A doença de Chagas afeta milhões de pessoas e os fármacos existentes não são seguros e apresentam eficácia limitada. Muitos produtos naturais mostraram efeitos inibitórios contra uma enzima importante para a sobrevivência do Trypanosoma cruzi, a gliceraldeído-3-fosfato desidrogenase (GAPDH). Dentre esses produtos naturais destacam-se aqueles da classe dos flavonoides, sendo que um deles, o tilirosídeo, mostrou-se interessante por inibir a enzima com valores de IC50 e Ki iguais a 46 e 25 µM, respectivamente, além de ter sido eficaz contra a cepa do T. cruzi resistente a fármacos (cepa Y) mostrando um valor de IC50 igual a 770 µM. Com objetivo de identificar novos potenciais inibidores da TcGAPDH baseados no tilirosídeo foram empregados métodos computacionais nos quais combinaram-se duas diferentes estratégias: os ensaios virtuais baseados na estrutura do ligante (LBVS) e os ensaios virtuais baseados na estrutura do receptor (SBVS). Os compostos que se ajustaram ao sítio catalítico da enzima e preditos para interagir de forma efetiva com o alvo foram adquiridos e testados contra a TcGAPDH. Os estudos de inibição enzimática foram realizados utilizando as técnicas de calorimetria de titulação isotérmica e espectroscopia de fluorescência obtendo como resultados as constantes de inibição dos compostos selecionados e seus modos de inibição. Dois flavonoides, o Nequimed 214 e o Nequimed 215 inibiram a TcGAPDH na mesma grandeza que o composto de partida, o tilirosídeo, mas como possuem cerca da metade da massa molecular, houve grande aumento da eficiência do ligante. A partir dessa informação, foram selecionados uma segunda geração de compostos preditos a interagir com a TcGAPDH. Deste modo, foram adquiridos bioisósteros de flavonoides que foram testados contra essa enzima, sendo que dois dos mesmos mostraram-se ativos e com alta eficiência do ligante. Foram adquiridos também compostos pertencentes à classe das hidantoínas, rodaninas, tio-hidantoínas e pirrolidina-2,4-dionas sendo que muitos dos mesmos foram ativos e mostraram os maiores valores de eficiência do ligante já relatados para a TcGAPDH, tornando-os excelentes candidatos para otimização molecular. Os resultados obtidos sugerem que vários inibidores possuem inibição não competitiva com relação ao substrato G3P. Os inibidores mais potentes foram testados contra a GAPDH de humanos e não foi verificada seletividade relevante. / Chagas disease affects millions of people worldwide. The available drugs are not safe and show limited efficacy. Many natural products inhibit the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an important Trypanosoma cruzi enzyme. Among them, flavonoids have stood out and one of them, the tiliroside, inhibited the enzyme with IC50 and Ki values of 46 and 25 µM, respectively. Furthermore, unpublished results showed that this compound was effective against the drug-resistant strain of T. cruzi (Y strain) with IC50 value of 770 µM. In order to select potential inhibitors of TcGAPDH based on the tiliroside structure, computational methods were used combining two different strategies, the ligand-based virtual screening (LBVS) and the structure-based virtual screening (SBVS). The compounds predicted to interact effectively with the target and fit into the active site of the enzyme were purchased and tested. Enzyme inhibition studies were performed using isothermal titration calorimetry and fluorescence spectroscopy from which the constants and mode of inhibition of the compounds were determined. Two of the tested flavonoids, Nequimed 214 and Nequimed 215, showed inhibition activity against TcGAPDH in the same magnitude values as the starting compound, the tiliroside, in spite of their lower molecular weight, thus greatly enhancing the ligand efficiency (LE). These data prompted us to search for some flavonoid bioisosters that were obtained and tested against this enzyme, and two of them proved to be active with high ligand efficiencies. We also purchased compounds belonging to the class of hydantoins, pyrrolidine-2,4-dione, thio-hydantoin and rhodanine. Many of them were active at low micromolar concentration range and exhibited the highest ligand efficiencies ever reported for this enzyme, therefore becoming excellent candidates for molecular optimization. The obtained results suggest that most of inhibitors tested behave as non-competitive inhibitors with respect to the G3P substrate. The most potent inhibitors were tested against human GAPDH and relevant selectivity was not observed.

Criptococose é uma doença causada pelo fungo C. neoformans que têm grande importância atualmente, devido ao aumento da população imunocomprometida,. Além disso, existem poucas opções terapêuticas contra micoses profundas. Neste trabalho foi avaliado se a via de biossíntese do triptofano seria um bom alvo para o desenvolvimento de novos antifúngicos. Com o uso da tecnologia de RNA de interferência, concluiu-se que esta via de síntese é essencial para a sobrevivência desta levedura, sendo, portanto, um ótimo alvo. Ainda neste estudo, demonstrou-se que a letalidade decorre da baixa captação de triptofano pelas permeases de aminoácidos, as quais sofrem repressão catabólica pela fonte de nitrogênio e efeito negativo da temperatura. Foram testados dois inibidores específicos que atuam sobre a antranilato sintase e a triptofano sintase, duas enzimas cruciais para a conversão do corismato em triptofano. Ambos compostos causaram inibição do crescimento de C. neoformans e C. gattii. / Cryptococcosis is a disease caused by C. neoformans, currently of great importance due to the increase in immunocompromised population. Furthermore, there are few therapeutic options for treating this disease. This study evaluated the tryptophan biosynthetic pathway as a possible target for the antifungal development. By using RNA interference technology we concluded that this metabolic pathway is essential for the survival of this yeast, and, therefore, it is a good target. In the same study, it was demonstrated that lethality results from the low uptake of the tryptophan amino acid by permeases, which undergo nitrogen catabolite repression and negative effect of temperature. Two specific inhibitors acting on the anthranilate synthase and tryptophan synthase, two key enzymes for the conversion of chorismate into tryptophan were tested. Both compounds caused growth inhibition of C. neoformans and C. gattii.

O estabelecimento de uma camada híbrida adequada no canal radicular representa um dos principais desafios clínicos devido à dificuldade de acesso. Dessa forma, o uso de inibidores proteolíticos poderia tornar-se um recurso favorável. O objetivo deste estudo foi avaliar o efeito de inibidores proteolíticos na união de pino de fibra de vidro fixado com cimento adesivo, considerando os terços radiculares e tempos distintos, por meio da resistência de união (RU). Cento e quarenta e quatro raízes bovinas foram selecionadas e divididas em 6 grupos de tratamento, e redivididas em 3 subgrupos de acordo com os tempos de avaliação de 24 horas, 6 e 12 meses (n=8). Após o tratamento endodôntico e desobturação padronizados, as raízes foram cimentadas com pinos de fibra de vidro cônicos (Exacto/Angelus). As raízes foram tratadas com sistema adesivo convencional de três passos, Adper Scotchbond Multipurpose/ 3M ESPE (SBMP) e cimento dual RelyX ARC/ 3M ESPE. Após prévia divisão, foram alocadas em grupos CN (Controle Negativo- sem pré tratamento associado), CP (Controle Positivo- com agentes ativador e catalisador), EDTA (ácido etilenodiamino tetra-acético a 17%), CHX (digluconato de clorexidina a 2%), E-5 (E- 64 a 5 M) e E-10 (E-64 a 10 M). Após 24 horas, as raízes foram seccionadas perpendicularmente ao longo eixo e identificadas quanto à região, obtendo-se fatias de 1 mm de espessura (cervical, médio e apical), que foram armazenadas em saliva artificial para serem testadas. Todas as fatias foram submetidas ao teste de extrusão (push-out) na máquina de teste universal (Instron) com célula de carga de 50 N a 0,5 mm/min. Os dados foram analisados pelo teste de ANOVA a três critérios e comparações múltiplas com Tukey, ambos com p<0,05. Após 24 horas, não se observou diferenças entre os tratamentos. Após 6 meses, a CHX demonstrou melhor desempenho, cujo efeito não se prorrogou até os 12 meses. O uso de inibidores proteolíticos não foram capazes de preservar a resistência de união dos pinos intrarradiculares até o tempo de 12 meses. / The adequate establishment of hybrid layer in the root canal on bonding process is still a clinical challenge due to its hard access. Thus, the use of proteolytic inhibitors could become a favorable tool. The aim of this study was to evaluate the effect of proteolytic inhibitors in the bonding of a glass- fiber post fixed with a luting cement, regarding the root thirds and different times through the bond strength. One hundred and forty four bovine roots were selected and divided into 6 treatment groups, and subdivided according to the time of evaluation of 24 hours, 6 and 12 months (n=8). After endodontic treatment and standardized removal procedure, the roots were cemented with tapered glass fiber posts (Exacto/ Angelus). The roots were treated with three-step etch-and-rinse adhesive system Adper Scotchbond Multipurpose/ 3M ESPE (SBMP) and dual cement RelyX ARC/ 3M ESPE. After previous division, CN (negative- control without pre associated treatment), CP (Control positive- with activator and catalyst agents) EDTA (17% ethylenediaminetetraacetic acid) CHX (2% chlorhexidine digluconate) E-5 (5M E-64) and E-10 (10M E-64). After 24h, the roots were sectioned perpendicular to the long axis and identified according to third in 1mm thick slices (cervical, middle and apical), which were stored in artificial saliva to be tested. All slices were subjected to extrusion tests (push-out) in the universal test machine (Instron) at 50 N load cell at 0.5 mm/min. Data were analyzed with three-way ANOVA and multiple comparisons with Tukey test, both with p <0.05. After 24 hours, no differences were observed between treatments. After 6 months, CHX showed better performance, which did not last up 12 months. The proteolytic inhibitors performed differently in the bonding process over time; only CHX promoted inhibition at 6 months. The use of proteolytic inhibitors were not able to maintain the bond strength of intraradicular posts up time of 12 months.

Wan Leong Hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 80-83). / Acknowledgments --- p.i / Bibliography --- p.ii / Contents --- p.iii / Abstract --- p.iv / Abbreviations --- p.v / Chapter I --- Introduction / Chapter I-1 --- General Background of Pseudo-sugar --- p.1 / Chapter I-2 --- Monocarba-sugar --- p.2 / Chapter I-3 --- Dicarba-sugar --- p.4 / Chapter I-4 --- Isolation of Valiolamine and Its Related Compounds --- p.6 / Chapter I-5 --- Previous Syntheses of Valiolamine --- p.8 / Chapter II --- Results and Discussions / Chapter II-1 --- General Strategy --- p.17 / Chapter II-2 --- "Synthesis of (lR,2R)-diol (62)" --- p.20 / Chapter II-3 --- Synthesis and Reactivity of Olefin 69 --- p.24 / Chapter II-4 --- "Synthesis of (1R,2S) and (lR,2R)-diastereoisomers 25 and 27" --- p.27 / Chapter II-5 --- "Synthesis of (1S,2R)-diastereoisomer 26 and Valiolamine" --- p.32 / Chapter II-6 --- "Comment on the Regio Chemistry of Nucleophilic Attack of 68, 65 and" --- p.85 / Chapter II-7 --- Results of Biological Test --- p.43 / Chapter III --- Conclusion --- p.46 / Chapter IV --- Experimental --- p.48 / Chapter V --- Reference --- p.80

Herein, we describe the design and synthesis of novel inhibitors of 17β-hydroxysteroid dehydrogenase type 3 which convert androstenedione into testosterone, which is then converted into dihydrotestosterone (DHT). This isozyme has been implicated in the growth of prostate cancer. Using an in silico pharmacophore model initial targets were planned, based around a diphenylether hydrophobic head linked to a 4-substituted piperidine ring. Over 45 compounds were synthesised and many show significant biological activity when evaluated in a 17β-HSD type 3 biological assay. The most potent compound in this series is 1-(4-[2-(4-chloro-phenoxy[-phenylamino]-piperidin)1-yl) ethanone with an IC₅₀ of 700 nM. The amine linked compounds are significantly more active than the amide equivalents. Synthesis of the amine-linked compounds was problematic and led to the development of a novel and general microwave assisted procedure for the reductive amination of anilines, enabling aromatic amine-linked compounds to be synthesised in excellent yields. A series of benzylamine linked inhibitors was also prepared. Over 30 analogues were synthesised and several show very promising biological activity. The most active compound is N-(2-([2-(4-Chloro-phenoxy)-phenylamino]-methyl)-phenyl)-acetamide, which exhibits an IC₅₀ of 900 nM. The synthesis of compounds with a benzophenone linked hydrophobic head group led to an unexpected product. X-ray crystallography was used to determine the structure, as a quinoline derivative. This led to optimisation of a novel modification of the Friedländer synthesis of quinolines. The potent inhibitors synthesised are selective over 17β-HASD Types 1 and 2. One inhibitor also shows potentially interesting activity against the leukaemia cell line CCRF-CEM, in the NCI screening, with a GI₅₀ of 10 nM.

Abstract not available

Ribonucleotide reductase is a remarkable enzyme that catalyzes the rate-limiting step in the synthesis of the 2'-deoxynucleoside triphosphates. The intent of this project was to characterize the ribonucleotide reductase encoded by the orthopoxvirus, vaccinia. The first objective was to study the structural and functional features of the viral small subunit protein of ribonucleotide reductase. The viral reductase gene was engineered into an expression vector and expressed in Escherichia coli. The purified recombinant protein was then characterized and compared with other ribonucleotide reductase small subunits from different organisms. The physical characteristics of the vaccinia virus enzyme showed a strong similarity to the features of the mammalian counterpart. A second aim of this project was to establish the transcriptional and translational kinetics of ribonucleotide reductase gene expression during the time course of viral infection in cultured mammalian cells. In addition, the activity and stability of the enzyme in the viral system was measured and the accumulation of ribonucleotide reductase protein was quantitated. By also quantitating the accumulation of viral DNA synthesis, a direct comparison can be made between the the synthesis and utilization of deoxynucleotide precursors. A third objective of this work was to detail the mechanism by which hydroxyurea inactivates the vaccinia virus ribonucleotide reductase. Visible spectroscopy and electron paramagnetic resonance spectroscopy clearly demonstrated that the inhibitor destroys the free radical moiety in the viral small subunit protein. In addition, in vivo studies revealed that inhibition by hydroxyurea can be circumvented during viral infection. The exogenous addition of deoxyadenosine reversed the block to viral growth that was imposed by hydroxyurea, and stabilized hydroxyurea induced deoxynucleotide pool imbalances. These inhibition studies suggest that there may be a differential sensitivity of the enzyme towards hydroxyurea in the presence of various substrates. / Graduation date: 1993

The boronic acid functional group is known to bind compounds with the diol group tightly and reversibly in aqueous environment and has been used as a recognition moiety for the design of carbohydrate sensors. The first chapter of the dissertation studies the synthesis and substitution effect on the affinity and selectivity of a known boronic acid-based glucose sensor. In such a sensor design effort, the availability of a signaling event, whether it is fluorescence or UV, is crucial. The second chapter studies the detailed mechanism on how a well-known fluorescent boronic acid compound changes fluorescent properties upon binding. A new mechanism has been established which corrected a decade old mistake. In the third chapter, a series of boronic acid-based sensors were designed and synthesized for sialic acid, which is part of tetrasaccharide found on many cell surface carbohydrates. Such sialic acid sensors could be very useful for the development of new type of anti-influenza therapy. The fourth is on the design and synthesis novel and selective inhibitors for phosphodiesterase 4 (PDE4), which are potential anti-asthma agents.

The present work has endeavored to survey the occurence of adenosine deaminase as well as its multiple forms in normal and some cancerous human tissues. A recent report by Akedo, Nishihara, Shinkai and Komatsu concerning the appearance of the C form adenosine deaminase in cancerous tissues is investigated. The thesis reports, however, the occurence of both A and C forms of adenosine deaminase in almost all normal and cancerous tissues investigated. An increase in C form adenosine deaminase does seem to occur in cancerous tissues, and a ratio method is developed to monitor such an increase in the C form enzyme.Fundamental catalytic and physical parameters are used to characterize the A and C forms of adenosine deaminase in several normal human tissues. Little difference is noted between the two forms of the enzyme. Only substrate specificity for cordycepin is of significant value in differentiating between the A and C forms of the enzyme.Ball State UniversityMuncie, IN 47306

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.