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1
Bolcato, Chiara. « Progettazione sintesi e valutazione biologica di sistemi eterociclici quali antagonisti per i recettori adenosinici. Validazione di modelli recettoriali ». Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2567.
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2006/2007La tesi illustra il lavoro di dottorato mirato allo sviluppo di nuovi antagonisti adenosinici attivi nei confronti dei vari sottotipi recettoriali del ligando naturale Adenosina.
XX Ciclo
1977
2
Retamoso, Leandro Thies. « PAPEL DO SISTEMA PURINÉRGICO E DOS RECEPTORES DE POTENCIAL TRANSITÓRIO VANILOIDE 1 (TRPV 1) NA DOR MUSCULAR TARDIA APÓS EXERCÍCIO EXCÊNTRICO EM RATOS ». Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/6715.
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Chronic exercise has been recommended as a strategy for preventing several diseases associated with lifestyle such as heart disease, hypertension, osteoporosis and type II diabetes. Although regular physical exercise has benefits for health, all sports practitioners, and even sedentary people, have already feel delayed onset muscle soreness (DOMS) once, characterized by discomfort in skeletal muscle. As the most DOMS generator, acute eccentric exercise induce fatigue, strength reduction and performance impairment. Despite some researches demonstrating reactive oxygen species (ROS) in this context, there are few information about purine degradation as well as transient receptor potential vanilloid 1 (TRPV1) on DOMS development. In this context, animals performed a downhill running test (eccentric exercise) on treadmill until exhaustion for histologic evaluation, mechanical allodynea, strength force test and biochemical analysis. The results showed an increase in mechanical allodynea and ADP, AMP, uric acid and TRPV1 immunoreactivity levels. In conclusion, the results support the contribution of ROS and the participation of purine and TRPV1 on delayed onset muscle soreness.O exercício físico crônico tem sido recomendado como estratégia para a prevenção de diversas doenças associadas ao estilo de vida, como doenças cardíacas, hipertensão, osteoporose e diabetes tipo 2. Embora o exercício físico regular traga benefícios para a saúde, todos os praticantes de atividade física e esporte e, até mesmo indivíduos sedentários, já experimentaram alguma vez na vida um episódio de dor muscular tardia (DMT), caracterizada pela sensação de desconforto na musculatura esquelética. Como grande gerador de DMT, destaca-se o exercício excêntrico agudo que induz fadiga, redução de força e perda de desempenho. Apesar de diversos estudos demonstrando a participação das espécies reativas de oxigênio neste quadro, pouco se sabe sobre a participação da degradação das purinas bem como a participação dos receptores de potencial transitório vaniloide 1 (TRPV1) no desenvolvimento da dor muscular tardia. Para tanto, os ratos wistar machos realizaram teste de downhill em esteira (exercício excêntrico) até a exaustão. Após foram analisados os danos histológicos nos músculos gastrocnêmio e sóleo, Outro set de animais após a exaustão foram avaliados nos testes de alodinea mecanica na pata traseira direita, teste funcional de força nas pastas dianteiras e análises bioquímicas no músculo gastrocnêmio. Os resultados demonstram aumento na alodinea, na carbonilação protéica, nos níves de ADP, AMP, ácido úrico, além de elevar os níveis de immureatividade do receptor TRPV1 e atividade da xantina oxidase. Esses dados apontam uma possível contribuição das espécies reativas de oxigênio, da degradação de purinas e dos receptores TRPV1 na dor muscular tardia.
3
Sobral, Ivoneide Santana. « Estudo químico e da atividade antimicrobiana do caule da Kielmeyera cuspidata ». Programa de Pós-Graduação em Química da UFBA, 2006. http://www.repositorio.ufba.br/ri/handle/ri/9997.
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O presente trabalho relata a investigação fitoquímica da espécie Kielmeyera cuspidata, pertencente à família Clusiaceae. Este é o primeiro estudo fitoquímico desta espécie. A coleta do material ? caule e folhas ? foi feita na região da Chapada Diamantina no município de Andaraí, estado da Bahia. Do extrato hexânico e da fase diclorometano do extrato metanólico do caule da K. cuspidata foram obtidas dez substâncias. Sendo que no extrato hexânico foi identificado uma mistura de esteróides (acetato de sitosterol e acetato de estigmasterol). Já na fase diclorometano foi identificada uma mistura de triterpenos (a-amirina e b-amirina) e seis xantonas. Na determinação estrutural das substâncias isoladas, foram utilizados métodos espectrométricos usuais; UV, RMN e espectro de massas, juntamente com comparação dos dados descritos na literatura. Foram realizados também testes de atividade antimicrobiana nos extratos trabalhados.
Salvador
4
Stockert, Amy L. « Spectroscopic and kinetic studies of bovine xanthine oxidase and Rhodobacter capsulatus xanthine dehydrogenase ». Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1089910515.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xv, 172 p.; also includes graphics. Includes bibliographical references (p. 165-172).
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Costa, Eliângela Cristina Cândida. « Estudo químico e avaliação do potencial biológico da raiz de Kielmeyera coriacea Mart. & ; Zucc (Calophyllaceae) ». Universidade Federal de Goiás, 2017. http://repositorio.bc.ufg.br/tede/handle/tede/8595.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Cerrado is a region whose biological richness is unique, being formed by about 10 thousand plants. The flora study, ethnobotanic stands out for understanding of the interaction of society whit plants. In this view, teacher Dr. Vanessa Pasqualotto research group’s has been carrying out ethnobotanic survey in collaboration with the Coqueiros community, with the objective of recovering and valuing the popular knowledge about medicinal plants, among which the Kielmeyera coriacea species, the focus of this study, stands out. In this group, 37 members were interviewed, of which 76% indicate K. coriacea for the treatment of infections, rheumatism, leukemia, tooth pain, among others. Thus, the chemical study of ethanolic extract of roots (EER) of this species, aiming at to characterize its secondary metabolites, since there are no chemical reports in the literature for this part of the plant. In addition antioxidant, antimicrobial and antitumor potential of K. coriacea were evaluated. From the liquid-liquid extraction of EER the hexane (FH), ethyl acetate (FAE) and hydroalcoholic (FHA) fractions were obtained; by the fractionation of FAE, the substance 3-hydroxy-2,4- dimethoxyxanthone was isolated. Additionally, a fingerprint study was performed by LC-MS technique, identifying major compounds such as δ-tocotrienol, prenylated acylphoroglucinol, 2-hydroxy-1-methoxyxanthone, quercitrin. EER, FH, FAE, FHA, its subfractions and the isolated substance were submitted to biological tests. FHA presented antioxidant action with EC50 de 201,53 μg mL-1. EER and FH-10 subfraction from FH fractionation, inhibited the bacterial growth of Streptococcus pyogenes and S. pneumoniae (Minimum Inhibitory Concentration of 6.25 and 1.56 μg mL-1, respectively); EER also inhibited the fungus Candida glabrata in 7.81 μg mL-1. Finally, FH, FAE and FH-10 presented an antitumor effect against the HeLa cells, which are related to cervical cancer (IC50 of 2.5 μg mL-1, 2.5 μg mL-1 and 0.89 μg mL-1, respectively). When correlating the chemical and biological data, it is possible that the FAE-4.7.3 subfractions, from the fractionation of FAE, and FH-10 are constituted by substances such as 4-hydroxy-2,3-methylenedioxy xanthone, 3-hydroxy-1,2-dimethoxy xanthone, lupeol, prenylated acylphoroglucinol and quercitrin, which could be associated with the biological potential found. Therefore, the knowledge acquired in this study contributed to the expansion of the chemical-biological knowledge of K. coriacea.
O Cerrado é uma região cuja riqueza biológica é singular, sendo formado por cerca de 10 mil plantas. No estudo da flora, a etnobotânica se destaca por compreeder a interação da sociedade com as plantas. Nesse contexto, o grupo de pesquisa da Profa. Dra. Vanessa Pasqualotto vem realizando estudos etnobotânicos em colaboração com a comunidade Coqueiros, visando o resgate e a valorização dos saberes populares sobre plantas medicinais, dentre as quais se destaca a espécie Kielmeyera coriacea, foco deste estudo. Neste estudo foram entrevistados 37 membros, em que 76% indicam K. coriacea para o tratamento de infecções, reumatismo, leucemia, dor no dente, dentre outras. Assim, foi realizado o estudo químico do extrato etanólico da raiz (EER) desta espécie, objetivando caracterizar seus metabólitos secundários, uma vez que não há relatos químicos na literatura para esta parte da planta. Ademais, foi avaliado os potenciais antioxidante, antimicrobiano e antitumoral de K. coriacea. A partir da extração líquido-líquido de EER foram obtidas as frações hexano (FH), acetato de etila (FAE) e hidroalcoólica (FHA); pelo fracionamento da FAE foi isolada a substância 3-hidroxi-2,4-dimetoxixantona. O estudo do perfil químico foi realizado por CLAE-EM, identificando-se compostos majoritários como δ-tocotrienol, acilforoglucinol prenilado, 2-hidroxi-1-metoxixantona e quercitrina. EER, FH, FAE, FHA e suas subfrações, bem como a substância isolada foram submetidos aos ensaios biológicos. FHA apresentou ação antioxidante com EC50 de 201,53 μg mL-1. EER e a subfração FH-10, proveniente do fracionamento de FH, inibiram o crescimento bacteriano de Streptococcus pyogenes e S. pneumoniae (Concentração Inibitória Mínima de 6,25 e 1,56 μg mL-1, respectivamente); EER também inibiu o fungo Candida glabrata na 7,81 μg mL-1. Por fim, FH, FAE e FH-10 apresentaram efeito antitumoral frente à célula HeLa, a qual está relacionada ao câncer do cólon do útero (IC50 de 2,5, 2,5 e 0,89 μg mL-1, respectivamente). Ao correlacionar os dados químicos com biológicos, tem-se que as subfrações FAE-4.7.3, proveniente do fracionamento de FAE, e FH-10 são constituídas por substâncias como 4-hidroxi-2,3-metilenodioxixantona, 3-hidroxi-1,2-dimetoxixantona, lupeol, acilforoglucinol prenilado e a quercitrina, as quais poderiam estar associadas ao potencial biológico encontrado. Portanto, o conhecimento adquirido neste estudo contribuiu para a ampliação dos saberes químico-biológicos de K. coriacea.
6
Fujisawa(Morita), Yukari. « Identification of xanthine dehydrogenase/xanthine oxidase as a rat Paneth cell zinc-binding protein ». Kyoto University, 2001. http://hdl.handle.net/2433/150188.
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Wilson, Wendy Lee. « Xanthine oxidase in the lung ». Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26669.
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The generation of oxygen free radicals by the cytosolic enzyme, xanthine oxidase (XO), has been implicated in post-ischemic or reperfusion damage in several organs. XO catalyzes the conversion of hypoxanthine to urate with the concomitant production of superoxide anion free radical (0₂̅˙) and hydrogen peroxide (H₂O₂). Oxygen free radical-mediated injury has also been demonstrated in inflammatory lung disease. The possible involvement of XO in oxidative injury in the lung has not yet been studied. Therefore, this research project was designed to determine whether XO is present in the lung and to investigate its characteristics in porcine, bovine, rat and human lung and other tissues.
Immunochemical analysis of xanthine oxidase in the tissues employed on polyclonal antibody raised to bovine milk XO. Proteins were separated by SDS-polyacrylamide gel electrophoresis of tissue homogenates. Proteins were transfered from the gels to nitrocellulose filters by Western blotting. After incubating the filters with a antisera containing the antibody to the purified bovine XO. XO on the filter was detected by its reaction with an enzyme-conjugated second antibody. XO was immunologically detectable in bovine lung and milk. Rat lung, kidney and liver all showed XO reactivity. XO was detectable in porcine liver but not detectable in porcine lung or kidney. Thus, the antibody to bovine XO was cross-reactive with porcine and rat XO. XO protein was not immunologically detectable in human lung possibly because the antibody was not cross reactive with the bovine antibody. In vivo, xanthine oxidase exists predominantly as a dehydrogenase rather than an oxidase. In this form as xanthine dehydrogenase (XDH) the enxyme does not produce either 0₂̅˙ or
H₂O₂. The activity of both XDH and XO was measured in several
tissues using a fluorometric assay which uses an artifical substrate,
pterin which is catalytically converted to the fluorescent product
isoxanthopterin (IXP). XO activity in porcine liver was of 1.1 x 10⁻³ µg IXP/mg protein/min although XO activity was not detectable
in porcine lung and kidney, in rat lung of 1.7 x 10⁻² µg IXP/mg
protein/min, rat kidney of 1.5 x 10⁻² µg IXP/mg protein/min, and
rat liver of 2.2 x 10⁻² µg IXP/mg protein/min. Seven human lung biopsy samples were obtained after lung resection and initially tested for viability by determination of NADH oxidase activity and then assayed for XO-XDH. Three of these samples showed NADH oxidase activity indicating tissue viability, but only one of these three showed measurable XO activity of 5.35 x 10⁻⁶ µg IXP/mg protein/min.
Irreversible conversion of XDH to XO is thought to be the result of limited proteolysis by a Ca²⁺/calmodulin activated protease, whereas reversible conversion of the enzyme occurs by oxidation of critical thiol groups. Studies on the rate and nature of fluorescence assay to detect catalytic activities of both enzyme forms. Incubation of lung homogenates with trypsin for 60 min caused
irreverisble conversion of 90% of the XDH to XO. In contrast,
incubation of homogenates at 15°C for 10 hours caused conversion of
100% of the XDH to XO. This conversion was reversible to the extent
of 80% by reduction of thiol groups with dithiothreitol (DTT). The
effects of free Ca²⁺ on the conversion of XDH to X0 was examined by
using EDTA, a chelator of Ca²⁺ and other divalent cations; and EGTA,
a more specific chelator of Ca²⁺. The presence of these chelating agents during homogenization of either normoxic or ischemic rat lung tissue did not inhibit reversible enzyme conversion. Increased XO activity was reversible by DTT. In the normoxic rat lung, homogenates prepared with EDTA and EGTA showed a similar conversion of 95% of XDH to XO which was reversible to 70% with DTT. In the ischemic rat lung, samples prepared with EDTA and EGTA showed a'conversion of 80% and 95% XDH to XO which was similar to control samples. The extent of reversibility to XDH was 75% with DTT incubation. In addition, perfusion of rat lungs with EDTA and DTT via a pulmonary artery cannula prior to 60 min of ischemia and homogenization did not affect the extent of XDH to XO conversion.
These results indicate that irreversible Ca²⁺-mediated proteolytic conversion of XDH to XO does not occur to a great extent in the rat lung during either normoxia or ischemia. However, reversible conversion of XDH to XO does occur, suggesting that reversible thiol dependent conversion may play a role in the lung under both physiological and pathophysiological states.Medicine, Faculty of
Pathology and Laboratory Medicine, Department of
Graduate
8
Gibson, Elizabeth. « Porphyrin probes for xanthine oxidase ». Thesis, University of York, 2007. http://etheses.whiterose.ac.uk/9915/.
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Martin, Hannah M. « Cellular expression of xanthine oxidoreductase ». Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426176.
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Wang, Jinfang. « Xanthine-imprinted polymers for decaffeination applications ». Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431777.
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Pauff, James Michael. « Structure-Function Studies of Xanthine Oxidoreductase ». The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1227480976.
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Leigh, Maria. « Non purine inhibitors of xanthine oxidase ». Thesis, University of York, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550273.
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The increase in the occurrence of hyperuricemia and gout in recent years, coupled with side- effects associated with use of the main anti-gout therapeutic, allopurinol, have triggered the search for non-purine alternatives. The first such inhibitor to be made available is Adenurlc", 2-(3-cyano-4-isobutoxyphenyl)-4-methylthiazole-5-carboxylic acid. The aim of this work was to synthesise a small library of non-purine compounds and evaluate their inhibitory activity against the enzyme, xanthine oxidase. Successful inhibitors are marked as those that gave a comparable or lower ICso value than allopurinol (3 ± 0 J.1M), under conditions employed in this work. A range of five-membered heterocyclic compounds, including 1,2,4-triazole-3-thiones, 2- amino-1,3,4-thiadiazoles and 1,3-thiazoles were synthesised. On testing, the heterocyciic compounds did not reveal significant inhibition of XO. SAR analysis marked the presence of alkyl chains and para-cyano substituents as contributors to inhibition. The most successful heterocyciics investigated were highlighted as [17b), 4-(4-cyanophenyl)-1,3-thiazole-2- carboxylic acid, (ICso= 150 ± 14 J.1M) and [15), [4-(4-bromophenyl)-1,3-thiazole-2- sulfanyl]acetonitrile, (ICso= 29 ± 4 J.1M). A concise library of Schiff base compounds was then investigated, incorporating thiosemicarbazones, dithiocarbazates and hydrazones, with varied number and positioning of aromatic substituents. SAR analysis revealed important structural features affecting inhibition, such as a para-hydroxyl benzaldehyde substituent and a para-hydroxyl/cyano substituent on hydrazide/thiosemicarbazide rings. The position rather than the number of hydroxyl substituents proved significant for inhibition. The most potent compounds were thiosemicarbazones 8-Tz3 (0.6 ± 0.2 IlM), 10-Tz2 (0.5 ± 0 ~LM), 10-Tz3 (0.6 ± 0.1 IlM), 11- Tz2 (O.B ± 0.1 J.1M), 11-Tz3 (0.6 ± 0 J.1M) and 11•DTz1 (0.7 ± 0.1 J.1M), giving four times lower ICso than allopurinol. Potent uncomplexed Schiff bases as XO inhibitors have not been previously reported. Steady-state kinetic studies on 8-Tz3, 11-Tz3, 8-DTz1 and 11•DTz1 revealed mixed-type inhibition. As 11•DTz1 gave the lowest Kj value (0.4 ± 0 IlM), coupled with its low ICso value, highlight it as a promising lead compound. Upon reduction of the imine bond, 11•DTz1 reduced retained improved activity over allopurinol, though less potent than its parent Schiff base. Complexation to Mo{VI) and Cu{lI) centres occurred, with the ligands acting as tridentate ONS/ONO donors. The distorted octahedral coordination geometry of Mo(Vl) complexes was confirmed via crystal structure determination. The Cu(lI) complexes, [Cun(l10-TZ2)n) and [Cun(L S-HS)n), revealed a 3-fold increase in potency over their free ligands. The presence of Cu(lI) therefore appears to have a cooperative effect and warrants further investigation as means of improving potency and hydrolytic stability.
13
Hewinson, James. « Vascular endothelial release of xanthine oxidoreductase ». Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418883.
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Khan, Jamshad. « Purification and stability of bovine xanthine oxidase ». Thesis, University of Bath, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307127.
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Bryant, Richard. « The immunoaffinity purification of human xanthine oxidase ». Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398413.
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Rouquette, Magali. « Xanthine oxidoreductase : a role in cell signalling ». Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300878.
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Page, Susanna. « Regulation and immunolocalisation of human xanthine oxidoreductase ». Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300881.
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Powell, Debbie. « Purification, characterisation and regulation of human xanthine oxidase ». Thesis, University of Bath, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307028.
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Choudhury, Sharmila. « Purification and characterisation of xanthine oxidoreductase from liver ». Thesis, University of Bath, 2001. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760763.
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Schmenk, Holger. « Xanten im 19. Jahrhundert : eine rheinische Kleinstadt zwischen Tradition und Moderne / ». Köln : Böhlau Köln, 2008. http://deposit.d-nb.de/cgi-bin/dokserv?id=3055441&prov=M&dok%5Fvar=1&dok%5Fext=htm.
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Silva, Saulo Luis. « Modelagem molecular de derivados fenilpirazolicos e flavonoides inibidores da xantina oxidase ». [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314678.
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Orientador: Sergio MarangoniTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Doutorado
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Urquhart, Michael William John. « Studies in xanthone chemistry ». Thesis, University of Central Lancashire, 1993. http://clok.uclan.ac.uk/20362/.
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A series of 3,4-dihydro-9H-xanthen- 1 ,9(2H)-diones has been prepared by the condensation of 2-fluorobenzoyl chlorides with cyclohexane- I ,3-diones followed by Fries rearrangement and cyclisation of the intermediate 3-oxocyclohexenyl 2-fluorobenzoates. Conversion to spim[ 1 ,2,3,4-tetrahydro-9H-xanthen- 1 ,2'-[ 1 ,3] -dioxolane] -9-one occurred on treatment of the xanthendione with ethane- 1 ,2-diol and trimethylsilyl chloride. 3,4-Dihydro-4-methyl-9H-xanthen- 1 ,9(2H)-dione has been synthesised by quenching the lithium dienolate of the ketal with iodomethane. Conjugate reduction of the xanthendione has been accomplished using sodium borohydride in pyridine to give 1hydroxy-2,3,4,4a-tetrahydro-9H-Xanthen-9-one whose chemistry has been investigated. Treatment of the xanthendione with tris(methylthio)methyllithium gave the 1,4-adduct. Subsequent mercuric ion catalysed solvolysis provided methyl 1 -hydroxy-2,3,4,4a-tetrahydro-9H-xanthen-9-one-4a-carboxylate which is the parent nng of the secalonic acid series of natural products. 4a-Alkyl derivatives have been prepared in excellent yield from the xanthendione and organocyanocuprate reagents. The corresponding Grignard reagents displayed less selectivity in their mode of addition. Reaction of the 1 -hydroxytetrahydroxanthones with hydroxylamine gave 4-substituted 6,7-dihydro-3-(2-hydroxyphenyl)-2, I -benzisoxazoles resulting from ring cleavage of the xanthone nucleus. Dehydrogenation of these systems with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and with palladium on charcoal catalyst has been explored. Treatment of 1 -hydroxy-2,3,4,4a-tetrahydro-9H-xanthen-9-ones with lithium diisopropylamide in tetrahydrofuran afforded dianions which provided an entry to 2-functionalised derivatives by quenching with electrophiles. Acid catalysed treatment of 1hydroxy2,3,4,4a-tetrahydro-9H-xanthen-9-One gave 3,4-dihydro-9H-xanthen-9-one by way of a retro-Michael ring cleavage-bond switch operation. The substituted analogues behaved similarly, although the products were dependent upon the nature of the substituents present. The value of some 3,4-dihydro-9H-xanthen-9-ones as dienes in [4+21-cycloaddition reactions has been established with a variety of dienophiles. The chemistry of some 2-(2-fluorobenzoyl)- I -hydroxy-2,3,4,4a-tetrahydroxanthones has been investigated. Treatment with DBU in toluene led to 4-(2-hydroxybenzoyl)- 9H-xanthen-9-ones, whereas with potassium carbonate in acetone novel 5H,13H-[l]benzopyrano[2,3 -ajxanthen -5, 1 3-diones were obtained. The mechanism of formation for these compounds is discussed.
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Liu, Chuangjun. « MODIFICATION OF XANTHENE AND SILICON ANALOGUES OF XANTHENE FLUOROPHORES FOR CHEMICAL PROBES DEVELOPMENT ». OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1158.
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Fluorescence techniques have been widely used in chemistry and many areas of biology due to its high sensitivity, simplicity, fast response, and capability of spatial imaging. Currently there are six major classes of small-molecular fluorophores-coumarins, boron dipyrromethene (BODIPY) dyes, fluoresceins, rhodamines, oxazines, and cyanines. This dissertation mainly focuses on modifications of fluoresceins and development of pH probes based on rhodamines. We have modified the xanthene core of fluorescein by replacing the xanthene oxygen with a dimethylsilyl group which shows 90 nm red-shift relative to fluorescein (λabs/λem =582 nm/598 nm). These fluorophores have advantages over their oxygen counterparts because longer-wavelength allows deeper penetration of the light, causing less damage to the cells and less interference from the biological medium. Based on this scaffold, we have tried to develop copper, mercury, and hydrogen peroxide probes by functionalizing the hydroxyl group of the fluorophore with different groups. Although the results weren’t satisfactory, we have gained some new insights about this scaffold. The hydroxyl group of the fluorophore is not very reactive and this scaffold is not stable under strong basic conditions and its electronic configuration is very different with the regular fluorescein. We have synthesized and characterized Si-rhodol fluorophore, the hybrid structure of Si-fluorescein and Si-rhodamine. The preliminary investigation of Si-rhodol, UV-vis and fluorescence, has been performed. It shows that the absorption and fluorescence emission of Si-rhodol are around 30 nm red-shift compared to Si-fluorescein (λabs/λem =617 nm/630 nm). And Si-rhodol is more fluorescent than Si-fluorescein (pKa = 6.8) at pH 7.4 (biological condition) due to its lower pKa (5.3). Despite the excellent photophysical properties of Si-rhodol, there are actually limited examples about its application. Among these examples, none of them gave the detailed information about functionalization of the hydroxyl group of Si-rhodol. We have found a method to functionalize the hydroxyl group of Si-rhodol. We have developed a series of pH probes through modification of rhodamines which possess either an aniline-methyl or cyclic ring moiety. These analogues maintain a coloress, non-fluorescent spirocyclic structure at high pH and the fluorescence goes up while the pH decreases. The substituent effects on anilinomethylrhodamines (AnMR) system follows Hammett’s equation. The effect of cycloalkane ring size on the acid/base properties of the AMR system can be predicted by Baeyer’s ring strain theory. The pKa of these rhodamine analogues can be tuned from around 3 to 8. We have also investigated aminomethylfluoroscein (AMF) system. In this system, we found that once the phenolic hydroxyl group was functionalized at one side, the fluorescence was off at pH>3. In addition, variation of the substituents on aminomethyl moiety didn't affect the pKa of this system significantly. Therefore, we were set out to develop mitochondria-targetable hydrogen peroxide probe. However, in the presence of triphenylphosphine cation, the conversion from the OTf group to the boronate group didn't work.
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Godber, Benjamin L. J. « Physicochemical and kinetic properties of human milk xanthine oxidoreductase ». Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760718.
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Dantas, Deyse de Souza. « Caracterização estrutural e bioquimica da hipoxantina-guanina-xantina fosforribosiltransferase ». [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314756.
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Orientadores: Gonçalo Amarante Guimarães Pereira, Francisco Javier Medrano MartinTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Os genes que codificam para a 6-oxopurina fosforribosiltransferase (HPRT, EC2.4.2.8) dos organismos Pyrococcus horikoshii e Schistosoma mansoni foram clonados em vetores de expressão. As proteínas foram expressas e purificadas em larga escala no sistema de expressão de Escherichia coli. Estudos cinéticos mostraram que a enzima de P. horikoshii é capaz de usar hipoxantina, guanina e xantina. Os dois primeiros substratos apresentam uma eficiência catalítica semelhante. A xantina apresenta um valor menor (ao redor de 20 vezes mais baixo), mas a constante catalítica é comparável com a da hipoxantina. A proteína não foi capaz de se ligar a GMP-agarose, mas sim pode ligar o outro substrato da reação reversa, pirofosfato inorgânico, com baixa afinidade (Kd = 4,7 ± 0,1 mM). Os dados de espalhamento dinâmico de luz, gel filtração e espalhamento de raios X a baixo ângulo mostram que esta proteína é um homohexâmero em solução. Este hexâmero é compacto e resistente à ação limitada de enzimas proteolíticas. Estudos de estabilidade frente a agentes químicos mostraram que a proteína é bastante estável resistindo os efeitos da uréia sem desenovelar completamente com a maior concentração do agente (8,0 M). Os dados obtidos com cloreto de guanidina mostraram que a proteína possui, no mínimo, um estado intermediário de desnaturação, como mostram os diferentes perfis obtidos com as diferentes técnicas usadas nos estudos de desnaturação. Os dados preliminares obtidos com a HPRT de S. mansoni mostraram que, na presença da cauda de histidinas, a proteína está presente como um octâmero alongado. Mas, muito provavelmente ela deve ser um tetrâmero. A presença de caudas fusionadas nas proteínas recombinantes pode afetar a estrutura e função das proteínas
Abstract: The genes that code for the 6-oxopurine phosphoribosyltransferase (HPRT, EC2.4.2.8) from the organisms Pyrococcus horikoshii and Schistosoma mansoni were cloned in expression vectors. The proteins were expressed and purified in large scale in the de Escherichia coli expression system. Kinetic studies showed that the enzyme from P. horikoshii is able to use hypoxanthine, guanine and xanthine. The first two substrates show a similar catalytic efficiency. Xanthine show a lower value (around 20 times), but the catalytic constant is comparable to that of hypoxanthine. The protein was unable to bind to GMP-agarose, but was able to bind the other substrate of the reverse reaction, inorganic pyrophosphate, with low affinity (Kd = 4.7 ± 0.1 mM). Dynamic light scattering, gel filtration and small angle X-ray scattering data show that the protein is a homohexamer in solution. This hexamer is compact and resistant to the limited action of proteolytic enzymes. Stability studies with chemical agents showed that the protein is very stable being able to stand the effects of urea without unfolding completely at the highest agent concentration (8.0 M). Data obtained with guanidine hydrochloride showed that the protein presents, at least, one unfolding intermediate state, as can be seen with the different profiles obtained with different techniques used in the unfolding studies. Preliminary data obtained from HPRT from S. mansoni showed that in the presence of the histidine tag, is present as a long octamer. But, most likely it should be a tetramer. The presence of histidine tag fused to the recombinant proteins could affect the structure and function of proteins
Doutorado
Bioquimica
Doutor em Biologia Funcional e Molecular
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NERI, David Fernando de Morais. « Imobilização de xantina oxidase em polissiloxano-álcool polivinílico magnetizado ». Universidade Federal de Pernambuco, 2005. https://repositorio.ufpe.br/handle/123456789/1888.
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Previous issue date: 2005Xantina oxidase (XOD, E.C. 1.17.3.2) é uma enzima que contem molibdênio de importância em análises clínicas com uma estrutura e ação bem definidas. XOD já foi imobilizada em diversas matrizes como contas de gel de poliacrilamida, poliamida-11, Dacron, polianilina-silicone, eletrodos de pasta de carbono modificada, eletrodos de nanocristais de ouro-carbono bem como vidro. No presente estudo um compósito híbrido inorgânico-orgânico magnetizado, baseado em uma rede de polissiloxano e álcool polivinílico (POS-PVA), ativado com glutaraldeído, é proposto como suporte para a imobilização de XOD extraída de leite bovino. A enzima foi parcialmente purificada através de fracionamento com sulfato de amônio (saturação entre 38 e 50%) com uma atividade específica de 69 mU/mg de proteína. A eficiência de imobilização foi de 42% da XOD oferecida com uma relação de 12,7μg de XOD/mg de suporte. A XOD imobilizada em POS-PVA magnetizado apresentou um pH e temperatura ótimas de 8,8 e 45°C, respectivamente. A constante de Michaelis para a XOD imobilizada foi de 8,42 μM para a xantina. Quando a 6-mercaptopurina foi utilizada como substrato a XOD imobilizada ainda foi capaz de reconhecer este substrato e convertê-lo em ácido 6-tioúrico. Baseado nestes resultados, podemos propor o POS-PVA magnetizado como suporte para imobilização de XOD
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Lira, Eduardo Carvalho. « Efeito anticatabólico dos derivados de xantina no metabolismo de proteínas em músculos esqueléticos de ratos sépticos : um estudo de microdiálise ». Faculdade de Medicina de São José do Rio Preto, 2006. http://bdtd.famerp.br/handle/tede/223.
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Previous issue date: 2006-04-20Introduction: The aim of the present study was to estimate the anticatabolic effect of xanthine derivatives on skeletal muscle protein metabolism from septic rats by using microdialysis. Methods: Sepsis was induced by cecal ligation and puncture (CLP). After 3, 6 and 10 hours of surgery, male Wistar rats (~250g) were anesthetized with thionembutal sodium (50mg/Kg body weight i.p.) and placed on heating pads to maintain adequate temperature (37oC). Microdialysis probe was inserted in the anterior tibial muscle and an equilibration period of 30 minutes was allowed. After connecting the catheter inlet to a microinjection pump, the system was perfused with 0,5% bovine serum albumin, 50 μM tyrosine and 1 mmol/l glucose in isotonic saline at a rate of 1.0 μl/min. Samples of the skeletal muscle interstitial fluid and arterial plasma from carotid artery were collected after 90 minutes of experiment and tyrosine was measured by fluorescence. The interstitial tyrosine concentration was estimated from the dialysate concentration. To calibrate catheters in vivo the internal reference calibration technique was used. The muscle blood flow was estimated by ethanol technique. Overall proteolysis was investigated in extensor digitorus longus (EDL) muscles from sham-operated and 3-hour septic rats (~70g) incubated in the presence or not of IBMX (1mM). Results: In sham-operated and septic rats, skeletal muscle interstitial tyrosine levels (μM) were significantly higher than arterial plasma tyrosine. Three-hour septic rats showed a 33% decrease in muscle blood flow and a 128% increase in the concentration of tyrosine in skeletal muscle interstitial (235 ± 16, n=10), when compared to sham-operated rats (95,5 ± 5,5, n=10). Interstitial (I) minus arterial (A) plasma tyrosine concentrations difference was also significantly increased after 3 hours of sepsis (117 ± 7 vs. 31 ± 6 in sham-operated, n=10). Pentoxifylline (PTX; 50mg/Kg body weigh, e.v.) treatment, during 1 hour immediately after CLP, reduced in 25% and 50% the interstitial tyrosine concentration and I-A difference, respectively. In situ isobutylmethylxanthine (IBMX; 1mM), but not PTX, reduced the interstitial tyrosine concentration (30-46%) and I-A difference (43-48%) in both groups. The increase of proteolysis induced by sepsis in EDL muscles was abolished by in vitro addition of IBMX (1mM). Conclusions: The data show that: (1) microdialysis is a perfectly adapted tool to investigate in vivo regulation of muscle protein metabolism during acute catabolic states; (2) the catabolic effect of sepsis on rat skeletal muscle protein metabolism in vivo can be observed 3 hours after CLP; (3) the xanthine derivatives reduce the muscle protein catabolism induced by sepsis in rats.
Objetivo: investigar o efeito anticatabólico dos derivados de xantinas no metabolismo de proteínas de ratos sépticos utilizando a técnica de microdiálise. Materiais e métodos: Ratos machos Wistar (~250g) foram anestesiados com tiopental (50mg/Kg, i.p.) e mantidos em mesa cirúrgica aquecida (37°C). A sepse foi induzida pela ligadura e punção do ceco (CLP) e os músculos estudados após 3, 6 e 10 horas da cirurgia. O cateter de microdiálise foi inserido no tibial anterior, o qual foi perfundido a um fluxo constante de 1,0μl/min com solução salina enriquecida com albumina bovina (0,5%), 50 μM de tirosina fria, 1 mmol/l de glicose e [14C]-tirosina. A tirosina foi quantificada por fluorescência no dialisado, sangue arterial e solução de perfusão, após 90 minutos de microdiálise. O cateter foi calibrado in situ pela técnica da referencia interna. O Fluxo Sanguíneo Muscular (FSM) foi avaliado pela técnica do clearance de etanol. A proteólise foi quantificada no extensor digitorus longus (EDL) de ratos (~70g) sham ou sépticos por meio da liberação de tirosina in vitro. Resultados: A concentração intersticial de tirosina foi sempre maior que a concentração arterial. A sepse de 3 horas reduziu em 33% o FSM e aumentou em 127% a concentração intersticial de tirosina (235 ± 16, n=10) em relação ao sham (95 ± 5, n=10). A diferença I-A também foi maior no grupo séptico (117 ± 16 vs. 31 ± 6 no sham, n=10). A infusão sistêmica da pentoxifilina (PTX; 50mg/Kg, e.v.), durante a primeira hora pós-CLP, reduziu em 25% e 50% a concentração intersticial e a diferença I-A de tirosina, respectivamente. O tratamento in situ com isobutil-metil-xantina (IBMX; 1mM), mas não com PTX, reduziu a concentração intersticial (30-46%) e a diferença I-A (43-48%) de tirosina, em ambos os grupos. O aumento da proteólise muscular induzido pela sepse foi abolido pela ação in vitro da IBMX (1mM) que reduziu a proteólise em 41%. Conclusões: os resultados mostram que: (1) a microdiálise é uma técnica perfeitamente adaptada ao estudo do metabolismo de proteínas em situações catabólicas; (2) o modelo da CLP de 3 horas ativa o catabolismo de proteínas em músculos esqueléticos de ratos; (3) As ações sistêmicas, in situ e in vitro dos derivados de xantinas reduzem o catabolismo de proteínas em músculos de ratos sépticos.
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招桂鳳 et Kwei-fung Chiu. « Syntheses and chemistry of some xanthone derivatives ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31234768.
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Kelkar, Avijit S. « Novel syntheses of substituted xanthones ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31238671.
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Chiu, Kwei-fung. « Syntheses and chemistry of some xanthone derivatives / ». Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17506633.
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Cavalcante, Rosane Souza. « AvaliaÃÃo das caracterÃsticas estruturais de bolos com reduÃÃo calÃrica ». Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7187.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorO consumo de bolos com reduÃÃo calÃrica vem crescendo, mas tem apresentado desafios a serem superados na formaÃÃo da sua estrutura quando o aÃÃcar ou a gordura sÃo substituÃdos por adoÃantes, gomas, espessantes ou substitutos de gordura. O presente trabalho propÃs avaliar as caracterÃsticas internas de bolos com reduÃÃo calÃrica e a viabilidade de produÃÃo do mesmo com caracterÃsticas similares ao bolo convencional. Inicialmente, foram definidos o tempo de mistura da massa e a fonte de gordura a ser utilizada na formulaÃÃo, utilizando-se o volume especÃfico como parÃmetro. Em seguida, determinou-se a formulaÃÃo do bolo padrÃo a partir de um delineamento experimental do tipo fatorial simples, medindo-se volume especÃfico e a contagem de cÃlulas. A partir dessa formulaÃÃo, a sacarose e a gordura foram parcialmente substituÃdos para a produÃÃo de bolos com valor calÃrico reduzido. A substituiÃÃo do aÃÃcar foi feita proporcionalmente por uma mistura de goma xantana (1,5%) e sucralose (1%), enquanto a zeÃna foi usada para substituir a gordura. Nos bolos com reduÃÃo de aÃÃcar avaliou-se o volume especÃfico (VE), a contagem de cÃlulas (CC) dos bolos, a viscosidade aparente da massa e as suas propriedades tÃrmicas por meio de calorimetria diferencial de varredura (DSC). Nos bolos com reduÃÃo do teor de gordura, as anÃlises realizadas foram VE, CC e viscosidade aparente. Verificou-se que o bolo com maior VE foi aquele elaborado com gordura vegetal hidrogenada e 1 (um) minuto de mistura da massa. A formulaÃÃo padrÃo foi definida como tendo 155,88 e 28,78 partes de aÃÃcar e de gordura, respectivamente. à medida que o teor de aÃÃcar decresceu (10,00-52,17%) foram reduzidos o volume especÃfico (1,94-0,7 mL/g) e a contagem de cÃlulas (36,2 â 4,0 cÃl/cmÂ) do bolo e a viscosidade aparente da massa (337,56-631,40 cP). Com a reduÃÃo do teor de gordura, nÃo foram observadas diferenÃas significativas entre as amostras para VE, CC e viscosidade aparente, sendo viÃvel a produÃÃo do bolo com reduÃÃo calÃrica substituindo-se a gordura em atà 46,86%. Pelos resultados encontrados, foi observado que a substituiÃÃo do aÃÃcar contribuiu mais acentuadamente que a substituiÃÃo da gordura na formaÃÃo de defeitos na estrutura do bolo. Os termogramas das massas dos bolos padrÃo e com reduÃÃo de sacarose sugeriram que a presenÃa de sucralose pode reduzir a temperatura de gelatinizaÃÃo do amido, acelerando esse processo e causando uma compactaÃÃo da estrutura durante o assamento, favorecendo assim a coalescÃncia das bolhas dispersas na massa.
The consumption of cakes with calorie reduction is growing, but has presented challenges to be overcome in the formation of its structure when the sugar or fat are replaced by sweeteners, gums, thickeners or fat substitutes. The present study was to investigate the internal characteristics of cakes with calorie reduction and viability of producing the same pattern similar to conventional cake. Initially, we defined the mixing time and mass of fat source to be used in the formulation, using as parameter the specific volume. Next, we determined the pattern of the cake formulation from a factorial experimental design of the simple type, measuring the specific volume and cell count. From this formulation, sucrose and fat were partially substituted for the production of calorie reduced cake. Replacement of sugar was made in proportion of a mixture of xanthan gum (1.5%) and sucralose (1%), while the zein was used to replace fat. In cakes with sugar lowering evaluated the specific volume (VE), the cell count (CC) of the cakes, the apparent viscosity of the mass and its thermal properties by differential scanning calorimetry (DSC). In cakes with reduced fat content, the analyzes were VE, CC and apparent viscosity. It was found that the cake with increased VE was prepared with one hydrogenated vegetable fat and one (1) minute of mixing the dough. The standard formulation was defined as having 155.88 and 28.78 shares of sugar and fat, respectively. As the sugar content decreased (10.00 to 52.17%) were reduced specific volume (1.94 to 0.7 ml / g) and cell counts (from 36.2 to 4.0 cells / cm Â) the cake and the apparent viscosity of the mass (337.56 to 631.40 cP). By reducing the fat content, there were no significant differences between the samples for VE, CC and viscosity, and viable to produce cake with reduced calorie fat replacing up to 46.86%. For the results, it was observed that replacement of sugar contributed more sharply than the replacement of fat in the formation of defects in the structure of the cake. Thermograms of the mass of standard and cakes with reduced sucrose suggested that the presence of sucralose can reduce the starch gelatinization temperature, accelerating the process and causing a compression of the structure during baking, thereby facilitating the coalescing of bubbles dispersed in mass.
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Lates, Vasilica-Adriana. « Systèmes bioanalytiques pour la détermination de la capacité antioxydante et l’ochratoxine A dans les denrées alimentaires ». Perpignan, 2011. http://www.theses.fr/2011PERP1054.
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L'apport journalier en antioxydants (composés chimiques naturellement présents dans certains aliments) contribue à la diminution du stress oxydatif sur le métabolisme humain. Nous avons mis au point un nouvel outil pour la détermination de la capacité antioxydante, basé sur une série des réactions enzymatiques qui se déroulent dans un bioréacteur dont le produit principal, l’eau oxygénée, est suivi en temps réel par un biocapteur ampérométrique. Ce système analytique s'avère beaucoup plus adéquat pour l’analyse des échantillons réels que d’autres variantes déjà connues. La présence des mycotoxines (métabolites de certains champignons) dans différents aliments est une préoccupation majeure et d’actualité. Un dépistage rapide peut aider la prévention de la toxicité aigue provoquée par la consommation des produits alimentaires contaminés. La reconnaissance immunospécifique, en utilisant des anticorps immobilisés sur des différents supports (électrodes sérigraphiées, billes en verre), couplée soit avec une sonde redox soit avec une réaction enzymatique, est à la base d’une nouvelle technique utilisée pour la détection in situ de l'ochratoxine A dans des échantillons de vinDaily intake of antioxidants (natural constituents of foodstuffs) reduces the appearance of oxidative stress related diseases. A fast method for quantification of antioxidant activity could serve as an attractive criterion for aliments quality. In this work, a new analytical tool for antioxidant capacity determination was developed. Based on an original coupling between a enzymatic bioreactor and an amperometric biosensor, the system was included in a flow manifold, allowing the processing of real samples with a high throughput rate. Foodstuffs contamination with mycotoxins, secondary fungal metabolites, is an increasing worldwide concern because of the hazard that these compounds present. Together with preventive measures, a fast screening is a way of avoiding the toxic effects upon human health. Hence, we have developed a new analytical tool for the detection of ochratoxin A in wine samples. The immunospecific recognition based on immobilized antibodies on different supports (screen-printed electrodes, porous glass beads), monitored via a redox probe or an enzymatic reaction, is the principle of our technique, capable of in situ measurements
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SANTANA, Raquel Araújo de. « Papel do molibdênio na anemia da infância ». Universidade Federal de Pernambuco, 2004. https://repositorio.ufpe.br/handle/123456789/8966.
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Previous issue date: 2004Trezentas e vinte e nove (329) crianças de 1 a 6 anos de idade, de 6 creches da Prefeitura da Cidade do Recife, foram submetidas a avaliação inicial do estado nutricional de ferro, pelos níveis de hemoglobina, e, divididas em três grupos, receberam, durante 30 dias, suplemento alimentar de 500μg de molibdênio (MO 105 crianças), 500μg de molibdênio e 15mg de sulfato ferroso (SFMO 91 crianças) ou somente 15mg de sulfato ferroso (SF 133 crianças), de segunda a sexta. Após trinta dias de consumo diário dos esquemas de suplementação, somente foi possível coletar material para avaliação em 159 crianças (50 no grupo MO, 48 no SFMO e 61 no SF), amostra que se tomou para comparação dos dois momentos da pesquisa. No geral, o segundo momento revelou que 81% das crianças apresentaram nível de hemoglobina acima de 11g/dl. O perfil de cada grupo mostrou que a anemia foi controlada em 52%, 82% e 79%, nos grupos MO, SF e SFMO, respectivamente, e a média de hemoglobina aumentou de 10,78 ± 1,3g/dl para 11,73 ± 1,4 g/dl no grupo MO, de 9,84 ± 1,7 g/dl para 11,75 ± 0,76 g/dl no grupo SF e de 10,72 ± 1,15 g/dl para 12,14 ± 0,83 g/dl no grupo SFMO. Pelo aumento significativo dos níveis de hemoglobina e pelo deslocamento da curva de distribuição de freqüência, conclui-se que o molibdênio se revelou biologicamente ativo e eficaz no tratamento da anemia
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Riche, Christian. « Xanthines : approches analytique, clinique, métabolique ». Besançon, 1988. http://www.theses.fr/1988BESAA001.
Texte intégralRésumé :
A partir de techniques de dosage des bases xanthiques par chromatographie en phase gazeuse, sur colonne capillaire de verre, avec détection thermoionique, et par chromatographie liquide de haute performance sur colonne C18, utilisant un gradient de solvant, sont abordés des problèmes de pharmacologie clinique et de métabolisme in vivo et in vitro. L'utilisation de la théophylline et de la caféine dans le cadre du traitement des apnées du nouveau-né est étudiée. Deux expérimentations cliniques, destinées à déterminer la zone thérapeutique de la théophylline et de la caféine sont rapportées. Le seuil minimal d'effecacité a été trouvé à 3 mg/l (17µmol/l) pour la théophylline et à 12 mg/l (63 µmol/l) pour la caféine. Pour la théophylline, le seuil de toxicité est de 8 mg/l (44µmol/l) et 20 mg/l (100 µmol/l) pour la caféine. Ce travail est complété par une approche du métabolisme in vitro, à l'aide d'hépatocytes en culture primaire d'homme adulte et de nouveau-né, en comparaison avec des résultats observés avec des hépatocytes de rat. Une transformation de la théophylline en caféine par les hépatocytes d'adulte a été mise en évidence. Le métabolisme du nouveau-né est limité. Pour la caféine chez l'adulte, on retrouve qualitativement et quantitativement les mêmes schémas métaboliques in vitro et in vivo, en ce qui concerne les déméthylations. D'autre part, il existe une différence importante entre espèces. Le modèle in vitro permet une bonne extrapolation de ce qui est connu in vivo.
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Al-Gonaiah, Majed A. « Investigating xanthine oxidase toxicity models in cultured cerebellar granule neurons ». Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/1057/.
Texte intégralRésumé :
In the last few decades, evidence has been accumulating for a role for xanthine oxidoreductase (XOR)-generated toxic reactive oxygen species (ROS) in a variety of pathological conditions that affect different organ systems. This enzyme in mammals exists in two inter-convertible forms: xanthine dehydrogenase (XDH) (the predominant intracellular form under physiological conditions) and xanthine oxidase (XO). A combination of XO and its oxidizable substrate xanthine (X) (or hypoxanthine (HX)) is widely used as a model to produce ROS and to study their effects in a variety of cell culture studies. However, the effect of the combination of XOR and the reduced nicotinamide adenine dinucleotide (NADH) in cell cultures is much less studied. NADH is another oxidizable substrate for XOR that binds to a different site on the enzyme from that of X binding. The aim of this project was to investigate some aspects of the in vitro toxicity of XOR, which might provide more insights into its in vivo toxicity. The main investigation was a comparison between the well studied X / XO and the much less studied NADH / XO toxicity models. Also, secondary studies were undertaken to investigate those aspects of X / XO toxicity where there are uncertainties about them. These studies were performed using primary cell cultures. Cell cultures are now widely used to study different diseases, and although they have their drawbacks, they have their advantages over the in vivo studies. For this project, primary cultures of cerebellar granule neurons (CGNs) were used. In the beginning, some problems were encountered with CGNs. The main problem was the immediate damage induced to the neurons (including those in the control groups) at the intervention/experiments day (i.e. day 8 or 9 after plating) by manipulating the cultures (i.e. aspirating the culture medium, adding treatment and control vehicles, and adding the restoration medium). After several months of investigation, it was serendipitously discovered that the immediate damage seen in the neurons (including those in the control groups) when they are manipulated at the experiments/intervention day was due to glutamate excitotoxicity (through activating its N-methyl-D-aspartate (NMDA) receptors). The source of glutamate was the fresh serum which is present at 10% V/V in the fresh culture medium that is added to the cultures at that day. After solving this problem, it was possible to conduct reliable experiments to investigate XO toxicity models. Regarding investigating XO toxicity, it was found that both of the X / XO and NADH / XO combinations were toxic to cultures of CGNs. However, the concentration of NADH needed to cause the toxicity was much higher than that of the other substrate, X, which is in agreement with previous cell-free experiments that showed that NADH is a much weaker substrate than X for the bovine milk XO used here. Blocking the site of X binding on XO prevented X / XO toxicity, but did not prevent NADH / XO toxicity. On the other hand, blocking the site of NADH binding prevented both X / XO and NADH /XO toxicities. Another difference between the two systems was that deactivating either superoxide or hydrogen peroxide (both are ROS) generated by XO prevented NADH / XO toxicity, whereas although deactivating hydrogen peroxide prevented X / XO toxicity, deactivating superoxide generated from this combination did not. In the NADH / XO system, an extracellular metal contaminant (likely contaminating XO powder/preparation) seemed to be involved in the toxicity. The two toxicity models were similar in the mediation of toxicity by intracellular iron ion. In X / XO toxicity, although superoxide generated extracellularly from the combination has no role in the toxicity, intracellularly produced superoxide seemed to play a role. Conclusions: 1. Culturing/experimental conditions have been optimised for viability studies in CGNs cultures. 2. The combination of NADH and XO induces damage to CGNs, where although blocking the NADH binding site prevents this damage, blocking the X binding site does not. It is feasible that the oxidation of NADH by some forms of XOR (other than the one used here) that are known to be very efficient in oxidizing NADH might produce in vivo toxicity. 3. A possibility raised by this study is that a metal (like the metal contaminant proposed to play a role in NADH / XO toxicity in this study) might contribute to XOR toxicity in vivo. 4. Intracellular superoxide often mediates XOR toxicity. 5. The results add support to many previous studies which suggested that intracellular hydroxyl radical (or a similar species) is involved in XOR toxicity.
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Doyle, Wendy Anne. « Biochemical and molecular genetic studies of Drosophila melanogaster xanthine dehydrogenase ». Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239022.
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Millar, Timothy Marc. « Novel aspects of the activity and function of xanthine oxidase ». Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311326.
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Best, Quinn Adams. « XANTHENE AND SILICON ANALOGS OF XANTHENE FLUOROPHORES AS CHEMICAL SENSORS FOR pH AND HYPOCHLOROUS ACID ». OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/662.
Texte intégralRésumé :
Chemical sensors capable of detecting a specific atom or molecule under various conditions have been utilized in biological and environmental analyses. Fluorescence based sensors are particularly advantageous in these studies because of their high sensitivity, relative ease in handling, and low technical costs. This dissertation focuses on the detection of two analytes, H+ and hypochlorous acid, which are of interest in biology because the presence of abnormal quantities of these analytes may be indicative of disease. We have established a new platform for which sensitive changes in various regions of pH can be detected using fluorescence. The aminomethylrhodamine (AMR) scaffold is highly versatile, i.e. the pH range in which the sensor is active can be tuned by introducing different substituents on the amine moiety. Overall this systematic approach to the design of pH sensitive fluorophores has allowed for a library of compounds that are responsive over a broad range of pH (pH 3 - 10) by simply changing the substituent on the amino group. We report the synthesis and characterization of a silicon analog of rhodamine for the fluorescence based detection of hypochlorous acid. This fluorophore exhibits a 90 nm bathochromic shift in its absorption and emission, relative to its oxygen counterpart. Hypochlorous acid is a biological agent linked to certain diseases. Therefore, the longer wavelength properties of the this far-red fluorescent sensor will be of significant benefit to imaging experiments of this analyte in biological media and tissue due to its spectral proximity of the so called NIR optical window. Furthermore, the novel synthetic methodology of this sensor possesses a key intermediate, which could potentially lead to future fluorescence based sensors. The characterization of a fluorescent probe designed for the detection of hypochlorous acid (HOCl) using a silicon analog of fluorescein (SiF) was also reported. Over a range of pHs, the probe reacts with a stoichiometric amount of HOCl resulting in a mixture of two pH dependent fluorescent species, a SiF disulfide product and a SiF sulfonate product. The unique colorometric properties of the individual SiF fluorophores were utilized to perform simultaneous detection of HOCl and pH. When an excess of HOCl is present, the SiF fluorophores become chlorinated, via an intermediate halohydrin, resulting in a more pH independent and red-shifted fluorophore. Finally, an attempt was made at developing a pH responsive photodynamic therapy agent. This system was designed to target the relatively low extracellular pH found around tumors. A di-bromohydroxymethylrhodamine system was synthesized and the photophysical properties were characterized. This system absorbs weakly under acidic conditions (ca. pH 3), however was shown to be a moderate photosensitizer under acidic conditions.
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Urso, Edith-Marie d'. « Biocapteur ampérométrique pour la détection des ions phosphate : étude approfondie de l'immobilisation du système bienzymatique PNP-XOD, performances et applications ». Lyon 1, 1992. http://www.theses.fr/1992LYO10145.
Texte intégralRésumé :
Ce travail presente l'etude d'un biocapteur bienzymatique specifique des ions phosphate. La purine nucleoside phosphorylase (pnp) et la xanthine oxydase (xod) sont co-immobilisees sur une membrane synthetique preactivee placee au contact d'une electrode amperometrique en platine capable de detecter l'eau oxygenee et l'acide urique generes enzymatiquement. L'influence sur les performances du biocapteur du rapport des activites enzymatiques dans la solution de couplage et des activites totales deposees a ete etudiee. Nous demontrons que l'optimisation de ces deux parametres permet d'ameliorer non seulement la sensibilite mais aussi l'etendue du domaine de linearite de la reponse au phosphate par rapport aux resultats obtenus lorsque la proportion des deux enzymes dans la solution de couplage est fixee de facon arbitraire. La correlation entre la sensibilite et l'activite retenue pour les deux enzymes impliques nous a permis de mettre en evidence un comportement inattendu pour la xod. Nous avons alors compare les caracteristiques des electrodes monoenzymatiques obtenues en immobilisant seule la xod ou d'autres enzymes, la glucose oxydase et la choline oxydase. Les qualites du biocapteur (fiabilite, specificite, sensibilite et stabilite operationnelle) ont ete testees en systeme batch et en flux continu. Si l'on envisage une application dans le controle de l'environnement, le dispositif en flux continu semble plus adapte que le systeme en batch compte tenu de sa sensibilite plus elevee: la reponse au phosphate est lineaire entre 0,5 et 56 nanomoles (soit entre 1 et 250 m dans l'echantillon). Les reponses non specifiques du biocapteur dues aux interferences electrochimiques ou a la specificite large de la xod peuvent etre supprimees si l'on introduit, dans le dispositif, une deuxieme electrode munie d'une membrane neutre ou d'une membrane xod. Par contre, malgre la specificite de la nucleoside phosphorylase, la reponse du biocapteur a l'arseniate, analogue de structure du phosphate, ne peut pas etre contournee
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Richter, Tanja. « Entwicklung alternativer Methoden zur Nukleotid-Analytik in der Bioprozessüberwachung ». [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=959651853.
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Murphy, Robert Scott. « Photophysical studies on the dynamics of guest complexation with cyclodextrins ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/NQ47292.pdf.
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Caldeira, Ana Teresa Fialho Caeiro. « Fisiologia da toxicidade ácida em culturas descontínuas de Xanthomonas campestris ». Master's thesis, Universidade de Évora, 1997. http://hdl.handle.net/10174/12545.
Texte intégralRésumé :
Estudou-se o efeito de 0,15mM de ácido acético, na forma não ionizada, no crescimento de Xanthomonas campestres e na produção de xantano. Em culturas descontínuas de Xanthomonas campestres o ácido acético promoveu uma diminuição do crescimento do microrganismo e um aumento na produção de xantano. Parece provável que estes dois parâmetros estejam relacionados entre si e sejam o resultado duma maior canalização da fonte de carbono da produção de células para a produção de xantano, devido à diminuição do pH interno, induzida pelo ácido. Observou-se, na presença de 0,15m1v1 de ácido acético, na forma não ionizada, uma estimulação da actividade enzimática da ATPase (aumentou 28,2%) e um decréscimo do teor em ATP (diminuiu 26,0%). A estimulação da actividade enzimática e a dinúnuição do teor de ATP foram relacionados com a saída de protões para o exterior da célula à custa de energia, hidrólise de ATP (como consequência da diminuição do pH interno, induzida pelo ácido), parecendo constituir um mecanismo de restabelecimento do gradiente de protões, de modo a manter um valor de pH interno homeostático. O aumento da produção de xantano parece estar relacionado com a possibilidade de formação de ATP por vias alternativas, devido ao desacoplamento energético que o ácido induz.
### Abstract - The effect of the adition of 0,15mM of the undissociated form of acetic acid in the microbial growth of Xanthomonas campestris and in the xanthan production, was studied. In batch cultures of Xanthomonas campestris 0,15mM of the undissociated form of acetic acid decreases cell growth and stimulates xanthan production. The stimulation of xanthan production and the decrease of microbial growth were apparently correlated. They were, probably, the result of a carbon flux divertion from cell formation to product synthesis. 0,15 mM of the undissociated form of acetic acid stimulated ATPase activity and decreased ATP. The ATPase activation and the decrease of ATP were associated with the passage of protons across the membrane at the expense of cell energy, linked to ATP hydrolysis, in consequence of the regulation of the intracellular pH. This appears to constitute a mechanism that generates a proton gradient for the maintenance of an intracellular pH homyostatic. Xanthan overproduction was related with the alternative pathways for ATP synthesis because the uncoupling conditions induced by the acid resulted in an energy deficiency.
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Donyai, Parastou. « Xanthine oxidase in oxidative stress : design and evaluation of novel inhibitors ». Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300381.
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Harris, Christopher Peter David. « Lipoprotein quality, anti-(xanthine oxidase) antibodies and coronary heart disease risk ». Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760669.
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Cultrone, Antonietta. « La xanthine dioxygénase α-kétoglutarate dépendante : une enzyme caractéristique des champignons ». Paris 11, 2004. http://www.theses.fr/2004PA112069.
Texte intégralRésumé :
Le sujet de cette thèse est le clonage du gène xanA et le caractérisation de la protéine XanA d'Aspergillus nidulans. XanA est une enzyme qui hydroxyle la xanthine en acide urique. Dans une souche sauvage la purine hydroxylase I (HxA) catalyse l'hydroxylation de l'hypoxanthine en xanthine et de la xanthine en acide urique. L'hypoxanthine peut aussi être hydroxylée par la purine hydroxylase II codée par le gène hxnS. Les purines hydroxylases I et II sont des enzymes associées à un cofacteur à molybdène, alors que XanA ne l'est pas. Nous avons cloné et séquencé le gène xanA. Il code une protéine de 370 acides aminés. XanA présente des similarités avec les protéines de la famille des dioxygénases. Des protéines fortement similaires à XanA n'ont été trouvées que chez les champignons (N. Crassa, S. Pombe, F. Graminearum, P. Chrysosporium, C. Cinereus, U. Maydis, C. Albicans). Une mutation dans le gène xanA a été isolée. Cette mutation (xanA1) est une transversion de C à A qui se traduit par le remplacement d'une alanine par une asparagine au niveau du codon 167. Le phénotype de la délétion du gène xanA est identique à celui de xanA1. La surexpression de xanA chez A. Nidulans a permis de caractériser l'enzyme. Nous avons démontré qu'il s'agit d'une xanthine dioxygénase dépendante de l'a-kétoglutarate. Le gène xanA (chromosome VIII) et son promoteur sont partiellement dupliqués sur le chromosome II. L'homologue de xanA chez S. Pombe (TC3962) ne complémente pas la mutation xanA1 d'A. Nidulans, tandis que cette mutation est complementée par l'homologue de xanA chez N. Crassa (xan1). L'expression de xanA est soumise au contrôle du facteur GATA AreA et est dépendante du facteur UaYThis work comprises the cloning of the xanA gene and the biochemical characterization of the XanA protein of aspergillus nidulans. This enzyme catalyses the oxidation of xanthine to uric acid. In the wild type strain, purine hydroxylase I (HxA) catalyses both the hydroxylation of hypoxanthine to xanthine and that of xanthine to uric acid. Hypoxanthine is also oxidized to xanthine by a second purine hydroxylase (purine hydroxylase II), which is coded by the hxnS gene. Both purine hydroxylases contain a molybdopterin co-factor while XanA does not. We have cloned and sequenced the xanA gene. XanA encodes a protein 370 amino acids long. The sequence of XanA has confirmed that it's not a molybdenum-containing enzyme; we found some similarities with proteins of the dioxygenase family. Proteins with high similarity to XanA were found only in fungi in N. Crassa, S. Pombe, F. Graminearum, p: chrysosporium, C. Cinereus, U. Maydis, C. Albicans. One mutation (xanA1) has been isolated. The xanA1 allele is a C to A transversion resulting in an alanine to asparagine change in codon 167. The phenotype of the xanA1 mutation is identical to that of xanA deletion. Overexpression of the xanAgene in A. Nidulans has permitted a preliminary characterization of the enzyme. We have shown it is an a-ketoglutarate dependent xanthine dioxygenase. The xanA gene (chromosome VIII), including its promoter is partially duplicated in chromosome II. The S. Pombe homologue of xanA, TC3962, is not able to complement the mutation xanA1. As all other enzymes of the purine utilization pathway xanA expression is under the control of the GATA factor AreA and the pathway specific transcription factor UaY
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Mokfi, Moloud [Verfasser]. « Xanthine-derived N-heterocyclic carbenes and their metal complexes / Moloud Mokfi ». Wuppertal : Universitätsbibliothek Wuppertal, 2021. http://d-nb.info/1240266960/34.
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Cho, Woo Cheal. « Synthesis of caged Garcinia xanthone analogues ». Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1469234.
Texte intégralRésumé :
Thesis (M.S.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed October 13, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Schmenk, Holger. « Xanten im 19. Jahrhundert : eine rheinische Stadt zwischen Tradition und Moderne ». Köln [u.a.] Böhlau, 2008. http://bvbm1.bib-bvb.de/webclient/DeliveryManager?pid=374531&customa̲tt2̲=simplev̲iewer.
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Schmenk, Holger. « Xanten im 19. Jahrhundert eine rheinische Kleinstadt zwischen Tradition und Moderne ». Köln Weimar Wien Böhlau, 2007. http://d-nb.info/987070088/04.
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Jawed, Shahid. « The role of the redox enzyme xanthine oxido-reductase in rheumatoid arthritis ». Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391624.
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