Este trabalho teve como objetivo estudar a interação de polimetacrilato com vesículas de metacrilato de dioctadecildimetílamônio (DODAM) e brometo de dioctadecildimetilamônio (DODAB). A fotoirradiação de vesículas de DODAM a formou polimetacrilato na superfície vesicular do polímero, através da polimerização do contra-íon. Vesículas polimerizadas foram mais estáveis frenta á adição de metanol do que vesículas não polimerizadas. A estabilização da bicamada vesicular foi confirmada com o aumento da retenção da carboxifluoresceína (CF). Vesículas injetadas de DODAM retiveram cerca de 25% de CF, enquanto que vesículas polimerizadas retiveram cerca de 75%. Experimentos de temperatura de transição de fase por turbidez e tensão superfícial mostraram que o polimetacrilato formado na superfície vesicular diminui a temperatura de transição de fase e reduz a cooperatividade. A interação de fosfatase alcalina (Fal) com vesículas de DODAM e colinametacrilato de dicetilfosfato (DCM) foi estudada, como um primeiro passo para a construção de um micro-reator. Foi observada a precipitação na presença de DODAM, mas não em presença de DCM. Isto pode ser explicado pela forte interação entre a superfície de vesículas de dioctadecildimetilamônio (bicamada com carga negativa) com a fosfatase alcalina (carga negativa). Esta precipitação não foi observada com vesículas de DCM (bicamada negativa). Experimentos de monocamada confirmaram estes resultados. DCM e DODAM formaram monocamadas mistas estáveis, sugerindo que vesículas mistas poderiam ser usadas para superar as interações eletrostáticas fortes entre os surfactantes e a enzima. / This work had as objective studying the interaction of polymethacrylate with dioctadecyldimethylammonium methacrylate (DODAM) and brornide (DODAB). The fotoirradiation of vesicular suspensions of DODAM formed polymethacrylate on the vesicle surface though counter-ion polymerization. Polymerized vesicles were more stables on methanol addition than non-polymerized vesicles. Bilayer stability was confirmed with the retention of carboxyfluorescein (CF). DODAM injected vesicles without polymerization retained about 25% of CF, while polymerized DODAM retained about 75%. Experiments of phase transition temperature by turbidity and surface tension showed that polymethacrylate formed at vesicle surface drops phase transition temperature and reduces cooperativity. Polymethacrylic acid and polymethacrylic acid containing rodhamine B covalently linked was used to monitor polymer-vesicle interaction. Experiments showed that the polymer interacts electrostatically with the DODAB bilayer, causing precipitation and or aggregation. The polymer, initially on a confonnation with many hipercoiled hydrophobic regions, opens as interacts with DODAB vesicles. The interaction of alkaline phosphatase (Fal) with vesicles of DODAM and colina-methacrylate dicetylphosphate (DCM) was studied, as a preliminary step for a micro-reactor construction. Precipitation was observed in presence of DODAM, but not in presence of DCM. This may be explained by the strong interaction between the surface of dioctadecyldimethy lammonium vesicles (positive charged bylayer) with Fal (negative charge). This precipitation was not observed with DCM vesicles (negative charged bilayer). Monolayer experiments confirm these results. Experiments showed that DCM and DODAM form stabled mixed monolayers. Suggesting that mixed vesicles could be tried to overcome strong electrostatic interactions between surfactants and enzyme.

A classificação é uma tarefa do aprendizado de máquina e mineração de dados, na qual um classificador é treinado sobre um conjunto de dados rotulados de forma que as classes de novos itens de dados possam ser preditas. Tradicionalmente, técnicas de classificação trabalham por definir fronteiras de decisão no espaço de dados considerando os atributos físicos do conjunto de treinamento e uma nova instância é classificada verificando sua posição relativa a tais fronteiras. Essa maneira de realizar a classificação, essencialmente baseada nos atributos físicos dos dados, impossibilita que as técnicas tradicionais sejam capazes de capturar relações semânticas existentes entre os dados, como, por exemplo, a formação de padrão. Por outro lado, o uso de redes complexas tem se apresentado como um caminho promissor para capturar relações espaciais, topológicas e funcionais dos dados, uma vez que a abstração da rede unifica a estrutura, a dinâmica e as funções do sistema representado. Dessa forma, o principal objetivo desta tese é o desenvolvimento de métodos e heurísticas baseadas em teorias de redes complexas para a classificação de dados. As principais contribuições envolvem os conceitos de conformidade de padrão, caracterização de importância e otimização estrutural de redes. Para a conformidade de padrão, onde medidas de redes complexas são usadas para estimar a concordância de um item de teste com a formação de padrão dos dados, é apresentada uma técnica híbrida simples pela qual associações físicas e topológicas são produzidas a partir da mesma rede. Para a caracterização de importância, é apresentada uma técnica que considera a importância individual dos itens de dado para determinar o rótulo de um item de teste. O conceito de importância aqui é definido em termos do PageRank, algoritmo usado na engine de busca do Google para definir a importância de páginas da web. Para a otimização estrutural de redes, é apresentado um framework bioinspirado capaz de construir a rede enquanto otimiza uma função de qualidade orientada à tarefa, como, por exemplo, classificação, redução de dimensionalidade, etc. A última investigação apresentada no documento explora a representação baseada em grafo e sua habilidade para detectar classes de distribuições arbitrárias na tarefa de difusão de papéis semânticos. Vários experimentos em bases de dados artificiais e reais, além de comparações com técnicas bastante usadas na literatura, são fornecidos em todas as investigações. Em suma, os resultados obtidos demonstram que as vantagens e novos conceitos propiciados pelo uso de redes se configuram em contribuições relevantes para as áreas de classificação, sistemas de aprendizado e redes complexas. / Data classification is a machine learning and data mining task in which a classifier is trained over a set of labeled data instances in such a way that the labels of new instances can be predicted. Traditionally, classification techniques define decision boundaries in the data space according to the physical features of a training set and a new data item is classified by verifying its relative position to the boundaries. Such kind of classification, which is only based on the physical attributes of the data, makes traditional techniques unable to detect semantic relationship existing among the data such as the pattern formation, for instance. On the other hand, recent works have shown the use of complex networks is a promissing way to capture spatial, topological and functional relationships of the data, as the network representation unifies structure, dynamic and functions of the networked system. In this thesis, the main objective is the development of methods and heuristics based on complex networks for data classification. The main contributions comprise the concepts of pattern conformation, data importance and network structural optimization. For pattern conformation, in which complex networks are employed to estimate the membership of a test item according to the data formation pattern, we present, in this thesis, a simple hybrid technique where physical and topological associations are produced from the same network. For data importance, we present a technique which considers the individual importance of the data items in order to determine the label of a given test item. The concept of importance here is derived from PageRank formulation, the ranking measure behind the Googles search engine used to calculate the importance of webpages. For network structural optimization, we present a bioinspired framework, which is able to build up the network while optimizing a task-oriented quality function such as classification, dimension reduction, etc. The last investigation presented in this thesis exploits the graph representation and its hability to detect classes of arbitrary distributions for the task of semantic role diffusion. In all investigations, a wide range of experiments in artificial and real-world data sets, and many comparisons with well-known and widely used techniques are also presented. In summary, the experimental results reveal that the advantages and new concepts provided by the use of networks represent relevant contributions to the areas of classification, learning systems and complex networks.

Existe, na América Latina, um paradoxo de inversão entre as conquistas democráticas, que tendem a ampliar e incluir os cidadãos, e a dinâmica de sociedades que historicamente produziram grandes desigualdades, levando ao aprofundamento da exclusão e à negação da cidadania inscrita nas regras dos direitos políticos e sociais auto-regulados. O que significa que o encaminhamento da questão social e da pobreza pressupõe considerar as variáveis das políticas societais, através das quais os Estados se vêem obrigados a (re)construírem instituições para acesso e/ou alternativas de oportunidade social, em beneficio da maioria. Dentro da análise comparativa, esta pesquisa analisa como no Brasil e na Argentina se constroem os arcabouços de formação dos cidadãos (e da cidadania), em tanto que instituição social. Diante do fenômeno cada vez mais abrangente das desigualdades e à medida que os conceitos de cidadania e sociedade civil dizem respeito aos campos de atuação de forças políticas em relação ao local (território) e ao campo social de origem, a pesquisa se centra na análise comparativa de dois programas oficiais de combate à pobreza: Bolsa Família (Brasil) e Plan Jefes y Jefas del Hogar Desocupados (Argentina) e seus resultados. Trata-se de período em que a questão social e a realidade da exclusão assumiram novas dimensões, exigindo medidas mais eficazes de combate à pobreza. O projeto centra na análise do enquadramento sistêmico macro e micro-sociológico dos agentes envolvidos, buscando desvendar as correlações de força, tensões e contradições das visões dos dois programas, e as estratégias de sobrevivência dos excluídos, analisando os conceitos, processos e teorizações dos discursos sobre a questão social, em contraste com as ações e práticas dos governos selecionados. A metodologia se articula em torno da composição documental dos dois programas e observação analítica dos dados primários e secundários de fontes oficiais, mapeamento e entrevista de agentes atuantes e outros documentos complementares à apreensão dos programas analisados. / There is in Latin America an inversion paradox in the terrain of democratic conquests that has tried to include its citizens into the Substantive Rights and a society dynamics that in its History, has produced huge inequalities deepening the exclusions, and denying the citizenship concerning its self-regulated Political and Social Rights. It does concerns the ways of facing the social question to the poverty condition foresee considering several social policies through where States seen forced to re-build its institutional access and/or creating social and alternative opportunities to the majority of its excluded population. This research centers the investigation in a comparative study of two official social programs (monetary transference programs) to fight poverty: Bolsa Família and Plan Jefes y Jefas del Hogar Desocupado (Argentina) and its results, facing the phenomena more all-purpose of inequality and as the citizenship and civil society concepts connect to its broad social fields of political sources, in connection to the local (territory), and also, its specific aspects, in contrast with official speeches and contradiction actions, also its correlated tensions. The monetary transference programs concerns the period where exclusion in the two countries increased, assuming new dimensions, and demanding more effect measures to fight poverty. The investigation centers the analysis of a systemic institution role reflecting the macro and micro sociological aspects concerning the agents involved into different states and in different governmental levels through the analytic and criticized view, mapping the internal circuits, actors involved in this process, its discursiveness through selected programs documents, primary and secondary sources of the socio-political field study.

O objetivo do experimento foi avaliar o desempenho e a qualidade da carcaça de novilhos superprecoces submetidos a alturas de manejo de pastos de aveia preta e azevém anual (10, 20, 30 e 40 cm) e uma testemunha sem pastejo, bem como avaliar os efeitos dessas alturas de manejo sobre o estabelecimento e o rendimento da cultura de soja subseqüente. O experimento foi realizado na Fazenda do Espinilho, município de Tupanciretã, entre julho de 2004 e maio de 2005. Animais jovens com idade média de dez meses e peso inicial de 190 kg foram distribuídos num delineamento experimental de blocos ao acaso, com três repetições. As ofertas diárias de forragem para os tratamentos 10, 20, 30 e 40 cm foram, respectivamente, 8,8, 14,7, 29,0 e 48,9 kg de matéria seca/100 kg de peso vivo (PV). O ganho de peso por hectare foi superior nos tratamentos com menor altura de manejo, em decorrência da maior carga animal empregada, sendo 529,7, 489,5, 320,9 e 201,6 kg de PV/ha, para os respectivos tratamentos. O ganho médio diário e peso ao abate apresentaram resposta quadrática (P<0,05) conforme o incremento na altura do pasto. A deposição de gordura apresentou média de 3,8 mm e o rendimento médio de carcaça fria foi de 53,3% (P<0,05). As alturas reais do pasto ficaram próximas daquelas pretendidas, havendo um aumento linear da massa de forragem com o aumento das alturas de manejo do pasto. A taxa de acúmulo não foi afetada pelos tratamentos. A taxa de lotação apresentou resposta linear decrescente com o aumento da altura do pasto. A massa de forragem remanescente aumentou na medida em que houve incremento na altura de manejo do pasto. Foi observada diferença entre os tratamentos para palhada residual e estande inicial de plantas de soja, porém, essas diferenças não afetaram o rendimento de grãos da cultura. Concluiu-se que novilhos superprecoces atingem peso de abate e grau de acabamento adequados quando terminados em pastagem de inverno e suplementados no terço final do ciclo de pastejo. O melhor ganho médio diário foi obtido em altura entre 25 a 30 cm e a maior produção por área em 10 cm de altura. A utilização de pastos durante o inverno não prejudica o rendimento de grãos na cultura de soja subseqüente, possibilitando aumento da renda do produtor pela oportunidade de gerar receitas durante a entressafra da soja. / This trial aimed to evaluate the performance and carcass quality of “superprecoce” steers grazing oat and annual ryegrass pastures managed at 10, 20, 30 and 40 cm with a no grazing reference, as well as sward height management effects on soybean establishment and grain yield. The experiment was carried at Fazenda do Espinilho, Tupanciretã municipality, from July 2004 until May 2005. Young animals with 10 months on average and initial live weight of 190 kg were distributed in a randomized block design with three replicates. The daily herbage allowances were 8.8, 14.7, 29.0 and 48.9 kg of dry matter/100kg of live weight, respectively treatments. The live weight gain per hectare was superior in treatments with lower management heights, due to the greater stocking rate employed, being 529.7, 489.5, 320.9 and 201.6 kg of LW, respectively for the treatments 10, 20, 30 and 40cm height. The average daily gain and slaughter weight increased with pasture height being fitted by a quadratic model (P<0.05). The fat deposition and the medium dressing of cold carcass averaged 3.8mm and 53.3%, respectively (P<0.05). The actual sward heights were very similar to those previously intended. There was a linear increase in herbage mass with the increase of sward height. The pasture accumulation rate was not influenced by treatments. The stocking rate showed a decreased linear response with increasing sward height. Post grazing herbage mass increased with increasing sward height. Treatments had effect on initial soybean stand, but not in soybean yield. It was concluded that “superprecoce” steers can reache slaughter weight and adequately finishing degree when finished in winter cultivated pasture supplemented in final third of the grazing cycle. Better individual animal performance is obtained when pasture height ranges from 25 to 30 cm and animal production per hectare when the pasture was managed at 10 cm height. Results suggest grazing animals do not damage succeeding soybean crop, allowing farmers profitability enhancement during soybean intercropping.

The β-acyloxyalkyl radical rearrangement has been known since 1967 but its mechanism is still not fully understood, despite considerable investigation. Since the migration of a β-trifluoroacetoxy group generally proceeds more rapidly and with more varied regiochemistry than its less electronegative counterparts, this reaction was studied in the hope of understanding more about the subtleties of the mechanism of the β- acyloxyalkyl radical rearrangement. The mechanism of the catalysed rearrangement of Nalkoxy- 2(1H)-pyridinethiones was also explored because preliminary studies indicated that the transition state (TS) for this process was isoelectronic with TSs postulated for the β-acyloxyalkyl radical and other novel rearrangements. ¶ A kinetic study of the rearrangement of the 2-methyl-2-trifluoroacetoxy-1-heptyl radical in solvents of different polarity was undertaken using a radical clock method. Arrhenius equations for the rearrangement in each solvent were: hexane, log10[kr (s-1)] = 11.8±0.3 – (48.9±0.7)/ θ; benzene, log10[kr (s-1)] = 12.0±0.2 – (43.7±0.8)/ θ; and propionitrile, log10[kr (s-1)] = 11.9±0.2 – (42.0±0.3)/ θ. Rate constants at 75˚C were: hexane, kr = 2.9 × 104; benzene, kr = 2.8 × 105; and propionitrile, kr = 4.0 × 105 s-1. The equilibrium constant for the reversible rearrangement at 80°C in benzene was 15.1 <K < 52.9. ¶ A regiochemical study with oxygen-labelled radicals revealed that trifluoroacetoxy group migration occurs with 66-83% label transposition (3,2 shift). The proportion of 3,2 shift is decreased by polar solvent, high temperature and low concentration of the reducing agent. Results of labelling experiments were consistent with cooperative 1,2 and 3,2 shifts, the former having Ea 9.5 kJmol-1 higher than the latter in benzene solution. ¶ An esr study of nine β-oxygenated radicals revealed that the temperaturedependent equilibrium conformation is controlled by a balance between steric and stereoelectronic effects. The influence of the latter is increased by electron-attracting β- substituents. Barriers to C α–C β rotation in β-oxyethyl radicals are approximately the same as for the propyl radical. Consequently, there is no significant through-space interaction between the β-substituent and the unpaired electron. ¶ Experimental results were consistent with a mechanism involving a combination of polarized 1,2 and 3,2 concerted shifts. The results may also be rationalised by the intermediacy of a contact ion pair, as well as combinations of the three options. ¶ The rearrangement of N-alkoxy-2(1H)-pyridinethiones is catalysed by oxidants, Lewis acids and protic acids. Pseudo first order kinetics are observed and there are moderate solvent effects. The migration of a 1,1-dideuteroallyl group occurs almost exclusively in a 1,4 sense. Migration of an enantiomerically enriched 1-phenylethyl group proceeds with predominant retention of configuration in chloroform, but with virtual racemisation in acetonitrile. Migrating groups do not become diffusively free during the rearrangement. Substituents which stablise positive charge at C1 migrate more rapidly. The bulk of evidence indicates that a catalyst activates the pyridinethione for rearrangement by promoting aromatisation. Mass-spectrometric analysis of an isolated intermediate and kinetic results are consistent with an intermolecular mechanism.

<p>This study addresses the issue of how to convert peptides into drug-like non- peptides with retained biological activities at peptide receptors. Angiotensin II (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe, Ang II) was used as a model peptide. </p><p>Knowledge of the bioactive conformations of endogenous peptides is invaluable for the conversion of peptides into less peptidic analogues. Effectively constrained cyclic analogues, with retained pharmacological activities, may provide valuable information about the bioactive conformations of the peptide in question. </p><p>This thesis describes the development of synthesis for a number of protected, aldehyde-functionalized building blocks for standard solid phase peptide synthesis, and their use for the preparation of cyclic peptide analogues. The effect of variations in the side-chain lengths of the building blocks, on the outcome of the cyclizations was studied. Incorporation of a building block derived from L-aspartic acid afforded bicyclization towards the C-terininal end of the peptide, while for the corresponding L-glutamic acid derived building block, N-terminal directed bicyclization was achieved. A building block derived from L-2-aminoadipic acid was exploited for monocyclization furnishing <i>cis-</i> and <i>trans-</i> vinyl sulfide bridged peptide analogues. </p><p>The described cyclization methods have been applied to the synthesis of a number of conformationally constrained Ang II analogues, for which the pharmacological properties have been evaluated. Two of the Ang II analogues synthesized displayed high affinities and full agonist activities at the AT₁ angiotensin receptor, and have proven to be useful tools in the search for the bioactive conformation of Ang II.</p>

La première partie de ce manuscrit est consacrée à l'inhibition des glycosidases. Ces enzymes sont impliquées dans de très nombreux processus biologiques et, par voie de conséquence, dans de nombreuses maladies (diabète, cancer, maldadies lysosomales etc...). Outre l'intérêt de développer de nouveaux médicaments, les glycosides hydrolases font aussi figure de cibles de choix pour étudier les itinéraires conformationnels au cours de l'hydrolyse de la liaison glycosidique et en particulier au niveau de l'état de transition. La mise en parallèle de l'importance de l'orientation des liaisons C2-O2 et C3-O3 dans la stéréosélectivité des réactions de b-mannopyranosylation dirigées par les groupements 4,6-O-benzylidène, avec le rôle des interactions avec la liaison C3-O3 dans la catalyse enzymatique pour les b-mannosidases, nous a conduits à nous intéresser au développement de nouveaux glycoimidazoles, potentiellement inhibiteurs de ces enzymes. Nous nous sommes attachés à développer ce type de molécules car ils sont considérés, à l'heure actuelle, comme les meilleurs mimes de l'état de transition. La catalyse par les b-mannosidases passerait par un état de transition de type B2,5. Ce chemin conformationnel semble inhabituel mais serait le plus approprié au développement du caractère de double liaison entre le carbone anomérique et l'oxygène endocyclique ainsi qu'à la charge positive lorsque le système est proche de l'état de transition. De plus, il semblerait que la conformation B2,5 soit aussi privilégiée pour les a-mannosidases, ce qui renforce l'intérêt thérapeutique de synthétiser de nouveaux inhibiteurs de glycosidases. La stratégie de synthèse s'appuie sur des travaux de Vasella. Elle repose sur la construction du squelette bicyclique des tétrahydroimidazopyridines, via une réaction de cyclisation intramoléculaire d'oxoéthylamidines intermédiaires, qui permet d'obtenir de nouveaux glycoimidazoles en une quinzaine d'étapes. Dans la seconde partie, sont exposés les travaux concernant la préparation et l'utilisation en synthèse de glutaconaldéhydes oxydés en position 2 et de N-acylaminopentadiènals. Après avoir rappelé l'importance des glutaconaldéhydes et des aminopentadiènals dans les hypothèses de biogenèse des alcaloïdes marins de la famille des manzamines, nous avons vu que ces espèces pouvaient être considérés comme des intermédiaires possibles pour la synthèse d'alcaloïdes marins de la famille des pyrrole-2-aminoimidazoles (P-2-AI). La nouvelle méthode de préparation des sels de glutaconaldéhydes nous a permis de synthétiser un glutaconaldéhyde oxydé en position 2 et de commencer à étudier la réactivité des 2-alkoxy-N-acylaminopentadiènals. Le dernier chapitre de cette partie traite d'une méthode de préparation de N-acyl-5-aminopenta-2,4-diènals via l'ouverture de furfurylamines N-acylées développée en parallèle avec les travaux précédemment cités.

This thesis is concerned with synthesis, structure and biochemical analysis of chemically modified oligonucleotides with potential therapeutic applications. The three types of chemical modifications described here are: (a) A North-East locked 1',2'-azetidine nucleoside (b) A North locked 2',4'-cyanomethylene bridged nucleoside and (c) A 2',4'-aza-ENA-T nucleoside. The synthesis of the 1',2'-azetidine fused nucleosides was described using two different approaches. A highly strained 2',4'-cyanomethylene locked nucleoside was synthesized but could not be converted to the phosphoramidite derivative due to instability during derivatization. The key cyclization step in the aza-ENA-T nucleoside synthesis gave rise to two separable diastereomers due to chirality at the exocyclic nitrogen. Conversion of diastereomer 55 to 56 occurred with a large free energy of activation (ΔG‡ = 23.4 kcal mol-1 at 298 K in pyridine-d5). Of the two isomers the equatorial NH product was more stable than the axial one due to reduced 1,3 diaxial interactions. As a result, all NH axial product was converted to the equatorial isomer during subsequent steps in the synthesis. NMR and ab initio experiments confirmed the North-East structure of the 1',2'-azetidine locked nucleoside and North conformation of aza-ENA-T locked nucleosides with a chair conformation of the piperidine ring. The amino modified nucleosides were incorporated into different positions of a 15mer oligonucleotide. The azetidine modified AONs did not form stable duplexes with complementary RNA (ΔTm ~-1 to -4 °C), but they performed better than previously synthesized isosequential 1',2'-oxetane modified oligonucleotides. The 2',4'-aza-ENA-T modified oligonucleotide, on the other hand, showed excellent target affinity with complementary RNA (ΔTm ~+4 °C). The azetidine and aza-ENA-T modified oligonucleotides showed significant stability in the presence of human serum and snake venom phosphodiesterase (3'-exonuclease) as compared to the unmodified native sequence. The singly modified 15mer oligonucleotides were also subjected to RNase H promoted digestion in order to evaluate their potential as effective antisense agents. The effective enzyme activity (kcat/Km) was found to be lower in the modified AONs due to reduced enzyme-substrate binding. However, the catalytic activity of RNase H with these modified-AON:RNA duplexes were higher than observed with the native duplex.

This study addresses the issue of how to convert peptides into drug-like non- peptides with retained biological activities at peptide receptors. Angiotensin II (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe, Ang II) was used as a model peptide. Knowledge of the bioactive conformations of endogenous peptides is invaluable for the conversion of peptides into less peptidic analogues. Effectively constrained cyclic analogues, with retained pharmacological activities, may provide valuable information about the bioactive conformations of the peptide in question. This thesis describes the development of synthesis for a number of protected, aldehyde-functionalized building blocks for standard solid phase peptide synthesis, and their use for the preparation of cyclic peptide analogues. The effect of variations in the side-chain lengths of the building blocks, on the outcome of the cyclizations was studied. Incorporation of a building block derived from L-aspartic acid afforded bicyclization towards the C-terininal end of the peptide, while for the corresponding L-glutamic acid derived building block, N-terminal directed bicyclization was achieved. A building block derived from L-2-aminoadipic acid was exploited for monocyclization furnishing cis- and trans- vinyl sulfide bridged peptide analogues. The described cyclization methods have been applied to the synthesis of a number of conformationally constrained Ang II analogues, for which the pharmacological properties have been evaluated. Two of the Ang II analogues synthesized displayed high affinities and full agonist activities at the AT1 angiotensin receptor, and have proven to be useful tools in the search for the bioactive conformation of Ang II.

La acetilcolinesterasa (AChE) hidroliza el neurotransmisor acetilcolina. La enzima se presenta en distintas formas moleculares. Tetrámeros hidrofílicos de AChE de suero fetal bovino se purificaron, sometieron a un tratamiento químico desnaturalizante o reductor, y estudiaron mediante análisis de sedimentación, cromatografía, fluorescencia intrínseca y unión de sondas hidrofóbicas. La transformación de los tetrámeros hidrofílicos en dímeros y monómeros anfifílicos demostró la alta flexibilidad conformacional de las subunidades de AChE, lo que podría ser crucial en la síntesis del conjunto completo de sus formas moleculares, y aportó una explicación de cómo algunas de sus formas interaccionan con las membranas. Para entender la heterogeneidad molecular de la AChE, también se empleó el anticuerpo AE-1, que interaccionó de forma desigual con oligómeros y monómeros de AChE de distintas fuentes. Experimentos de Western blot demostraron que el epítopo de AE-1 es de naturaleza confor macional. Finalmente, los datos experimentales descartaron la fosforilación de la AChE con proteína quinasa A. / Acetylcholinesterase (AChE) hydrolyzes the neurotransmitter acetylcholine. The enzyme exists in several molecular forms. AChE hydrophilic tetramers from fetal bovine serum were purified, chemically denatured or reduced, and studied by sedimentation analysis, hydrophobic chromatography, intrinsic fluorescence spectra and binding of amphiphilic probes. Conversion of the hydrophilic tetramers into amphiphilic dimers and monomers showed that AChE subunits possess a flexible conformation, which may be important for generating a full set of molecular forms, and gave an explanation of the interaction of certain AChE forms with membranes. Another approach to determine the molecular basis for the structural heterogeneity of AChE was to use the antibody AE-1, which distinctly reacted with AChE oligomers and monomers from different sources. The results of Western blot revealed that the determinant for AE-1 consisted of a conformational domain, not a primary sequence region. Finally, the experimental data rejected the phosphorylation of AChE at non-consensus protein kinase A sites.