This work aimed at studying biophysical properties of two membrane proteins, one of potential nanotechnological use, bacteriorhodopsin, and one potential drug target, the NTS1 neurotensin receptor, at the single molecule scale. Bacteriorhodopsin (BR) is the only protein in the purple membrane (PM) of the halophilic organism Halobacterium salinarium. It is a light-driven proton pump converting light into a transmembrane proton gradient through isomerization of its retinal chromophore. Its stability, as well as its photoactivity remaining in dry protein layers, has made BR an attractive material for biomolecular devices. Numerous studies have been published on this topic; however, they have all used BR within the PM, on relatively large (µm-wide) surfaces. Here, conducting-probe atomic force microscopy (C-AFM) analysis was performed after removing most of the membrane lipids. For the first time, it was shown that the molecular conductance of BR can be reversibly photoswitched with predictable wavelength sensitivity. Intimate and robust coupling to gold electrodes was achieved by using a strategically engineered cysteine which, combined with partial delipidation, generated protein trimers homogenously orientated on the surface. Numerous controls using biophysical (SPR, ellipsometry, Kelvin-probe AFM) and chemical (photocurrent, cyclic voltammetry) techniques confirmed the wavelength specificity of the photoswitch, the anchoring role of the mutation and the homogenous orientation of the protein on the gold surface. Neurotensin is a brain and gastrointestinal 13 amino acid peptide acting as a neuromodulator in the central nervous system and as a hormone in the periphery. Its wide range of biological activities is primarily mediated through its binding to the neurotensin type 1 receptor (NTS1). NTS1 expressed in E.coli was purified and inserted into 100 nm brain polar lipid liposomes in a conformation which retained its ligand-binding capabilities. Initial AFM characterisation was performed as a prelude for ligand-receptor interaction studies, including high resolution imaging, force spectroscopy and solid state NMR approaches.

The arrival of the North American Monsoon System (NAMS) terminates a presummer hyperarid period in the southwestern United States (U.S.), providing summer moisture that is favorable for forest growth. Montane forests in this region rely on winter snowpack to drive much of their growth; the extent to which they use NAMS moisture is uncertain. We addressed this by studying stable carbon and oxygen isotopes in earlywood and latewood from 11 sites along a latitudinal gradient extending from Arizona and New Mexico to Utah. This study provides the first regional perspective on the relative roles of winter versus summer precipitation as an ecophysiological resource. Here we present evidence that Ponderosa pine uses NAMS moisture differentially across this gradient. C-13/C-12 ratios suggest that photosynthetic water use efficiency during latewood formation is more sensitive to summer precipitation at the northern than at the southern sites. This is likely due to the fact that NAMS moisture provides sufficiently favorable conditions for tree photosynthesis and growth during most years in the southern sites, whereas the northern sites experience larger summer moisture variability, which in some years is limiting growth. Cellulose O-18 and C-13 values revealed that photoassimilates in the southern sites were produced under higher vapor pressure deficit conditions during spring compared to summer, demonstrating a previously underappreciated effect of seasonal differences in atmospheric humidity on tree ring isotope ratios. Our findings suggest that future changes in NAMS will potentially alter productivity and photosynthetic water use dynamics differentially along latitudinal gradients in southwestern U.S. montane forests.

Writing about a personal traumatic event has been found to have psychological and physical health benefits. Focusing on traumatic memories in writing may be a form of exposure. In imagery exposure and trauma writing, greater physiological reactivity was predictive of better outcomes. Given the importance of physiological output in emotional processing, response training was developed and found to be effective in increasing appropriate physiological reactivity in imagery exposure. If response training amplifies physiological reactivity and the benefits of writing, the hypothesis that writing is a form of exposure would be strengthened, and training may be a valuable tool to improve the efficacy of psychotherapy approaches that use writing as a form of exposure. The present study examined whether response training enhances the benefits of trauma writing. In this study, participants wrote for 20 minutes on three occasions about a personal traumatic event (n = 113) or a trivial topic (n = 133) and received response imagery training (n = 79), stimulus imagery training (n = 84) or no training (n = 83). Heart rate and skin conductance were recorded in sessions one and three throughout a 10-minute baseline, writing, and a ten-minute recovery period. Self-reported trauma symptoms and emotion were assessed in each session. One month after completing the sessions, participants completed follow-up assessments of psychological and physical health outcomes. As predicted, trauma writing elicited greater physiological reactivity and self-reported trauma symptoms and emotion than neutral writing. Response training amplified physiological reactivity to trauma writing more than neutral writing, without amplifying levels of self-reported emotion or trauma symptoms. The physiological reactivity and self-reported emotion elicited by trauma writing habituated across sessions and response training enhanced these effects. Finally, increased heart rate predicted better outcomes for all trauma writers; however, response trained trauma writers who evidenced greater heart rate showed the greatest reductions in trauma, depression and physical illness symptoms at follow-up. These results support previous research which found that greater physiological reactivity was predictive of writing outcomes. The findings are the first to demonstrate that response training facilitates emotional processing and thus may be a beneficial adjunct to trauma writing.

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

Organic electrode materials are finding increasing use in energy storage devices due to their attractive properties that allow building of flexible and low weight devices in an environmentally friendlier manner than traditional alternatives. Among these organic electrode materials, conducting redox polymers (CRPs), consisting of conducing polymer (CP) with covalently attached redox active pendant groups (PG), have attracted our interests. This is due to the advantageous synergy between CP and PG, e.g. electronic conductivity, high stability and large charge storage capacity. In this thesis polypyrrole has been selected as CP and quinones as PGs. A series of quinone-pyrrole dyad polymers has been synthesized with a variety of quinone substituents, demonstrating the adjustability of quinone formal potentials by choice of substituents. Importantly, in this series we show that the CP-PG redox match, i.e. that the formal potential of the PG is within the conducting region of the CP, is a requirement for fast charge transfer from the electrode to the PGs. Moreover, a series of quinone-pyrrole dyad polymers with various linkers was synthesized, showing that the choice of linker has a pronounced impact on the interactions between the PG and CP. In addition, the temperature dependence of conductance during doping of the polymers reveals the charge transport mechanism. To summarize, the adjustability of the quinone formal potential as well as the fast charge transport in the bulk material ensures the applicability of the CRPs as electrode materials in organic batteries.

Graph-partitioning problems can be generically defined as a family of problems in which we are asked to partition a graph into two or more components. We present overview of methods and concepts used to find best graph partitions according to several criteria. We prove duality of multi-commodity flow and sparsest cut problem due to work of Leighton and Rao by describing algorithm using a Linear programming relaxation and a geometric embedding. Then we present the work of Arora, Rao and Vazirani (ARV) and their algorithm based on Semidefinite programming relaxation and a geometric embedding. We also explain the concept of expander flows first introduced in the work of ARV. One section of our work is devoted to the spectral graph theory, introducing the concepts of the spectral gap, random walks, conductance and relations between them. We connect the ideas of expander flows and spectral theory in chapter about so called Cut-Matching game framework. Finally we present the performance results of our implementation of the Leighton-Rao and the Cut-Matching game algorithms. Powered by TCPDF (www.tcpdf.org)

Des troubles de la familiarité ont été décrits dans de nombreuses pathologies psychiatriques et neurologiques et seraient à l’origine d’anomalies de la cognition sociale. Dans la schizophrénie, ces troubles peuvent se développer selon deux polarités : l’hyper- et l’hypofamiliarité. Dans l’hyperfamiliarité, les sujets atteints pensent que des proches prennent l’apparence d’inconnus pour les persécuter ; le syndrome le plus décrit est le syndrome de Frégoli. A l’opposé, dans l’hypofamiliarité, les sujets reconnaissent leurs proches d’après les traits de leurs visages, mais pensent que ce sont des imposteurs qui ont pris l’apparence de leurs proches. Le syndrome de Capgras est le plus décrit dans l’hypofamiliarité et le plus étudié des troubles de la familiarité. Dans la schizophrénie, ces troubles concernent principalement les proches, mais également le sujet lui-même qui peut voir chez des inconnus des doubles de lui-même, par exemple. Bien que fréquents et largement décrits dans la schizophrénie, ces troubles restent très peu étudiés. Ainsi, les mécanismes sous-tendant les troubles de la familiarité dans la schizophrénie sont encore bien mal connus.L’objectif de ce travail de thèse a été de mieux comprendre les mécanismes sous-jacents aux troubles de la familiarité dans la schizophrénie au moyen d’études comportementales, utilisant la conductance cutanée et d’une étude en imagerie fonctionnelle par résonance magnétique (IRMf).Dans un premier temps, nous avons cherché à développer une échelle clinique permettant le diagnostic des troubles de la familiarité. En effet, à notre connaissance, aucun outil n’est actuellement validé. Il est alors difficile de caractériser ces troubles et les données épidémiologiques sont manquantes. Cette échelle a été construite d’après la proposition d’items par des experts des troubles de la familiarité, puis par la sélection des items les plus pertinents par d’autres experts. Elle est actuellement en cours de validation. Elle explore 4 dimensions de la familiarité : le soi, les proches, les lieux et les objets et cote ces dimensions respectivement pour l’hypo- et l’hyperfamiliarité.Dans un second temps, nous avons cherché à tester l’hypothèse selon laquelle les troubles de la familiarité, dans la schizophrénie, résulteraient d’une anomalie de la réponse émotionnelle lors de la reconnaissance normale d’un visage connu. Pour cela, nous avons enregistré, dans 2 études, la réponse électrodermale (RED) engendrée par la présentation de visages de soi, familiers, célèbres et inconnus. En effet, la RED est utilisée comme le reflet de l’émotion inconsciente générée par la présentation d’un stimulus (ici un visage). Les principaux résultats de nos 2 études ont montrés que : alors que chez les sujets sains, l’amplitude de la RED était faible pour la condition « inconnu », elle augmentait pour la condition « célèbre » et était encore plus élevée pour les conditions « soi » et « familier », chez les patients schizophrènes, l’amplitude de la RED était faible dans toutes les conditions. Plus spécifiquement, les patients schizophrènes ayant des troubles de la familiarité avaient une RED avec une amplitude similaire dans les différentes conditions : soi, familier, célèbre et inconnu. Ces résultats suggèrent qu’une atteinte émotionnelle puisse être responsable des troubles de la familiarité dans la schizophrénie et que cette atteinte soit du même ordre pour la familiarité que pour le soi.Enfin, dans une étude en IRMf, nous avons pu mettre en évidence une anomalie de fonctionnement des circuits neuronaux du soi et des circuits de la familiarité dans la schizophrénie. Ces résultats suggèrent une demande cognitive plus importante chez les patients (implication de régions du traitement cognitif) pour résoudre l’ambigüité créée par la présentation de visages hautement familiers, nous posons l’hypothèse que le soi et le familier sont difficiles à distinguer chez les patients. [...] / Familiarity disorders have been described in many neurological and psychiatric diseases and would be responsible for abnormal social cognition. In schizophrenia , these disorders can take two polarities: hyper- and hypofamiliarity. In hyperfamiliarity , people think relatives take appearance of strangers to persecute them;The most described syndrome is Fregoli. In contrast, in hypofamiliarity, people recognize their relatives from their facial features, but think they are imposters who took the appearance of people close to them. Capgras syndrome is the most described inhypofamiliarity and the most studied in familiarity disorders. In schizophrenia, these disorders concern mainly relatives or close people, but also the subject itself, who can see his double in unknown people, for example. Although common and extensively described in schizophrenia, these disorders remain poorly studied. Thus, the mechanisms underlying familiarity disorders in schizophrenia are still unknown.The objective of this work was to better understand the mechanisms underlying familiarity disorders in schizophrenia with behavioral studiesusing skin conductance and a study in functional magnetic resonance imaging (fMRI).As a first step, we sought to develop a clinical scale for the diagnosis of familiarity disorders. Indeed, to our knowledge, no tool is currently validated. It is difficult to characterize these disorders and epidemiological data are missing. This scale has been built with items proposed by experts in familiarity disorders, and then the most relevantof them have been selected by other experts. It is currently being validated. It explores four dimensions of familiarity: self, familiar persons, places and objects. Tthe score is rated according to these dimensions respectively for hypo- and hyperfamiliarity.In a second step, we sought to test the hypothesis that impaired familiarity in schizophrenia would result from an abnormal emotional response in regard to a normal recognition of a familiar face. For this, in 2 studies, we recorded the skin conductance response (SCR) generated by the presentation of self, familiar, famous and unknown faces. Indeed, SCR is used as an indirect measure of emotional arousal generated by the presentation of a stimulus (here a face). The main results of ours 2 studies have shown that: whereas in healthy subjects, the amplitude of the SCR was low in the “unknown” condition, it increased for the \\\\\\\"famous\\\\\\\" condition and was even higher for \\\\\\\"self\\\\\\\" and \\\\\\\"familiar\\\\\\\" conditions, in schizophrenia patients, the amplitude of the SCR was low in all conditions. More specifically, schizophrenia patients with familiarity disorders showed similar SCR magnitude whatever the conditions: self, familiar, famous and unknown. These results suggest that emotional impairment may be responsible for familiarity disorders in schizophrenia and that this impairment could be similar for familiarity and self.Finally, in an fMRI study, we were able to identify a dysfunction of neural circuits of self and familiarity in schizophrenia. These results suggest a greater cognitive demand for patients to resolve the ambiguity created by the introduction of highly familiar faces (i.e. the self and familiar are difficult to distinguish for patients).Thus, it appears that, in schizophrenia, familiarity desorders are present in all patients with varying degrees, resulting in recognition impairments of self and others that undermine interpersonal relationships and allow the emergence of delirium in the disease. Thus, familiarity disorders would be based on unconscious emotional processes, common in self and familiarity processing, and that would be disturbed in schizophrenia.

Plant domestication led to a loss of genetic variation in many crops, due to the excessive emphasis in the selection of edible organs (root, leaf, stem or fruit) and the low selection pressure for other traits in the cultivated environment. This \'genetic erosion\' led to loss of alleles associated with resistance to environmental stresses, such as drought and salinity, which can in turn culminate in productivity losses. In tomato (Solanum lycopersicum L.), it is possible to tap into a reservoir of valuable genetic variation in its wild relatives. Identification of genetic variants associated with tomato domestication, and with stress resistance mechanisms which may have been lost during domestication, could be used to aid in breeding programs. In the present work, which was divided into two chapters, we carried out crosses between the wild species S. pennellii and the miniature tomato cultivar Micro-Tom (MT) and created two introgression lines (ILs), one with reduced organ size and another with increased drought tolerance. In the first chapter, we report the characterization and mapping of the IL denominated as Tiny organs and reduced yield (Toy). Toy harbors a S. pennellii genome segment on chromosome 7 and presents a considerable reduction in both vegetative (leaves) and reproductive (fruit) organs. We discuss how this could be a relevant trait underpinning tomato domestication. In the second chapter, we describe the drought tolerance mechanism of the IL Water Economy Locus in Lycopersicon (Well). Well harbors a S. pennellii genome segment on chromosome 1 and shows lower hydraulic conductance, possibly related to decreased xylem vessel size. The results shown suggest that this lower hydraulic conductance promotes a disturbance in the soil-plant-atmosphere hydraulic continuum leading to changes in stomatal behavior, which, in turn, are probably related to the delayed wilting of Well under conditions of water deficit. / A domesticação das plantas levou a uma perda de variação genética em muitas culturas, devido à ênfase excessiva na seleção de órgãos comestíveis (raiz, folha, caule ou fruto) e a baixa pressão de seleção para outras características no ambiente cultivado. Essa \"erosão genética\" levou à perda de alelos associados à resistência de diversos estresses ambientais, como seca e salinidade, os quais, por sua vez, podem conduzir a perdas significativas na produtividade das plantas. Entretanto, no tomate (Solanum lycopersicum L.), é possível acessar um banco valioso de variação genética nas espécies selvagens relacionadas. Assim, a identificação de variantes genéticas associadas ao processo de domesticação do tomateiro e a mecanismos de resistência a estresses ambientais, os quais podem ter sido perdidos durante a domesticação, pode auxiliar em programas de melhoramento do tomateiro e de outras culturas de interesse comercial. Diante disso, no presente trabalho, o qual foi dividido em dois capítulos, realizamos cruzamentos entre a espécie selvagem, S. pennellii, e a cultivar miniatura de tomateiro Micro-Tom (MT) para criamos duas linhas de introgressão (ILs), uma com tamanho de órgão reduzido e outra com maior tolerância à seca. No primeiro capítulo, relatamos a caracterização e mapeamento da IL denominada como Tiny organs and reduced yield (Toy). O genótipo Toy carrega um segmento do genoma de S. pennellii no cromossomo 7 e apresenta uma considerável redução em órgãos vegetativos (folhas) e reprodutivos (frutos). Os resultados obtidos conduziram a uma discussão de como esse genótipo pode ser relevante para a domesticação do tomateiro, devido ao seu impacto no tamanho de diversos orgão. Por outro lado, no segundo capítulo, descrevemos o mecanismo de tolerância à seca da IL Water Economy Locus em Lycopersicon (Well). Plantas Well carregam um segmento do genoma de S. pennellii no cromossomo 1 e exibem uma menor condutância hidráulica, possivelmente relacionada ao tamanho reduzido do vaso xilemático. A menor condutância hidráulica do genótipo Well conduz a perturbações no contínuo solo/planta/atmosfera levando a mudança no comportamento estomático, que, por sua vez, provavelmente está relacionado a maior resistência ao murchamento apresentada por esse material em condições de déficit hídrico.

O aumento para demanda na produção de alimentos associado a possíveis alterações climáticas globais tem promovido um interesse renovado em pesquisas envolvendo o metabolismo fotossintético. Acredita-se que com o melhoramento fotossintético a produtividade das culturas aumente. Para se alcançar este objetivo, além do uso de práticas biotecnológicas, ainda são necessários estudos abordando as limitações intrisecas do processo fotossintético que possam contribuir com a identificação de alvos para a engenharia genética. Neste contexto, esta tese aborda perguntas especificas sobre a regulação da fotossíntese C4 pela nutrição nitrogenada, o deficit hídrico e a interação destes dois fatores. No primeiro capítulo experimental foi desenvolvido um estudo envolvendo os efeitos da nutrição nitrogenada na difusão interna de CO2. Foi observado que o conteúdo de nitrogênio (N) foliar é determinante para a condutância interna de CO2 (? 18O-gm). Um menor conteúdo de N induz reduções iniciais em ? 18O-gm devido menor atividade das enzimas carboxilativas. Conforme o conteúdo de N reduz em folhas mais velhas alterações na antomia passaram a contribuir com a regulação de ? 18O-gm. No segundo capítulo, foi explorada a variação genotipica de cana-de-açúcar quanto a parâmetros relacionados a fotossíntese e o nitrogênio foliar, envolvendo a eficiência de uso de nitrogênio fotossintética (PNUE) e índices de herdabilidade. A variabilidade dos materiais genéticos foi explicada principalmente pelos parâmetros de trocas gasosas que contribuíram com o agrupamento dos materiais em três grupos. A partir deste agrupamento é possível verificar as diferenças entre os materiais em reposta a nutrição nitrogenada. Além disto, parâmetros de trocas gasosas como a taxa de assimilação de CO2 e condutância estomática junto com PNUE apresentaram altos índices de herdabilidade no sentido restrito. Por fim, o terceiro capítulo investigou a regulação do metabolismo de assimilação de CO2 em resposta ao deficit hídrico em folhas de cana-de-açúcar e como o metabolismo de nitrogênio está envolvido neste processo. Diferentes fatores envolvidos na regulação negativa da fotossíntese foram identicados. Interesantemente, alterações nos componentes nitrogenados só contribuíram com a inibição metabólica na fase de estresse severo. Adicionalmente foi observado que a superação da inibição metabólica durante a reidratação é mais rápida quando a cultivar apresenta decréscimos mais lentos no metabolismo de N no período de seca, associado a menores danos na capacidade fotossintética. / Increased demand for food production and the possibility of global climate change has promoted renewed interest in photosynthesis research. It is expected that with the photosynthetic improving the crop productivity increase. For this, besides of the use of biotechnological practices, further studies are needed about intrinsic limitations of the photosynthetic process that can contribute to the identification of targets for genetic engineering. In this context, this thesis discusses specific questions about photosynthesis regulation C4 by nitrogen nutrition, water deficit and the interaction of these two factors. In the chapter I, it was developed a study of the effects of nitrogen nutrition in the internal diffusion of CO2. It was observed that the leaf nitrogen (N) is essential for the internal CO2 conductance (Δ 18O-gm). A lower leaf N induces initial reductions in Δ18O-gm by lower activity of the carboxylation enzymes. With N leaf reduction in older leaves anatomy changes began to contribute to the regulation of Δ18 O-gm. In the chapter II, the genotypic variation of sugarcane to photosynthetic parameters and leaf nitrogen was explored, involving the photosynthetic nitrogen use efficiency (PNUE) and heritability analysis. The variability of the genetic material is explained mainly by gas exchange parameters that contributed to the grouping of materials into three groups. From this, it is possible examine the differences between the materials in response to nitrogen nutrition. Furthermore, gas exchange parameters such as CO2 assimilation rate and stomatal conductance along with PNUE showed high heritability in the narrow sense. Finally, the chapter III investigated the regulation of CO2 assimilation metabolism in response to water deficit sugarcane leaves and how nitrogen metabolism is involved in this process. Different factors involved in the negative regulation of photosynthesis were identified. Interestingly, changes in nitrogen components only contributed to metabolic inhibition in severe stress. Additionally it noted that overcoming metabolic inhibition during rehydration is faster when the cultivar presents slower decreases in N metabolism during water deficit, associated with less damage to the photosynthetic capacity.

O transporte de água nas plantas é um processo complexo e que envolve a passagem por membranas celulares. Nelas existem aquaporinas, proteínas integrais de membrana, que facilitam o fluxo passivo de água e pequenos solutos. Um fator importante que influencia o transporte de água nas plantas é a condutância hidráulica radicular (LPr), que pode contribuir com até 50% de toda a resistência ao fluxo de água na planta. Várias metodologias são propostas para estimar a LPr, porém os dados obtidos são altamente variáveis, ainda que para a mesma espécie vegetal. Diante do exposto, pretende-se desenvolver e propor uma nova metodologia, o sistema hidráulico de sucção para estimativa da LPr e avaliar a contribuição das aquaporinas no transporte de água radicular em plântulas de milho. O sistema hidráulico de sucção foi construído no Laboratório de Estudos de Plantas sob Estresse (LEPSE/USP) em parceria com Laboritoire d\'Ecophysiologie des Plants sous Stress Environnementaux de Montpellier, França. Os experimentos foram conduzidos no LEPSE, onde as plântulas cresceram em hidroponia na casa de vegetação. Para avaliação da atividade de aquaporinas foi utilizado o tratamento com peróxido de hidrogênio, que em concentrações milimolares inibe os canais de água. As medidas de condutância foram realizadas sempre na mesma hora do dia, uma vez que a própria LPr e as aquaporinas apresentam ritmo circadiano. Houve redução de 53% da condutância no tratamento com peróxido em relação ao controle e correlação significativa entre a LPr e o pH, de modo que o aumento do pH provocou queda de LPr, provavelmente causada por alterações na abundância e/ou atividade de aquaporinas nas raízes de milho. Esses resultados permitem afirmar que o método de sucção foi eficaz na estimativa da condutância hidráulica, podendo ser adotado como técnica alternativa na estimativa da LPr em plantas. / The water transport in plants is a complex process which involves passage through cell membranes. In them there are aquaporins, integral membrane proteins, that facilitate passive flux of water and small solutes. An important factor influencing the water transport in plants is root hydraulic conductance (LPr), which can contribute up to 50% of the water flow resistance in the plant. Various methods are proposed for estimating LPr, but the data are highly variable, even for the same plant species. Therefore, we intend to develop and propose a new methodology, the hydraulic suction system to estimate LPr and evaluate the contribution of aquaporins in root water transport in maize seedlings. The hydraulic suction system was built at the Laboratório de Estudos de Plantas sob Estresse (LEPSE / USP) in partnership with Laboritoire d\'Ecophysiologie Plants des sous Stress Environnementaux Montpellier, France. The experiments were conducted in LEPSE where the seedlings grew in the hydroponics greenhouse. To evaluate the activity of aquaporins was used treatment with hydrogen peroxide, which in millimolar concentrations inhibits water channels. The conductance measurements were performed at the same time of day, since the LPr itself and aquaporins presents the circadian rhythm. There was a 53% reduction in conductance peroxide treatment compared to control and significant correlation between LPr and pH, so that the pH increase caused a drop LPr probably caused by alterations in the abundance and/or activity of aquaporins in maize roots. These results indicate that the suction method was efficient in estimated hydraulic conductance, may be adopted as an alternative technique to estimate the LPr in plants.