelerado por 3, 6 e 9 dias e cultivadas em papel-toalha umedecido durante 72h. Adicionalmente, antes de serem submetidas ao envelhecimento acelerado, sementes de girassol foram pr?- tratadas por osmopriming com 10 mM de ascorbato (ASC) ou 3 amino 1,2,4 triazole(3-AT), inibidor espec?fico da CAT. O m?todo de envelhecimento artificial utilizado foi eficiente para ambas esp?cies, pois promoveu diminui??o na germina??o, no desenvolvimento de pl?ntulas e no crescimento destas, principalmente no c?rtamo. O envelhecimento provocou inibi??o da atividade CAT para ambas as esp?cies e para compensar tal inibi??o, o girassol aumentou a express?o do mRNA desta enzima, enquanto o c?rtamo mobilizou mais a atividade da APX. A an?lise da express?o da malato sintase e do conte?do de a?ucares demonstrou que o girassol consome suas reservas lip?dicas no estado quiescente, enquanto o c?rtamo ? mais dependente dos carboidratos. O pr?-tratamento com 3-AT inibiu a atividade CAT e estimulou a da APX, enquanto o ASC atuou de forma inversa nesses sistemas. Nenhum dos tratamentos recuperou o decl?nio fisiol?gico decorrente do envelhecimento. Conclui-se que o envelhecimento alterou significativamente o metabolismo antioxidante das oleaginosas e, apesar das varia??es interespec?ficas na resposta a esse processo, a deple??o do sistema antioxidante da CAT foi comum, deforma que a mensura??o da atividade desta enzima pode ser utilizada para identifica??o de lotes de sementes envelhecidas. / World consumption of vegetable oils has increased in recent years because of its application in food, chemical, pharmaceutical and, more recently, energy industry. However, oilseeds, which these oils are extracted, have low viability, affecting the cultivation and productivity of these species. The aim of this study was to analyze the effect of aging on the coordination of catalase (CAT) and ascorbate peroxidase (APX) antioxidant systems in safflower and sunflower. . Therefore, seeds were subjected to accelerated aging for 3, 6 and 9 days and grown in moistened paper towel for 72 hours. Additionally, before accelerated aging, sunflower seeds were pretreated by osmopriming with 10 mM ascorbate (ASC) or 3 amino 1,2,4 triazol (3-AT), a specific inhibitor of CAT activitie. The method of artificial aging used was efficient in both species, because it caused a decrease in germination, seedling development and growth, especially in safflower. The aging caused inhibition of CAT activity for both species and to compensate for such inhibition , sunflower increased mRNA expression of this enzyme , while safflower mobilized over the activity of APX. Analysis of the expression of malate synthase and sugar content demonstrated that sunflower seeds consumes lipid reserves in quiescent state, while the safflower is more dependent on carbohydrate. Pretreatment with 3-AT inhibited CAT activity and stimulated the APX, though with ASC acted reverse on these systems. None of the treatments recovered the physiological decline aging. It is concluded that aging change the oilseeds antioxidant metabolism, despite interspecies variations in response to this process, the depletion of the CAT antioxidant system was common. Because of this we propose that the measurement of CAT activity can be used to identify aging seed lots.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Os estresses salino e osmÃtico sÃo responsÃveis por perdas significativas na produÃÃo agrÃcola, particularmente nas regiÃes semiÃridas. Nessas condiÃÃes, a raiz à o ÃrgÃo da planta que sofre os primeiros efeitos e à responsÃvel pela percepÃÃo e sinalizaÃÃo bioquÃmica dos estresses. Em folhas, as peroxidases do ascorbato do citosol sÃo as principais isoformas envolvidas com a proteÃÃo antioxidativa contra o excesso de H2O2 e sÃo tambÃm relacionadas na sinalizaÃÃo em condiÃÃes de estresses. Entretanto, esses mecanismos de aÃÃo em raÃzes sÃo pouco conhecidos. O objetivo deste estudo foi testar a hipÃtese de que as APXs citosÃlicas sÃo essenciais para a proteÃÃo antioxidativa de raÃzes de arroz expostas Ãs condiÃÃes de estresse salino e osmÃtico. Para isso, plantas transgÃnicas silenciadas nas duas isoformas de APXs citosÃlicas (APX1/2) e plantas nÃo transformadas (45 dias de idade) foram expostas a duas condiÃÃes de estresse: (1) NaCl e manitol em concentraÃÃes iso-osmÃticas (-0,62 MPa) durante oito dias e (2) manitol 268 mM (-0,62 MPa) por dois dias. Em plantas silenciadas, a quantidade de transcritos (RNAs) de OsAPX1 e OsAPX2 foi reduzida em 90% enquanto que a abundÃncia das duas proteÃnas mensurada por western blotting nÃo foi detectÃvel. A atividade total de APX foi diminuÃda em 66% em comparaÃÃo com as NTs na condiÃÃo controle, evidenciando que o silenciamento foi efetivo nas raÃzes. Como consequÃncia da deficiÃncia das APX1/2, o nÃvel de H2O2 foi aumentado em 51% comparado com as NTs. Ambos os estresses afetaram de modo similar o crescimento da raiz e parte aÃrea das APX1/2, em comparaÃÃo com as plantas nÃo transformadas (NT). Os valores de danos de membrana nas raÃzes foram aumentados na mesma intensidade nos dois genÃtipos e nos dois tipos de estresses, indicando que as APX1/2 apresentaram mesma sensibilidade aos estresses estudados. Nas plantas NT, as quantidades de transcritos de OsAPX1 e OsAPX2 foram aumentadas discretamente por NaCl e manitol enquanto que a atividade de APX foi aumentada somente pelo NaCl. As plantas APX1/2 mostraram a mesma tendÃncia das NTs quanto a expressÃo e atividade de APX. O aumento na quantidade relativa dos transcritos das outras isoformas de APX, principalmente de OsAPX3, OsAPX5 e OsAPX8, em ambos os genÃtipos sob estresse salino, foi correlacionado com o aumento da atividade da APX. AlÃm disso, outras peroxidases (GPX e GPOD) apresentaram a mesma tendÃncia de aumento de atividade apenas sob estresse salino. Diferentemente, manitol induziu um aumento proeminente na atividade de catalase nas plantas NT enquanto que nas APX1/2 essa enzima jà apresentava atividade aumentada antes do estresse e permaneceu no mesmo nÃvel. As concentraÃÃes de H2O2 foram aumentadas intensamente por manitol e reduzidas na presenÃa de NaCl. O nÃvel de TBARS (indicador de peroxidaÃÃo lipÃdica) foi mantido inalterado na presenÃa dos dois estresses e nos dois tipos de plantas. Os resultados deste estudo, quando analisados em conjunto, mostram que raÃzes de arroz expostas aos estresses salino e osmÃtico exibiram respostas complexas em termos de metabolismo redox. Aparentemente, as duas APXs citosÃlicas nÃo sÃo essenciais para a proteÃÃo antioxidativa, uma vez que as plantas mutantes apresentaram uma performance fisiolÃgica semelhante as plantas NT. As respostas aos dois fatores de estresse, NaCl e manitol, foram contrastantes nos dois genÃtipos, sugerindo que diferentes mecanismos de proteÃÃo antioxidante foram acionados para cada tipo de estresse. / Os estresses salino e osmÃtico sÃo responsÃveis por perdas significativas na produÃÃo agrÃcola, particularmente nas regiÃes semiÃridas. Nessas condiÃÃes, a raiz à o ÃrgÃo da planta que sofre os primeiros efeitos e à responsÃvel pela percepÃÃo e sinalizaÃÃo bioquÃmica dos estresses. Em folhas, as peroxidases do ascorbato do citosol sÃo as principais isoformas envolvidas com a proteÃÃo antioxidativa contra o excesso de H2O2 e sÃo tambÃm relacionadas na sinalizaÃÃo em condiÃÃes de estresses. Entretanto, esses mecanismos de aÃÃo em raÃzes sÃo pouco conhecidos. O objetivo deste estudo foi testar a hipÃtese de que as APXs citosÃlicas sÃo essenciais para a proteÃÃo antioxidativa de raÃzes de arroz expostas Ãs condiÃÃes de estresse salino e osmÃtico. Para isso, plantas transgÃnicas silenciadas nas duas isoformas de APXs citosÃlicas (APX1/2) e plantas nÃo transformadas (45 dias de idade) foram expostas a duas condiÃÃes de estresse: (1) NaCl e manitol em concentraÃÃes iso-osmÃticas (-0,62 MPa) durante oito dias e (2) manitol 268 mM (-0,62 MPa) por dois dias. Em plantas silenciadas, a quantidade de transcritos (RNAs) de OsAPX1 e OsAPX2 foi reduzida em 90% enquanto que a abundÃncia das duas proteÃnas mensurada por western blotting nÃo foi detectÃvel. A atividade total de APX foi diminuÃda em 66% em comparaÃÃo com as NTs na condiÃÃo controle, evidenciando que o silenciamento foi efetivo nas raÃzes. Como consequÃncia da deficiÃncia das APX1/2, o nÃvel de H2O2 foi aumentado em 51% comparado com as NTs. Ambos os estresses afetaram de modo similar o crescimento da raiz e parte aÃrea das APX1/2, em comparaÃÃo com as plantas nÃo transformadas (NT). Os valores de danos de membrana nas raÃzes foram aumentados na mesma intensidade nos dois genÃtipos e nos dois tipos de estresses, indicando que as APX1/2 apresentaram mesma sensibilidade aos estresses estudados. Nas plantas NT, as quantidades de transcritos de OsAPX1 e OsAPX2 foram aumentadas discretamente por NaCl e manitol enquanto que a atividade de APX foi aumentada somente pelo NaCl. As plantas APX1/2 mostraram a mesma tendÃncia das NTs quanto a expressÃo e atividade de APX. O aumento na quantidade relativa dos transcritos das outras isoformas de APX, principalmente de OsAPX3, OsAPX5 e OsAPX8, em ambos os genÃtipos sob estresse salino, foi correlacionado com o aumento da atividade da APX. AlÃm disso, outras peroxidases (GPX e GPOD) apresentaram a mesma tendÃncia de aumento de atividade apenas sob estresse salino. Diferentemente, manitol induziu um aumento proeminente na atividade de catalase nas plantas NT enquanto que nas APX1/2 essa enzima jà apresentava atividade aumentada antes do estresse e permaneceu no mesmo nÃvel. As concentraÃÃes de H2O2 foram aumentadas intensamente por manitol e reduzidas na presenÃa de NaCl. O nÃvel de TBARS (indicador de peroxidaÃÃo lipÃdica) foi mantido inalterado na presenÃa dos dois estresses e nos dois tipos de plantas. Os resultados deste estudo, quando analisados em conjunto, mostram que raÃzes de arroz expostas aos estresses salino e osmÃtico exibiram respostas complexas em termos de metabolismo redox. Aparentemente, as duas APXs citosÃlicas nÃo sÃo essenciais para a proteÃÃo antioxidativa, uma vez que as plantas mutantes apresentaram uma performance fisiolÃgica semelhante as plantas NT. As respostas aos dois fatores de estresse, NaCl e manitol, foram contrastantes nos dois genÃtipos, sugerindo que diferentes mecanismos de proteÃÃo antioxidante foram acionados para cada tipo de estresse. / Salt and osmotic stresses are responsible for significant losses in agriculture, particularly in semiarid regions. In such conditions, roots are the first plant organ in contact with the stress and are responsible for perception and signaling. In leaves, cytosolic ascorbate peroxidases (APX) are the main isoforms involved with antioxidative defence against H2O2 excess and signaling under stressful conditions. Nevertheless, such metabolic mechanisms in roots are still unknown. The aim of this study was to test the hypothesis that cytosolic APX isoforms are essential to antioxidant protection in rice roots exposed to salt and osmotic stresses. To test this hypothesis, rice mutants double silenced for cytosolic APXs (APX1/2) and non-transformed plants, both with 45 day-old, were submitted to two stressful treatments: (1) NaCl and mannitol in iso-osmotic concentrations (-0.62MPa) for eight days and (2) mannitol 268 mM (-0.62MPa) for two days. In mutant plants, OsAPX1 and OsAPX2 transcript amounts (RNAs) were reduced by 90% whereas both protein abundance measured by Western blotting were not detectable. Under control conditions, total APX activity was reduced by 66% in comparison with NT plants, showing that the silencing was effective in roots. In APX1/2 roots, H2O2 level was increased by 51% as a consequence of APX1/2 silencing. Both stresses affected similarly root and shoot growing compared with NT. Membrane damage was increased at the same level in both genotypes and in both stresses, showing that APX1/2 were as sensible as NT plants. In NT roots, OsAPX1 and OsAPX2 transcript amounts was slightly increased by NaCl and mannitol whereas only NaCl increased APX activity. Under salt stress, both genotypes increased other APX isoforms, especially OsAPX3, OsAPX5 and OsAPX8. These increases were correlated with the increased APX activity. In addition, other peroxidases (GPX and GPOD) displayed the same trend as APX, increasing their activity in response to NaCl. On the other hand, mannitol induced a prominent increase in catalase activity in NT plants, while in APX1/2 plants CAT activity did not changed. The H2O2 content was increased in both genotypes exposed to mannitol treatments, and was reduced for NaCl. TBARS level was not altered in the presence of both stresses for both genotypes. This study shows that rice plants exposed to salt or osmotic stresses display complex responses regarding to redox metabolism. Apparently, both cytosolic APXs are not essential to antioxidative protection, since mutant plants presented similar physiological performance to NT plants. The responses to both stresses, NaCl and mannitol, were contrasting for both genotypes, suggesting that different mechanisms of antioxidative protection were triggered for each different stress condition. / Salt and osmotic stresses are responsible for significant losses in agriculture, particularly in semiarid regions. In such conditions, roots are the first plant organ in contact with the stress and are responsible for perception and signaling. In leaves, cytosolic ascorbate peroxidases (APX) are the main isoforms involved with antioxidative defence against H2O2 excess and signaling under stressful conditions. Nevertheless, such metabolic mechanisms in roots are still unknown. The aim of this study was to test the hypothesis that cytosolic APX isoforms are essential to antioxidant protection in rice roots exposed to salt and osmotic stresses. To test this hypothesis, rice mutants double silenced for cytosolic APXs (APX1/2) and non-transformed plants, both with 45 day-old, were submitted to two stressful treatments: (1) NaCl and mannitol in iso-osmotic concentrations (-0.62MPa) for eight days and (2) mannitol 268 mM (-0.62MPa) for two days. In mutant plants, OsAPX1 and OsAPX2 transcript amounts (RNAs) were reduced by 90% whereas both protein abundance measured by Western blotting were not detectable. Under control conditions, total APX activity was reduced by 66% in comparison with NT plants, showing that the silencing was effective in roots. In APX1/2 roots, H2O2 level was increased by 51% as a consequence of APX1/2 silencing. Both stresses affected similarly root and shoot growing compared with NT. Membrane damage was increased at the same level in both genotypes and in both stresses, showing that APX1/2 were as sensible as NT plants. In NT roots, OsAPX1 and OsAPX2 transcript amounts was slightly increased by NaCl and mannitol whereas only NaCl increased APX activity. Under salt stress, both genotypes increased other APX isoforms, especially OsAPX3, OsAPX5 and OsAPX8. These increases were correlated with the increased APX activity. In addition, other peroxidases (GPX and GPOD) displayed the same trend as APX, increasing their activity in response to NaCl. On the other hand, mannitol induced a prominent increase in catalase activity in NT plants, while in APX1/2 plants CAT activity did not changed. The H2O2 content was increased in both genotypes exposed to mannitol treatments, and was reduced for NaCl. TBARS level was not altered in the presence of both stresses for both genotypes. This study shows that rice plants exposed to salt or osmotic stresses display complex responses regarding to redox metabolism. Apparently, both cytosolic APXs are not essential to antioxidative protection, since mutant plants presented similar physiological performance to NT plants. The responses to both stresses, NaCl and mannitol, were contrasting for both genotypes, suggesting that different mechanisms of antioxidative protection were triggered for each different stress condition.

Made available in DSpace on 2014-06-12T18:05:14Z (GMT). No. of bitstreams: 2 arquivo6217_1.pdf: 2483193 bytes, checksum: f2860b2d4524260bff6f057c6580ff7d (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / Uma das alternativas para suprir o aumento pela demanda por etanol combustível é a engenharia metabólica de linhagens industriais de Saccharomyces cerevisiae visando o aumento do rendimento em etanol. Portanto, a deleção ou superexpressão de algumas desidrogenases pode contribuir para se alcançar este objetivo. Nesse contexto, a expressão epissomal do gene que codifica para a alanina desidrogenase bacteriana em linhagem laboratorial de S. cerevisiae resultou na diminuição da produção de glicerol e de biomassa, e aumento de 9% na produção de etanol, quando cultivada anaerobicamente em quimiostato (dados não publicados). Neste trabalho, investigamos essa alteração fisiológica mediante a clonagem do gene em diferentes linhagens industriais e de laboratório, usando tanto vetores para integração cromossomal em cópia única como para a expressão epissomal em cópias múltiplas. Em cultivos descontínuos em anaerobiose, não foi possível evidenciar diferenças estatisticamente significativas entre as linhagens recombinantes e suas parentais nos rendimentos em glicerol ou etanol. A análise da variância dos resultados mostrou que nestes ensaios descontínuos a diferença mínima significativa entre os rendimentos em glicerol e em etanol das linhagens recombinantes e parentais foi da ordem de 9-10% e 10-11% respectivamente, valores superiores às diferenças de rendimento observadas anteriormente em ensaios contínuos. A fim de detectar eventuais diferenças nos rendimentos em glicerol e etanol das linhagens modificadas será necessário compará-las em cultivos contínuos em anaerobiose, condições em que a variância dos dados experimentais será menor

Abstract Sulfide-poor deposits of platinum-group elements (PGE) occur in two main types: silicate-type and oxide-type. In the silicate-type mineralization PGE form discrete platinum-group minerals (PGM) that occur as inclusions in various silicate minerals. In the oxide-type mineralization PGM may have different modes of occurrence. They may be associated with silicates or they may occur as inclusions in chromite, magnetite or ilmenite, for example. In some cases they may even be associated with base metal sulfides. The approach chosen in this work is mainly a mineralogical one. PGM parageneses, their modes of occurrence and associations with other minerals were studied from different deposits. These are then compared to some well-recorded examples of PGE deposits. The case studies presented, the Duluth Complex in Minnesota, U.S.A., the Hanumalapur Complex in Karnataka, India, and the Penikat Layered Intrusion in northern Finland, are examples that illustrate the multitude of possibilities regarding PGE mineralization versus the traditional approach where any significant quantities of PGE are supposed to occur only in association with base metal sulfides. As the traditional orthomagmatic and hydrothermal models cannot explain the genesis of some sulfide-poor PGE occurrences, a new theory of PGE mineralization was developed. This “redox theory” is an attempt at explaining the association of PGE with various oxide minerals, most importantly chromite.

A conspicuous feature of plants responding to pathogen invasion is the synthesis of nitric oxide (NO), a redox signal. NO regulates protein function by S-nitrosylation, the addition of an NO moiety to a cysteine thiol to form an S-nitrosothiol. A key theme of NO function is reprogramming plant immune-related gene expression. However, it is still not clear how the NO signal is translated into transcriptional changes. Here we explored the potential role of a sub-group of SNO Regulated Genes (SRGs) uncovered by global expression profiling. Firstly, transgenic plants containing the SRG1 or SRG3 promoter fused to glucuronidase gene GUS together with qRT-PCR assays confirmed that transcripts of SRGs could be induced by NO and pathogen challenge, suggesting that SRGs may be involved in NO signalling related to plant immunity. More importantly, transient and stable overexpression of SRG genes induced hypersensitive response (HR)-like cell death development, which is often associated with pathogen effector-triggered immunity. Furthermore, transgenic plants constitutively expressing SRG genes exhibited enhanced ROS accumulation, PR1 transcript accumulation, and increased resistance to Pseudomonas syringae (Pst) DC3000 compared with Col-0 wild type plants. In contrast, lines with T-DNA insertions into SRG genes exhibited susceptibility to Pst DC3000. These data suggested SRGs act as the positive regulators in plant immunity. In order to further explore how NO regulates these SRGs in plant immunity, we focused on SRG1 and found SRG1 could be S-nitrosylated in vitro and in vivo. Moreover, electrophoretic mobility shift assays showed SRG1 could bind to an AGT motif and the transcriptional activity was blunted in the presence of NO, suggesting that the DNA binding activity of SRG1 is redox-modulated. Further, a transient repression activity assay showed that SRG1 has repression activity and this activity was impaired in the gsnor1-3 mutant, which has a high S-nitrosothiols level. These data suggested NO could block SRG1 transcriptional activity in vitro and in vivo. Furthermore when the SRG1 overexpression line was crossed with gsnor1-3 the SRG1-mediated resistance related phenotypes were suppressed. These data demonstrated NO negatively regulates SRG1 transcriptional activity during plant immunity. SRG1 may therefore be an important regulator of NO signalling and subsequent regulate transcription during plant immunity. Additionally, NO may negatively feedback to inhibit transcriptional activity of SRG1 to control its repression activity, to enable the activation of plant immunity.

Les dendrimères et polymères contenant des métaux de transition comme le fer, lecobalt et le rhodium peuvent servir à la fabrication des nanomatériaux utiles à lacatalyse, la reconnaissance moléculaire et l’électronique moléculaire. Pour leurconstruction, des liaisons ioniques, de la chimie click : CuAAC et hydroamination, lapolymérisation ROMP et la polymérisation radicalaire ont été utilisés et ont permis laformation de nouveaux types de polyélectrolytes metallocéniques. La synthèse denouvelles nanoparticules d’or, d’argent et de palladium à partir de cesmétallopolymères et métallodendrimères ont été mises au point, conduisant à desréseaux à architecture spécifique bien définie. Ces assemblages supramoléculaireset ingénierie moléculaire ouvrent la voie vers l’application de la chimieorganométallique dans la conception de nouveaux nanomatériaux nanoparticulairesstructurés à l’aide des propriétés rédox des métallomacromolécules. / Dendrimers and polymers containing transition metals such as iron, cobalt andrhodium can serve in the fabrication of useful nanomaterials for catalysis, molecularrecognition and molecular electronics. For their construction, ionic bonds, clickchemistry: CuAAC and hydroamination, ROMP and radical polymerization were usedand allowed the formation of new types of metallocenyl polyélectrolytes. Thesynthesis of new gold, silver and palladium nanoparticles from these metallopolymersand metallodendrimers has been developed, leading to specific and well-definedarchitectures. These supramolecular assemblies and molecular engineering opensthe way towards the application of organometallic chemistry in the design of newstructured nanoparticle-containing nanomaterials using the redox properties ofmetallomacromolecules.

Contrôle de l'oxydation et de la dégradation du pool de vitamine C chez la tomate et impact sur la qualité du fruit et la tolérance au stress. Le métabolisme de l’ascorbate et plus principalement le statut redox du pool d’ascorbate sont impliqués dans la tolérance au stress et dans les processus primaires de croissance et de développement de la plante. La teneur et le statut redox de l’ascorbate chez les plantes sont régulés par (i) ses voies de biosynthèse, (ii) par le cycle ascorbate-glutathion permettant le recyclage des formes semi-oxydées et oxydées de l’ascorbate et (iii) par sa dégradation, l’ensemble de ces processus étant sous le contrôle de l’environnement. Au cours de ce travail de thèse, des méthodes de transgénèse nous ont permis d’identifier, chez différents génotypes de tomate à petit et gros fruits, les bouleversements physiologiques et métaboliques permettant de compenser des modifications de l’activité des enzymes monodéhydroascorbate réductase (impliqué dans le cycle ascorbate-glutathion) et ascorbate oxydase. Nous avons observé d’importantes modifications phénotypiques altérant le rendement en fruits de la plante sous conditions de culture pouvant générer un stress et également en condition normale de culture. Des liens entre l’activité des enzymes précités avec le métabolisme des sucres, la photosynthèse et la conductance stomatique sont révélés. Le déséquilibre entre les activités oxydantes et réductrices de ces enzymes constitue la première étape vers une dégradation de l’ascorbate. Le taux de dégradation se révèle très faible à la lumière, tandis qu’à l’obscurité une forte accumulation des produits de dégradation l’oxalate, le thréonate ainsi que l’oxalyl-thréonate est observé dans les feuilles de tomate. Enfin, l’activité de l’enzyme MDHAR est corrélée au taux de dégradation à l’obscurité. Les travaux de cette thèse mettent en avant l’importance du statut redox du couple ascorbate / monodéhydroascorbate dans les processus de croissance cellulaire et entre dans la régulation du rendement chez la tomate, et influe la dégradation de l’ascorbate. / Ascorbate metabolism and particularly ascorbate redox status are involved in stress tolerance and growth processes of plant cells. The concentration of ascorbate and its redox status are under control of (i) its biosynthetic pathways, (ii) the ascorbate-glutathione cycle allowing recycling of semi-oxidized and oxidized forms of ascorbate and (iii) its degradation rate. These processes are under environmental control. Transgenic lines modified for the activity of monodehydroascorbate reductase (involved in ascorbate-glutathione cycle) and ascorbate oxidase were generated in cherry and large-fruited genotypes of tomato. Physiological and metabolic modifications related to the modification of these enzyme activities were studied. We observed large phenotypic alterations that affected fruit yield under both stress conditions and normal growth conditions. Links between ascorbate recycling and sugar metabolism, photosynthesis and stomatal conductance were also revealed. An imbalance between the oxidizing and reducing activities of these enzymes is the first step leading to ascorbate degradation. We have shown that the degradation rate was very low under light, whereas under darkness the degradation compounds oxalate, threonate and oxalyl-threonate accumulated in tomato leaves. Also, the degradation rate is correlated with MDHAR activity. These results highlight the crucial role of the redox status of the ascorbate / monodehydroascorbate couple in growth processes and yield stability in tomato, and the impact on ascorbate degradation.

In this dissertation, gold catalyst was employed to catalyze intermolecular reactions. Intramolecular reactions were far more advanced than intermolecular reaction in gold catalysis. With finding suitable ligands for gold catalysts, we were able to develop several transformations to synthesize interesting building blocks in organic chemistry including: allenes, furans, spiros, oxepines, propargyl ethers and ketones. These functionalities were synthesized by the use of triazole-gold(I) catalyst. Triazole, as a ligand bond to gold, showed enhanced stability of the catalyst, which resulted in better yields. Gold(I)/(III) redox chemistry also used for cyclopropanol ring openings which resulted in synthesizing substituted ketones.