La recherche sur le cancer s'oriente vers le développement de « stratégies ciblées » comme la vectorisation de composés actifs permettant d'augmenter l'efficacité thérapeutique et de réduire la toxicité du traitement. Dans ce contexte, ces travaux ont été consacrés à la conception de vecteurs peptidiques pour des applications anticancéreuses. Ces systèmes ont été élaborés à partir d'un châssis moléculaire cyclodécapeptidique présentant des propriétés conformationnelles particulières. Deux approches différentes ont été envisagées. La première a consisté à rechercher de nouveaux ligands de récepteurs tumoraux en s'inspirant du domaine de reconnaissance d'un anticorps monoclonal thérapeutique. Dans ce contexte, nous proposons la conception de mime du Rituximab ciblant l'antigène CD20 utilisé dans le traitement des lymphomes Non-Hodkinien. Dans la seconde approche, nous avons développé des vecteurs destinés à des applications d'imagerie tumorale. Pour cela, des châssis multivalents présentant des ligands peptidiques RGD ciblant l'intégrine alpha-v-beta-3 ont été conjugués avec différents agents de détection puis évalués par techniques d'imagerie TEP, IRM et imagerie optique. Dans ces deux stratégies, les systèmes de vecteurs sont constitués d'un domaine de reconnaissance présentant un ou plusieurs ligands, et d'un module effecteur composé d'un élément de détection, le tout assemblé sur le châssis moléculaire. Nous nous sommes donc intéressés à développer des procédures d'assemblages biomoléculaires permettant de moduler les sites d'accrochages du châssis. Pour cela, nous avons mis au point des méthodologies de synthèse originales combinant plusieurs ligations chimiosélectives orthogonales. On démontrera que cette stratégie offre de multiples avantages et permet un assemblage macromoléculaire en une seule étape sans déprotection ni purification intermédiaire.

Assembly of the extracellular matrix (ECM) protein fibronectin (FN) is a mechanical process that involves cell binding to FN through cell surface integrin receptors and application of tensional forces generated in the cell's contractile actin cytoskeleton. Deformation-induced exposure of cryptic sites, defined as buried molecular recognition sites, in FN has been proposed as a mechanism by which cell tension drives FN fibrillogenesis. The primary integrin attachment site on FN is the RGD loop in the 10FNIII domain. In this thesis, I set out to define the molecular biophysical mechanism by which cell tension application at the RGD site promotes unfolding and thereby induces FN-FN self-assembly leading to matrix fibril formation. Chapter 1 of this dissertation provides an overview of the current knowledge behind the biophysical and molecular basis of FN assembly in the ECM and its key role in development and disease. In Chapter 2, steered molecular dynamic simulations show that the 10FNIII domain under force applied through its N-terminus and RGD loop (N-to-RGD) unfolds to a preferred kinetic intermediate with solvent-exposed N-terminal hydrophobic residues in a manner different from past analyses in the literature where force through the N- and C- termini leads to multiple unfolding pathways. Use of single-molecule atomic force spectroscopy in Chapter 3 experimentally reveals that a mechanically stable intermediate of 10FNIII exposed by N-to-RGD pulling shows a length extension that agrees with the predicted kinetic intermediate. Results of biochemical and cellular studies using synthetic peptides with sequences from the 10FNIII intermediate show in Chapter 4 that the twenty-three amino acid sequence that spans the unraveled N-terminus of the predicted intermediate mediates FN multimerization and contains a minimal seven amino acid sequence we call the multimerization motif that is sufficient to induce FN-FN multimer assembly. Finally, Chapter 5 summarizes the new insights supported by this work regarding the role that mechanical forces applied at the cell binding site in 10FNIII plays in the physiological unfolding of FN with respect to FN fibrillogenesis and ECM assembly.

Diamond is a promising material with unique chemical properties. In this thesis, nano-scale diamond quantum size effects were investigated using several chemical property indicators. The results show that the chemical properties are strongly dependent on size for film thicknesses smaller than 1 nm (1D), and for nanodiamond particle diameters less than 2 nm (3D). When the sizes exceed these ranges there are no longer any quantum effects. The influence of surface termination coverage on the surface chemical properties has been calculated for the 2×1 reconstructed diamond (100) surface and for the diamond (111) surface. The terminating species included COOH and NH2 groups, which both are beneficial for the immobilization of biomolecules. The results of the calculations show that it is energetically possible to terminate the diamond surfaces up to 100% with NH2, while it is only possible to cover the surfaces up to 50% with COOH species. The reason for the latter result is most probably the larger sterical hindrance amongst the adsorbates. Both types of termination species were shown to influence the diamond surface electronic properties (e.g., HOMO/LUMO levels). In order to extend the diamond utility for biomedical applications, especially implant design, interactions of various growth factors with the diamond surfaces were also simulated. For non-solvent diamond-biomolecule systems, the results show that adhesion affinities are strongly dependent on biomolecule molecular weights. When including a water based solvent in the systems, the results show good physisorption affinities between proteins and diamond. Proteins structures, before and after physisorption, were visualized, and further investigated with respect to electrostatic properties and functional groups. By comparing the biomolecular structural changes during the adhesion processes, it can be concluded that both the general structures, as well as the binding pocket structures, were kept intact after the adhesion to the diamond surfaces (regardless of the adhesion affinities). In addition, the surface electronic potential distributions were maintained, which indicate preserved biomolecule functionalities. / Vascubone

Regensburg, Univ., Diss., 2003. / Erscheinungsjahr an der Haupttitelstelle: 2003.

A falha por descompressão rápida de gás (Rapid Gas Decompression, RGD) de o’rings elastoméricos assume a forma de trincas, bolhas e cisões, apresentandose após a queda da pressão à qual o selo está exposto. A resistência à RGD tem um papel fundamental nas especificações dos materiais elastoméricos para a indústria do petróleo e gás. No presente trabalho foi desenvolvida uma bancada para ensaios de qualificação de o’rings elastoméricos para testes de resistência por RGD seguindo a norma ISO 23936-2. Para avaliar o desempenho da bancada, quatro ensaios foram realizados utilizando o’rings comerciais com e sem certificado para RGD. A análise das curvas de ensaio evidencia que os parâmetros de ensaio foram atingidos satisfatoriamente. Além disso, taxas lineares de descompressão foram atingidas utilizando um método manual, não obstante uma relevante proposta de melhora é apresentada. / Rapid gas decompression (RGD) damage of elastomeric o’ring seals is the structural failure in the form of blistering, internal cracking and splitting caused upon the release of the pressure the seals are exposed to. RGD resistance plays a key role in the specifications of these components for the oil & gas industry. During this work a test bench was developed for qualification of o’rings RGD resistance according to wellknown international standard ISO 23936-2. In order to evaluate the test bench’s performance, four tests were carried out using o’rings with and without RGD qualification certificates. Analysis of test curves show that test parameters were attained satisfactorily. Furthermore, adequate linear decompression processes were achieved using a manual method, nonetheless a relevant improvement is proposed.

Hidrogéis são redes poliméricas tridimensionais ligadas entre si por reticulações químicas ou físicas, e podem absorver água ou fluidos biológicos. A estrutura permite que estes materiais tenham altos níveis de hidrofilicidade e biocompatibilidade, que em conjunto com as demais propriedades, fazem com que os hidrogéis sejam vistos como promissores biomateriais. Devido a estas características, hidrogéis possuem diversas aplicações voltadas as áreas médica e farmacêutica. Alguns hidrogéis apresentam um comportamento responsivo a variações de alguma condição do ambiente, são os chamados hidrogéis responsivos ou hidrogéis inteligentes. Neste trabalho foi escolhido o polímero poli (vinil álcool) funcionalizado com o tripeptídeo RGD. A investigação foi desenvolvida através de simulações de dinâmica molecular a fim de primeiramente observar a formação do hidrogel. Para então observar a influência do tripeptídeo, da temperatura e do pH na capacidade do polímero de absorver água e em sua estrutura. Para isso, foram realizadas análises de desvio quadrático médio estrutural, raio de giro e ligações de hidrogênio. As análises de função de distribuição radial mostraram indícios da formação de ligações de hidrogênio, tanto de interações intramolecular como intermolecular. Enquanto as demais análises mostraram que pode ocorrer comportamento responsivo para a temperatura de 310 K. Quando a pH do meio passa de neutro para ácido, ocorrem mudanças nas ligações de hidrogênio e na estrutura. Estudos experimentais de hidrogéis ainda possuem algumas limitações, visto que certas características do material não podem ser determinadas com precisão. Através de métodos computacionais medidas como a quantidade e localização de reticulações e de peptídeo podem ser determinadas. Assim, estudos computacionais prévios ou posteriores podem ajudar a esclarecer dados obtidos experimentalmente. / Hydrogels are three-dimensional polymeric network crosslinked to each other by chemical or physical crosslinks, and can imbibe water or biological fluids. The materials structure allows it to have high levels of hydrophilicity and biocompatibility, which together with the other properties make them promising biomaterials. Due to these two characteristics hydrogels have numerous biomedical and pharmaceutical applications. Some hydrogels have a responsive behavior due to changes in their environment, the so-called stimuli-responsive hydrogels, or “smart” hydrogels. For this work the poli(vinyl alcohol) polymer functionalized with RGD peptide was chosen. The work was developed using molecular dynamics simulations in order to observe the hydrogel formation and also the influence of tripeptide, temperature and pH in water imbibe capacity and polymer structure. For this analysis of root-mean-square deviation, radius of gyration and radial distribution function was performed. The analysis of radial distribution function showed signs of hydrogen bond formation of both intramolecular and intermolecular interactions. Other analysis showed that thermoresponsive behavior may occur for 310 K. When the environment pH value is modified from neutral to acidic, changes occur in hydrogen bonds and structure. Experimental studies of hydrogels have some limitations because some characteristics of the material can’t be precisely determinated. With computational methods the amount and the location of crosslinks and peptide can be determinated. Therefore, previous or posterior computational studies can help to elucidate experimental data.

A falha por descompressão rápida de gás (Rapid Gas Decompression, RGD) de o’rings elastoméricos assume a forma de trincas, bolhas e cisões, apresentandose após a queda da pressão à qual o selo está exposto. A resistência à RGD tem um papel fundamental nas especificações dos materiais elastoméricos para a indústria do petróleo e gás. No presente trabalho foi desenvolvida uma bancada para ensaios de qualificação de o’rings elastoméricos para testes de resistência por RGD seguindo a norma ISO 23936-2. Para avaliar o desempenho da bancada, quatro ensaios foram realizados utilizando o’rings comerciais com e sem certificado para RGD. A análise das curvas de ensaio evidencia que os parâmetros de ensaio foram atingidos satisfatoriamente. Além disso, taxas lineares de descompressão foram atingidas utilizando um método manual, não obstante uma relevante proposta de melhora é apresentada. / Rapid gas decompression (RGD) damage of elastomeric o’ring seals is the structural failure in the form of blistering, internal cracking and splitting caused upon the release of the pressure the seals are exposed to. RGD resistance plays a key role in the specifications of these components for the oil & gas industry. During this work a test bench was developed for qualification of o’rings RGD resistance according to wellknown international standard ISO 23936-2. In order to evaluate the test bench’s performance, four tests were carried out using o’rings with and without RGD qualification certificates. Analysis of test curves show that test parameters were attained satisfactorily. Furthermore, adequate linear decompression processes were achieved using a manual method, nonetheless a relevant improvement is proposed.

Hidrogéis são redes poliméricas tridimensionais ligadas entre si por reticulações químicas ou físicas, e podem absorver água ou fluidos biológicos. A estrutura permite que estes materiais tenham altos níveis de hidrofilicidade e biocompatibilidade, que em conjunto com as demais propriedades, fazem com que os hidrogéis sejam vistos como promissores biomateriais. Devido a estas características, hidrogéis possuem diversas aplicações voltadas as áreas médica e farmacêutica. Alguns hidrogéis apresentam um comportamento responsivo a variações de alguma condição do ambiente, são os chamados hidrogéis responsivos ou hidrogéis inteligentes. Neste trabalho foi escolhido o polímero poli (vinil álcool) funcionalizado com o tripeptídeo RGD. A investigação foi desenvolvida através de simulações de dinâmica molecular a fim de primeiramente observar a formação do hidrogel. Para então observar a influência do tripeptídeo, da temperatura e do pH na capacidade do polímero de absorver água e em sua estrutura. Para isso, foram realizadas análises de desvio quadrático médio estrutural, raio de giro e ligações de hidrogênio. As análises de função de distribuição radial mostraram indícios da formação de ligações de hidrogênio, tanto de interações intramolecular como intermolecular. Enquanto as demais análises mostraram que pode ocorrer comportamento responsivo para a temperatura de 310 K. Quando a pH do meio passa de neutro para ácido, ocorrem mudanças nas ligações de hidrogênio e na estrutura. Estudos experimentais de hidrogéis ainda possuem algumas limitações, visto que certas características do material não podem ser determinadas com precisão. Através de métodos computacionais medidas como a quantidade e localização de reticulações e de peptídeo podem ser determinadas. Assim, estudos computacionais prévios ou posteriores podem ajudar a esclarecer dados obtidos experimentalmente. / Hydrogels are three-dimensional polymeric network crosslinked to each other by chemical or physical crosslinks, and can imbibe water or biological fluids. The materials structure allows it to have high levels of hydrophilicity and biocompatibility, which together with the other properties make them promising biomaterials. Due to these two characteristics hydrogels have numerous biomedical and pharmaceutical applications. Some hydrogels have a responsive behavior due to changes in their environment, the so-called stimuli-responsive hydrogels, or “smart” hydrogels. For this work the poli(vinyl alcohol) polymer functionalized with RGD peptide was chosen. The work was developed using molecular dynamics simulations in order to observe the hydrogel formation and also the influence of tripeptide, temperature and pH in water imbibe capacity and polymer structure. For this analysis of root-mean-square deviation, radius of gyration and radial distribution function was performed. The analysis of radial distribution function showed signs of hydrogen bond formation of both intramolecular and intermolecular interactions. Other analysis showed that thermoresponsive behavior may occur for 310 K. When the environment pH value is modified from neutral to acidic, changes occur in hydrogen bonds and structure. Experimental studies of hydrogels have some limitations because some characteristics of the material can’t be precisely determinated. With computational methods the amount and the location of crosslinks and peptide can be determinated. Therefore, previous or posterior computational studies can help to elucidate experimental data.

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