Ce travail de thèse concerne la synthèse et la caractérisation d'homo et de copolymères stimulables à base de N,N-diéthylacrylamide (DEAm). Des homopolymères ont été préparés par polymérisation radicalaire contrôlée par transfert réversible par addition-fragmentation (RAFT). Cette polymérisation a été conduite en présence de trois agents de transfert différents et s'est avérée contrôlée quelles que soient les conditions expérimentales. Deux types de copolymères ont ensuite été préparés, de type PEG-b-PDEAm et PDEAm-b-polypeptides par polymérisation RAFT et combinaison RAFT/ polymérisation par ouverture de cycle (ROP), respectivement. Ces copolymères double hydrophiles ont été caractérisés et leur comportement en solution aqueuse a été évalué. Nous avons montré la formation de micelles c?ur-couronne au dessus de la LCST. Nous avons également développé une stratégie de synthèse originale dans le cas des PDEAm-b-polypeptides puisque la ROP a été réalisée en utilisant un macroamorceur de type thiol. Après déprotection des copolymères sensibles au pH et à la température ont été obtenus et montre des propriétés de structuration différentes en fonction de ces deux stimuli. / This manuscript deals with the synthesis and characterization of responsive copolymers containing N,N-diethylacrylamide (DEAm). Homopolymers were prepared by controlled radical polymerization, especially Reversible Addition-Fragmentation Transfer (RAFT). Polymerization was achieved using three different chain transfer agents and was controlled whatever the experimental conditions. PEG-b-PDEAm and PDEAm-b-polypeptides were synthesized by RAFT polymerization and RAFT/Ring Opening Polymerization (ROP) respectively. These double hydrophilic block copolymers were characterized and their behavior in aqueous solution was evaluated. We showed that core/corona micelles were obtained above the lower critical solution temperature. We also developed a new strategy for the synthesis of PDEAm-b-polypeptides as ROP was achieved using a thiol macroinitiator. After deprotection pH- and thermo-sensitive copolymers were afforded which proved different structuration as a function of both stimuli.

The primary objective of the research was to study the physiological and biochemical changes in Hass avocado fruit stored in different combination of oxygen and carbon dioxide concentrations at both 0 degrees and 5 degrees Centigrade (C), and to determine whether storage in controlled atmosphere (CA) can decrease the incidence of chilling injury (CI). A secondary objective was to identify possible correlations between CA, the incidence of CI, the activity of some ripening related enzymes and changes in proteins during ripening at 20 degrees C following storage at low temperatures. Fruit suffered no CI and ripened normally following CA storage for 3 weeks at both 0 degrees and 5 degrees C, then transferred to air for 6 days at 20 degrees C. CI symptoms did develop after CA storage for 6 and 9 weeks at 0 degrees C. Changes in proteins during ripening were analysed by 2D-PAGE. Some polypeptides were detected in unripe fruit but decreased with ripening. Polypeptides of 16.5, 25, 36 and 56 kD (kilo Dalton) were present early in ripening and their levels further increased during ripening. The appearance of three ripening related polypeptides with estimated molecular weights 80 kD (pI 3.6), 36 kD (pI 5.8) and 16.5 kD (pI 5.7) was observed in fruit at the climacteric stage. Three polypeptides with estimated molecular weights of 41 kD (pI7.8), 36 kD (pI 5.8) and 33 kD (pI 5.1) were found in air stored fruit but were not detected in fruit stored in CA. This research showed that CA did not ameliorate CI at 0 degrees C, instead storage at 0 degrees C caused a premature increase in ethylene production when the fruit were returned to air at 20 degrees C. In contrast, CA storage at 5 degrees C retarded ethylene production and ripening in fruit after it was returned to air at 20 degrees C. / Doctor of Philosophy (PhD)

Made available in DSpace on 2014-10-09T12:51:58Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:22Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:51:58Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:22Z (GMT). No. of bitstreams: 0 / S179D prolactina (hPRL) é uma mímica molecular da prolactina humana fosforilada. Demonstrou-se que a S179D-hPRL era anti angiogênica nos ensaios de angiogênese baseados na membrana corialantóica de galinha e na córnea de camundongos. Investigações posteriores realizadas empregando modelos in vitro demonstraram que o tratamento com S179D-hPRL diminuiu o número de células viáveis, reduziu a formação de túbulos em Matrigel e interferiu com a migração e invasão da matriz extracelular. A análise dos fatores de crescimento de células endoteliais humanas tratadas com S179D-hPRL revelou: uma diminuição na expressão ou liberação da PRL endógena, da heme-oxigenase-1, do fator de crescimento de fibroblasto básico (bFGF) e um aumento na expressão de dois inibidores teciduais de metaloproteases. A S179D-hPRL também bloqueou a sinalização provocada por bFGF nessas células. Nós concluímos que essa mímica molecular do hormônio pituitário fosforilado é uma potente proteína anti-angiogênica, em parte devido á sua habilidade de reduzir o estímulo autócrino de fatores de crescimento de células endoteliais de cordão umbilical humano (HUVEC), por sua capacidade de bloquear a sinalização promovida pelo bFGF e por sua habilidade de interferir na migração endotelial. Também foi estudada a influência da S179D-hPRL na apoptose em células endoteliais humanas, empregando caspase-8 como um marcador da via extrínseca, e a liberação de citocromo C como um marcador da via intrínseca. As duas cascatas convergem na ativação da caspase-3, que cliva a fator de fragmentação de DNA (DFF45). Uma incubação de três dias com 50 ng/mL de S179D-hPRL quadruplicou o número de células apoptóticas; esse efeito duplicou-se com uma concentração de 100 ng/mL e atingiu um ápice com 500 ng/mL. A clivagem de DFF45 e da pro-caspase-8 foi detectado com 100 ng/mL. Citocromo C, porém, só foi observado com concentrações de 500 ng/mL. O regulador de ciclo celular p21 (um marcador pró-apoptótico) elevou-se com 100 ng/mL, enquanto que um incremento do supressor tumoral p53 necessitou três vezes o tempo de incubação e 500 ng/mL. A atividade do promotor de p21 foi máxima com 50 ng/mL do análogo de hPRL, enquanto que 500 ng/mL foram necessários para se visualizar uma alteração significativa na atividade do promotor de Bax (um indicador da atividade de p53). Como previamente demonstrado na literatura, S179D-hPRL bloqueou a fosforilação da quinase regulada extracelularmente (ERK) em resposta ao bFGF, mas também causou uma ativação tardia e prolongada da ERK. PD 98059 [inibidor específico da proteína quinase ativada por mitógeno (MAPkinase)] inibiu essa ativação tardia e sustentada assim como outros efeitos da S179D-hPRL, exceto aquele sobre a indução de p53 e ativação do promotor de Bax. Podemos concluir que baixas doses de S179D-hPRL bloqueiam a sinalização de ERK induzida por bFGF e concomitantemente ativam a ERK em um tempo diferente, resultando na elevação de p21 e ativando a via extrínseca de apoptose. Maiores tempos de incubação e concentração, entretanto, ativam a via intrínseca empregando uma cascata intracelular diferente. Esses achados sugerem que níveis circulantes de PRL fosforilada podem inibir a progressão do câncer e, portanto, S179D-hPRL poderia ser um agente anti-angiogênico útil na terapêutica. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Although nonflexible, scaled molecular models like Pauling-Corey's and its descendants have made significant contributions in structural biology research and pedagogy, recent technical advances in 3D printing and electronics make it possible to go one step further in designing physical models of biomacromolecules: to make them conformationally dynamic. We report the design, construction, and validation of a flexible, scaled, physical model of the polypeptide chain, which accurately reproduces the bond rotational degrees-of-freedom in the peptide backbone. The coarse-grained backbone model consists of repeating amide and alpha-carbon units, connected by mechanical bonds (corresponding to phi and psi angles) that include realistic barriers to rotation that closely approximate those found at the molecular scale. Longer-range hydrogen-bonding interactions are also incorporated, allowing the chain to easily fold into stable secondary structures. This physical model can serve as the basis for linking tangible bio-macromolecular models directly to the vast array of existing computational tools to provide an enhanced and interactive human-computer interface. We have explored the boundaries of this direction at the interface of computational tools and physical models of biological macromolecules at the nano-scale. Using a CAD-biocomputational framework, we have provided a methodology to design and build physical protein models focusing on shape and dynamics. We have also developed a workflow and an interface implemented for such bio-modeling tools. This physical-digital interface paradigm, at the intersection of native state proteins (P), computational models (C) and physical models (P), provides new opportunities for building an interactive computational modeling tool for protein folding and drug design. Furthermore, this model is easily constructed with readily obtainable parts and promises to be a tremendous educational aid to the intuitive understanding of chain folding as the basis for macromolecular structure. / Ph. D.

A lipoproteína de baixa densidade (LDL) pode sofrer modificações, oxidativas ou enzimáticas, gerando compostos, lipídicos e proteicos, capazes de interagir com macrófagos, contribuindo para a resposta inflamatória presente na aterosclerose. Os macrófagos interagem tanto com LDL contendo baixo ou alto grau de oxidação (LoxLDL e HoxLDL) e também com fragmentos proteicos provenientes da ApoB-100, os quais podem exercer efeitos biológicos em macrófagos, contribuindo para a formação de células espumosas. Neste trabalho demonstramos que formas modificadas da LDL interagem com monócitos e/ou macrófagos, dependendo do grau de oxidação. A expressão de FcgRII por HoxLDL em macrófagos é dependente de PPARg. Parte da expressão de CD36 induzida por LoxLDL e HoxLDL em macrófagos é dependente de PAF-R. A LoxLDL induz uma maior produção de IL-6 e IL-8. Já, a HoxLDL de TNF-a, IL-10 e TGF-b em macrófagos. Encontramos um peptídeo da ApoB-100 é capaz de aumentar o fluxo intracelular de cálcio, ativar a via das MAP quinases em monócitos humanos, induzindo a produção de IL-8. / The Low Density Lipoprotein (LDL) may undergo oxidative or enzymatic modifications, producing lipid or proteic compounds that interact with macrophages, contributing to inflammatory response in the atherosclerosis. Into the arterial intima, the macrophages interact with minimally modified LDL (LoxLDL) and with highly oxidized LDL (HoxLDL). Moreover, in the arterial intima, enzymes may induce cleavage of the apoB-100, releasing protein fragments, which may have biological effects on macrophages. In this study, we showed that modified forms of LDL interact with monocytes or macrophages, depending on oxidation degree. The expression of FcgRII-induced HoxLDL in macrophages is dependent on PPARg and part of the expression of CD36 induced by LoxLDL and HoxLDL in macrophages is dependent on PAF-R. In macrophages, LoxLDL induced higher production of IL-6 e IL-8, whereas HoxLDL induced TNF-a, IL-10 e TGF-b. Furthermore, we found one peptide from apoB-100 capable to increase calcium flux and activate MAP kinase pathway, inducing production of IL-8 in human monocytes.

A lipoproteína de baixa densidade (LDL) pode sofrer modificações, oxidativas ou enzimáticas, gerando compostos, lipídicos e proteicos, capazes de interagir com macrófagos, contribuindo para a resposta inflamatória presente na aterosclerose. Os macrófagos interagem tanto com LDL contendo baixo ou alto grau de oxidação (LoxLDL e HoxLDL) e também com fragmentos proteicos provenientes da ApoB-100, os quais podem exercer efeitos biológicos em macrófagos, contribuindo para a formação de células espumosas. Neste trabalho demonstramos que formas modificadas da LDL interagem com monócitos e/ou macrófagos, dependendo do grau de oxidação. A expressão de FcgRII por HoxLDL em macrófagos é dependente de PPARg. Parte da expressão de CD36 induzida por LoxLDL e HoxLDL em macrófagos é dependente de PAF-R. A LoxLDL induz uma maior produção de IL-6 e IL-8. Já, a HoxLDL de TNF-a, IL-10 e TGF-b em macrófagos. Encontramos um peptídeo da ApoB-100 é capaz de aumentar o fluxo intracelular de cálcio, ativar a via das MAP quinases em monócitos humanos, induzindo a produção de IL-8. / The Low Density Lipoprotein (LDL) may undergo oxidative or enzymatic modifications, producing lipid or proteic compounds that interact with macrophages, contributing to inflammatory response in the atherosclerosis. Into the arterial intima, the macrophages interact with minimally modified LDL (LoxLDL) and with highly oxidized LDL (HoxLDL). Moreover, in the arterial intima, enzymes may induce cleavage of the apoB-100, releasing protein fragments, which may have biological effects on macrophages. In this study, we showed that modified forms of LDL interact with monocytes or macrophages, depending on oxidation degree. The expression of FcgRII-induced HoxLDL in macrophages is dependent on PPARg and part of the expression of CD36 induced by LoxLDL and HoxLDL in macrophages is dependent on PAF-R. In macrophages, LoxLDL induced higher production of IL-6 e IL-8, whereas HoxLDL induced TNF-a, IL-10 e TGF-b. Furthermore, we found one peptide from apoB-100 capable to increase calcium flux and activate MAP kinase pathway, inducing production of IL-8 in human monocytes.

Ce travail concerne l'influence de la température sur la structure et la dynamique des protéines collectrices de lumière des bactéries pourpres dans leur environnement natif, les membranes intracytoplasmiques.<br />Pour mener à bien ces études, nous avons développé au laboratoire une approche de “calorimétrie fonctionnelle” dans les membranes intracytoplasmiques par des techniques de spectroscopie d'absorption, de dichroïsme circulaire et de Raman de résonance. Nous avons analysé l'effet de la température sur les propriétés spectrales de la protéine LH1 en utilisant les molécules de bactériochlorophylles comme marqueur naturel de l'assemblage des polypeptides transmembranaires, constituant l'anneau de LH1. Il existe dans la littérature de nombreuses études sur les processus d'auto-assemblage de ces protéines antennes, mais toutes réalisées après solubilisation en présence de détergent. C'est pourquoi nos études ont été réalisées sans ajout de détergent ou autres agents chaotrophes, mais directement sur les membranes intracytoplasmiques contenant la protéine LH1 surexprimée naturellement, dans le but de comparer les chemins de dissociation-réassociation de ces protéines selon qu'elles sont extraites ou non de leur milieu natif.<br />Nous avons montré que la variation de température autour de valeurs proches des conditions physiologiques révèle la dynamique de la structure des protéines LH1 et LH2. Ces résultats mettent en évidence l'existence d'un équilibre entre deux formes spectrales démontrant une flexibilité conformationnelle des protéines antennes dans leur environnement natif. <br /> A des températures élevées, nous montrons qu'il est possible de dissocier de manière réversible la protéine LH1, mais que le processus de dissociation et réassociation de la protéine suit un chemin différent de celui observé à partir de la protéine solubilisée.<br /> Ces études montrent l'importance des interactions entre bactériochlorophylles pour l'oligomérisation et le fonctionnement des protéines antennes dans leur “milieu naturel”

Major constituents of the venom of various animals are peptidogenic in nature. Marine snails belonging to the species Conus are venomous predators that use small, structurally constrained peptides present in their venom for prey capture and defense. It is known that ~500 Conus species are present in nature and the venom of each of these Conus species is a complex mixture of nearly 100 peptides accounting for > 50,000 peptides with little overlap among the different species. The peptides isolated from the venom of Conus species are commonly known as conotoxins or conopeptides. Some of the common targets of these peptides include the different ion channels like Na+, K+, and Ca2+, and receptor subtypes such as nicotinic acetylcholine and NMDA receptors. The ion channels and receptor subtypes were targeted by conopeptides with high degree of specificity and selectivity. The structural information on the peptides from cone snails can prove to be a valuable starting tool for the understanding of the function of different ion channels and hence in the design of neuropharmacologically active drugs. Conotoxins are disulfide-rich peptides and the number of disulfide generally ranges from two to five. Based on the arrangement of cysteines in their primary sequence, they are classified into different superfamilies. The signal sequences of the precursors belonging to a particular superfamily are highly conserved and hence the members within the same family have, in common, the unique disulfide arrangement and pharmacological activity. Conotoxins are classified into eleven superfamilies till date. In order to understand the underlying the principles involved in the action of these peptides on different ion channels, one needs to know the three-dimensional structures which, in potential, will help in the identification of the pharmacophores responsible for the observed pharmacological activity. With the aim of studying the structure-activity relationships found among the conotoxins, we have initiated a study on the peptides isolated from the marine snails found in the Indian coastal waters. This thesis is focused in the structural studies of the peptide toxins from marine cone snails and a terrestrial scorpion. The tool used for the structural studies of these peptide toxins is Nuclear Magnetic Resonance Spectroscopy. Chapter 1 provides an overview of the peptide toxins found among various animal species with more emphasis on conotoxins and scorpion toxins. In addition, the rationale behind the present study has also been explained. Chapter 2 describes the structure determination of two conopeptides isolated from Conus amadis, δ-Am2766 and Am2735, which are active on mammalian sodium channels. The structural aspects and comparison with other known conopeptides belonging to the same superfamily as that of these two peptides have also been described. Solution NMR studies of Ar1446 and Ar1248, two conopeptides isolated from the species Conus araneosus have also been studied using Homonuclear NMR methods. Ar1446 is a three disulfide-bonded peptide. Our studies have revealed that this peptide has a novel disulfide connectivity not previously observed in the M superfamily or any other superfamily of conotoxins. The structural features of Ar1446 will be described along with the NMR studies on two-disulfide bonded peptide, Ar1248, belonging to the A-superfamily of conotoxins. The main problem faced in the kind of study of peptides isolated from natural sources is the amount that can be isolated and purified to homogeneity. In order to obtain large quantities of peptides, we have successfully used Cytochrome b5 as fusion host to clone, over express and purify these peptides using recombinant methods. The use of recombinant methods has aided in the preparation of isotopically enriched peptides. The use of cyt b5 as fusion host for the large scale production of some of the peptides from Indian marine snails is described in Chapter 4. A novel pharmacologically active linear peptide, Mo1659 isolated from Conus monile, have been studied using Heteronuclear NMR methods. This peptide was cloned, over expressed and purified using Cytochrome b5 as a fusion host. Another linear peptide, Mo1692 (also from Conus monile), has been prepared using the same method and was studied using Homonuclear NMR methods. Both these peptides were liberated from the fusion host using cyanogen bromide cleavage and were subsequently purified using RP-HPLC. The results of the biosynthetic preparation and NMR studies of these two peptides have been described in Chapter 5. Chapter 6 describes the solution structure determination of a novel scorpion toxin characterized in the venom of the Indian red scorpion Buthus tamulus. The cloning, over expression, folding and purification of BTK-2 is described here. The structure and the function of this recombinantly produced BTK-2 will also be described.

The cellular response to a biomaterial, such as a dental implant, is mainly governed by the surface properties, and can thus be altered by the introduction of a surface coating. In this thesis the buildup of a biomacromolecule-based coating formed by layerby-layer (LbL) deposition of the charged polypeptides poly(L-lysine) (PLL) and poly(L-glutamic acid) (PGA) has been studied. In an attempt to make these coatings bioactive and useful for bone-anchored implants, an amelogenin protein mixture (EMD), has been immobilized in these thin polyelectrolyte multilayer (PEM) films. Multilayers were also built by LbL deposition of the natural biomacromolecules collagen (Col) and hyaluronic acid (HA). Multilayer films of these two extra-cellular biomacromolecules should be of interest for use as a scaffold for tissue engineering. The buildup of the multilayer films has been followed in situ, using ellipsometry, quartz crystal microbalance with dissipation (QCM-D), and dual polarization interferometry (DPI). The studied PLL/PGA multilayers were found to be highly hydrated, and to exhibit a two-regime buildup behavior, with an initial “slow-growing” regime, and a second “fast-growing” regime with a linear growth in film thickness and more than linear growth in mass. A net diffusion of polypeptides into the film during the buildup led to an increase in density of the films for each layer adsorbed. A change in density was also observed in the Col/HA film, where HA penetrated and diffused into the porous fibrous Col network. The formed PLL/PGA films were further found to be rather stable during drying, and post-buildup changes in temperature and pH, not losing any mass as long as the temperature was not raised too rapidly. The film thickness responded to changes in the ambient media and collapsed reversibly when dried. A swelling/de-swelling behavior of the film was also observed for changes in the temperature and pH. The EMD protein adsorbed to silica surfaces as nanospheres, and could by itself form multilayers. The adsorption of EMD onto PLL/PGA multilayer films increased at lower pH (5.0), and EMD could be immobilized in several layers by alternate deposition of EMD and PGA. / QC 20101019