Asymmetric epoxidation of alkenes by a chiral manganese(III) salen complex anchored onto a functionalised hexagonal mesoporous silica

A Jacobsen-type catalyst was anchored onto an amine functionalised hexagonal mesoporous silica (HMS) through the diimine bridge fragment of the complex. The new heterogeneous catalyst, as well as the precedent materials, were characterised by elemental analyses, FTIR-DRIFT, UV-vis, porosimetry and XPS which showed that the complex was successfully anchored. This material was active in the epoxidation of styrene and α-methylstyrene in dichloromethane at 0°C using, respectively, m-CPBA/NMO and NaOCl. With the former substrate no asymmetric induction was found in the epoxide, whereas with the latter substrate higher %ee was found than in homogeneous phase. Using the latter experimental conditions, catalyst reuse led to no significant loss of catalytic activity and enantioselectivity. © 2005 Elsevier B.V. All rights reserved.

Covalent protein adduction by drugs of abuse

Recreational abuse of the drugs cocaine, methamphetamine, and morphine continues to be prevalent in the United States of America and around the world. While numerous methods of detection exist for each drug, they are generally limited by the lifetime of the parent drug and its metabolites in the body. However, the covalent modification of endogenous proteins by these drugs of abuse may act as biomarkers of exposure and allow for extension of detection windows for these drugs beyond the lifetime of parent molecules or metabolites in the free fraction. Additionally, existence of covalently bound molecules arising from drug ingestion can offer insight into downstream toxicities associated with each of these drugs. This research investigated the metabolism of cocaine, methamphetamine, and morphine in common in vitro assay systems, specifically focusing on the generation of reactive intermediates and metabolites that have the potential to form covalent protein adducts. Results demonstrated the formation of covalent adduction products between biological cysteine thiols and reactive moieties on cocaine and morphine metabolites. Rigorous mass spectrometric analysis in conjunction with in vitro metabolic activation, pharmacogenetic reaction phenotyping, and computational modeling were utilized to characterize structures and mechanisms of formation for each resultant thiol adduction product. For cocaine, data collected demonstrated the formation of adduction products from a reactive arene epoxide intermediate, designating a novel metabolic pathway for cocaine. In the case of morphine, data expanded on known adduct-forming pathways using sensitive and selective analysis techniques, following the known reactive metabolite, morphinone, and a proposed novel metabolite, morphine quinone methide. Data collected in this study describe novel metabolic events for multiple important drugs of abuse, culminating in detection methods and mechanistic descriptors useful to both medical and forensic investigators when examining the toxicology associated with cocaine, methamphetamine, and morphine.

Desenvolvimento de novos biolubrificantes hidráulicos derivados dos óleos de maracujá e de moringa in natura e epoxidados

With the increasing environmental awareness, maximizing biodegradability and minimizing ecotoxicity is the main driving force for new technological developments. Thus, can be developed new biodegradable lubricants for use in environmentally sensitive areas. The aim of this study was to obtain new bio-lubricants from passion fruit (Passiflora edulis Sims f. flavicarpa Degener) and moringa (Moringa oleifera Lamarck) epoxidized oils and develop a new additive package using experimental design for their use as a hydraulic fluid. In the first stage of this work was performed the optimization of the epoxidation process of the oils using fractional experimental design 24-1 , varying the temperature, reaction time, ratio of formic acid and hydrogen peroxide. In the second step was investigated the selectivity, thermodynamics and kinetics of the reaction for obtaining the two epoxides at 30, 50 and 70 °C. The result of the experimental design confirmed that the epoxidation of passion fruit oil requires 2 hours of reaction, 50 °C and a ratio H2O2/C=C/HCOOH (1:1:1). For moringa oil were required 2 hours reaction, 50 °C and a ratio of H2O2/C=C/HCOOH (1:1:1.5). The results of the final conversions were equal to 83.09% (± 0.3) for passion fruit oil epoxide and 91.02 (±0,4) for moringa oil epoxide. Following was made the 23 factorial design to evaluate which are the best concentrations of corrosion inhibitor and anti-wear (IC), antioxidant (BHA) and extreme pressure (EP) additives. The bio-lubricants obtained in this step were characterized according to DIN 51524 (Part 2 HLP) and DIN 51517 (Part 3 CLP) standards. The epoxidation process of the oils was able to improve the oxidative stability and reduce the total acid number, when compared to the in natura oils. Moreover, the epoxidized oils best solubilized additives, resulting in increased performance as a lubricant. In terms of physicochemical performance, the best lubricant fluid was the epoxidized moringa oil with additives (EMO-ADI), followed by the epoxidized passion fruit oil with additives (EPF-ADI) and, finally, the passion fruit in natura oil without additives (PFO). Lastly, was made the investigation of the tribological behavior under conditions of boundary lubrication for these lubricants. The tribological performance of the developed lubricants was analyzed on a HFRR equipment (High Frequency Reciprocating Rig) and the coefficient of friction, which occurs during the contact and the formation of the lubricating film, was measured. The wear was evaluated through optical microscopy and scanning electron microscopy (SEM). The results showed that the addition of extreme pressure (EP) and anti-wear and corrosion inhibitor (CI) additives significantly improve the tribological properties of the fluids. In all assays, was formed a lubricating film that is responsible for reducing the coefficient of metal-to-metal wear. It was observed that the addition of EP and IC additives in the in natura vegetable oils of passion fruit and moringa did not favor a significant reduction in wear. The bio-lubricants developed from passion fruit and moringa oils modified via epoxidation presented satisfactory tribological properties and shown to be potential lubricants for replacement of commercial mineral-based fluids.

O Uso terapêutico de mediadores anti-inflamatórios da via do ácido araquidônico

Arachidonic acid (AA) a precursor in the formation of eicosanoids which are lipid mediators with a number of functions in human physiology and pathology. The most of the eicosanoids act as proinflammatory mediators and contribute to the development and proliferation of tumors. In this thesis we evaluated two mediators: 15-deoxy-Δ12,14-PGJ2 (15d- PGJ2) and epoxieicosatrienoic acids (EETs) both act with an opposite activity of most eicosanoids, with an anti-inflammatory and and anti-tumoral action these two distinct mediators from AA pathway were used in this thesis in two different projects. First: 15d- PGJ2, was described that to have an antiproliferative activity and to induce apoptosis in several types of tumor cells however, the effect of 15d- PGJ2 in thyroid cancer cells was unknown in this sense, we tested in vitro cultured thyroid tumor cells, here in TPC1 cells, and treated with different concentrations of 15d- PGJ2 (0 to 20 uM) the treated cells showed a decrease in proliferation and an increase in apoptosis and a decrease in IL-6 release and relative expression. These key results together demonstrate that 15d- PGJ2 can be used as a new therapy for thyroid cancer. Second: The EETs are converted to their diols by soluble epoxy hydrolase (sEH) to maintain the stability of EETs and their anti-inflammatory activity, an inhibitor (TPPU) against was used to sEH in a periodontitis model induced with Aggregatibacter actinomycetemcomitans. The oral treatment in mice with TPPU and sEH Knockout animals showed bone loss reduction accompanied by a decrease in the osteoclastogenic molecules, like RANK, RANKL and OPG, demonstrating that pharmacological inhibition of sEH may have therapeutic value in periodontitis and inflammatory diseases that involve bone resorption.

The application of aryne chemistry and use of α-diazo carbonyl derivatives in indazole synthesis with biological evaluation

This thesis outlines the synthetic chemistry involved in the preparation of a range of novel indazole compounds and details the subsequent investigation into their potential as biologically active agents. The synthetic route utilised in this research to form the indazole structure was the [3+2] dipolar cycloaddition of diazo carbonyl compounds with reactive aryne intermediates generated in situ. The preparation of further novel indazole derivatives containing different functional groups and substituents was performed by synthesising alternative 1,3- dipole and dipolarophile analogues and provided additionally diverse compounds. Further derivatisation of the indazole product was made possible by deacylation and alkylation methods. Transformation reactions were performed on alkenecontaining ester side chains to provide novel epoxide, aldehyde and tertiary amine derivatives. The first chapter is a review of the literature beginning with a short overview on the structure, reactivity and common synthetic routes to diazo carbonyl derivatives. More attention is given to the use of diazo compounds as 1,3-dipoles in cycloaddition reactions or where the diazo group is incorporated into the final product. A review of the interesting background, structure and reactivity of aryne intermediates is also presented. In addition, some common syntheses of indazole compounds are presented as well as a brief discussion on the importance of indazole compounds as therapeutic agents. The second chapter discusses the synthetic routes employed towards the synthesis of the range of indazoles. Initially, the syntheses of the diazo carbonyl and aryne precursors are described. Next, the synthetic methods to prepare the indazole compounds are provided followed by discussion on derivatisation of the indazole compounds including N-deacylation, N-benzylation and ester side-chain transformation of some alkene-containing indazoles. A series of novel indazole derivatives were submitted for anti-cancer screening at the U.S National Cancer Institute (NCI). A number of these derivatives were identified as hit compounds, with excellent growth inhibition. The results obtained from biological evaluation from the NCI are provided with further results pending from the Community for Open Antimicrobial Drug Discovery. The third chapter details the full experimental procedures, including spectroscopic and analytical data for all the compounds prepared during this research.

Concentrations of brominated and chlorinated contaminants in adipose tissue of polar bears (Ursus maritimus) between 1991-2007

Adipose tissue was sampled from the western Hudson Bay (WHB) subpopulation of polar bears at intervals from 1991 to 2007 to examine temporal trends of PCB and OCP levels both on an individual and sum-contaminant basis. We also determined levels and temporal trends of emerging polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), polybrominated biphenyls (PBBs) and other current-use brominated flame retardants. Over the 17-year period, sum DDT (and p,p'-DDE, p,p'-DDD, p,p'-DDT) decreased (-8.4%/year); alpha-hexachlorocyclohexane (alpha-HCH) decreased (-11%/year); beta-HCH increased ( + 8.3%/year); and sum PCB and sum chlordane (CHL), both contaminants at highest concentrations in all years (>1 ppm), showed no distinct trends even when compared to previous data for this subpopulation dating back to 1968. Some of the less persistent PCB congeners decreased significantly (-1.6%/year to -6.3%/year), whereas CB153 levels tended to increase (+ 3.3%/year). Parent CHLs (c-nonachlor, t-nonachlor) declined, whereas non-monotonic trends were detected for metabolites (heptachlor epoxide, oxychlordane). sum chlorobenzene, octachlorostyrene, sum mirex, sum MeSO2-PCB and dieldrin did not significantly change. Increasing sum PBDE levels (+13%/year) matched increases in the four consistently detected congeners, BDE47, BDE99, BDE100 and BDE153. Although no trend was observed, total-(alpha)-HBCD was only detected post-2000. Levels of the highest concentration brominated contaminant, BB153, showed no temporal change. As long-term ecosystem changes affecting contaminant levels may also affect contaminant patterns, we examined the influence of year (i.e., aging or "weathering" of the contaminant pattern), dietary tracers (carbon stable isotope ratios, fatty acid patterns) and biological (age/sex) group on congener/metabolite profiles. Patterns of PCBs, CHLs and PBDEs were correlated with dietary tracers and biological group, but only PCB and CHL patterns were correlated with year. DDT patterns were not associated with any explanatory variables, possibly related to local DDT sources. Contaminant pattern trends may be useful in distinguishing the possible role of ecological/diet changes on contaminant burdens from expected dynamics due to atmospheric sources and weathering.

Understanding immobilised enzymes by NMR spectroscopy

Enzyme immobilisation is the conversion of a soluble enzyme molecule into a solid particle form. This allows the recovery of the enzyme catalyst for its re-use and avoids protein contamination of the product streams. A better understanding of immobilised enzymes is necessary for their rational development. A more rational design can help enormously in the applicability of these systems in different areas, from biosensors to chemical industry. Immobilised enzymes are challenging systems to study and very little information is given by conventional biochemical analysis such as catalytic activity and amount of protein. Here, solid-state NMR has been applied as the main technique to study these systems and evaluate them more precisely. Various approaches are presented for a better understanding of immobilised enzymes, which is the aim of this thesis. Firstly, the requirements of a model system of study will be discussed. The selected systems will be comprehensibly characterised by a variety of techniques but mainly by solid-state NMR. The chosen system will essentially be the enzyme α-chymotrypsin covalently immobilised on two functionalised inorganic supports – epoxide silica and epoxide alumina – and an organic support – Eupergit®. The study of interactions of immobilised enzymes with other species is vital for understanding the macromolecular function and for predicting and engineering protein behaviour. The study of water, ions and inhibitors interacting with various immobilised enzyme systems is covered here. The interactions of water and sodium ions were studied by 17O and 23Na multiple-quantum techniques, respectively. Various pore sizes of the supports were studied for the immobilised enzyme in the presence of labelled water and sodium cations. Finally, interactions between two fluorinated inhibitors and the active site of the enzyme will be explored using 19F NMR, offering a unique approach to evaluate catalytic behaviour. These interactions will be explored by solution-state NMR firstly, then by solid-state NMR. NMR has the potential to give information about the state of the protein in the solid support, but the precise molecular interpretation is a difficult task.

Aplicação de peroxidase para degradação de deoxinivalenol

Deoxinivalenol (DON), uma das principais micotoxinas encontradas em matrizes alimentares, é um composto químico que possui em sua estrutura um anel epóxido que lhe confere alto grau de toxicidade. A aplicação de enzimas em processos de degradação de DON vem se destacando, pela estabilidade durante o processo reacional e baixo custo de produção. O objetivo desse trabalho foi estudar o potencial de peroxidase proveniente de farelo de arroz (FA) e farelo de soja (FS) para degradar DON. As condições de obtenção da PO a partir de FA foram definidas por planejamento experimental DCCR 23 , sendo extraída de 5 g de farelo com 50 mL de tampão fosfato 0,04 mol L-1 pH 5, agitados orbitalmente durante 60 min a 100 rpm, e para a PO obtida de FS as condições diferenciaram somente quanto a solução extratora, tampão fosfato 0,01 mol L-1 pH 4,7. A técnica que apresentou melhores índices de purificação para a enzima foi a partição trifásica apresentando fator de purificação e recuperação de 5,6 e 50 % para a obtida de FA e 13,61 e 50 % para FS. A PO de FA apresentou maior atividade em tampão fosfato 5 mmol L-1 pH 5,5 para as formas bruta e pura, diferindo na temperatura de reação de 25 °C e 10 °C, KM de 0,15 e 0,06 mmol L-1 e Vmáx de 769 e 667 U mg-1 , respectivamente. A PO de FS as condições foram: tampão fosfato 5 mmol L-1 pH 5, reação a 35 e 30 °C durante 10 e 5 min, KM de 0,17 e 0,05 mmol L-1 e Vmáx de 196 e 182 U mg-1 , respectivamente. A PO de FA demonstrou maior estabilidade em pH 5 enquanto que a de FS em pH 6, ambas enzimas apresentaram maior estabilidade térmica a 0 °C, as massas moleculares encontradas por eletroforese foram 41 e 34 kDa, respectivamente. Ao final das etapas de obtenção, purificação e caracterização obteve-se uma atividade específica de 116 e 794 U.mg-1 , e 4363 e 17453 U g-1 , respectivamente para PO de FA e FS. A determinação de DON e De-DON foi realizada por HPLC-DAD e LC-ESI-MS/MS para avaliação dos ensaios de degradação. A enzima comercial HRP, mostrou maior potencial de redução sobre DON (55% após 1 h de reação), no entanto em 3 h de reação, a concentração inicial da micotoxina DON foi verificada, o que evidencia que a redução pode ocorrer por adsorção ou por formação de um composto de degradação que apresente a mesma massa molecular. O emprego da enzima PO obtida de FA e FS na degradação necessita de uma avaliação cinética micotoxicologica para definição das condições de redução significativa dos níveis de DON.

Towards the total synthesis of amphidinolides C and F

The amphidinolides are marine macrolides extracted from dinoflagellates of the genus Amphidinium. To date, 37 amphidinolides have been isolated and identified, most of them possessing cytotoxicity against human cancer cell lines. Among these, amphidinolides C, F, C2 and C3 represent synthetic targets of interest owing to their scarcity, structural complexity and promising biological activities. This thesis describes the work realised towards the total synthesis of amphidinolides C and F, with a focus on the different strategies investigated and the key fragments synthesised. In the first approach, the C18−C29 fragment of amphidinolide F was prepared using an intramolecular etherification of an epoxide under acidic catalysis to produce the 2,5-trans-disubstituted tetrahydrofuran ring featured in the natural product. Unfortunately, dithiane alkylation with the C1−C17 iodide counterpart generated the desired coupling product in low yield. A second approach proposing to build the C17−C18 bond by a silicon-tethered RCM proved unsuccessful, because the requisite diene could not be obtained. It was then envisioned to form the C18−C19 bond by displacement of a triflate with an alkyne and install the ketone at C18 by a protoborylation/oxidation sequence. To this end, the C19−C29 triflate precursor was synthesised. Displeasingly, the C1−C18 alkyne counterpart (work by Dr Filippo Romiti) could not be prepared and coupling of the two fragments was not attempted. In the latest approach, the C10−C29 fragment of amphidinolide F was obtained employing a boron-mediated aldol condensation and a dithiane alkylation to form the C13−C14 and C18−C19 bonds. Several endgame strategies were examined including the successful Yamaguchi esterification of the C13-epi C10−C29 fragment and the C1−C9 acid. A challenging Stille crosscoupling was then effected to close the macrocycle but only yielded the desired macrolactone in trace amounts after global desilylation.

Síntese e estudo de polioxotungstatos do tipo Keggin com interesse catalítico

O objectivo principal deste trabalho foi estudar as propriedades e comportamento de polioxotungstatos (POM) do tipo Keggin com interesse em catálise oxidativa. Os estudos efectuados centraram-se no comportamento electroquímico dos aniões em meio não aquoso, na estabilidade das suas estruturas em diferentes meios, na sua capacidade de catalisar a oxidação de diferentes substratos orgânicos e na sua eficácia em oxidar, de forma selectiva, um modelo não fenólico da lenhina. Efectuou-se, igualmente, o estudo estrutural de diversos aniões pela técnica de EXAFS. Neste trabalho, prepararam-se e caracterizaram-se alguns dos sais de tetra-n-butilamónio (TBA) dos polioxotungstatos estudados: compostos de Keggin, TBAx[XW12O40], lacunares, TBAxHy[XW11O39], mono-substituídos, TBAxHy[XW11M(H2O)O39]·nH2O, com X= P e Si e M = CoII, NiII, ZnII, CuIl, RuIII, MnIII e FeIII e os compostos com mistura de átomos adenda TBAx[XW11VO40]·nH2O (X = P e Si). Seleccionou-se este conjunto de polioxotungstatos de forma a efectuar-se um estudo comparativo da influência da natureza do heteroátomo central (P e Si) e dos metais de transição M nas propriedades estudadas. O conjunto de sais de TBA dos silicotungstatos estudados mostraram ser isoestruturais, apresentando a mesma estrutura dos fosfotungstatos análogos. O comportamento electroquímico dos polioxotungstatos foi estudado em soluções de acetonitrilo por voltametria cíclica e electrólise a potencial controlado. Verificou-se a ocorrência de vários processos mono-electrónicos de oxi-redução, reversíveis ou quasi-reversíveis, associados aos átomos de WVI/V e a alguns dos metais de transição. Os metais em estado de oxidação +3 reduziram-se mais facilmente do que os átomos de WVI. O metal CuII apresentou um comportamento diferente dos outros metais de transição. Este metal, na estrutura do POM, reduziu-se a CuI, proporcionando a observação do anião [PW11CuIO39]6- pela primeira vez. A redução posterior do CuI conduziu à formação de Cu0, que se depositou na superfície do eléctrodo. A re-oxidação do cobre a CuII conduziu à reconstituição da estrutura do POM, nas condições estudadas. Constatou-se que a ocorrência de protões na fórmula molecular dos POMs influenciou o seu comportamento electroquímico. Para os compostos que apresentam protões, a redução dos átomos de tungsténio ocorreu a potenciais menos negativos do que para aqueles que não apresentam protões na sua fórmula. Para os primeiros observou-se a transferência global de um maior número de electrões no mesmo intervalo de potencial, originando soluções fortemente azuladas. Quando os catiões tetra-n-butilamónio foram substituídos por catiões de menor dimensão, como Li+ e Na+, ocorreu a formação de pares iónicos com os polianiões [PW12O40]3- e [SiW11VO40]5-, originando um aumento do potencial de redução. Não houve evidência da formação de pares iónicos com os catiões TBA+. Este foi o primeiro estudo sistemático do comportamento electroquímico dos aniões lacunares e mono-substituídos em meio não aquoso. Estudou-se a estrutura dos polioxotungstatos em sais de TBA e em soluções de acetonitrilo. A aplicação da técnica de EXAFS ao estudo deste tipo de compostos em solução foi realizada pela primeira vez. Pela análise estrutural nos sólidos verificou-se que, a natureza do metal de transição M e do átomo central X, na estrutura do POM, influenciam o tamanho dos vários octaedros que o constituem. Não se observaram diferenças significativas nas estruturas dos polianiões em solução. A estabilidade da estrutura dos polioxometalatos na presença de um excesso de H2O2, em soluções de acetonitrilo/H2O foi analisada por espectroscopia de absorção de EXAFS, RMN de 31P, IV e espectrofotometria de absorção no UV-Vis. De uma forma geral, os POMs em que o átomo central da estrutura é o Si apresentaram maior estabilidade do que os POMs correspondentes com átomo de P no centro. Em solução de acetonitrilo, na ausência de H2O2, todos os aniões mostraram ser estáveis durante vários dias. Em solução, na presença de H2O2 em excesso (H2O2/POM = 1300), o anião lacunar [PW11O39]7- não é estável, transformando-se no anião de Venturello, {PO4[W(O)(O2)2]4}3-, após a formação de [PW12O40]3-, como produto intermediário. Em relação aos aniões substituídos [PW11M(H2O)O39]p-, M = MnIII, RuIII, FeIII, CoII e ZnII, verificou-se o seguinte na presença de H2O2: os aniões com MnIII e CoII transformaram-se no anião de Keggin, [PW12O40]3-. Os aniões de RuIII e FeIII mantiveram as suas estruturas e o anião de ZnII decompôs-se em {HPO4[W(O)(O2)2]2}2- e fosfato. Para estes casos de não estabilidade estrutural, o processo de decomposição foi mais rápido na presença de maiores conteúdos de água. Pela análise de EXAFS, na presença de um menor excesso de H2O2 (H2O2/POM = 70) e apenas 8% de parte aquosa, verificou-se que os aniões substituídos por MnIII mantiveram a sua estrutura, embora o ligando H2O, coordenado ao Mn, tivesse sido substituído por um grupo oxo no polianião [SiW11Mn(H2O)O39]5-, e por um grupo peroxo no polianião [PW11Mn(H2O)O39]4-. O anião com RuIII, nestas condições, também mostrou substituir o seu ligando H2O por um grupo peroxo ou hidrogenoperoxo. Os polioxotungstatos mono-substituídos e lacunares mostraram ser catalisadores eficientes para a oxidação de cis-cicloocteno, geraniol e ciclooctano com H2O2. A maior novidade deste trabalho residiu na actividade catalítica apresentada pelos silicotungstatos estudados, contrariando o que é referido na literatura. Outro aspecto inovador foi o elevado valor de conversão obtido para a oxidação de ciclooctano. Este substrato foi oxidado com 74% de conversão, após 2h de reacção e com 80% de selectividade para o hidroperóxido de ciclooctilo, na presença do anião [PW11Fe(H2O)O39]4-. Os restantes produtos de reacção foram o ciclooctanol e a ciclooctanona. Os silicotungstatos apresentaram maior selectividade para o hidroperóxido de ciclooctilo do que os fosfotungstatos. O geraniol foi completamente oxidado após 3h de reacção, com 82% de selectividade para o 2,3-epoxigeraniol, na presença do anião [PW11Mn(H2O)O39]4-. O cis-cicloocteno foi oxidado ao seu epóxido, com 92% de conversão ao fim de 5h de reacção, na presença do anião lacunar [PW11O39]7-. O estudo da capacidade oxidativa do anião [SiW11VO40]5- foi analisada utilizando-se um modelo não fenólico da lenhina, a anisoína. Estudaram-se as condições favoráveis à obtenção de uma reacção selectiva para o anisilo, de forma a poder estudar-se a cinética da reacção. A estequiometria da reacção mostrou ser de 1:2 anisoína/POM. As ordens de reacção foram determinadas pelo método das velocidades iniciais e, a partir destes resultados, conheceu-se que o POM não estava envolvido no passo que limita a velocidade da reacção, sendo esta limitada pela transformação da anisoína. O estudo realizado sobre o efeito isotópico sugeriu que o passo que limitou a velocidade de reacção correspondeu à enolação da anisoína. Desta forma, observou-se pela primeira vez, que o POM oxida um modelo não fenólico da lenhina por via de enolação.

Síntese estereosseletiva da naftotectona

Tese (doutorado)—Universidade de Brasília, Instituto de Química, 2016.

MOLECULAR MODELING OF EPON 862-DETDA / CARBON COMPOSITES

The thermoset epoxy resin EPON 862, coupled with the DETDA hardening agent, are utilized as the polymer matrix component in many graphite (carbon fiber) composites. Because it is difficult to experimentally characterize the interfacial region, computational molecular modeling is a necessary tool for understanding the influence of the interfacial molecular structure on bulk-level material properties. The purpose of this research is to investigate the many possible variables that may influence the interfacial structure and the effect they will have on the mechanical behavior of the bulk level composite. Molecular models are established for EPON 862-DETDA polymer in the presence of a graphite surface. Material characteristics such as polymer mass-density, residual stresses, and molecular potential energy are investigated near the polymer/fiber interface. Because the exact degree of crosslinking in these thermoset systems is not known, many different crosslink densities (degrees of curing) are investigated. It is determined that a region exists near the carbon fiber surface in which the polymer mass density is different than that of the bulk mass density. These surface effects extend ~10 Å into the polymer from the center of the outermost graphite layer. Early simulations predict polymer residual stress levels to be higher near the graphite surface. It is also seen that the molecular potential energy in polymer atoms decreases with increasing crosslink density. New models are then established in order to investigate the interface between EPON 862-DETDA polymer and graphene nanoplatelets (GNPs) of various atomic thicknesses. Mechanical properties are extracted from the models using Molecular Dynamics techniques. These properties are then implemented into micromechanics software that utilizes the generalized method of cells to create representations of macro-scale composites. Micromechanics models are created representing GNP doped epoxy with varying number of graphene layers and interfacial polymer crosslink densities. The initial micromechanics results for the GNP doped epoxy are then taken to represent the matrix component and are re-run through the micromechanics software with the addition of a carbon fiber to simulate a GNP doped epoxy/carbon fiber composite. Micromechanics results agree well with experimental data, and indicate GNPs of 1 to 2 atomic layers to be highly favorable. The effect of oxygen bonded to the surface of the GNPs is lastly investigated. Molecular Models are created for systems with varying graphene atomic thickness, along with different amounts of oxygen species attached to them. Models are created for graphene containing hydroxyl groups only, epoxide groups only, and a combination of epoxide and hydroxyl groups. Results show models of oxidized graphene to decrease in both tensile and shear modulus. Attaching only epoxide groups gives the best results for mechanical properties, though pristine graphene is still favored.

Covalent Protein Adduction by Drugs of Abuse

Recreational abuse of the drugs cocaine, methamphetamine, and morphine continues to be prevalent in the United States of America and around the world. While numerous methods of detection exist for each drug, they are generally limited by the lifetime of the parent drug and its metabolites in the body. However, the covalent modification of endogenous proteins by these drugs of abuse may act as biomarkers of exposure and allow for extension of detection windows for these drugs beyond the lifetime of parent molecules or metabolites in the free fraction. Additionally, existence of covalently bound molecules arising from drug ingestion can offer insight into downstream toxicities associated with each of these drugs. This research investigated the metabolism of cocaine, methamphetamine, and morphine in common in vitro assay systems, specifically focusing on the generation of reactive intermediates and metabolites that have the potential to form covalent protein adducts. Results demonstrated the formation of covalent adduction products between biological cysteine thiols and reactive moieties on cocaine and morphine metabolites. Rigorous mass spectrometric analysis in conjunction with in vitro metabolic activation, pharmacogenetic reaction phenotyping, and computational modeling were utilized to characterize structures and mechanisms of formation for each resultant thiol adduction product. For cocaine, data collected demonstrated the formation of adduction products from a reactive arene epoxide intermediate, designating a novel metabolic pathway for cocaine. In the case of morphine, data expanded on known adduct-forming pathways using sensitive and selective analysis techniques, following the known reactive metabolite, morphinone, and a proposed novel metabolite, morphine quinone methide. Data collected in this study describe novel metabolic events for multiple important drugs of abuse, culminating in detection methods and mechanistic descriptors useful to both medical and forensic investigators when examining the toxicology associated with cocaine, methamphetamine, and morphine.