Les maladies neurodégénératives amyloïdes sont caractérisées par la dégénération et l'agrégation de protéines spécifiques. Ces processus d'agrégations restent mal compris par les spécialistes, et pour la plupart, hypothétiques seulement. Dans cette thèse, faîte en collaboration avec des biophysiciens, nous analysons ces méchanismes d'agrégations en nous basant sur des données expérimentales. Pour cela, la modélisation est une étape incontournable. Nous présentons deux modèles que nous confrontons aux expériences. Le premier modèle, connu de la littérature, est celui de Becker-Döring. Un système infini d'équations différentielles ordinaires. Ce premier modèle nous permet de reproduire se manière satisfaisante les premières étapes des expériences. Le second modèle que nous introduisons, se base sur une hypothèse réactionnelle additionnelle, formulée à partir des simulations du premier modèle, et qui consiste en la formation de fibres différentes. Ce deuxième modèle nous permet de mieux reproduire les expériences. / The amyloid neurodegenerative diseases are characterized by the degeneration and the aggregation of specific proteins. These aggregation processes remain misunderstood by specialists and, mostly, only hypothetical. In this thesis, and in collaboration with biophysicists, we analyze the mechanisms of aggregation, relying on experimental data. Modeling is then a must. We present two models which we compare with the experiments. The first model, well-known from the literature is the Becker-Döring system. An infinite system of ordinary differential equations. This first model allows us to reproduce satisfactorily the early stages of the experiments. The second model we introduce is based on an additional hypothesis which is about the formation of different fibers. This second model allows us to reproduce the experiments.

The phase separation of mixed Langmuir-Blodgett (LB) monolayers was investigated using a combination of atomic force microscopy (AFM), X-ray photoelectron emission microscopy (X-PEEM) and confocal fluorescent microscopy measurements. Shapes of phase-separated domains that formed on solid substrate surfaces depended on a competition between line tension and dipole-dipole interactions. In the mixed LB film of arachidic acid (C19H39COOH) (C20) and perfluorotetradecanoic acid (C13F27COOH) (F14), the components phase separated into elevated hexagonal domains of C20 surrounded by a continuous domain primarily consisting of F14. The underlying molecular arrangement of C20 was found to be an oblique packing. The domains in this system grew via Ostwald ripening and the kinetics of their growth was modeled by twodimensional LifshitzSlyozov equation. In the stearic acid (C17H35COOH) (C18) and F14 mixed films, the C18 domains formed a linear pattern where the F14 molecules filled the areas in between the lines occupied by C18. For the mixed film of palmitic acid (C15H31COOH) (C16) and perfluorooctadecanoic acid (C17F35COOH) (F18), the surfactants phaseseparated into elevated hexagonal domains with hairy extensions radiating from them. These domains were composed of F18 and surrounded by C16. Ostwald ripening was found to be the mechanism of domain growth. Phase separation was controlled by different forces such as line tension and dipole interactions, as well as the diffusion of the molecules, solubility of the surfactant in the sub-phase, temperature and surface pressure. Simple mechanisms regarding phase separation and pattern formation were discussed in these mixed systems. It was observed that all fatty acid / F14 systems in this study were immiscible at all molar fractions examined. The fatty acid / F18 systems were immiscible at short chains of fatty acids (myristic acid (C13H27COOH) C14, C16, C18), whereas at longer fatty acid chains (C20, C22 behenic acid (C21H43COOH)) the components of the mixed system became miscible. When perfluorocarboxylic acid chain combined with fatty acids, the domains changed from large hexagonal domains into narrow lines as the fatty acid chain decreased in length.

The phase separation of mixed Langmuir-Blodgett (LB) monolayers was investigated using a combination of atomic force microscopy (AFM), X-ray photoelectron emission microscopy (X-PEEM) and confocal fluorescent microscopy measurements. Shapes of phase-separated domains that formed on solid substrate surfaces depended on a competition between line tension and dipole-dipole interactions. In the mixed LB film of arachidic acid (C19H39COOH) (C20) and perfluorotetradecanoic acid (C13F27COOH) (F14), the components phase separated into elevated hexagonal domains of C20 surrounded by a continuous domain primarily consisting of F14. The underlying molecular arrangement of C20 was found to be an oblique packing. The domains in this system grew via Ostwald ripening and the kinetics of their growth was modeled by twodimensional LifshitzSlyozov equation. In the stearic acid (C17H35COOH) (C18) and F14 mixed films, the C18 domains formed a linear pattern where the F14 molecules filled the areas in between the lines occupied by C18. For the mixed film of palmitic acid (C15H31COOH) (C16) and perfluorooctadecanoic acid (C17F35COOH) (F18), the surfactants phaseseparated into elevated hexagonal domains with hairy extensions radiating from them. These domains were composed of F18 and surrounded by C16. Ostwald ripening was found to be the mechanism of domain growth. Phase separation was controlled by different forces such as line tension and dipole interactions, as well as the diffusion of the molecules, solubility of the surfactant in the sub-phase, temperature and surface pressure. Simple mechanisms regarding phase separation and pattern formation were discussed in these mixed systems. It was observed that all fatty acid / F14 systems in this study were immiscible at all molar fractions examined. The fatty acid / F18 systems were immiscible at short chains of fatty acids (myristic acid (C13H27COOH) C14, C16, C18), whereas at longer fatty acid chains (C20, C22 behenic acid (C21H43COOH)) the components of the mixed system became miscible. When perfluorocarboxylic acid chain combined with fatty acids, the domains changed from large hexagonal domains into narrow lines as the fatty acid chain decreased in length.