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Orientador: Edvaldo Sabadini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T13:40:57Z (GMT). No. of bitstreams: 1 Sant'AnnaJunior_Walcyr_M.pdf: 635340 bytes, checksum: 1249edac738f7933eee08fdecb6d0d7f (MD5) Previous issue date: 2001 / Resumo: Este trabalho envolve o estudo do equilíbrio de fase líquido-líquido apresentado pelo sistema poli(etileno glicol), (PEG) e hidrocarbonetos aromáticos (HA). Os diagramas de fase são do tipo UCST (upper critical solution temperature), sendo que o grau de miscibilidade é fortemente dependente da massa molar do PEG e do número de CH2 presentes na cadeia alifática das moléculas dos HA. Também são mostrados estudos realizados com os isômeros o, m, e p-xileno e n e iso-propil benzeno, permitindo, nestes casos, verificar a influência da posição do substituinte e da estrutura da cadeia alifática na miscibilidade deste sistema. Os diagramas foram obtidos a partir de medidas visuais de turbidez (ponto de névoa) para as diferentes soluções poliméricas. Neste trabalho procuramos discutir os aspectos entálpicos e entrópicos que levam à separação de fases. O modelo de Flory-Huggins para soluções poliméricas foi utilizado para determinar os parâmetros de interação PEG- HA / Abstract: This work is concerned with the liquid-liquid phase equilibrium shown by a system composed of poly(ethylene glycol) [PEG] and aromatic hydrocarbons [AH]. The diagrams were obtained by cloud point titration. Studies were carried out using o, m, p-xylene isomers and normal and iso-propyl benzene isomers, in order to verify the influence of the substituent position and of the aliphatic chain structure on the miscibility of the system. The phase diagrams obtained are of the UCST (upper critical solution temperature) class. The miscibility is strongly dependent on PEG molar weight and on the number of CH2 units of the aliphatic chain. The Flory-Huggins model for polymeric solutions was employed to determine the PEG-AH interaction parameters. The enthalpic and entropic contribution which lead to phase separation are discussed / Mestrado / Físico-Química / Mestre em Química

Computational methodologies were employed to study a supramolecular micellar structure and its application, nanoreactor. This task was done through rigorous scale-up procedure using both atomistic and mesoscopic simulations. Primarily, density functional theory (DFT) calculation was used to characterize the smallest unit of complex molecules in the multicomponent mixture system. The following step involved transferring the information achieved by DFT calculation to larger scale simulation, such as molecular dynamics (MD) simulation. Lastly, based on the atomistic simulation results, we performed a series of dissipative particle dynamics (DPD) simulations to study a full body of polymeric multicompartment micelle. In the course of research, we built a systematic procedure to minimize the complexity of computation and efficiently characterize macromolecular structures and its application.

La perception des emballages alimentaires est passée d’utile à source majeure de contaminants dans les aliments et menace pour l’environnement. La substitution du verre par des con-tenants en plastiques recyclés ou biosourcés réduit l’impact environnemental des boissons embouteillées. La thèse a développé de nouveaux outils de simulation 3D et d’optimisation pour accélérer le prototypage des emballages éco-efficaces pour les boissons alcoolisées. La durée de conservation des boissons, la sécurité sanitaire des matériaux plastiques recyclés, les contraintes mécaniques, et la quantité de déchets sont considérées comme un seul problème d'optimisation multicritères. Les nouvelles bouteilles sont générées virtuellement et itérativement en trois étapes comprenant : i) une [E]valuation multiéchelle des transferts de masse couplés ; ii) une étape de [D]écision validant les contraintes techniques (forme, capacité, poids) et réglementaires (durée de conservation, migrations); iii) une étape globale de ré[S]olution recherchant des solutions de Pareto acceptables. La capacité de prédire la durée de vie des liqueurs dans des conditions réelles a été testée avec succès sur environ 500 miniatures en PET (polyéthylène téréphtalate) sur plusieurs mois. L’ensemble de l’approche a été conçu pour gérer tout transfert de matière couplé (perméation, sorption, migration). La sorption mutuelle est prise en compte via une formulation polynaire de Flory-Huggins. Une formulation gros grain de la théorie des volumes libres de Vrentas et Duda a été développée pour prédire les propriétés de diffusion dans les polymères vitreux de l’eau et des solutés organiques dans des polymères arbitraires (polyesters, polyamides, polyvinyles, polyoléfines). 409 diffusivités issues de la littérature ou mesurées ont été utilisée pour validation. La contribution de la relaxation du PET vitreux a été analysée par sorption différentielle (binaire et ternaire) de 25 à 50 °C. Une partie du code source sera partagé afin d'encourager l'intégration de davantage de paramètres affectant la durée de conservation des boissons et des produits alimentaires (cinétique d'oxydation, piégeage d'arômes). / The view of plastic food packaging turned from useful to a major source of contaminants in food and an environmental threat. Substituting glass by recycled or biosourced plastic containers reduces environmental impacts for bottled beverages. The thesis developed a 3D computational and optimization framework to accelerate the prototyping of eco-efficient packaging for alcoholic beverages. Shelf-life, food safety, mechanical constraints, and packaging wastes are considered into a single multicriteria optimization problem. New bottles are virtually generated within an iterative three steps process involving: i) a multiresolution [E]valuation of coupled mass transfer; ii) a [D]ecision step validating technical (shape, capacity, weight) and regulatory (shelf-life, migrations) constraints; iii) a global [Solving] step seeking acceptable Pareto solutions. The capacity to predict shelf-life of liquors in real conditions was tested successfully on ca. 500 hundred bottle min iatures in PET (polyethylene terephthalate) over several months. The entire approach has been designed to manage any coupled mass transfer (permeation, sorption, migration). Mutual sorption is considered via polynary Flory-Huggins formulation. A blob formulation of the free-volume theory of Vrentas and Duda was developed to predict the diffusion properties in glassy polymers of water and organic solutes in arbitrary polymers (polyesters, polyamides, polyvinyls, polyolefins). The validation set included 433 experimental diffusivities from literature and measured in this work. The contribution of polymer relaxation in glassy PET was analyzed in binary and ternary differential sorption using a cosorption microbalance from 25 to 50°C. Part of the framework will be released as an open-source project to encourage the integration of more factors affecting the shelf-life of beverages and food products (oxidation kinetics, aroma scalping).

<p>A new kind of lipid/polymer composite particle, consisting of a biodegradable polymer matrix with well-defined lipid domains, has been created. The lipid used is the water-swelling lipid monoolein (MO), which forms a reversed bicontinuous cubic diamond structure in aqueous solutions. The polymer is poly(d,l-lactide-co-glycolide) (PLG), which degrades into water-soluble monomers through hydrolysis. This new particle might be a good alternative for encapsulation of active substances intended to be released over a longer period of time, i.e. sustained/retained/controlled release.</p><p>To prepare such particles can be difficult. Suitable phase behaviour and a solvent with the right properties are needed. For this reason, the phase behaviours of several different lipid/polymer/solvent/water systems have been explored. From the phase behaviour of a suitable system (i.e. MO/PLG/ethyl acetate/water), a route for formation of lipid/polymer composite particles has been deduced. Particles have been formed and distinct, water-swelling, lipid domains have been confirmed by characterization by means of confocal laser scanning probe microscopy (CLSM). </p><p>The sample preparation process has been automated and a method based on using a robotic liquid handler has been developed. Phase diagrams have been determined by examination of macroscopic behaviours and the microstructures of the phases have been studied by small- and wide-angle X-ray scattering (L₃, V₂, L_α, L), nuclear magnetic resonance self-diffusion (L, L₃), viscosimetry (L) and rheology (L). Several different theoretical models have been applied for interpretation of the results. For example, the swelling of the reversed bicontinuous cubic phases and the sponge phase have been modelled by applying the theory of infinite periodical minimal surfaces, the sponge phase has been shown to be bicontinuous according to the theory of interconnected rods and the phase behaviour of the polymer has been described by the Flory-Huggins theory. The main focus of this work (4/5) concerns phase studies in multicomponent systems from a physical-chemical point of view.</p>

A new kind of lipid/polymer composite particle, consisting of a biodegradable polymer matrix with well-defined lipid domains, has been created. The lipid used is the water-swelling lipid monoolein (MO), which forms a reversed bicontinuous cubic diamond structure in aqueous solutions. The polymer is poly(d,l-lactide-co-glycolide) (PLG), which degrades into water-soluble monomers through hydrolysis. This new particle might be a good alternative for encapsulation of active substances intended to be released over a longer period of time, i.e. sustained/retained/controlled release. To prepare such particles can be difficult. Suitable phase behaviour and a solvent with the right properties are needed. For this reason, the phase behaviours of several different lipid/polymer/solvent/water systems have been explored. From the phase behaviour of a suitable system (i.e. MO/PLG/ethyl acetate/water), a route for formation of lipid/polymer composite particles has been deduced. Particles have been formed and distinct, water-swelling, lipid domains have been confirmed by characterization by means of confocal laser scanning probe microscopy (CLSM). The sample preparation process has been automated and a method based on using a robotic liquid handler has been developed. Phase diagrams have been determined by examination of macroscopic behaviours and the microstructures of the phases have been studied by small- and wide-angle X-ray scattering (L3, V2, Lα, L), nuclear magnetic resonance self-diffusion (L, L3), viscosimetry (L) and rheology (L). Several different theoretical models have been applied for interpretation of the results. For example, the swelling of the reversed bicontinuous cubic phases and the sponge phase have been modelled by applying the theory of infinite periodical minimal surfaces, the sponge phase has been shown to be bicontinuous according to the theory of interconnected rods and the phase behaviour of the polymer has been described by the Flory-Huggins theory. The main focus of this work (4/5) concerns phase studies in multicomponent systems from a physical-chemical point of view.

Plusieurs indices suggèrent que le repliement du chromosome et la régulation de l’expression génétique sont étroitement liés. Par exemple, la co-expression d’un grand nombre de gènes est favorisée par leur rapprochement dans l’espace cellulaire. En outre, le repliement du chromosome permet de faire émerger des structures fonctionnelles. Celles-ci peuvent être des amas condensés et fibrillaires, interdisant l’accès à l’ADN, ou au contraire des configurations plus ouvertes de l’ADN avec quelques amas globulaires, comme c’est le cas avec les usines de transcription. Bien que dissemblables au premier abord, de telles structures sont rendues possibles par l’existence de protéines bivalentes, capable d’apparier des régions parfois très éloignées sur la séquence d’ADN. Le système physique ainsi constitué du chromosome et de protéines bivalentes peut être très complexe. C’est pourquoi les mécanismes régissant le repliement du chromosome sont restés majoritairement incompris.Nous avons étudié des modèles d’architecture du chromosome en utilisant le formalisme de la physique statistique. Notre point de départ est la représentation du chromosome sous la forme d’un polymère rigide, pouvant interagir avec une solution de protéines liantes. Les structures résultant de ces interactions ont été caractérisées à l’équilibre thermodynamique. De plus, nous avons utilisé des simulations de dynamique Brownienne en complément des méthodes théoriques, car elles permettent de prendre en considération une plus grande complexité dans les phénomènes biologiques étudiés.Les principaux aboutissements de cette thèse ont été : (i) de fournir un modèle pour l’existence des usines de transcriptions caractérisées in vivo à l’aide de microscopie par fluorescence ; (ii) de proposer une explication physique pour une conjecture portant sur un mécanisme de régulation de la transcription impliquant la formation de boucles d’ADN en tête d’épingle sous l’effet de la protéine H-NS, qui a été émise suite à l’observation de ces boucles au microscope à force atomique ; (iii) de proposer un modèle du chromosome qui reproduise les contacts mesurés à l’aide des techniques Hi-C. Les conséquences de ces mécanismes sur la régulation de la transcription ont été systématiquement discutées. / Increasing evidences suggest that chromosome folding and genetic expression are intimately connected. For example, the co-expression of a large number of genes can benefit from their spatial co-localization in the cellular space. Furthermore, functional structures can result from the particular folding of the chromosome. These can be rather compact bundle-like aggregates that prevent the access to DNA, or in contrast, open coil configurations with several (presumably) globular clusters like transcription factories. Such phenomena have in common to result from the binding of divalent proteins that can bridge regions sometimes far away on the DNA sequence. The physical system consisting of the chromosome interacting with divalent proteins can be very complex. As such, most of the mechanisms responsible for chromosome folding and for the formation of functional structures have remained elusive.Using methods from statistical physics, we investigated models of chromosome architecture. A common denominator of our approach has been to represent the chromosome as a polymer with bending rigidity and consider its interaction with a solution of DNA-binding proteins. Structures entailed by the binding of such proteins were then characterized at the thermodynamical equilibrium. Furthermore, we complemented theoretical results with Brownian dynamics simulations, allowing to reproduce more of the biological complexity.The main contributions of this thesis have been: (i) to provide a model for the existence of transcrip- tion factories characterized in vivo with fluorescence microscopy; (ii) to propose a physical basis for a conjectured regulatory mechanism of the transcription involving the formation of DNA hairpin loops by the H-NS protein as characterized with atomic-force microscopy experiments; (iii) to propose a physical model of the chromosome that reproduces contacts measured in chromosome conformation capture (CCC) experiments. Consequences on the regulation of transcription are discussed in each of these studies.