Cette thèse présente une étude de la structure de solutions de polyélectrolytes (PEs) dans les liquides ioniques (LIs) et de la structure locale des LIs en présence de PEs. Les techniques de diffusion de rayons X et de neutrons ont été principalement utilisées pour cette étude. Dans une première partie, la capacité des LIs à former des « clusters » à l’échelle nanoscopique est démontrée. Dans une seconde partie, l’influence de la nature des contreions et du solvant sur le comportement du polystyrène sulfonate (PSS) en solution est abordée. La conformation moyenne du PSS et son état de dispersion dans les milieux aqueux et organiques sont alors explorés dans une troisième partie. Une étude similaire pour le cas spécifique des milieux LIs est présentée dans une quatrième partie. Finalement, d’autres polymères, chargés ou neutres, en solution dans les LIs, sont considérés dans une cinquième et dernière partie. / In this thesis the structure of polyelectrolyte (PE) solutions in ionic liquids (ILs) and mutual influence of bothcomponentsthe local structure of the latter in the presence of PEs are studied. X-ray and neutron scatteringtechniques have been mainly used for the present investigation. In a first part, the ability of considered ILs toform clusters at nanoscale is demonstrated. In a second part, the influence of the nature of counterions andthe solvent on the polystyrene sulfonate (PSS) behavior in solution is tackled. PSS average conformation anddispersion state in aqueous and organic media are then explored in a third part. A similar investigation, carriedout on the specific case of PSS in IL media, is described in a fourth part. Finally, other polymers, both chargedand neutral, in IL solutions are considered in a fifth and last part.

L’acier inoxydable martensitique durci par précipitation 15-5PH est utilisé dans le domaine del’aéronautique comme matériau constitutif des pièces liant les réacteurs aux ailes, il est ainsi soumisen utilisation à des températures de l’ordre de 300°C, ce qui entraine sa fragilisation. Cettefragilisation des aciers inoxydables dans ce domaine de températures est causée par la démixtion dufer et du chrome, principaux constituants de la matrice, par décomposition spinodale. De plus, lamicrostructure complexe du 15-5PH contient également des précipités de cuivre assurant ledurcissement initial de l’alliage, de l’austénite de réversion, connue dans ce type d’aciers pourapporter un regain de ductilité, apparaissant lors du traitement de précipitation du cuivre et de laphase G apparaissant au cours du vieillissement. L’évolution de ces phases pourrait égalemententrainer une modification des propriétés mécaniques de l’alliage. Pour observer les différentesévolutions de la microstructure nous avons utilisé une combinaison de techniques apportant desinformations complémentaires afin d’en obtenir une caractérisation la plus complète possible. Nousavons ainsi pu montrer que les modifications de propriétés sont causées par la décompositionspinodale de la matrice. L’évolution de ses caractéristiques microstructurales a pu être décrite pardes lois phénoménologiques, fonctions de la durée et de la température de vieillissement. Nousavons également pu fournir une méthode permettant la mesure indirecte de l’avancée duvieillissement du 15-5PH, validée par les observations microstructurales, ainsi qu’un modèlephénoménologique permettant de prévoir la dureté de l’alliage.Mots clés : acier martensitique, décomposition spinodale, vieillissement, diffusion aux petits angles,sonde atomique tomographique, calorimétrie différentielle à balayage. / The precipitation hardened martensitic stainless steel grade 15-5PH is used in the airplane industryas constitutive material of parts joining reactors to wings. Due to its application it is subjected totemperatures around 300°C leading to its embrittlement. Stainless steels embrittlement in thistemperature range is due to iron-chromium unmixing by spinodal decomposition. In addition, the 15-5PH grade has a complex microstructure comprising copper precipitates responsible for the initialhardening of the alloy, reversed austenite, known in this kind of steels to improve the toughness,which appears during the precipitation thermal treatment and G phase that precipitates duringaging. The evolutions of these microstructure components could also lead to some modifications ofthe material mechanical properties. In order to study the microstructure evolutions we use acombination of characterization techniques aiming at their most complete description. We show thatthe mechanical properties evolution is controlled by the spinodal decomposition of the matrix whoseevolution we are able to depict by simple phenomenological laws. We propose an indirect methodfor the measurement of aging kinetics of the 15-5PH steel, which we have correlated to directmeasurements, and a phenomenological law allowing the prediction of the alloy hardness based onits thermal history.

Les protéines régulatrices de la transcription de type LysR (LTTR) appartient à la plus grande famille de facteur de transcription chez les procaryotes. Malgré l'importance de cette famille, les informations structurelles sur les protéines pleine-longueur sont très limitées car elles sont souvent insolubles et très difficiles à cristalliser. Les quelques structures existantes, couplés à d'autres analyses biophysiques ont pu montrer que ces protéines s'associent principalement sous forme d'homotétramère comprenant un dimère de dimères. Les dimères s'associent par un large domaine C-terminal dans une position " tête-bêche " et sont reliés en " tête-à-tête " par leurs domaines N-terminal et sont activées par la liaison de molécules inductrices. Le domaine dimèrique C-terminal qui contient la poche de liaison inductrice (Inducer Binding Cavity : IBC) est appelé domaine de liaison inductrice (Inducer Binding Domain : IBD), tandis que les dimères N-terminaux se lient chacun à une région de l'ADN par un motif hélice-tour-hélice ‘winged' (wHTH). Contrairement à d'autres facteurs de transcription, les protéines LTTR ne régulent pas l'expression par association/dissociation avec l'ADN. Ils se lient à l'ADN dans leur état actif et inactif. Le consensus actuel est qu'elles régulent l'expression des gènes par d'importants changements conformationnels qui relâchent la liaison avec l'ADN. À ce jour, aucune structure de LTTR pleine longueur homotétramérique dans une conformation active ou inactive n'a été résolu par cristallographie, et leur mécanisme d'action sur le gène reste structurellement non caractérisé.Le travail décrit dans cette thèse a utilisé DntR de la famille des LTTR. La première structure cristalline de l'apo-DntRis est présentée ici, ainsi que la structure du mutant H169TDntR, qui présente une activité en l'absence d'inducteur. L'analyse par fluorimétrie de différentiel thermique (TSA) montre que la température de dénaturation du mutant H169TDntR est similaire à DntR IBDs lié à une molécule inductrice. La comparaison de ces deux structures avec celle de DntR lié au salicylate révèle que la protéine dans son état apo adopte une conformation compacte de l'IBC, ce qui empêche la liaison d'une molécule inductrice. Dans l'IBC, les mouvements des résidus H169 et H206 permettent la liaison à l'inducteur. Pour éviter les limitations dues à l'empaquetage du cristal nous avons étudié la structure DntR en solution par diffusion des rayons X aux petits angles (SAXS).L'étude SAXS de DntR révèle que dans son état inactif, la conformation apo adopte un repliement plus compact par rapport à celle de la structure cristalline. Tout en maintenant un noyau compact de C-terminal, le repliement du dimère de wHTH est beaucoup plus fermé que dans la structure cristalline et adopte une conformation qui entrainerait une flexion beaucoup plus importante de l'ADN lié que postulé précédemment. Les études du mutant H169TDntR constitué actif ont confirmé comme l'analyse par TSA l'a suggéré que, la structure de cette protéine est nettement différente en solution que sous forme cristalline.En effet, la structure en solution de H169TDntR est très semblable à la forme ouverte de l'homotétramères observés dans la structure cristalline de TsaR. L'hypothèse de départ était que, lors de l'activation de LTTR, cet homotétramère subirait un changement de conformation d'une forme compact vers une forme ouverte, qui se traduirait par un relâchement de l'ADN lié. Cette hypothèse a été confirmée par des études de diffusion en solution de DntR activée par un inducteur.Le travail présenté dans cette thèse valide l'hypothèse précédemment, que lors de l'activation de DntR, et probablement tous les LTTRs homotétramériques, entraine un changement de conformation d'une forme compacte vers une forme beaucoup plus ouverte et permet l'accès aux régions promotrices par l'ARN polymerase et ainsi initier la transcription. / LysR type transcriptional regulatory (LTTR) proteins are the largest family of transcription factors amongst prokaryotes. In spite of the size of the family, structural information on full-length constructs of these proteins is very limited as they are often insoluble and very difficult to crystallize. From the few existing crystal structures, coupled with other biophysical evidence, it is known that the proteins mainly associate as homotetramers comprising a dimer of dimers. The dimers associate through large C-terminal domains in a “head-to-tail” fashion and are connected “head-to-head” through their N-terminal domains and the resulting homotetramers are activated by the binding of inducer molecules. Each C-terminal domain contain an inducer binding cavity (IBC) and is denoted an inducer binding domain (IBD), while the N-terminal dimers each bind a region of DNA via a winged helix-turn-helix (wHTH) motif.Unlike other transcription factors, LTTR proteins do not regulate expression by associating or disassociating with DNA. They bind to DNA in both their active and inactive states and the current consensus is that they regulate gene expression through large conformational changes that relax the bending of bound DNA. However, to this date, no crystal structures of a full length homotetrameric LTTR in both an active and inactive conformation exists, and thus their mechanism of transcriptional regulation remains structurally uncharacterized.The work described in this thesis has used the LTTR DntR as a model protein to futher structurally characterizes the activation mechanism of LTTR proteins. The first crystal structure of apo-DntR is presented as is the crystal structure of H169TDntR, a mutant which shows activity in the absence of an inducer molecule. Thermofluor assays performed on this mutant, show that it has a melting temperature similar to that of inducer bound DntR. Comparison of these crystal structures with the crystal structure of salicylate-bound DntR reveals that the protein in its apo-state adopts a compact IBC, which precludes the binding of an inducer molecule. Despite the evidence of thermofluor assays, the crystal structure of H169TDntR is very similar to that of apo-DntR suggesting that crystal packing effects impose strong limitations on the use of crystallography to elucidate the active and inactive conformations of DntR. Small Angle X-ray Scattering (SAXS) was thus used to study the structure of DntR in solution.SAXS study reveals that in solution DntR in its inactive apo-state is found in a slightly different conformation compared to that seen in its crystal structure. While maintaining a compact tetrameric C-terminal core the DNA binding wHTH dimers pack much closer to this than seen in the crystal structure and adopt a conformation that would result in much higher bending of bound DNA than previously postulated.SAXS studies of the constitutively active H169TDntR mutant confirm, as thermofluor assays had suggested, that in solution the structure of this protein is markedly different from its crystal structure. Indeed the solution structure of H169TDntR appears very like that of open-form homotetramers seen in the crystal structure of TsaR. This same effect was observed in solution scattering studies of inducer bound-and thus activated, DntR.The work presented in this thesis thus appears to confirm, as previously hypothesized, that upon activation DntR, and presumably all homotetrameric LTTRs, undergo a conformational change from a compact, to a much more open form that allows the relaxation of the bound DNA promoter region, exposing it to solvent and allows RNA polymerase access and thus initiate transcription.

Estudos sistemáticos utilizando a técnica de SAXS foram realizados no síncrotom do LURE (Orsay) com feixe intenso de geometria pontua:, para descrever a cinética e as estruturas obtidas durante as etapas de transformação sol -> gel úmido -> gel seco -> vidros de sílica . As análises foram feitas em termos de uma lei de potência I = q-? cujo expoente está relacionado a dimensão fractal de massa ou de superfície das estruturas. Devido a polidispersividade das unidades espalhadoras as dimensões fractais verificadas podem ser resultados de dimensões reais encobertas por uma distribuição de tamanhos. As curvas obtidas para a cinética de gelificação e envelhecimento dos géis úmidos mostram expoentes que indicam fractalidade de massa e, posteriormente, de superfície. Uma microestrutura composta, que pode resultar de uma agregação limitada por difusão (DLA) seguido de agregação de agregados (C-C) foi observado nas soluções básicas. Por outro lado, os agregados ácidos parecem surgir do crescimento contínuo de cadeias até atingir a interligação com outros agregados com uma cinética que pode ser descrita pelo modelo DLA. No estado de aerogeis outras técnicas como picnometria de mercúrio e hélio, microscopia eletrônica de transmissão e adsorção de gás de nitrogênio, foram também aproveitadas. Nestes materiais encontramos em uma faixa estreita de escala, um expoente indicando fractalidade de massa, embora com superfície lisa. Os resultados estão de acordo com um modelo de estrutura que tem uma matriz de SiO2 densa. A estrutura fractal desaparece durante o tratamento térmico de densificação devido ao rearranjo estrutural. / Systematic SAXS studies have been performed at the LURE synchrotron (Orsay) using an intense beam of point-like cross-section to describe the kinetic and the structure obtained during the sol-> humid gel -> dry gel ->silica glass. The analysis were done in terms of a power law, I = q-? , whose exponent is related to mass and surface fractal dimensions of the structures. Due to polidispersity of the scattering units the found fractal dimensions can be \"smeared\" dimensions that result from a size distribution. All the kinetic and aging humids curves showed evidenced of fractal structures. A composed microstructure that can be originated by clustering of clusters (C-C) of primary units grown by diffusion limited-aggregation (DLA), was observed for basic gels. By other hand, the acidic cluster seems to grow continuously reaching gelation through crosslinking of the clusters. The DLA model seems to describe this process. In the aerogels study others techniques like density measurements using Hg and He, TEM and adsorption of N2 gas were done along with SAXS measurements. Here we could find a narrow range in which the system is a mass fractal, although its surface has been already smoothened. The results agree with a dense SiO2 matrix model. During the densification no fractal structure was verified due to structural rearrangements at high temperature.

Movimentos coletivos prestam um papel fundamental na dinâmica e energética de biomoléculas em solução. Estes movimentos permitem o acoplamento de regiões significativamente distantes, apresentando considerável influência, por exemplo, no alosterismo para a formação de complexos macromoleculares e no funcionamento integrado de proteínas multidomínios como \"máquinas moleculares\". Neste trabalho de doutoramento, serão apresentados os resultados referentes à aplicação conjunta de técnicas experimentais biofísicas, de modelagem estrutural e de dinâmica molecular no estudo de dois sistemas para os quais estes movimentos coletivos demonstram considerável importância funcional. Para a interação do receptor nuclear do ácido 9-cis-retinóico com seu elemento responsivo específico no DNA (HRE), a comparação de estudos de dinâmica molecular com ensaios de afinidade por anisotropia de fluorescência sugere que a resistência inicial para a associação do monômero, seguida da acentuada colaboratividade na associação do dímero é regida por um impedimento da associação do domínio de ligação ao DNA (DBD) para o primeiro à sequência responsiva devido, em última análise, a uma não complementaridade dos modos coletivos mútuos. Este impedimento para a associação monomérica inicial é mais acentuado para o monômero 5\' (para o qual a menor especificidade de ligação à seqüência específica já é bem documentada), devido aos efeitos conjuntos de um \"defeito\" natural no empacotamento de bases da seqüência responsiva, que se manifesta mais significativamente na interface entre o meio-sítio 5\' e a seqüência espaçadora, e dos modos vibracionais entre os dois sítios decorrentes de seu faseamento relativo na topologia do DNA na seqüência responsiva, caracterizando um mecanismo \"chave e fechadura\" para a interação obrigatoriamente simultânea dos dois monômeros ao DNA. No segundo caso, um estudo integrado utilizando a técnica experimental de espalhamento de raios X a baixos ângulos e uma abordagem de modelagem estrutural baseada em dinâmica molecular foi realizado para a celobiohidrolase I de Trichoderma harziannum. Este estudo permitiu tanto a elaboração de um modelo estrutural de maior resolução para esta enzima de alto potencial biotecnológico como a constatação dos possíveis mecanismos moleculares a partir dos quais as glicosilações no peptídeo conector impõem restrições à orientação e modos vibracionais entre seus dois domínios de forma condizente com sua ação concertada na interação e no deslize da enzima sobre a superfície celulósica, ambos de fundamental importância para a processividade da enzima na hidrólise do substrato microcristalino. / Collective motions play a fundamental role in solution biomolecule dynamics and energetics. These movements can couple very distant regions in the protein structures affection, for instance, allosteric mechanisms, the establishment of macromolecular complexes, and on the integrated function of multidomain proteins as molecullar machines. In this thesis, we present results concerning to the joint use of experimental biophysical techniques, structural modeling and molecular dynamics simulations on the study of two systems for which these collective motions have substantial importance. First, we study the interaction of the nuclear retinoid X receptor with its specific DNA hormone response element (HRE) using a combination of molecular dynamics simulations and affinity assays performed by using fluorescence anisotropy. We find out that collective motions mediate the low binding affinity of monomers and the high cooperative binding of HRE dimers. The lower binding affinity of the monomer is more prominent for 5´ monomers. This occur due to an natural ineffective stacking of the last base pair step at the 5´-half-site and to the phasing of the two binding half-sites in the DNA topology, that impose a collective motions that tends to occlude the 5´ binding site. This behavior, in turn, is concurrent with the well known 3´ polarity and the decreased binding specificity to the 5´ half site for the hRXRα monomer. This same pattern impose a lock-and-key mechanisms dependent on the binding of the full dimer. Second, an integrated Small angle X ray scattering and molecular dynamics based structural modeling was used to comprehend the interdomain motions of cellobiohydrolase I of Trichoderma harziannum. We manage to build a refined model for this enzime, with important biotechnological potential. We also provide insights into molecular mechanisms of linker and glycosylation imposed restraints on the orientation and vibrational modes of the full-length enzyme, supporting a mechanism of sliding of on the cellulose surface. This mechanism is fundamental for the high processivity on the hydrolysis of microcrystalline cellulose.

Orientador: Carlos Kenich Suzuki / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-22T19:32:43Z (GMT). No. of bitstreams: 1 Ogata_DanielaYuri_M.pdf: 14373801 bytes, checksum: 37390613963c28ba54f71a665d3cefb7 (MD5) Previous issue date: 1997 / Resumo: Neste trabalho procurou-se investigar a influência do tratamento da superficie (tensão/rugosidade provocado pelo processo de desbaste com pó abrasivo) na devitrificação e na dissolução da sílica vítrea. Para tanto, utilizou-se de métodos de caracterização de materiais, tais como difratometria de raios-X, espectroscopia de infravermelho, microscopia óptica e eletrônica e espalhamento de raios-X a baixo ângulo. Para o estudo da influência do tratamento superficial na devitrificação, os resultados de difração de raios-X e microscopia, mostraram que a devitrificação possui forte correlação com o tratamento superficial da sílica vítrea, onde amostras com maior rugosidade, apresentaram também uma maior devitrificação em comparação à outra com menor rugosidade. A dissolução da sílica vítrea por ácido fluorídrico ("etching") também foi estudado, e os resultados mostraram que a taxa de dissolução é dependente da rugosidade superficial, concentração do ácido e tempo de "etching". Resultados adicionais mostraram a formação de cavidades arredondadas na forma de "larvas" (padrão superficial) após "etching". Após um tempo de "etching" entre 33 e 88 horas, as amostras apresentaramum padrão superficial semelhante a "grãos" e no interior dos "grãos", outros "sub-grãos" da ordem de 4-10 'mu¿m, que denotam a existência de microtensões na estrutura amorfa. Neste trabalho, este resultado inédito foi denominado "grão ou sub-grão amorfo", que podem estar relacionados com heterogeneidades em nível atômico da estrutura da sílica vítrea / Abstract: The effect of surface stress and roughness, produced by polishing process with abrasive powder, was investigated on the devitrification and dissolution of silica glass. The characterization studies of the silica glass treated by grinding, polishing and etching and their effect on the devitrification were conducted by X-ray diffraction, optical and electronic microscopy, inftared spectroscopy and small-angle X-ray scattering. The samples were heat treated at 1250°C for a period of 15 min and 150 mino X-ray diffraction and optical microscopy observation showed more intense devitrification effect into a-cristobalite for higher degree of surface roughness, and the samples treated with HF etching presented the lowest devitrification effect. The silica glass surfaces exposed to the furnace atmosphere (air) presented a much bigger crystallization effect, inversely to the bottom surface in contact with a silica base. The dissolution of silica glass by chemical etching (HF solutions) was studied, and the results showed that dissolution rate is dependent on the surface roughness, HF concentration and etching time. For example, the dissolution rate of samples treated with SiC #320 and 'Ce IND. 2¿¿O IND. 3¿, were estimated as 0.16 'mu¿m/min and 0.14 'mu¿m/min, respectively. The results showthat sampleswith longtime etching(~1000 min) revealed grain-like etch pattern of 4 to 10 11min diameter, which suggests reveals the existence of micro-stress in the amorphous structure. This "amorphous grains or sub-grains" might be correlated with atomic into inhomogeneities of amorphous silica structure / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

This thesis deals with the preparation, characterization methods and in vitro imaging of nanoparticles with great potential for medical diagnostics. A key role in this work occupy nanoparticles comprising a core of calcium tungstate, CaWO4, covered by a natural polysaccharide together serve as a suitable model contrast agent for cell imaging techniques. CaWO4 natural properties such as the absorption of X-rays, natural fluorescence capabilities and capacities for doping fluorescently active lanthanides, makes from nanoparticles suitable candidates for the position of contrast agents for imaging in the diagnosis of oncological diseases. Moreover, by coverage of the inorganic core by natural polysaccharide nanoparticles reach the desired size and the possibility of active targeting to specific or nonspecific interactions with the cell membrane, which are key factors in in vitro cell studies. It was found the most suitable synthesis both doped and undoped core of this model reaching the formation of spherical particles of colloidal dimensions. Doping was realized by red fluorescent trivalent europium, Eu3+ , and green fluorescent trivalent terbium, Tb3+ , and neither of these dopants affected the original crystalline structure CaWO4. In the next stage, these fluorescent nuclei successfully dispersed...

Les phases concentrées de protéines sont au centre de nombreuses études visant à identifier et caractériser les interactions et transitions de phases mises en jeu, en utilisant le large corpus de connaissances acquis sur les phases concentrées de colloïdes. Ces phases concentrées de protéines possèdent en outre une grande importance dans des domaines aussi variés que l’industrie agroalimentaire, l’industrie pharmaceutique et la médecine. L’établissement d’équations d’état présentant la pression osmotique (Π) en fonction de la fraction volumique (Φ) est une méthode efficace de caractérisation des interactions entre les composants d’un système. Nous l’avons appliquée à des solutions de deux protéines globulaires, le lysozyme et l’ovalbumine, en balayant une gamme de fractions volumiques allant d’une phase diluée (Φ < 0,01) à une phase concentrée, solide (Φ > 0,62). Les équations d’état obtenues, couplées à d’autres techniques (SAXS, simulations numériques), ont permis de mettre en évidence un comportement très différent des deux protéines lors de la concentration et ont montré leur complexité en comparaison avec des colloïdes modèles. La mise en relation des équations d’état et du comportement interfacial de ces deux protéines a montré des points de convergence et permis de formuler une nouvelle hypothèse expliquant certaines observations portant sur l’adsorption des protéines à l’interface air-eau. / Concentrated phases of proteins are the subject of numerous studies aiming at identifying and characterizing the interactions and phase transitions at play, using the large corpus of knowledge in the field of concentrated colloids. Those concentrated phases of proteins have, in addition, a great importance in various fields, such as food industry, pharmaceutical industry and medicine. The establishment of equations of state relating osmotic pressure (Ð) and volume fraction (Φ) is an efficient way of characterization of the interactions between the components of a system. We applied this method to solutions of two globular proteins, lysozyme and ovalbumin, spanning volume fractions ranging from a dilute phase ( Φ < 0,01) to a concentrated, solid phase ( Φ > 0,62). The equations of state, coupled to other methods (SAXS, numerical simulations), enabled us to show that the two proteins carry a very different behavior when submitted to concentration and that their complexity is beyond that of colloids. Relating equations of state and interfacial behavior of these two proteins also showed points of convergence and enabled us to formulate a new hypothesis which explains some of the results obtained in the study of adsorption of proteins at the air-water interface.

Die heterogene Struktur von aus Rattenhirn isolierten Synaptischen Vesikeln wird untersucht mittels Daten aus Kleinwinkel-Röntgenstreuexperimenten unter Berücksichtigung von Daten erhalten durch cryogene Elektronenmikroskopie, dynamische Lichtstreuung und biochemische Analysen. Es werden niedrig aufgelöste Strukturmodelle des funktionellen Synaptischen Vesikels unter quasi-physiologischen Bedingungen vorgeschlagen. Details des Dichteprofils der Membran, einschließlich Beiträgen von Lipiden und Proteinen werden bestimmt. Die typische Konformation und die allgemeine laterale Organisation der Proteine in Mikrodomänen werden ermittelt. Entropische Beiträge zur freien Energie aufgrund möglicher Bildung und Auflösung der Proteinmikrodomänen auf dem Synaptischen Vesikel werden untersucht. Ferner werden zellfreie Fusionssysteme mittels dynamischer Lichtstreudaten charakterisiert und mögliche Anwendungen von Kleinwinkel-Röntgenstreuung für die Untersuchung von Membran-Fusionsprozessen erörtert.

Les nanofils d’or ultrafins sont des objets fascinants présentant une morphologie quasi 1D, leur diamètre n’excédant par 2 nm pour une longueur micrométrique. Les quelques 30 atomes qui composent la section de ses fils sont principalement des atomes de surface, permettant d’envisager des applications de type capteurs. De plus, l’anisotropie de forme unique pourrait permettre un confinement électronique unidimensionnel, menant à de nouvelles propriétés physiques. Nous avons réalisé une étude fondamentale de la synthèse et réaliser une première étude de transport sur une assemblée de nanofils.La première partie du manuscrit, divisée en quatre chapitres, consiste en l’étude du mécanisme de croissance de ces nanofils ultrafins. Suite à une analyse détaillée des modèles proposés, nous introduisons la technique de diffusion des rayons X aux petits angles (SAXS) utilisée pour nos études mécanistiques. Le chapitre 3 est consacré à l’étude de la synthèse de nanofils en milieu confiné. Contrairement aux postulats précédents, un suivi cinétique in-situ par SAXS nous a permis de montrer que la phase lamellaire n’intervenait pas dans la croissance des objets, voir même qu’elle était détrimentaire à leur formation. Le dernier chapitre présente la synthèse en milieu isotrope. Un mécanisme de croissance efficace où les sphères jouent le rôle de germe est avancé. L’auto-organisation des fils en solution suivant une phase hexagonale appuie l’hypothèse d’une stabilisation des fils par une double couche d’oleylamine et de chlorure d’ammonium. Un mécanisme de croissance analogue aux mécanismes proposés pour les bâtonnets d’or dans l’eau est donc proposé.La deuxième partie du manuscrit, divisée en trois chapitres, consiste en une caractérisation des propriétés de transport électronique dans ces nanofils d’or ultrafins. Nous dressons, dans un premier temps, un bilan des différents régimes de transport observés au sein de nano-objets de basse dimensionnalité. Suite aux étapes indispensables de dépôt et de connexion, le troisième chapitre présente les premières mesures de transport effectuées sur des assemblées de nanofils d’or faiblement couplées. Nous mettons ainsi en évidence, grâce à une étude sur une large gamme de températures et de tensions de polarisation, un transport de charge coopératif dans le cadre d’un régime de blocage de Coulomb. / Ultra-narrow gold nanowires are captivating objects with a quasi-1D morphology, with a diameter lower than 2 nm and a micrometric length. The few 30 atoms which compose the wire section are mainly surface atoms, allowing to consider applications such as sensors. Moreover, the unique anisotropic shape may permit a one-dimensional electronic confinement, leading to new physical properties. We conducted a fundamental study of the synthesis and a preliminary transport study on an assembly of nanowires.The first part of the manuscript, divided into four chapters, consist of the growth mechanism study of these ultra-narrow gold nanowires. Further to a detail analysis of the proposed models, we present the small angle X-rays scattering (SAXS) technique used for our mechanistic studies. The third chapter deals with the study of the nanowires synthesis in a confined environment. Unlike the previous postulates, a in-situ kinetic monitoring by SAXS allow us to point out that the lamellar phase was not involved in the objects’ growth, even more that it was detrimental for their formation. The last chapter presents the synthesis in an isotropic system. An efficient growth mechanism where the spheres act as seeds is advanced. The wires’ self-assembly in solution in a hexagonal super-lattice supports the hypothesis of wire stabilization by a bilayer of oleylamine and oleylammonium chloride. Therefore, a growth mechanism similar to the one proposed in the case of gold nanorods in water is proposed.The second part of the manuscript, divided into three chapters, consist in a characterization of the electronic transport properties in these ultra-narrow gold nanowires. At first, we report on the different types of transport observed low-dimensionality nano-objects. Further to the necessary deposit and connection steps, the third chapter presents the first transport measurements performed weakly coupled assemblies of gold nanowires. We highlight, through a study on a wide range of temperatures and bias voltages, a cooperative charges transport through a Coulomb blockade regime.