Oxidant stress and injury is inherent in many human diseases such as ischemic vascular and respiratory diseases, heart failure, myocardial infarction, stroke, perinatal and placental insufficiencies, diabetes, cancer, and numerous psychiatric and neurodegenerative disorders. Finding novel therapeutics to combat the deleterious effects of oxidative stress is critical to create better therapeutic strategies for many conditions that have few treatment options. This study used the anoxia-tolerant fruit fly, Drosophila melanogaster, to investigate endogenous cellular protection mechanisms and potential interactions to determine their ability to regulate synaptic functional tolerance and cell survival during acute oxidative stress. The Drosophila larval neuromuscular junction (NMJ) was used to analyze synaptic transmission and specific motor axon contributions. Drosophila Schneider 2 (S2) cells were used to assess viability. Acute oxidative stress was induced using p harmacological paradigms that generate physiologically relevant oxidant species: mitochondrial superoxide production induced by sodium azide (NaN3) and hydroxyl radical formation via hydrogen peroxide (H2O2). A combination of genetic and pharmacological approaches were used to explore the hypothesis that endogenous protection mechanisms control cellular responses to stress by manipulating ion channel conductance and neurotransmission. Furthermore, this study analyzed a group of marine natural products, pseudopterosins, to identify compounds capable of modulating synaptic transmission during acute oxidative stress and potential novel neuromodulatory agents. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Biological homeostasis relies on protective mechanisms that respond to cellular oxidation caused primarily by free radical reactions. Methionine sulfoxide reductases (Msr) are a class of enzymes that reverse oxidative damage to methionine in proteins. The focus of this study is on the relationship between Msr and dopamine levels in Drosophila. Dopaminergic neurons in Drosophila have comparable roles to those found in humans. A deficit in dopamine leads to the onset of many neurological disorders including the loss of fine motor control—a neurodegenerative condition characteristic of Parkinson’s disease (PD). We found that dopamine levels in the heads of MsrAΔ/ΔBΔ/Δ mutants are significantly reduced in comparison to MsrA ⁺/⁺ B⁺/⁺ heads. In addition, wefound protein and expression levels are markedly reduced in an Msr-deficient system. Our findings suggest an important role for the Msr system in the CNS. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Cardiac ischemia, stroke and some neurodegenerative disorders are all characterized by cell damage and death due to low oxygen levels. Comparative studies show that anoxia tolerant model systems present a unique opportunity to study "survival" instead of death in the complete absence of oxygen. The freshwater turtle (Trachemys scripta elegans) is unique in its ability to survive total oxygen deprivation for hours to days, as well as reoxygenation insult after anoxia. The broad objective of this study is to understand the modulation of key molecular mechanisms involving stress proteins and VEGF that offer neuroprotection and enhance cell survival in the freshwater turtle through anoxia and reoxygenation. In vivo analyses have shown that anoxia induced stress proteins (Hsp72, Hsp60, Grp94, Hsp60, Hsp27, HO-1); modest changes in the Bcl2/Bax ratio and no change in cleaved caspase-3 expression suggesting resistance to neuronal damage. These results were corroborated with immunohistochemical evidence indicating no damage in turtle brain when subjected to the stress of anoxia and A/R. To understand the functional role of Hsp72, siRNA against Hsp72 was utilized to knockdown Hsp72 in vitro (neuronally enriched primary cell cultures established from the turtle). Knockdown cultures were characterized by increased cell death associated with elevated ROS levels. Silencing of Hsp72 knocks down the expression of Bcl2 and increases the expression of Bax, thereby decreasing the Bcl2/Bax ratio. However, there was no increase in cytosolic Cytochrome c or the expression levels of cleaved Caspase-3. Significant increase in AIF was observed in the knockdown cultures that increase through anoxia and reoxygenation, suggesting a caspase independent pathway of cell death. / Expression of the master regulator of hypoxia, HIF1 alpha and its target gene, VEGF, were analyzed at the mRNA and protein levels. The results showed no significant increase in HIF-1 alpha levels but anoxia VE GF The levels of stress proteins and VEGF returned to control levels during reoxygenation suggesting robust ROS protection mechanisms through reoxygenation. The present study thereby emphasizes Trachemys scripta as an advantageous model to examine anoxia and reoxygenation survival without major damage to the brain due to it's modulation of molecular mechanisms. / by Shailaja Kesaraju. / Thesis (Ph.D.)--Florida Atlantic University, 2008 / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

The methionine sulfoxide reductase (Msr) enzymes catalyze the reduction of methionine sulfoxide (Met(O)) to methionine. The Msr enzymes protect cells against oxidative stress and may have a role in aging. The MsrA family of enzymes reduces stereospecifically the S epimer of free and protein-bound Met(O) while the MsrB family reduces the R epimer of Met(O) in proteins. It has been generally accepted, primarily from studies on MsrA, that the biological reductant for the Msr enzymes is thioredoxin (Trx), although high levels of dithiothreitol (DTT) can be used as the reductant in vitro. In contrast, certain MsrB enzymes show less than 10% of the activity with Trx as compared to DTT. This raises the possibility that in animal cells Trx may not be the direct hydrogen donor for the MsrB enzymes. Studies with bovine liver extracts have shown that thionein, the apoprotein of metallothionein, can function as a reductant for the Msr proteins. Certain selenium compounds such as selenocystamine and selenocystine can also serve as potent reducing agents for the Msr enzymes. Since an increased activity of Msr enzymes can reduce the level of oxidative damage in tissues, compounds that could activate Msr may have therapeutic potential. A high-throughput screening assay has been developed to screen large chemical libraries to find activators of MsrA, as well as specific inhibitors that could be useful research tools. This study will be done in collaboration with The Scripps Florida Research Institute. Sulindac was originally developed as a non-steroidal anti-inflammatory drug but has also shown efficacy in the treatment of certain cancers. The S epimer of sulindac is known to be reduced by MsrA, but the enzymes responsible for reduction of the R epimer are not known. / An activity has been purified from rat liver which is capable of reducing the R epimers of sulindac, free Met(O) and a dabsylated Met(O) substrate, the latter suggesting that this enzyme may have properties similar t o the MsrB enzymes. The oxidation of the epimers of sulindac to sulindac sulfone has also been characterized, and the members of the cytochrome P450 family involved in the oxidation have been identified. / by David J. Brunell. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

O aproveitamento de dejetos industriais como fonte de insumos, apresenta além da vantagem econômica pelo uso de materiais de baixo valor comercial, um forte apelo ambiental. A presença de grande produção de resíduos orgânicos em abatedouros, como as penas de frango, leva à necessidade do desenvolvimento de tecnologias que possibilitem a sua reciclagem. As penas se constituem como os materiais queratinosos mais abundantes na natureza, e por isso, podem ser usados como material de partida para diferentes aplicações biotecnológicas, químicas e farmacêuticas. Existem na literatura vários métodos de extração de queratina das penas de frango, como as extrações por hidrólises ácidas e alcalinas, que além da desvantagem da hidrólise total da proteína, rompem também os sítios principais de reação de crosslinkings da proteína. Outros procedimentos envolvem o uso de grandes concentrações de reagentes onerosos, como o 2-mercaptoetanol e as enzimas proteolíticas. Estudo realizado por planejamento fatorial visou à extração e fragmentação da queratina, através da combinação de diferentes concentrações de sulfito de sódio, uréia e papaína. Ensaios preliminares de modificação da queratina foram conduzidos após esta extração. Temperaturas acima de 80°C, e concentrações intermediárias de uréia (3,75M) combinadas a baixas concentrações de sulfito de sódio (0,1M - 0,18M) foram os melhores parâmetros de extração. A hidrólise enzimática apresentou-se adequada somente quando combinada ao prévio tratamento químico. A combinação dos dois processos extrativos resultou em redução do tempo de reação da hidrólise enzimática. A queratina obtida apresentava tamanho de fragmentos homogêneos, ao redor de 650nm, e um grau de pureza de 72%-89% em massa seca de proteína purificada. A caracterização físico-química dos derivados da queratina demonstra a amplitude desta proteína como insumo para aplicações diversas. O estudo da inserção de grupamentos polares na molécula de queratina é feita por análise da solubilidade em diferentes solventes e por espectroscopia vibracional Raman. / The use of industrial wastes as a source of raw materials presents, besides the cost-effective advantages, an eco-friendly approach. Great amount of feather waste discharged from slaughterhouses demands the development of biotechnological alternatives for its recycling. Feather is the most keratinous material in nature and may be used for different applications in biotechnology, pharmaceutical and chemical industry. Several authors have written methods for feather keratin extraction, as acid and alkaline hydrolysis. Those methods presented disadvantages like damage to the backbone protein chain and loss of its main function as well as loss of cross linking groups. Other chemical treatments require large amounts of expensive reagents such as 2-mercaptoethanol and proteolytic enzymes. The present work comprises a factorial planning for extraction and fragmentation of feather keratin by combining sodium sulfide (0,1M 0,26M), urea (2M- 6M) and papain (0,13mg/ml). Feather keratin modification assay was conducted after protein extraction. The experiment presented satisfactory results when temperature extraction is maintained around 80° C, urea is used in an intermediate concentration (3,75M) and sodium sulfide in a low concentration(0,1M- 0,18M). Enzymatic hydrolysis is viable only after previous chemistry extraction. The combination of both treatment types resulted in a decrease of enzymatic time reaction and therefore an optimized keratin production. Extracted feather keratin presented homogenous size fragments with most particle diameters around 650nm. The percentage of proteins found was around 72%-89% compared to the total dry weight. The physicochemical characterization of feather keratin derivatives bring this protein of interest as a potencial component to renewable raw materials synthesis. Modification analysis of feather keratin was carried by qualitative solubility evaluation and vibrational spectrometry Raman.

O aproveitamento de dejetos industriais como fonte de insumos, apresenta além da vantagem econômica pelo uso de materiais de baixo valor comercial, um forte apelo ambiental. A presença de grande produção de resíduos orgânicos em abatedouros, como as penas de frango, leva à necessidade do desenvolvimento de tecnologias que possibilitem a sua reciclagem. As penas se constituem como os materiais queratinosos mais abundantes na natureza, e por isso, podem ser usados como material de partida para diferentes aplicações biotecnológicas, químicas e farmacêuticas. Existem na literatura vários métodos de extração de queratina das penas de frango, como as extrações por hidrólises ácidas e alcalinas, que além da desvantagem da hidrólise total da proteína, rompem também os sítios principais de reação de crosslinkings da proteína. Outros procedimentos envolvem o uso de grandes concentrações de reagentes onerosos, como o 2-mercaptoetanol e as enzimas proteolíticas. Estudo realizado por planejamento fatorial visou à extração e fragmentação da queratina, através da combinação de diferentes concentrações de sulfito de sódio, uréia e papaína. Ensaios preliminares de modificação da queratina foram conduzidos após esta extração. Temperaturas acima de 80°C, e concentrações intermediárias de uréia (3,75M) combinadas a baixas concentrações de sulfito de sódio (0,1M - 0,18M) foram os melhores parâmetros de extração. A hidrólise enzimática apresentou-se adequada somente quando combinada ao prévio tratamento químico. A combinação dos dois processos extrativos resultou em redução do tempo de reação da hidrólise enzimática. A queratina obtida apresentava tamanho de fragmentos homogêneos, ao redor de 650nm, e um grau de pureza de 72%-89% em massa seca de proteína purificada. A caracterização físico-química dos derivados da queratina demonstra a amplitude desta proteína como insumo para aplicações diversas. O estudo da inserção de grupamentos polares na molécula de queratina é feita por análise da solubilidade em diferentes solventes e por espectroscopia vibracional Raman. / The use of industrial wastes as a source of raw materials presents, besides the cost-effective advantages, an eco-friendly approach. Great amount of feather waste discharged from slaughterhouses demands the development of biotechnological alternatives for its recycling. Feather is the most keratinous material in nature and may be used for different applications in biotechnology, pharmaceutical and chemical industry. Several authors have written methods for feather keratin extraction, as acid and alkaline hydrolysis. Those methods presented disadvantages like damage to the backbone protein chain and loss of its main function as well as loss of cross linking groups. Other chemical treatments require large amounts of expensive reagents such as 2-mercaptoethanol and proteolytic enzymes. The present work comprises a factorial planning for extraction and fragmentation of feather keratin by combining sodium sulfide (0,1M 0,26M), urea (2M- 6M) and papain (0,13mg/ml). Feather keratin modification assay was conducted after protein extraction. The experiment presented satisfactory results when temperature extraction is maintained around 80° C, urea is used in an intermediate concentration (3,75M) and sodium sulfide in a low concentration(0,1M- 0,18M). Enzymatic hydrolysis is viable only after previous chemistry extraction. The combination of both treatment types resulted in a decrease of enzymatic time reaction and therefore an optimized keratin production. Extracted feather keratin presented homogenous size fragments with most particle diameters around 650nm. The percentage of proteins found was around 72%-89% compared to the total dry weight. The physicochemical characterization of feather keratin derivatives bring this protein of interest as a potencial component to renewable raw materials synthesis. Modification analysis of feather keratin was carried by qualitative solubility evaluation and vibrational spectrometry Raman.

Neste Trabalho foi preparada e estudada a blenda de poli(tereftalato de etileno) (PET) com polietileno de baixa densidade (PEBD). Esta blenda apresenta interesse científico e tecnológico decorrente da possibilidade de associar as propriedades de resistência térmica e elevado módulo de elasticidade do PET à boa resistência à fratura e à flexibilidade a baixas temperaturas do PEBD. Duas séries de misturas contendo diferentes proporções de PET:PEBD foram preparadas através de mistura em fusão numa extrusora dupla-rosca, contendo como agente compatibilizante poli(etileno-butileno)-bloco-poliestireno (produto comercial) ou poli(etileno-butileno)-bloco-poliestireno sulfonado (produto sintetizado), respectivamente, na proporção de 0 a 6 %. O agente compatibilizante poli(etilenobutileno)- bloco-poliestireno sulfonado foi preparado neste Trabalho a partir do poli(etileno-butileno)-bloco-poliestireno. Todas as misturas preparadas foram caracterizadas quanto às suas propriedades mecânicas através de ensaios de impacto e de tração. As superfícies de fratura criogênica das misturas foram observadas através de microscopia eletrônica de varrredura para caracterização da sua textura. As blendas apresentaram valores de módulo de Young intermediários àqueles observados para o PET (3,54 GPa) e PEBD (110 MPa), entre 1,32 GPa e 2,84 GPa. O mesmo foi observado para a resistência à tração na ruptura, cujos valores das blendas variaram de 13,3 MPa a 33,9 MPa, comparados com 59,6 MPa e e 0,49 MPa para PET e PEBD, respectivamente. / In these work blends of poly(ethylene tereftalate) (PET) and low density polyethylene (LDPE) were prepared and studied. The PET/PEBD blend presents scientific and technological interests due to the possibility of combining the high thermal stability and high elasticity modulus of PET with the fracture resistance and low temperature flexibility of LDPE. Two series of PET:LDPE blends with different relative proportions were prepared by melting mixture in a twin-screw extruder having as compatibilizing agent poly(ethylene-butylene)-block-polystyrene (commercial product) or sulfonated poly(ethylene-butylene)-block-polystyrene (synthesized product), respectively, in the range 0-6 %. The compatibilizing agent sulfonated poly(ethylene-butylene)-blockpolystyrene was prepared in this work from poly(ethylene-butylene)-blockpolystyrene. The mechanical properties of the blends were characterized by impact resistance tests and extensional tension tests. Textural analysis of blends was performed by observing their cryogenically fractured surfaces were characterized by scanning electron microscopy. The blends presented Young modulus values between those observed for PET (3.54 GPa) and LDPE (110 MPa), in the range from 1.32 GPa to 2.84 GPa. The same behavior was observed for the tensile strength, which values varied from 13.3 MPa to 33.9 MPa, compared to 59.6 MPa and 0.49 MPa for PET and LDPE, respectively.

Les fibres naturelles telles que le coton et le lin sont utilisées depuis longtemps dans l'industrie textile. De plus, elles prennent de plus en plus d'importance dans l'industrie des composites comme substituants des fibres de verre, de carbone ou d'aramide. Cependant, les fibres naturelles doivent être modifiées pour surmonter certains inconvénients tels que l'inflammabilité, l'hydrophilie et l'oléophilie. Dans ce travail, les retardateurs de flamme (RF) phosphorés et fluoro-phosphorés sont greffés par bombardement électronique et par modification chimique sur des tissus de lin afin d’améliorer leur comportement au feu, l’hydrophobicité et l’oléophobie. L'effet de la composition chimique sur le greffage a été également évalué en utilisant des fibres de miscanthus comparativement aux tissus de lin. La réactivité de la double liaison C = C des monomères phosphorés est étudiée pour contrôler l’efficacité de greffage de différents RF. Les étapes du radiogreffage sont étudiées et contrôlées. L'efficacité de greffage a été évaluée par fluorescence X et analyse par rayons X à dispersion d'énergie (EDS) / microscopie électronique à balayage (SEM). La résonance magnétique nucléaire du proton est utilisée pour analyser l'effet de l'irradiation sur les différents monomères. Le comportement au feu des tissus modifiés est étudié en utilisant l’analyse thermogravimétrique, la microcalorimétrie de combustion, cône calorimètre et un test au feu préliminaire. Des tissus ignifuges et oléophobes ont été développés avec succès. / Many natural fibers have been used for a long time in textile industry as cotton and flax. Moreover, natural fibers are getting more importance in composites industry as a substitute for glass, carbon, or aramid fibers. However, they must be modified to overcome some disadvantages such as flammability, hydrophilicity and oleophilicity. In this work, phosphorus and fluoro-phosphorus flame retardants were grafted by e-beam radiation and chemical modification on flax fabrics to improve their flame retardancy, hydrophobicity and oleophobicity. The effect of chemical composition on grafting were also evaluated using miscanthus fibers in comparison to flax fabrics. The reactivity of the double bond C=C of the P-monomers was studied to control the grafting yield of various FRs. Radiation grafting steps were studied and controlled carefully. Grafting efficiency was assessed by X-ray fluorescence and Energy Dispersive X-Ray Analysis (EDX) / Scanning Electron Microscopy (SEM). Proton nuclear magnetic resonance was used to analyze the effect of irradiation on different monomers. Fire behavior of the modified fabrics was studied using thermogravimetric analysis, pyrolysis combustion flow calorimetry, cone calorimetry and a preliminary fire test. Flame retardant and oleophobic fabrics were successfully developed.

Neste trabalho a reação de modificação química da poliacrilonitrila pela incorporação de grupos 2-oxazolina foi estudada através da interação dos grupos nitrila do polímero com 2-amino-etanol catalisada por acetato de cádmio. Os copolímeros foram obtidos em diferentes condições reacionais para alcançar a reação de incorporação do heterocíclico preferencialmente à reação de ciclização dos grupos nitrila que ocorre na presença de catalisador. O grau de modificação química obtido foi relacionado às alterações nas propriedades dos polímeros modificados, que foram caracterizados por espectroscopias na região do infravermelho com transformada de Fourier, do ultravioleta-visível e de ressonância magnética nuclear de hidrogênio, e por calorimetria diferencial de varredura e termogravimetria. As condições ótimas de reação foram alcançadas a 70C após 35h. E o polímero obtido a partir destas condições foi avaliado como inibidor de corrosão para aço-carbono em solução de ácido clorídrico. Sob estas condições experimentais, uma eficiência de inibição de 63 % foi obtida / In this work the chemical modification reaction of polyacrylonitrile by the incorporation of 2-oxazoline groups was obtained through the interaction of the polymer nitrile groups with 2-amino-ethanol, catalyzed by cadmium acetate. The copolymer were obtained from different reaction condictions, in order to achieve the incorporation reaction of the heterocycle rather than the cyclization reaction of nitrile groups, which occurs in the presence of the catalist. The chemical modification degree obtained was related to changes in the properties of the modified polymers, which were characterized by Fourier transform infrared, and ultraviolet-visible spectroscopy, hydrogen nuclear magnetic ressonance and differential scanning calorimetry and thermogravimetric analysis. The optimum reaction condiction condictions were achieved after 35 h at 70C and the polymer obtained from such condictions was evaluated as a corrosion inhibitor for carbon-steel in chloridric acid solution. Under these experimental condictions as inhibition efficiency of 63 % was obtained

Choline oxidase from Arthrobacter globiformis is a flavin-dependent enzyme that catalyzes the oxidation of choline to betaine aldehyde through two sequential hydride-transfer steps. The study of this enzyme is of importance to the understanding of glycine betaine biosynthesis found in pathogenic bacterial or economic relevant crop plants as a response to temperature and salt stress in adverse environment. In this study, chemical modification of choline oxidase using two irreversible inhibitors, tetranitromethane and phenylhydrazine, was performed in order to gain insights into the active site structure of the enzyme. Choline oxidase can also be inactivated irreversibly by freezing in 20 mM sodium phosphate and 20 mM sodium pyrophosphate at pH 6 and -20 oC. The results showed that enzyme inactivation was due to a localized conformational change associated with the ionization of a group in close proximity to the flavin cofactor and led to a complete lost of catalytic activity.