The emergence of complex, carefully designed, molecular architectures incorporating either a lanthanide ion or the porphyrinic macrocycle have stimulated significant interest of late, particularly in the fields of molecular switches, molecular machines and data storage systems. The integration of these emissive species has been shown to permit the analysis of conformational, coordinative, or electronic change, and employed, in the case of the porphyrinic macrocycle, to acquire a deeper understanding of the natural process of photosynthesis, thus opening up the possibility of developing more efficient and inexpensive photovoltaic cells. This thesis begins by providing insight into the generation of cathodic photocurrent density within both monophasic and biphasic self-assembled monolayers, before documenting how the magnitude of such photoelectochemical output can be gated upon the integration of an electron relay moiety, both at the interface and into solution. The introduction of an electron relay moiety into solution has been shown to bring about increases of up to 283 % in the magnitude of the cathodic photocurrent density acquired, whilst optimisation of the distances between the metallic interface, the electron relay moiety and the porphyrinic macrocycle has also proven beneficial. Greatest photoelectrochemical output (5.1 x 1014 nA mol-1 cm-2) is realised when the porphyrinic macrocycle is covalently tethered at a distance of 4.6 nm from the quenching, metallic interface, and the relay moiety integrated at a distance of 1.7 nm from the interface and 2.9 nm from the porphyrinic macrocycle, respectively. However, greatest variation (94 %) in the magnitude of the cathodic photocurrent densities acquired is observed when the distance between the porphyrinic macrocycle and the gold surface is kept at 3.3 nm, and the relay moiety situated at either 1.2 nm or 1.7 nm from the interface, respectively. Research then moved towards trying to integrate this established conformational ruler within a porphyrin-appended, bistable [2]rotaxane. Its implementation served to try to ensure that photoelectrochemical differentiation of the ground state coconformation (GSCC) and the metastable state co-conformations (MSCC) was viable, thus enabling the efficient resolution of anion-induced molecular motion within a dynamic supramolecular architecture by means of a novel approach. The focus of this thesis then shifts to the assembly of novel, optically switchable, ternary complexes exhibiting charge-transfer based on the donor-acceptor interaction between an electron-rich naphthalene derivative (EuNap) and MV2+, an electron-poor, redox-addressable moiety. Prior to the deposition of (MV, EuNap)-CB[8] at the interface, the homoternary analogue ((MV+.)2-CB[8]) was acquired upon one electron reduction of (MV, EuNap)-CB[8] in the presence of excess MV2+. This process was revealed to be reversible upon the application of a stream of oxygen, and the relative concentration of each complex present in solution quantified upon mathematical manipulation of the biexponential decay curve acquired; upon the addition of sodium thiosulfate (Na2S2O3), the percentage of uncomplexed EuNap (τ = 0.60 ms cf. τ = 0.1 ms (MV, EuNap)-CB[8]) present in solution increased in accordance with the generation of ((MV+.)2-CB[8]) and loss of the charge-transfer interaction (λmax = 390, 490 nm), of which has been shown to quench lanthanide luminescence (Eu3+, Yb3+, Nd3+). Thus, the assembly of a molecular switch is documented which may be followed qualitatively at higher concentration by a visible colour change, and at low concentrations quantitatively by virtue of luminescence spectroscopy. No optical output (λex = 227 nm, λem = 616 nm) was acquired upon the deposition of (MV, EuNap)CB[8]) due to the occurrence of surface energy transfer (SET). As a result, 1-(10-mercaptodecyl)-1'methyl-[4,4'-bipyridine]-diium bromide and 1-methyl-1'-(10-(naphthalen-2yloxy)decyl)-[4,4'bipyridine]-1,1'-diium bromide iodide were synthesised and the assembly of a molecular film envisaged in which the molecular recognition properties of CB[n] were maintained and significant optical output from the lanthanide ion (Eu3+, λem 616 nm) detected; the assembly of such a film centred on the formation of 1:2 intermolecular heteroternary complexes and the recruitment of EuNap at a distance ≥ 3.2 nm from the gold substrate. It was envisaged that the modulation of any emissive output would be brought about upon manipulating the oxidation state of a surface-confined metallocene. This thesis ends by summarising the research conducted and assessing how the inclusion chemistry of cucurbit[8]uril and the photophysical properties of the porphyrinic macrocycle can be combined in order to fabricate a dynamic, photoresponsive molecular assembly. The electrical energy generated from the efficient harvesting of light energy could be used in a multitude of applications, most notably as a nanoscale power supply to drive and control molecular and supramolecular actuations.

Earths most abundant biomolecules, carbohydrates, offer tremendous potential forelectricity production. Carbohydrate fuel cells are electrical fuel cells that can harvest the stored electrons in carbohydrates and offer a cheap and efficient method that could help solve growing energy demands, while providing a renewable green energy source. Viologen-mediated carbohydrate fuel cells have demonstrated the ability to accelerate carbohydrate oxidation while decreasing partial or incomplete oxidation products reducing the electricity production. Subsequent studies suggested polymeric viologen compounds could improve the efficiency by increasing the local concentration of viologen. This thesis presents the utility of surface-immobilized viologen mediators for the oxidation of simple carbohydrates. Methyl viologen formed a self-assembled monolayer on a gold electrode surface to enhance its electrocatalytic oxidation of dihydroxyacetone, fructose, and glucose. The thiolated viologen formed surface adsorbed films on the gold electrodes that where consistent with monolayers and were characterized by quartz crystal microbalance and cyclic voltammetry. Cyclic voltammetry indicated that carbohydrates can generate electricity when combined with methyl viologen. Monolayer formation of methyl viologen indicates that immobilized mediators can be used to enhance oxidation of simple carbohydrates to generate electricity. This same tethered mediator strategy could be used for other mediators to increase their electrochemical efficiency in carbohydrate fuel cells.

Methyl Viologen (MV) is an electron mediator that has great possibilities to be used with an electrode system in which the electrode system provides electrons towards reducing MV species. MV has three redox states and they can be converted to each other via redox reactions on the surface of the electrode. The concentration of the three species of MV was related to the voltage potential applied to the system through a thermodynamic model. With the thermodynamic model the concentration of the three species can be predicted with different applied voltage potentials towards providing guidance for controlling the redox state of MV in a system. The kinetic rates of MV reduction were also assessed using a preliminary kinetic model. The kinetic model predicted all three species concentration changes with time although only the MV+ concentration was measured with time. Analysis revealed that the rate of MV reduction was three orders of magnitude slower than the rate of electrons required for bioethanol production. However, increasing the affinity of MV+ on the surface and blocking the H+ on the surface potentially can increase the reduction rate of MV by up to three orders of magnitude and can potentially enable MV to be used in commercial applications. As for the efficiency study, the coloumbic efficiency was less than 22% which was much lower than the efficiency of more than 85% observed in other studies for the direct electron transfer between electrode and bio organism. The efficiency was lowered mainly by the reduction of H+ and minimizing H+ on the electrode can largely increase the efficiency. Medium used for cell growth can also affect the efficiency through medium species consuming electrons provided by the electrode. Electron mediators, such as MV, have potential promise in applications such as microbial fuel cells, biofuel formation, and waste water treatment. However, engineering analysis of electron mediators is critical to provide better engineering control, design, and economic analysis for future applications.

Betalaínas são alcalóides coloridos que atuam como mediadores químicos e sensores em processos de interesse tecnológico. Esta Tese de Doutorado investiga o comportamento de betalaínas naturais, betanina e indicaxantina, em três sistemas químicos diferentes. O primeiro capítulo discute a estabilidade de emulsões água-óleo-água contendo betanina. As emulsões foram preparadas em um sistema de microcanais empregando-se óleo de soja e tensoativos grau alimentício. Betanina pura tende a estabilizar a emulsão em relação ao controle sem o pigmento, enquanto suco de beterraba liofilizado e betanina comercial diluída com maltodextrina não mostram a mesma atividade. No capítulo seguinte, a interação entre indicaxantina e cloreto de 7-metil-4-metóxiflavílio revela a ocorrência de transferência de energia e dados de espectroscopia de 1H-RMN indicam a formação de um complexo no estado fundamental. Finalmente, a interação entre betanina e paraquat na presença e ausência de luz e oxigênio é investigada. Dados de espectroscopia de 1H-RMN sugerem a formação de um complexo entre as espécies e o estudo cinético sugere que betanina interfere na regeneração da forma oxidada do paraquat por oxigênio. / Betalains are colored alkaloids that act as chemical mediators and sensors in processes of technological interest. This doctoral thesis investigates the behavior of natural betalains, betanin and indicaxanthin, in three different chemical systems. The first chapter discusses the stability of water-oil-water emulsions containing betanin. The emulsions were prepared in a microchannel system using soybean oil and food grade surfactants. Pure betanin tends to stabilize the emulsion relative to the control without the pigment, while freeze-dried beet juice and commercial betanin diluted with dextrin do not show the same activity. In the following chapter, the interaction between indicaxanthin and 7-methyl-4-methoxyflavylium chloride reveals the occurrence of energy transfer and 1H-NMR spectroscopy data suggests the formation of a complex in the ground state. Finally, the interaction between betanin and paraquat in the presence and absence of light and oxygen is investigated. 1H-NMR spectroscopy data suggest the formation of a complex between species and the kinetic study suggests that betanin interferes in the regeneration of the oxidized form of paraquat by oxygen

Betalaínas são alcalóides coloridos que atuam como mediadores químicos e sensores em processos de interesse tecnológico. Esta Tese de Doutorado investiga o comportamento de betalaínas naturais, betanina e indicaxantina, em três sistemas químicos diferentes. O primeiro capítulo discute a estabilidade de emulsões água-óleo-água contendo betanina. As emulsões foram preparadas em um sistema de microcanais empregando-se óleo de soja e tensoativos grau alimentício. Betanina pura tende a estabilizar a emulsão em relação ao controle sem o pigmento, enquanto suco de beterraba liofilizado e betanina comercial diluída com maltodextrina não mostram a mesma atividade. No capítulo seguinte, a interação entre indicaxantina e cloreto de 7-metil-4-metóxiflavílio revela a ocorrência de transferência de energia e dados de espectroscopia de 1H-RMN indicam a formação de um complexo no estado fundamental. Finalmente, a interação entre betanina e paraquat na presença e ausência de luz e oxigênio é investigada. Dados de espectroscopia de 1H-RMN sugerem a formação de um complexo entre as espécies e o estudo cinético sugere que betanina interfere na regeneração da forma oxidada do paraquat por oxigênio. / Betalains are colored alkaloids that act as chemical mediators and sensors in processes of technological interest. This doctoral thesis investigates the behavior of natural betalains, betanin and indicaxanthin, in three different chemical systems. The first chapter discusses the stability of water-oil-water emulsions containing betanin. The emulsions were prepared in a microchannel system using soybean oil and food grade surfactants. Pure betanin tends to stabilize the emulsion relative to the control without the pigment, while freeze-dried beet juice and commercial betanin diluted with dextrin do not show the same activity. In the following chapter, the interaction between indicaxanthin and 7-methyl-4-methoxyflavylium chloride reveals the occurrence of energy transfer and 1H-NMR spectroscopy data suggests the formation of a complex in the ground state. Finally, the interaction between betanin and paraquat in the presence and absence of light and oxygen is investigated. 1H-NMR spectroscopy data suggest the formation of a complex between species and the kinetic study suggests that betanin interferes in the regeneration of the oxidized form of paraquat by oxygen

Abstract Methyl Viologen is a kind of organic molecular magnet of current interest which comprises with organic radicals (unpaired electrons). The molecular formula of the sample is (C12H14N2)2+X2-, where ¡§X2-¡¨ denotes a non-magnetic anion (CdI42-, I3-I- etc.). We perform the magnetization (using SQUID magnetometer) and electron paramagnetic resonance (EPR) measurements. Two absorption peaks are observed in EPR spectrum indicating that there are two radical forms in our samples. One of the radicals exists in every sample having the g1-factor value 2.004. The other radical which has the g2-factor 2.001 exists only in certain samples. Interestingly, we find that these samples exhibit ferromagnetism at room temperature. We use Lorentzian profile to quantitatively analyze the EPR spectrum of the samples and derive the ratio (A2/A1) of two different absorption peaks, which represents the amount of g2 radical. The remanent magnetization and saturation magnetization are found to increase as the ratio value increases, indicating that the strength of ferromagnetism is strongly correlated with g2 radical.

No description available.

Superoxide dismutases (SODs) catalyze the dismutation of superoxide radicals to oxygen and hydrogen peroxide. Mn SOD is localized in mitochondria, Cu-Zn SOD is in the cytosol and chloroplast, and Fe SOD is in chloroplasts. The effects of a chloroplast-localized oxidative stress, caused by methyl viologen or 3-(3, 4-dichlorphenyl)-1-1′ dimethylurea (DCMU) on SOD populations were investigated. A cloned Arabidopsis thaliana Fe SOD gene was expressed in Escherichia coli and was purified from transformed cells. This protein was used to raise antibodies against A. thaliana Fe SOD which in turn were used to quantify the effects of oxidative stress on Fe SOD protein. Effects of oxidative stress on enzyme activity were measured in native gels. Fe SOD responded to oxidative stress with an increase in activity, but not in antibody reactive protein. Two novel forms of Fe SOD activity, with faster migration rates in activity gels, were detected. Mn SOD, a mitochondrial enzyme, responded to the stress with an increase in activity. In contrast, the activity or amount of Cu-Zn SOD protein did not respond to this oxidative stress. In light of these results, we propose that SODs respond to oxidative stress at the enzyme and gene levels. Mitochondrial Mn SOD responded to a chloroplast-localized stress with an increase in activity, suggesting either that the site of action for methyl viologen is not exclusively in the chloroplast or that there are other signals among the compartments of the cell. Fe SOD, but not Cu-Zn SOD responded to stress, suggesting that Fe SOD may be the stress responsive enzyme in this organelle. Evolutionary relationships among different isoforms were investigated based on the known primary, secondary, and tertiary structures of these isoforms. The three dimensional structure of A. thaliana Fe SOD was modeled by using structures of crystallized E. coli and Pseudomonas ovalis Fe SODs as templates. Comparison of prokaryotic Fe SOD with eukaryotic isoforms showed that Fe and Mn SODs are structurally homologous, whereas Cu Zn SOD is not. / Ph. D.

La mort cellulaire programmée, ou MCP, est un processus dynamique où les cellules ont la capacité de déclencher et de contrôler leur propre mort. Elle est essentielle et présente chez tous les organismes multicellulaires. Chez les plantes, la MCP permet le développement optimal (ex : formation du xylème, morphologie des feuilles, etc.) de la plante tout en protégeant contre divers stress biotiques et abiotiques (ex : la sécheresse, la chaleur, les UV, etc.). Malgré les avancées de ces dernières années, peu de gènes impliqués dans la mise en place de la MCP induite par les UV-C ont été identifiés chez les plantes. L'objectif était donc de caractériser ces gènes chez Arabidopsis thaliana. L'un des candidats est le gène BI-1, pour Bax Inhibitor-1. Il code pour un facteur anti-apoptotique de la MCP animale également retrouvé chez Arabidopsis thaliana. BI-1 régule aussi le taux de calcium du réticulum endoplasmique, ainsi que la formation des espèces réactives de l'oxygène (ROS), permettant l'activation de la réponse de la cellule au stress. L'expression de ce gène suite à une exposition aux UV-C est augmentée, faisant de lui un candidat pour la réponse aux UV-C. Une fusion du promoteur du gène AtBI-1 au gène rapporteur de la luciférase (pAtBI-1::luciférase) a été insérée dans le génome d'Arabidopsis. Une plante homozygote pour l'insertion de l'ADN-T, 5PL20E, a été isolée. Cette lignée parentale a été ensuite mutagénéisée, et un crible effectué sur la descendance exposée aux UV-C a permis d'identifier un mutant, 2017, dont l'expression de la luciférase était modifiée. Le premier objectif de ce projet était de caractériser ce mutant et de déterminer le lien potentiel avec la régulation de BI-1. Dans une deuxième partie, nous nous sommes intéressés aux rôles des thiorédoxines (TRX) dans la MCP végétale. Ces protéines sont présentes chez tous les organismes vivants. Elles régulent les activités de beaucoup d'enzymes en réduisant leurs ponts disulfures. Peu représentées chez l'homme (deux gènes), elles ont néanmoins un rôle de protection dans la voie de signalisation de l'apoptose. Par contre, chez Arabidopsis, une vingtaine de gènes codant pour les thiorédoxines sont connus. Suite à un autre crible aux UV-C d'une banque de mutants d'insertion, un nouveau mutant pour lequel l'insertion de l'ADN-T était dans le promoteur du gène codant pour la thiorédoxine f1 (AtTRX f1) a été identifié. Chez Arabidopsis, deux gènes codent pour les TRX f. Ces protéines ont d’abord été étudiées en tant que régulateur d’enzymes du cycle de Calvin. Plus récemment, d’autres fonctions ont été attribuées, surtout à la TRX f1. Nous avons obtenu de simples mutants pour les deux gènes et produit par croisement des doubles mutants, pour étudier l'implication des TRX f dans la MCP végétale induite par les UV-C (ultraviolets de type C), le MV (methyl viologen) et l'ABA (acide abscissique). En parallèle, des surexpresseurs de la TRX f1 ont été analysés pour ces mêmes stress abiotiques. L'objectif était de déterminer s'il y a une redondance de fonction entre les deux gènes, puisque ces deux protéines, de la même sous-famille, sont localisées au niveau des chloroplastes. Suite à une induction de la MCP par l'un des stress abiotiques, les réponses observées chez les simples mutants sont similaires à celles des plantes sauvages. Par contre, les doubles mutants paraissent plus résistants aux divers stress, alors que les surexpresseurs semblent nettement plus sensibles que les plantes sauvages. Enfin, un dernier axe a été développé sur le rôle des TRX f dans le contrôle des voies de synthèse et de dégradation de l'amidon pour l'ensemble des plantes de notre essai. Il s'avère que les surexpresseurs produisent une plus grande quantité d'amidon que les plantes sauvages. À l'opposé, les simples mutants ont moins d'amidon au niveau des différents tissus étudiés que les plantes sauvages, et les doubles mutants n'en présentent quasiment pas. La présence d'une quantité plus importante d'amidon chez les surexpresseurs de TRX f influence la sensibilité de ces plantes aux stress abiotiques. À l'inverse, les doubles mutants sont plus résitants à ces mêmes stress, où cette quantité d'amidon est fortement diminuée pour ces plantes.

Biofuel production via fermentation is produced primarily by fermentation of simple sugars. Besides the sugar fermentation route, there exists a promising alternative process that uses syngas (CO, H2, CO2) produced from biomass as building blocks for biofuels. Although syngas fermentation has many benefits, there are several challenges that still need to be addressed in order for syngas fermentation to become a viable process for producing biofuels on a large scale. One challenge is mass transfer limitations due to low solubilities of syngas species. The hollow fiber reactor (HFR) is one type of reactor that has the potential for achieving high mass transfer rates for biofuels production. However, a better understanding of mass transfer limitations in HFRs is still needed. In addition there have been relatively few studies performing actual fermentations in an HFR to assess whether high mass transfer rates equate to better fermentation results. Besides mass transfer, one other difficulty with syngas fermentation is understanding the role that CO and H2 play as electron donors and how different CO and H2 ratios effect syngas fermentation. In addition to electrons from CO and H2, electrodes can also be used to augment the supply of electrons or provide the only source of electrons for syngas fermentation. This work performed an in depth reactor comparison that compared mass transfer rates and fermentation abilities. The HFR achieved the highest oxygen mass transfer coefficient (1062 h-1) compared to other reactors. In fermentations, the HFR showed very high production rates (5.3 mMc/hr) and ethanol to acetic acid ratios (13) compared to other common reactors. This work also analyzed the use of electrons from H2 and CO by C. ragsdalei and to study the effects of these two different electron sources on product formation and cell growth. This study showed that cell growth is not largely effected by CO composition although there must be at least some minimum amount of CO present (between 5-20%). Interestingly, H2 composition has no effect on cell growth. Also, more electron equivalents will lead to higher product formation rates. Following Acetyl-CoA formation, H2 is only used for product formation but not cell growth. In addition to these studies on electrons from H2 and CO, this work also assessed the redox states of methyl viologen (MV) for use as an artificial electron carrier in applications such as syngas fermentation. A validated thermodynamic model was presented in order to illustrate the most likely redox state of MV depending on the system setup. Variable MV extinction coefficients and standard redox potentials reported in literature were assessed to provide recommended values for modeling and analysis. Model results showed that there are narrow potential ranges in which MV can change from one redox state to another, thus affecting the potential use as an artificial electron carrier.