Дисертації з теми "Glucose reaction"
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Bersuder, Philippe. "Investigation of Maillard reaction products as antioxidants." Thesis, University of Lincoln, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319773.
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Ge, Xue. "Covalent catalysis in the UDP-glucose dehydrogenase reaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0019/NQ48638.pdf.
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DAI, ZHENYU. "PROTEIN CROSSLINKING BY THE MAILLARD REACTION WITH ASCORBIC ACID AND GLUCOSE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1184176746.
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Mshayisa, Vusi Vincent. "Antioxidant effects of Maillard reaction products (MRPs) derived from glucose-casein model systems." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2505.
Повний текст джерелаАнотація:
Thesis (MTech (Food Technology))--Cape Peninsula University of Technology, 2016.The Maillard reaction (MR) involves the condensation reaction between amino acids or proteins with reducing sugars, which occurs commonly in food processing and storage. Maillard reaction products (MRPs) were prepared from glucose-casein model system at pH 8, heated at 60, 75 and 90°C for 6, 12 and 24 h, respectively. Browning intensity (BI) of MRPs, as monitored by absorbance at 420 nm increased with an increase in reaction temperature. The reducing power (RP) of MRPs increased (p < 0.05) as the reaction time increased at 60 and 75°C, while at 90°C an increase in RP was observed from 6 to 12 h and thereafter a slight decrease was observed up to 24 h. The 2,2-Azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging activity (ABTS-RS) and Peroxyl radical scavenging (PRS) activity of glucose-casein MRPs produced at 90°C decreased as the reaction time increased. In this study, the ferrous chelation activity of MRPs was higher than that of tert-butylhydroquinone (TBHQ) (0.02%) and Trolox (1 mM), respectively. Moreover, the 1, 1-diphenyl-2-picryl-hydrazil radical scavenging (DPPH-RS) of MRPs increased (p < 0.05) as the reaction time increased irrespective of the heating temperature. The primary and secondary lipid oxidation products were measured using the Peroxide value (PV) and Thiobarbituric acid reactive substance (TBARs) assay in sunflower oil-in-water emulsion, respectively. MRPs derived at 90°C for 12 h had the lowest peroxide value, while the TBARs inhibitory by MRPs ranged from 39.05 – 88.66%. Glucose-casein MRPs displayed superior antioxidant activity than TBHQ (0.02%) and Trolox (1 mM), respectively, as measured by the TBARs assay. The differential scanning calorimetry (DSC) and Rancimat techniques set at 110°C were used to evaluate the oxidative stability the lipid-rich media containing MRPs. At the same temperature program, DSC gave significantly lower reduction times than the Rancimat. Furosine (N-ε-Fructosyl-lysine) and Pyrraline (2-amino-6-(2-formyl-5-hydroxymethyl-1-pyrrolyl)-hexanoic acid) were determined using high pressure liquid chromatography to evaluate the extent of the MR. Furosine concentration of glucose-casein MRPs ranged between 0.44 – 1.075 mg.L-1 in MRPs derived at 60°C, while at 75°C an increase as function of time was observed. MRPs derived at 60 and 75°C exhibited a varied concentration of pyrraline as the reaction time increased with higher temperatures resulted in higher concentrations (0.39 mg.L-1). The results of this study clearly indicated that MRPs possess antioxidant activity and can be used as natural antioxidants in the food industry.
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Topin, Agnès. "Contribution à l'étude de quelques interactions acides aminés-glucose dans des solutions de nutrition parentérale." Paris 5, 1993. http://www.theses.fr/1993PA05P029.
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Botero, Carrizosa Sara C. "Synthesis, Characterization, and Properties of Graphene-Based Hybrids with Cobalt Oxides for Electrochemical Energy Storage and Electrocatalytic Glucose Sensing." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1941.
Повний текст джерелаАнотація:
A library of graphene-based hybrid materials was synthesized as novel hybrid electrochemical electrodes for electrochemical energy conversion and storage devices and electrocatalytical sensing namely enzymeless glucose sensing. The materials used were supercapacitive graphene-family nanomaterials (multilayer graphene-MLG; graphene oxide-GO, chemically reduced GO-rGO and electrochemical reduced GOErGO) and pseudocapacitive nanostructured transition metal oxides including cobalt oxide polymorphs (CoO and Co3O4) and cobalt nanoparticles (CoNP). These were combined through physisorption, electrodeposition, and hydrothermal syntheses approaches. This project was carried out to enhance electrochemical performance and to develop electrocatalytic platforms by tailoring structural properties and desired interfaces. Particularly, electrodeposition and hydrothermal synthesis facilitate chemically-bridged (covalently- and electrostatically- anchored) interfaces and molecular anchoring of the constituents with tunable properties, allowing faster ion transport and increased accessible surface area for ion adsorption. The surface morphology, structure, crystallinity, and lattice vibrations of the hybrid materials were assessed using electron microscopy (scanning and transmission) combined with energy dispersive spectroscopy and selected-area electron diffraction, X-ray diffraction, and micro-Raman Spectroscopy. The electrochemical properties of these electrodes were evaluated in terms of supercapacitor cathodes and enzymeless glucose sensing platforms in various operating modes. They include cyclic voltammetry (CV), ac electrochemical impedance spectroscopy, charging-discharging, and scanning electrochemical microscopy (SECM).
These hybrid samples showed heterogeneous transport behavior determining diffusion coefficient (4⨯10-8 – 6⨯10-6 m2/s) following an increasing order of CoO/MLG < Co3O4/MLG < Co3O4/rGOHT < CoO/ErGO < CoNP/MLG and delivering the maximum specific capacitance 450 F/g for CoO/ErGO and Co3O4/ rGOHT. In agreement with CV properties, these electrodes showed the highest values of low-frequency capacitance and lowest charge-discharge response (0.38 s – 4 s), which were determined from impedance spectroscopy. Additionally, through circuit simulation of experimental impedance data, RC circuit elements were derived. SECM served to investigate electrode/electrolyte interfaces occurring at the solid/liquid interface operating in feedback probe approach and imaging modes while monitoring and mapping the redox probe (re)activity behavior. As expected, the hybrids showed an improved electroactivity as compared to the cobalt oxides by themselves, highlighting the importance of the graphene support. These improvements are facilitated through molecular/chemical bridges obtained by electrodeposition as compared with the physical deposition.
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Essis-Yei, L. Hortense. "Oxydation electrocatalytique du glucose sur le platine et l'or en milieu aqueux." Poitiers, 1987. http://www.theses.fr/1987POIT2277.
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Lee, Jeehyun. "Analyse et modélisation de la réactivité au cours de la cuisson d’un produit modèle mimétique d’un produit céréalier type génoise." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS606.
Повний текст джерелаАнотація:
Dans un contexte de mise en place d’outils pour contrôler la formation de composés néoformés, à impact positif ou négatif, lors de la transformation des produits alimentaires, ce travail de thèse avait pour objectif de comprendre et de décrire les réactions de Maillard et de caramélisation au cours de la cuisson d’un produit modèle et de proposer une approche de modélisation pour la prédiction des cinétiques couplées aux transferts de chaleur et de matière. Un produit modèle structurellement mimétique d’une génoise, mais non réactif, était utilisé. Ainsi, il a été possible d’induire des réactions de manière spécifique en ajoutant le glucose seul pour la formule G ou avec la leucine pour la formule G+L. Le développement de dosages quantitatifs pour vingt marqueurs réactionnels (précurseurs, intermédiaires et produits) a été réalisé permettant d’acquérir les données cinétiques. L’effet accélérateur de la température et l’absence d’effet du niveau de convection sur la formation et la dégradation de la plupart des marqueurs réactionnels ont pu être quantifiés par les données cinétiques. L’ajout du précurseur leucine a activé les voies réactionnelles de Maillard et de dégradation de Strecker et l’effet catalytique de la leucine a pu être souligné et mesuré par rapport aux voies de caramélisation présentes exclusivement dans le modèle G. Grâce aux données expérimentales acquises, un modèle de prédiction de température et de teneur en eau dans la génoise modèle a été proposé et puis couplé au modèle cinétique. L’identification simultanée d’un grand nombre de paramètres, sur une plage de valeurs très large est à poursuivre. Deux preuves de concepts sont néanmoins présentés sur le modèle de caramélisation (modèle G), l’une sur la totalité des marqueurs pour une condition de cuisson, et l’autre sur la dégradation du précurseur glucose, pour la totalité des conditions de cuisson. Elles sont encourageantes pour la poursuite des travaux de modélisationIn the context of developing tools to control the formation, during food processing, of newly-formed compounds having positive or negative impact on food quality and safety, this work aimed to understand and to describe the Maillard reaction and caramelization during the baking of a model product and to propose a modelling approach for predicting kinetics coupled with heat and mass transfers. An inert model product structurally imitative of a sponge cake was used. Thus, it was possible to specifically induce reactions by adding glucose alone for the G formula and with leucine for the G+L formula. The development of quantitative methods for twenty reaction markers (precursors, intermediates and products) was carried out to be able to acquire the kinetic data. The accelerating effect of the temperature and the absence of effect of the level of convection on the formation and the degradation of most of the markers were highlighted and quantified by kinetic results. The addition of leucine activated the Maillard reaction pathways including the Strecker degradation and the catalytic effect of leucine could be observed relatively to the caramelization routes exclusively present in the reaction model (G). Thanks to the experimental data acquired, a model of prediction of temperature and moisture content was developped, and then coupled to the kinetic model. The simultaneous identification of a large number of parameters over a wide range of values need to be pursued. However, two proofs of concept could be conducted on the caramelization model (G formula), one on all the markers for a single baking condition, and the other on glucose degradation for all baking conditions. They are encouraging for further modeling work
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Krishna, Rahul. "Transition metal doped graphene for energy and electrical applications." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/16543.
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Doutoramento em Nanociências e NanotecnologiaIn the view of rapid progress in the fabrication of nanoscale energy storage and electronic devices, graphene is a subject of great interest. As a truly two dimensional (2D) system, graphene possess extraordinary properties of high conductivity, high carrier mobility, large surface area (>2600 m2/g), flexibility, and chemical stability which are favourable for energy applications. Synthesis of high quality graphene still remains as a major challenge in graphene research. Various methods including mechanical exfoliation, thermal exfoliation and thermal chemical vapour deposition (CVD) methods are used for the production of high quality graphene. However, mass production of graphene is possible only by chemical exfoliation of graphite under strong oxidizing agents. This thesis deals with the state of the art mass production of reduced graphene oxide (RGO) using graphene oxide (GO) as the intermediate agent. One of the exciting ideas about graphene oxide is that, due to the functional groups attached, it could act as a laboratory for various catalytic reactions and led to the fabrication of novel devices. Transition metals were used to aid the reaction and to achieve desired novel properties. By catalytic reactions, high quality nanoparticles (NPs) such as Ni, Co, Pd Ag, Cu, NixB, CoxB and SiO2 were synthesized and anchored on graphene sheet for energy applications. Particularly, for hydrogen storage a nanocomposite catalyst containing palladium@ nickel boride–silica and reduced graphene oxide (Pd@NixB–SiO2/RGO, abbreviated as Pd@NSG) was successfully fabricated. The H2 adsorption experiment directly reveals the spillover effect on the Pd@NSG nanocomposite and its enhanced H2 uptake capacity (0.7 wt.%) compared to SiO2/RGO (0.05 wt.%) under 50 bar hydrogen pressure at RT. On the basis of results a detailed mechanism of hydrogen spillover is established that exhibited the facile H2 dissociation on the Pd activator (active sites) and subsequent transportation of hydrogen atoms on receptor sites. Similarly, highly active and cost effective nanocomposite CoxB@Ni/RGO was also synthesized for hydrogen production through electrochemical oxidation of ethanol in alkaline medium under catalysis reaction. The electrochemical behavior of nanocomposite was evaluated by cyclic voltammetry (CV) technique. The catalytic activity of nanocomposite was evaluated continuously for 50 cyclic run; amazingly, results shows that the increase of current density after 50 cycle run suggests the self-cleaning process and robustness of catalyst system. For energy application, graphene based nanocomposite has also been employed for catalysis reduction of 4-nitrophenol (4-NP) organic pollutant. For this work, a wide range of graphene nanocomposite catalysts has been synthesized and the effort was to reduce reaction time and cost of nanocatalyst system. Finally, graphene based nanocomposite (Ni/RGO) is used for electrical and electronics applications also, to fabricate the memristor devices and glucose biosensor. A wide range of characterization techniques mainly X-ray diffraction (XRD), fourier transform infra-red (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), current vs. voltage (I-V) measurements, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed for analysis of transition metals doped graphene nanocomposites for various kind of energy applications.
Do ponto de vista do rápido progresso na fabricação de dispositivos eletrónicos de armazenamento de energia em nanoescala, o grafeno é um assunto de grande interesse. Como um sistema verdadeiramente bidimensional (2D), o grafeno possui propriedades extraordinárias de alta condutividade, grande mobilidade de portadores de carga, grande área de superfície (> 2600 m2 / g), flexibilidade e estabilidade química, que são favoráveis para aplicações energéticas. A síntese de grafeno de alta qualidade ainda permanece como um grande desafio na investigação no grafeno. Vários métodos, incluindo esfoliação mecânica, térmica e deposição química por vapor (CVD) são métodos utilizados para a produção de grafeno de alta qualidade. No entanto, a produção em massa de grafeno só é possível por esfoliação química de grafite sob agentes oxidantes fortes. Esta tese lida com o estado da arte de produção de óxido de grafeno reduzido (RGO) em massa usando óxido de grafeno (GO) como agente intermediário. Uma das ideias empolgantes em relação ao óxido de grafeno é a de que, devido aos grupos funcionais ligados, ele poderia actuar como um laboratório para várias reacções catalíticas e conduzir à fabricação de novos dispositivos. Os metais de transição foram usados para auxiliar a reacção e para atingir as novas propriedades desejadas. Por reações catalíticas, as nanopartículas de alta qualidade (NPs), tais como Ni, Co, Pd, Ag, Cu, NixB, CoxB e SiO2 foram sintetizadas e ancoradas numa folha de grafeno para aplicações de energia. Particularmente, para o armazenamento de hidrogénio um catalisador nanocompósito contendo paládio@níquel boreto-sílica e óxido de grafeno reduzido (Pd @ NixB-SiO2 / RGO, abreviado como Pd @ NSG) foi fabricado com sucesso. A experiência de adsorção de H2 revela diretamente o efeito de transbordo (spillover) no nanocompósito Pd @ NSG e sua maior capacidade de absorção de H2 (0,7 wt.%) em comparação com SiO2 / RGO (0,05 wt.%), sob uma pressão de 50 bar de hidrogénio à temperatura ambiente. Com base nos resultados um mecanismo detalhado de transbordo de hidrogénio é estabelecido que exibe a dissociação fácil de H2 no ativador Pd (centros activos) e o transporte subsequente de átomos de hidrogénio em locais receptores. Da mesma forma, o altamente ativo e rentável nanocompósito CoxB @ Ni / RGO foi também sintetizado para produção de hidrogénio através de oxidação eletroquímica de etanol em meio alcalino sob catálise de reacção. O comportamento eletroquímico do nanocompósito foi avaliado pela técnica de voltametria cíclica (CV). A atividade catalítica do nanocompósito foi avaliada continuamente por 50 ciclos; surpreendentemente, os resultados mostram que o aumento da densidade de corrente após 50 ciclos sugere o processo de auto-limpeza e robustez do sistema de catalisador. Para a aplicação de energia, o nanocompósito baseado em grafeno também tem sido usado para a redução catalítica de 4- nitrofenol (4- NP ) poluente orgânico . Para este trabalho, uma ampla gama de catalisadores de grafeno nanocompósito foi sintetizada e o esforço foi o de reduzir o tempo de reacção e o custo do sistema nanocatalisador. Finalmente, o nanocompósito baseado em grafeno (Ni / RGO ) é usado para aplicações elétricas e eletrónicas, e também para fabricar os dispositivos memresistivos e biossensores de glicose. Uma vasta gama de técnicas de caracterização, principalmente difração de raios X (XRD), espectroscopia de infravermelhos (FTIR, Raman, espectroscopia de fotoeletrões de raios-X (XPS), microscopia eletrónica de varrimento (SEM), microscopia eletrónica de transmissão (TEM), medições de corrente vs. tensão (I-V), voltametria cíclica (CV) e espectroscopia de impedância eletroquímica (EIS), foram usadas para análise de nanocompósitos de grafeno dopados com metais de transição para vários tipos de aplicações de energia.
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Leygue, Jean-Philippe. "Coproduction d'acide gluconique, de fructose et de fructooligosides par Aspergillus niger sur saccharose." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37615198m.
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MELI, Alessandro. "DEEP EUTECTIC SOLVENTS E LIQUIDI IONICI: SOLVENTI PER LO SVILUPPO DI PROCESSI ECO-COMPATIBILI." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395244.
Повний текст джерелаАнотація:
L’obiettivo di questi tre anni di Dottorato è stato lo studio e l’utilizzo nuovi solventi di reazione in grado di sostituire i solventi organici classici. In particolare sono stati studiati i Deep Eutectic Solvent (DES) e le miscele di Liquidi Ionici (IL).
I DES sono stati utilizzati come solventi per lo studio di reazioni organiche, usate per la formazione di nuovi legami C-C. Nello specifico sono state studiate la reazione di Diels-Alder, e diverse reazioni di coupling C-C catalizzate da Pd.
In seguito, i DES sono stati utilizzati per la formazione di nuovi gel supramolecolari, chiamati eutectogel. Questi gel sono stati formati usando come gelator amminoacidi naturali, consentendo quindi di ottenere gel interamente costituiti da composti non tossici. Questi materiali sono stati usati come fasi adsorbenti per la rimozione di coloranti cationici da soluzioni acquose.
Infine, miscele di IL sono state utilizzate per la conversione di tre diversi carboidrati in 5-HMF, ottenendo rese soddisfacenti specialmente per la conversione del fruttosio.
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Devaiah, Shivakumar P., Cheng Zhang, and Cecelia A. McIntosh. "Structure and Functional Analysis of Glucosyltransferase from Citrus paradisi." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/344.
Повний текст джерелаАнотація:
Glucosyltransferases (GTs) are enzymes that expedite the incorporation of UDP-activated glucose to a corresponding acceptor molecule. This enzymatic reaction stabilizes structures and affects solubility, transport, and bioavailability of flavonoids for other metabolic processes. Flavonoid glycosides affect taste characteristics in citrus making the associated glucosyltransferases particularly interesting targets for biotechnology applications. Custom design of enzymes requires understanding of structure/function of the protein. The present study focuses on creating mutant flavonol-3-O-glucosyltransferase (F-3-O-GT) proteins using site-directed mutagenesis and testing the effect of each mutation on substrate specificity, regiospecificity and kinetic properties of the enzyme. Mutations were selected on the basis of sequence similarity between grapefruit F-3-O-GT, an uncharacterized GT gene in blood orange (98%), and grape F3GT (82%). Grapefruit F-3-O-GT prefers flavonol as a substrate whereas the blood orange sequence is annotated to be a flavonoid 3GT and the grape GTs could glucosylate both flavonols and anthocyanidins. Mutants of F-3-O-GT were generated by substituting L41M, N242K, E296K and N242K+E296K and proteins were expressed in Pichia pastoris using the pPICZA vector. Analysis of these mF-3-O-GTs showed that all of them preferred flavonols over flavanone, flavone, isoflavones, or anthocyanidin substrates and showed decrease in enzyme activity of 16 to 51% relative to the wild type F-3-O-GT.
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Adidou, Ouissam. "Ligands dérivés de saccharides et, ou supportés par un bras poly(éthylène) glycol : synthèse et applications en catalyse organométallique." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10171.
Повний текст джерелаАнотація:
La synthèse de deux familles de ligands a été envisagée. La première famille de ligands concerne la préparation de nouveaux ligands dérivés de la D-glucosamine ou du D-glucose qui seront engagés dans la réaction de substitution allylique de type Tsuji-Trost en phase homogène. La deuxième famillede ligands concerne la préparation de ligand supportés par un bras poly(éthylène) glycol et dérivés dela D-glucosamine ou de la di-(2-pyridyl)méthylamine. Ces ligands hydrosolubles ont été engagés dans deux réactions pallado-catalysées en phase aqueuse à savoir la substitution allylique de type Tsuji-Trost et la réaction de couplage croisé de type Suzuki-Miyaura, respectivementLigands derived from saccharides and, or supported on poly(ethylene) glycol arm: synthesis and applications in organometallic catalysis. The synthesis of two types of ligands has been investigated. The first family of ligands has been the preparation of new ligands derived from D-glucosamine or D-glucose, which have been tested in the allylic substitution of Tsuji-Trost in homogeneous phase. The second one has een the preparation of ligand supported on poly(ethylene) glycol arm and derived from D-glucosamine or di-(2- pyridyl)methylamine. These last hydrosoluble ligands have been tested in two Pd-catalyzed reactions in aqueous phase: the allylic substitution of Tsuji-Trost and the cross-coupling Suzuki-Miyaura reaction, respectively
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Hanover, Karl Frederic. "The hydrogenation of glucose with Raney-nickel : an examination of the side reactions /." Thesis, Connect to this title online; UW restricted, 1987. http://hdl.handle.net/1773/5514.
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Goran, Benedeković. "Enantiodivergentna totalna sinteza odabranih stiril laktona i preliminarno ispitivanje njihove citotoksičnosti." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2012. http://dx.doi.org/10.2298/NS20121011BENEDEKOVIC.
Повний текст джерелаАнотація:
U radu je ostvarena enantiodivergentna totalna sinteza oba enantiomera goniofufurona, 7-epi-goniofufurona i krasalaktona C polazeći iz D-glukoze. Ključne faze u sintezi 7-epi-(+)-goniofufurona bile su stereoselektivna adicija fenilmagnezijum bromida na aldehidnu grupu pogodno zaštićene dialdoze, i stereospecifično formiranje furano-laktonskog prstena ciklokondenzacijom odabranog hemiacetalnog derivata sa Meldrum-ovom kiselinom. Sinteza (+)-goniofufurona i (+)-krasalaktona C zahtevala je inverziju konfiguracije na C-5u zajedničkom intermedijeru, koja je efikasno ostvarena u uslovima Mitsunobu-ove reakcije, ili alternativno oksidacijom benzilne hidroksilne grupe u prohiralni keton, uz naknadnu stereoselektivnu redukcijom sa borohidridom. Sličan pristup je zatim primenjen za sintezu neprirodnih (−)-enantiomera goniofufurona, 7-epi-goniofufurona i krasalaktona C, dva nova konformaciono ograničena analoga (+)- i (−)-goniofufurona (oksetani 36 i ent-36), kao i odgovarajućih 7-deoksigenovanih derivata (31 i ent-31). Takodje je razvijena i prva totalna sinteza prirodnog (+)-krasalaktona B (3) i alternativna sinteza (+)-krasalaktona C (4) polazeći iz D-glukoze. Selektivni pristup molekulima 3, odnosno 4 omogućen je promenom uslova za TBDPS deprotekciju u finalnom intermedijeru 53. Osnovna karakteristika pomenutih pristupa je njihova generalnost i fleksibilnost. Na taj način je omogućena sinteza serije analoga i derivata (+)-goniofufurona, ili 7-epi-goniofufurona, uključujući i do sada nepoznate 7-epi-(+)-krasalaktone B (6) i C (7), 5,7-di-O-cinamoil derivate 8 i 9, 5,7-di-O-izopropilidenske derivate 5 i 10, kao i više lipofilnih derivata (jedinjenja 26, 30, 33, 65, ent-30 i ent-33). Konačno, u drugom delu rada, ispitan je uticaj sintetizovanih stiril-laktona na rast odabranih tumorskih ćelijskih linija in vitro.Enantiodivergent total syntheses of both (+)- and (−)-enantiomers of goniofufurone, 7-epi-goniofufurone and crassalactone C have been accomplished starting from D-glucose. The key steps of the synthe-sis of 7-epi-(+)-goniofufurone were a stereo-selective addition of phenyl magnesium bromide to a protected dialdose, followed by a stereospecific furano-lactone ring formation by condensation of a partially protected lactole with Meldrum’s acid. The synthesis of (+)-goniofufurone and (+)-crassalactone C required a configurational inversion at C-5 in the common intermediate that was efficiently achieved under the standard Mitsunobu conditions, or alternatively through a sequential oxidation of the benzylic hydroxyl group followed by a stereo-selective reduction with borohydride. A similar approach was applied to the synthesis of the unnatural enantiomers of goniofufurone, 7-epi-goniofufurone and crassalactone C, two novel, conformationally constrained analogues of both (+)- and (−)-goniofufurone (oxetanes 34 and ent-34). as well as the corresponding 7-deoxygenated derivatives (31 and ent-31). We have also developed the first total synthesis of (+)-crassalactone B (2) and an alternative synthesis of (+)-crassalactone C (3) starting from D-glucose. Finally, the synthesized styryl-lactones were evaluated for their antiproliferative activity against a panel of human tumor cell lines.
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Sathanantham, Preethi, Shiva K. Devaiah, and Cecelia A. McIntosh. "Structure-Function Analysis of Grapefruit Glucosyltransferase Protein – Identification of Key Amino Acid Residues for its Rigid Substrate Specificity." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/352.
Повний текст джерелаАнотація:
Flavonoids are an important class of secondary metabolites widely distributed in plants. The majority of naturally occurring flavonoids are found in glucosylated form. Glucosyltransferases are enzymes that enable transfer of glucose from an activated donor (UDP-glucose) to the acceptor flavonoid substrates. A flavonol specific glucosyltransferase cloned from Citrus paradisi (Cp3OGT) has strict substrate and regiospecificity. In this study, amino acid residues that could potentially alter the rigidity observed in this enzyme were mutated to position equivalent residues of a putative anthocyanin specific glucosyltransferase from Clitorea ternatea and a GT from Vitis vinifera that can glucosylate both flavonols and anthocyanidins. Using homology modeling followed by site directed mutagenesis to identify candidate regions, three double mutations were made. To test the basis of substrate specificity, biochemical analysis of the three recombinant mutant proteins was carried out. Recombinant protein with mutation S20G+T21S revealed that the enzyme retained activity similar to the wildtype (Cp3OGT) (WT- Km app-104.8 µM; Vmax = 24.6 pmol/min/µg, Mutant- Km app-136.42 µM; Vmax -25pmol/min/µg) but the mutant was more thermostable compared to the WT. The (S290C+S319A) mutant protein retained 40% activity relative to wildtype and has an optimum pH shifted towards the acidic side (pH 6) (Km app-8.27 µM; Vmax-90.9 pmol/min/µg). Mutation of Glutamine87 and Histine154 (H154Y+Q87I) have rendered this recombinant protein inactive with every class of flavonoid tested. Interestingly, the single point mutations H154Y and Q871I had significant activity, slightly greater than that of wildtype enzyme. The two active recombinant proteins will further be analyzed to determine whether the mutations have altered regiospecificity of the original enzyme. Product identification is being conducted using HPLC.
17
Olsson, Rickard. "Surface reactions on mineral particles controlling the hydrolysis of glucose phosphates." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46578.
Повний текст джерелаАнотація:
Phosphorus (P) is an essential nutrient. A significant amount of soil P may be in the form of organophosphates. Due to the size of these compounds, hydrolysis is often required before P can be assimilated by organisms. Hydrolysis may be mediated by mineral surfaces, or catalyzed by extra cellular enzymes. Since both organophosphates and enzymes have a strong affinity for environmental particles, a study of the hydrolysis of organophosphates must focus on reactions at the water/particle interface. This thesis is a summary of four papers, discussing the adsorption, desorption, and abiotic and enzymatic hydrolysis of glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P) in aqueous goethite suspensions. A new technique for simultaneous infrared and potentiometric titrations (SIPT) allowed in-situ measurements of the interfacial reactions. It was found that glucose phosphates form pH-dependent inner sphere complexes on goethite, which coordinate in a monodentate fashion, and are stabilized by hydrogen bonding. Desorption involves a change in speciation of the surface complexes, illustrating the difficulty in determining desorption rates for individual complexes. The surface mediated hydrolysis is primarily base catalyzed for G1P, and acid catalyzed for G6P. The difference is partly due to electronic factors, and partly to differences in glucose group/goethite interactions. Considerably more extensive is the hydrolysis catalyzed by an acid phosphatase (AcPase). The rate of the enzymatic hydrolysis are strongly dependent on the glucose phosphate surface coverage, showing that surface properties affect the adsorption mode of enzymes, and thus their catalytic activity. In solution, AcPase showed a greater specificity towards G6P, but this specificity was partly lost after adsorption onto goethite.
18
Keyhani, Anahita. "PYGCMS investigation of the mechanism of Maillard reaction using isotopically enriched amino-acids and d-glucoses." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42066.
Повний текст джерелаАнотація:
Pyrolysis/GC/MS was utilized as an integrated reaction, separation and identification system to study the thermal degradation products of non-volatile Maillard flavor precursors. Model systems of scL-phenylalanine (aromatic amino acid), glycine and scL-alanine (aliphatic amino acids), scL-serine ($ beta$-hydroxy amino acids) and scL-methionine (sulphur containing amino acid) were investigated. Quartz tube pyrolysis of scD-glucose/amino acid or dicarbonyl/amino acid mixtures shortened the analysis time (from hours to minutes) and eliminated the need for extraction since the volatiles generated from the precursors are directly transferred into the GC column.Phenylalanine Amadori product and different model systems containing phenylalanine and different reducing sugars were studied. Ribbon pyrolysis was used to study the effect of temperature (150, 200, 250$ sp circ$C) on the efficiency of formation of initial pyrolysis products from phenylalanine and Amadori phenylalanine. Quartz tube pyrolysis was used at 250$ sp circ$C to enhance the secondary reactions. These studies revealed the formation of pyridine and naphthalene derivatives such as 3,5-diphenylpyridine, 1(2)-naphthaleneamine, N-methyl-1(2)-aminonaphthalene, 1-aminoanthracene, 2$ sp prime$-phenyl-pyrrolo (4,5-A) dihydronaphthalene, 1(2)-(N-phenethyl)napthaleneamine and 1(2)-(N-phenethyl-N-methyl)naphthaleneamine.
Model studies using scD- ($ sp{13}$C) glucoses and a series of dicarbonyl compounds with labeled ($ sp{15}$N/$ sp{13}$C) glycines and ($ sp{15}$N/$ sp{13}$C) alanines identified a new chemical transformation of $ alpha$-dicarbonyls, that lead to the addition of alkyl groups from the amino acid to the $ alpha$-dicarbonyl compounds, instead of the amino group as in the case of the Strecker type interaction between the two reactants. Thus, glyoxal and pyruvaldehyde can be transformed into pyruvaldehyde and 2,3-butanedione respectively, by glycine and 2-ketobutanal and 2,3-pentanedione respectively, by scL-alanine. The labeled glycine model studies indicated that methyl substituted pyrazines and pyrazinones formed in the model systems, have a common intermediate. Two pathways of pyrazinone formation were distinguished based on the labeling experiments, one involving the reaction of three moles of glycine and the other the interaction of the dipeptide glycylglycine with an $ alpha$-dicarbonyl compound.
A major product of the reaction of scD-glucose with excess glycine was detected by Py/GC/MS analysis and subsequently synthesized and isolated using focused microwave irradiation at atmospheric pressure conditions. Spectroscopic analysis by NMR, FTIR, MS and UV in conjunction with labeling studies have indicated the unknown compound to be 5-hydroxy-1,3-dimethyl-2 (1H) -quinoxalinone. The labeling studies indicated the incorporation of ten carbon atoms (six from sugar, one C-1 atom of glycine, and three C-2 atoms of glycine) and two nitrogens.
scL-Serine was found to be a unique amino acid generating in the absence of sugar a variety of heterocyclic compounds. Under pyrolytic conditions scL-serine can be viewed as a potential mixture of glycine, alanine, serine, formaldehyde and dicarbonyl compounds.
Model studies with scL-methionine provided evidence that methional (Strecker aldehyde) generated under Quartz tube pyrolysis undergoes secondary reactions with amino compounds generating 1,3-thiazines or 3-substituted pyridine in a similar fashion to that of scL-phenylalanine systems where 3-substituted pyridines were also identified. (Abstract shortened by UMI.)
19
Shizas, Ioannis. "Start-up of a laboratory-scale anaerobic sequencing batch reactor treating glucose." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/MQ49734.pdf.
Повний текст джерела
20
Chretien, Chloé. "Un nouvel acteur dans la détection hypothalamique du glucose : les canaux Transient Receptor Potential Canonical (TRPC)." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS027/document.
Повний текст джерелаАнотація:
L’hyperglycémie est détectée et intégrée au niveau de l’hypothalamus médio-basal (MBH) qui inhibe la prise alimentaire et déclenche la sécrétion d’insuline. Le MBH renferme des neurones spécialisés gluco-sensibles (GS) qui détectent directement ou indirectement des variations de la concentration extracellulaire en glucose. Dans une première étude, nous suggérons que la détection indirecte du glucose par les neurones GS hypothalamiques repose sur la libération d’endozépines par les astrocytes, un gliotransmetteur connu pour inhiber la prise alimentaire en réponse à l’hyperglycémie. Nous travaux montrent que les endozépines activent spécifiquement les neurones à pro-opiomélanocortine (POMC) du MBH pour générer leur effet anorexigène. Dans une seconde étude, nous montrons que la détection directe de l’hyperglycémie implique les neurones hypothalamiques dits « high gluco-excited » (HGE). Grâce à des approches pharmacologiques et génétiques, nous mettons en évidence que les canaux redox sensibles Transient Receptor Potential Canonical 3 et 4 (TRPC3/4) sont fondamentaux pour la détection du glucose par les neurones HGE in vitro, la stimulation de la sécrétion d’insuline et la diminution de la prise alimentaire en réponse à l’hyperglycémie cérébrale in vivo. De plus, nos travaux démontrent que les canaux TRPC3 du MBH jouent un rôle clef dans le contrôle de l’homéostasie énergétique. Les travaux de cette thèse permettent de mettre en évidence deux nouveaux mécanismes de détection hypothalamique de l’hyperglycémie : l’un reposant sur l’implication des canaux TRPC3/4 dans les neurones HGE et l’autre proposant les endozépines astrocytaires comme relai du signal « glucose » aux neurones POMCHyperglycemia is detected and integrated by the mediobasal hypothalamus (MBH) which, in turn, inhibits food intake and triggers insulin secretion. The MBH houses specialized glucose-sensitive (GS) neurons, which directly or indirectly modulate their electrical activity in response to changes in glucose level. In a first study, we hypothesized that indirect detection of glucose by MBH GS neurons involves the secretion of endozepine by astrocytes, a gliotransmitter known to inhibit food intake in response to hyperglycemia. The present work shows that endozepines selectively activate anorexigenic MBH pro-opiomelanotortine (POMC) neurons. In the second study, we show that the direct detection of increased glucose level involves hypothalamic glucose-excited (HGE) neurons. Using pharmacological and genetic approaches, we demonstrate that the redox-sensitive Transient Receptor Potential Canonical 3 et 4 (TRPC3/4) channels are involved in MBH HGE response to glucose in vitro and increased insulin secretion and decreased food intake in response to cerebral hyperglycemia in vivo. We also obtained evidences that MBH TRPC3 channel is a critical new player for energy homeostasis. This thesis work identifies two new mechanisms involved in hypothalamic detection of hyperglycemia: the first based on the involvement of TRPC3/4 channels in HGE neurons and the second highlighting the astroglial endozepines as a relay of the “glucose” signal to POMC neurons
21
MIRIBEL, VERONIQUE. "Synthese d'anticorps bispecifiques par voie chimique. Application au couplage de deux reactions enzymatiques : glucose oxydase/peroxydase." Compiègne, 1992. http://www.theses.fr/1992COMP0481.
Повний текст джерелаАнотація:
Le transfert direct ou «channeling» d'un produit intermédiaire de son site actif de synthèse à son site de transformation dans une chaine de réactions enzymatiques consécutives, constitue une des hypothèses relative au contrôle des voies métaboliques. L'originalité de cette étude repose sur la co-immobilisation de deux activités enzymatiques sur un anticorps bispécifique servant d'agent de couplage. L'anticorps bispécifique permet la juxtaposition des deux sites actifs dans une configuration spatiale définie avec un rapport stoechiométrique de 1/1. Le système modèle étudié est celui de l'oxydation du glucose par la réaction consécutive catalysée par la glucose oxydase d'Aspergillus piger et la peroxydase du raifort. Le but est de déterminer les effets de la concentration en H2O2 sur la cinétique de la réaction globale dans le système couplé (immobilisé) et non couplé (en solution). Ce système expérimental couplé se caractérise par une diminution du temps de latence. La comparaison des résultats expérimentaux et théoriques a permis de mettre en évidence que 60% du substrat intermédiaire est transféré directement du premier site actif vers le second. Les anticorps polyclonaux hybrides spécifiques de la glucose oxydase et de la péroxydase sont synthétisés suivant le protocole de Brennan et al. , après dissociation et recombinaison chimique des fragments Fab' au niveau de leur région charnière. Le rendement de recombinaison des deux monomètres est de 17%
22
Mele, Stephen Louis. "Effects of glucose and flow on reactive oxygen species in brain artery endothelial cells." Thesis, State University of New York at Buffalo, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1594755.
Повний текст джерелаАнотація:
Endothelial cells play a vital role in the normal physiology of the vasculature. The cerebrovascular region is highly populated by endothelial cells with distinct morphology and functions. However, endothelial cells are also a vital region in the pathophysiology of the vasculature, such as aneurysm formation, due to reactive oxygen species (ROS) production. To study the effects of glucose and flow on ROS production in brain arterial endothelial cells, ROS production was measured. This thesis is divided into three parts: glucose effect on ROS, flow effect on ROS, and glucose effect on flow-induced ROS. Previous endothelial cultures were provided by Joeseph Moran-Guiati and Jason Kushner. The effect of high glucose on static endothelial cells was shown to increase ROS production as compared to the effect of normal glucose. Under chronic treatment of endothelial cells with high flow, ROS production was significantly greater that in endothelial cells under chronic treatment of normal flow. High glucose was shown to exacerbate the high flow response. These studies provide insight to a possible connection between intracranial aneurysm formation and a major risk factor, Diabetes Mellitus.
23
AGUIARI, Paola. "High Glucose Induces Adipogenic Differentiation of Muscle-Derived Stem Cells." Doctoral thesis, Università degli studi di Ferrara, 2009. http://hdl.handle.net/11392/2388681.
Повний текст джерелаАнотація:
Regeneration of mesenchymal tissues depends on a resident stem cell population, that in
most cases remains elusive in terms of cellular identity and differentiation signals. We here
show that primary cell cultures derived from adipose tissue or skeletal muscle differentiate
into adipocytes when cultured in high glucose. High glucose induces ROS production and
PKCβ activation. These two events appear crucial steps in this differentiation process that can
be directly induced by oxidizing agents and inhibited by PKCβ siRNA silencing. The
differentiated adipocytes, when implanted in vivo, form viable and vascularized adipose
tissue. Overall, the data highlight a previously uncharacterized differentiation route
triggered by high glucose that drives not only resident stem cells of the adipose tissue but
also uncommitted precursors present in muscle cells to form adipose depots. This process
may represent a feed‐forward cycle between the regional increase in adiposity and insulin
resistance that plays a key role in the pathogenesis of diabetes mellitus.
24
Saiepour, Daniel. "Glucose and insulin modulate phagocytosis and production of reactive oxygen metabolites in human neutrophil granulocytes." Doctoral thesis, Umeå : Integrativ medicinsk biologi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-683.
Повний текст джерела
25
Hooper, Stephanie Elaine. "Development of an Ionically-Assembled On-Column Enzyme Reactor for Capillary Electrophoresis." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28190.
Повний текст джерелаАнотація:
This work describes the integration of a separation capillary for capillary electrophoresis (CE) with an on-column enzyme reactor for selective determination of the enzyme substrate. The enzyme reaction occurs during a capillary separation, allowing selective determination of the substrate in complex samples without the need for pre- or post- separation chemical modification of the analyte. The overall goal of this work is to develop a system in which sample introduction, separation of the analyte/substrate from other biological species, enzymatic conversion of the analyte/substrate into a detectable product, and sensitive detection are all included within a single analysis scheme.
Immobilization of the enzyme is achieved by electrostatic assembly of poly(diallydimethylammonium chloride) (PDDA) followed by adsorption of a mixture of the negatively charged enzyme glucose oxidase (GOx) and anionic poly(styrenesulfonate) (PSS). The reaction of glucose with the immobilized glucose oxidase produces H2O2 which migrates the length of the capillary under the influence of electroosmotic flow and is detected amperometrically at the capillary outlet.
The optimal response, kinetics, and stability for the enzyme reactor are determined through characterization of several parameters including the concentration ratio of PSS:GOx, applied separation voltage, and the inner diameter of the separation capillary. Various analyte mixtures containing the substrate and other biological species were evaluated to illustrate selective separation and determination of the substrate from other biomolecules. Optimization of this electrostatically assembled capillary enzyme reactor lead to application of these parameters to similar enzymes such as glutamate oxidase. Future application to similar enzymes like L-amino acid oxidase and possible microfluidic systems is a long-term goal of the system.Ph. D.
26
Fujita, Yoshihito. "Metformin suppresses hepatic gluconeogenesis and lowers fasting blood glucose levels through reactive nitrogen species in mice." Kyoto University, 2010. http://hdl.handle.net/2433/123334.
Повний текст джерела
27
Keyhani, Anahita. "Py/GC/MS investigation of the mechanism of Maillard reaction using isotopically enriched amino acids and D-glucoses." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0025/NQ30308.pdf.
Повний текст джерела
28
Modenbach, Alicia. "Sodium hydroxide pretreatment of corn stover and subsequent enzymatic hydrolysis: An investigation of yields, kinetic modeling and glucose recovery." UKnowledge, 2013. http://uknowledge.uky.edu/bae_etds/17.
Повний текст джерелаАнотація:
Many aspects associated with conversion of lignocellulose to biofuels and other valuable products have been investigated to develop the most effective processes for biorefineries. The goal of this research was to improve the efficiency and effectiveness of the lignocellulose conversion process by achieving a more basic understanding of pretreatment and enzymatic hydrolysis at high solids, including kinetic modeling and separation and recovery of glucose.
Effects of NaOH pretreatment conditions on saccharide yields from enzymatic hydrolysis were characterized in low- and high-solids systems. Factors associated with pretreatment and hydrolysis were investigated, including duration of pretreatment at different temperatures and NaOH loadings, as well as different solids and enzyme loadings. Under relatively mild pretreatment conditions, corn stover composition was essentially equivalent for all time and temperature combinations; however, components were likely affected by pretreatment, as differences in subsequent cellulose conversions were observed. Flushing the hydrolyzate and reusing the substrate was also studied as a method for inhibitor mitigation while increasing overall glucose yields. Flushing the PCS throughout the hydrolysis reaction eliminated the need to wash the pretreated biomass prior to enzymatic hydrolysis when supplementing with low doses of enzyme, thus reducing the amount of process water required.
The robustness of an established kinetic model was examined for heterogeneous hydrolysis reactions in high-solids systems. Michaelis-Menten kinetics is the traditional approach to modeling enzymatic hydrolysis; however, high-solids reactions violate the main underlying assumption of the equation: that the reaction is homogeneous in nature. The ability to accurately predict product yields from enzymatic hydrolysis in high-solids systems will aid in optimizing the conversion process.
Molecularly-imprinted materials were studied for use in both bulk adsorption and in column chromatography separations. Glucose-imprinted materials selectively adsorbed glucose compared xylose by nearly 4:1. Non-imprinted materials were neither selective in the type of sugar adsorbed, nor were they capable of adsorbing sugar at as high a capacity as the glucose-imprinted materials. Liquid chromatography with imprinted materials was not a suitable means for separating glucose from solution under the conditions investigated; however, many factors impact the effectiveness of such a separation process and warrant further investigation.
29
Cavalcante, Isadora Pontes. "Correlação da expressão de GLUT1, HK1, HK2 e HK3 com alta captação de 18/F-FDG em hiperplasia macronodular adrenal primária." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/5/5135/tde-12012015-125308/.
Повний текст джерелаАнотація:
Introdução: Hiperplasia Macronodular Adrenal Primária (PMAH) é uma causa rara de Síndrome de Cushing (SC), caracterizada por macronódulos funcionantes geralmente acometendo ambas as glândulas adrenais. Recentemente, o exame 18F-FDG PET/CT detectou três pacientes com PMAH apresentando captação aumentada de 18F-FDG. No entanto, ainda não foi elucidado o mecanismo pelo qual a PMAH apresentaria uma alta captação de 18F-FDG. Objetivos: Os objetivos deste estudo foram investigar se a expressão de GLUT1, HK1, HK2 e/ou HK3 estão relacionados à alta captação de 18F-FDG na PMAH e comparar estas expressões com tecidos adrenais provenientes de pacientes com AAC e CAA. Métodos: 12 pacientes com PMAH que realizaram 18F-FDG-PET/CT, previamente à adrenalectomia. A captação de 18F-FDG foi quantificada como maximum standardized uptake value (SUVmax). Expressão do RNAm foi investigada através de RT-PCR e a expressão proteica através de técnicas de imunoistoquímica. Expressão gênica e proteica dos pacientes com PMAH foi comparada com 15 pacientes com AAC e 10 pacientes com CAA. As correlações foram realizadas através do teste de coeficiente de correlação de Pearson e as comparações, através do teste Kruskal-Wallis, seguido do ajuste de Dunn. Significância estatística foi considerada quando p < 0.05. Resultados: Todos os pacientes com PMAH apresentaram alta captação de 18F-FDG, cujo SUVmáx variou de 3.3 a 8.9 e o tamanho do maior nódulo variou de 3.5 a 15cm. Foi observada forte correlação positiva entre o tamanho do maior nódulo e o SUVmáx nos pacientes com PMAH. No entanto, não foi estabelecida correlação entre a expressão de GLUT1, HK1, HK2 e HK3 e o SUVmáx nos pacientes com PMAH. A expressão do SLC2A1 e HK2 foi significativamente maior nos pacientes com CAA do que nos pacientes com AAC e PMAH. Conclusões: A captação aumentada de 18F-FDG na PMAH não está relacionada ao aumento da expressão de GLUT1, HK1, HK2 e HK3. Estudos futuros serão necessários para elucidar a via glicolítica que é responsável pelo metabolismo da glicose na PMAHIntroduction: Primary macronodular adrenal hyperplasia (PMAH) is a rare cause of Cushing\'s syndrome, characterized by functioning adrenal macronodules and increased cortisol production. Recently, integrated 18F-FDG-PET/CT examination revealed an increased 18F-FDG uptake in patients with PMAH. However, it is still unclear the mechanism by which PMAH would present with a high 18F-FDG uptake in PET/CT. Objectives: The aim of this study was to investigate whether GLUT1, HK1, HK2 and/or HK3 expression would account for the high18F-FDG uptake in PMAH and compare these expressions with ACA and ACC adrenal tisuue. Methods: 12 patients undergoing adrenalectomy for PMAH with previous 18F-FDG-PET/CT. 18F-FDG uptake was quantified as the maximum standardized uptake value (maxSUV). mRNA expression was investigated through quantitative RT-PCR and protein expression was investigated using immunohistochemical studies. PMAH gene and protein expression were compared to 15 patients with ACA and 10 with ACC. Correlations were performed through Pearson\'s correlation coefficient test and comparisons through Kruskal-Wallis test, followed by Dunn adjust. Statistical significance was considered when p < 0.05. Results: All patients with PMAH presented with high 18F-FDG uptake, the range of SUVmax in these patients varied from 3.3 to 8.9 and the nodule sizes varied from 3.5 to 15 cm. There was a strong positive correlation between the nodule size and 18F-FDG uptake. However, no correlation could be established between gene and protein expression of GLUT1, HK1, HK2 and HK3 and 18F-FDG uptake. SLC2A1 and HK2 expression was significantly higher in patients with CCA than in patients with AAC and PMAH. Conclusions: Increased 18F-FDG uptake in PMAH does not arise from the overexpression of GLUT1, HK1, HK2 or HK3. Further investigation is required to elucidate the glycolytic pathway involved in glucose metabolism in PMAH
30
Khouri, Tarek Zaki. "The effects of glucose and fatty acids on enhanced biological phosphorus removal using a sequencing batch reactor." Master's thesis, University of Central Florida, 1996. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/16679.
Повний текст джерелаАнотація:
University of Central Florida College of Engineering ThesisTwo anaerobic/aerobic sequencing batch reactors (SBRs) were used to evaluate enhanced biological phosphorus removal (EBPR). The first SBR, designated the Glucose SBR, was run for a period of four months. It received a synthetic wastewater plus glucose as a supplemental carbon source. The second SBR, the Isovaleric SBR, was run for three months. During the first month, isovaleric acid was its supplemental carbon source while for the remaining time period, no supplemental carbon source was added to the feed. Steady-state data from the SBR receiving isovalerate yielded the highest phosphorus (P) removals observed during the study, with a mixed liquor volatile suspended solid (MLVSS) P content of 7.2%. The next highest removals were observed when prefermented glucose was received, which yielded a MLVSS P content of 6.4%. The lowest removals were observed when no supplemental carbon source was added to the SBR influent, with at 4.4% MLVSS P content. Batch experiments were also conducted to quantify the effect of EBPR of glucose and the volatile fatty acids (VFAs) acetic acid, propionic acid, valeric acid, and isovaleric acid. Compounds giving the largest anaerobic P release ultimately yielded the lowest effluent P concentrations. At 0.80 mmoles/l, isovaleric acid resulted in anaerobic P released 9.5 mg/l greater than an equal amount of glucose or propionic acid, but ultimately gave effluent P values roughly 4 mg/l lower than either. Ratios of aerobic P uptake/anaerobic P release were found to be roughly equal for all the VFAs when the VFAs were compared on a molar basis. Propionic acid had aerobic P uptake/anaerobic P release ratios similar to the other VFAs. It also behaved the same as all the other VFAs with respect to the effect of concentrations added to the batch experiment; however, the magnitude of its removal was significantly lower than all the other substrates. Glucose, on the other hand, behaved differently from all the VFAs. Glucose aerobic P uptake/anaerobic P release ratios varied with concentration, which was not the case for the others substrates. Also, glucose P net removals decreased at concentrations higher than 0.60 mmoles/l. Glucose also resulted in net P removals roughly 2mg/l higher than propionic acid, but ultimately gave lower net P removal than isovaleric, valeric and acetic acids.
M.S.;
Civil and Environmental Engineering
Engineering;
Environmental Engineering Sciences
111 p.
xi, 111 leaves, bound : ill. ; 28 cm.
31
Löbner, Jürgen. "N-Terminale Glykierung von Proteinen in Lebensmitteln und unter physiologischen Bedingungen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-233695.
Повний текст джерелаАнотація:
Kohlenhydrate und Proteine gehören neben Wasser und Fetten zu den quantitativ bedeutendsten Grundbestandteilen biologischer Systeme und der Lebensmittel. Unter milden Bedingungen in lebenden Organismen oder unter thermischer Belastung bei der Lebensmittelverarbeitung können reduzierende Kohlenhydrate amin-katalysiert durch die Abspaltung von Wasser und Fragmentierungen des Kohlenstoffgerüsts abgebaut werden, wobei die noch reaktiveren 1,2-Dicarbonylverbindungen entstehen. Aus der Reaktion der N-α-Aminogruppe und funktioneller Gruppen der Seitenketten von Aminosäuren mit Kohlenhydraten bzw. 1,2-Dicarbonylverbindungen können stabile Endprodukte entstehen.
In vivo können proteingebundene Maillard-Produkte (MRPs) aus der Reaktion mit Glucose (Amadori-Produkte) oder 1,2-Dicarbonylverbindungen (Advanced Glycation Endproducts: AGEs) entstehen. Beispielsweise ist das „N-terminale“ N-α-Fructosylderivat der β-Kette des Hämoglobins ein etablierter Parameter zur Diagnose von Diabetes mellitus (HbA1c-Wert). Diese nicht-enzymatische, posttranslationale Modifizierung von Proteinen wird allgemein als Glykierung bezeichnet und kann die Funktionalität von Proteinen beeinträchtigen. Deshalb wird untersucht, ob die Trübung der Augenlinsen, die Versteifung von Blutgefäßen oder Schädigungen von Nervenzellen durch eine erhöhte Glykierung verursacht werden. Diese Veränderungen treten im Alter und bei Stoffwechselkrankheiten wie Diabetes mellitus und Urämie auf, die durch eine erhöhte Glucosekonzentration bzw. die Anreicherung von 1,2-Dicarbonylverbindungen im Blut gekennzeichnet sind. Zwar gibt es Publikationen zum Vorkommen N-terminaler Amadori-Produkte an Hämoglobin und in Lebensmitteln, aber die Bildung N-terminaler AGEs wurde bisher nur in wenigen Studien untersucht. Deshalb waren die Bildung und das Vorkommen N-terminaler AGEs im physiologischen Modell, in Hämoglobin und in Backwaren Gegenstand der vorliegenden Arbeit.
In der vorliegenden Arbeit wurde erstmals systematisch die Sequenzabhängigkeit der Bildung der Fructosylderivate bzw. der CM-Derivate in Konkurrenz zu den Glyoxal-2(1H)-Pyrazinonen am N-Terminus von Peptiden unter physiologischen und backtechnologischen Bedingungen untersucht. Dabei wurde nachgewiesen, dass die Variation der C-terminalen Aminosäure in Dipeptiden den Glykierungsgrad und das Produktspektrum erheblich beeinflusst. Mit dem konsequenten Nachweis der N-terminalen von Glyoxal und Methylglyoxal ableitbaren Carboxyalkylderivate und 2(1H)-Pyrazinone in humanen Hämoglobin wurde die Relevanz der N-terminalen Glykierung in vivo untermauert. Damit wird eine umfassendere Beurteilung des Dicarbonylstresses und der Glykierung insbesondere bei Urämikern und Diabetikern ermöglicht. Am Beispiel von Backwaren wurde für Lebensmittel gezeigt, dass unter trockenen Reaktionsbedingungen die 2(1H)-Pyrazinone und in wasserhaltigen Systemen die Carboxyalkylderivate bevorzugt zu erwarten sind.
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Aigster, Annelisse. "Physicochemical and Sensory Properties of Resistant Starch-Based Cereal Products and Effects on Glycemic and Oxidative Stress Responses in Hispanic Women." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28934.
Повний текст джерелаАнотація:
The incidence of type 2 diabetes is considered an epidemic in Western countries, and its prevalence is more common in the Hispanic population than in non-Hispanic whites. Postprandial hyperglycemia has been associated with oxidative stress (OS), thus; reducing postprandial glycemia and/or OS through dietary consumption of resistant starch (RS) may be one approach to help modulate glucose and insulin responses. The purpose of this study was twofold: 1) to evaluate the physicochemical and sensory properties of cereal food products supplemented with RS. 2) to compare the effects of a single ingestion of granola bars with high (~18 grams of RS) and low (~0 grams of RS) RS compositions on the postprandial glucose and insulin responses (n=14) and oxidative stress parameters (cellular glutathione peroxidase, F2- isoprostanes, and oxygen radical absorbance capacity) in Hispanic women (n=9). Granola bars and cereals were developed to provide 2 levels (10% and 15%) of RS; isocaloric (0% RS) control samples were prepared with readily digestible (high amylopectin) starch. Samples were stored for up to 4 weeks at 20 °C. Mean composition of the high RS granola bars was 6% protein, 15% moisture, and 18% lipid. RS levels slightly increased from 14 to 16 g/serving after 4 weeks of storage, supporting published research that RS increases with storage due to retrogradation and crystallization of amylose chains. Color became lighter as the level of RS increased (p<0.001). Granola bars containing RS were less brittle (p=0.0043) than control granola bars. Sensory results indicated granola bars/cereals were acceptable. RS-supplemented granola bars were then used for the evaluation of RS ingestion in humans.
There was no difference in postprandial glucose and insulin responses after a single ingestion of a RS-supplemented (18 g) granola bar. No differences were found in the oxidative stress parameters measured. In a subgroup of subjects (n=9), a lower glucose response 30 minutes after RS consumption was found (p=0.0496). Thus, RS consumption may lower fluctuations in blood glucose, which may help manage glucose levels in individuals at risk of type 2 diabetes. Further studies of short term RS consumption are warranted to elucidate its benefits in glucose management.Ph. D.
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Vincens, Hélène. "Synthèse et utilisation de nouveaux groupements nucléofuges : application à l'alkylation énantiosélective." Rouen, 1987. http://www.theses.fr/1987ROUES010.
Повний текст джерелаАнотація:
Synthèses d'alpha-aminoacides optiquement actifs, d'alpha-hydroxyacides et d'une nouvelle série d'agents d'alkylation : des benzènesulfonates porteurs d'une fonction éther sur la chaine latérale en ortho
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Desmoulins, Lucie. "Détection hypothalamique du glucose chez le rat soumis à un régime gras enrichi en saccharose : rôle de la dynamique mitochondriale et des espèces actives de l'oxygène d'origine mitochondriale." Thesis, Dijon, 2016. http://www.theses.fr/2016DIJOS024/document.
Повний текст джерелаАнотація:
L’hypothalamus participe au contrôle de l’homéostasie énergétique en détectant les signaux circulants tels que le glucose. L’hypothalamus médiobasal (MBH) en particulier, est capable de détecter l’hyperglycémie afin d’initier des réponses physiologiques adaptées, comme par exemple la sécrétion d’insuline via le système nerveux autonome (par un contrôle vagal). Notre équipe a récemment montré que la détection du glucose nécessite la production d’espèces actives de l’oxygène d’origine mitochondriale (mROS), fortement dépendante de la dynamique mitochondriale (fusion et fission). Récemment, l’étude de modèles génétiques ont permis de faire un lien entre ces évènements dynamiques dans le MBH et le développement de pathologies métaboliques. L’objectif de ma thèse a été tout d’abord été de mettre en place un modèle expérimental présentant uniquement une altération de la détection hypothalamique du glucose induite par l’exposition à un régime gras enrichi en saccharose (HFHS) chez le rat. Après avoir caractérisé ce modèle, nos objectifs ont été de déterminer si l’exposition à ce régime hypercalorique avait un impact sur la dynamique mitochondriale ainsi que la signalisation mROS, via la fonction respiratoire de la mitochondrie dans l’hypothalamus. Nous avons finallement réversé quelques acteurs métaboliques dérégulés, potentiellement impliqués dans la dynamique mitochondriale, dans le but de réverser le phénotype observé chez les rats HFHS. Nos résultats montrent qu’après 3 semaines d’exposition au régime HFHS, les rats ont un poids corporel normal malgré l’augmentation de leur masse grasse, comparés aux rats contrôles. Les rats HFHS présentent aussi une intolérance au glucose et une augmentation de la glycémie basale sans modification de leur insulinémie. La sécrétion d’insuline en réponse à la détection hypothalamique du glucose, mesurée après une injection intra-carotidienne de glucose en direction du cerveau qui induit une hyperglycémie uniquement cérébrale, a été fortement diminuée. Cependant, la capacité sécrétoire des îlots pancréatiques est normale chez les rats HFHS. Ces défauts sont associés à une diminution de la production de ROS dans le MBH en réponse au glucose, sans modification du status redox. L’efficacité de la respiration mitochondriale hypothalamique a été mesurée par oxygraphie, et les résultats montrent une déficience de la respiration mitochondriale chez les rats HFHS. La translocation de la protéine de fission DRP1 à la mitochondrie est diminuée en réponse au glucose, suggérant une diminution de la fission mitochondriale. L’augmentation de l’activation de l’AMPK dans l’hypothalamus n’est pas responsable de l’altération de la détection hypothalamique du glucose car sa réversion avec une injection intracérébroventriculaire (ICV) de composé C, n’a pas permis de restaurer la sécrétion d’insuline en réponse à l’hyperglycémie cérébrale. De même, une injection ICV de leptine induisant l’activation de STAT3 n’a pas permis de restaurer la sécrétion d’insuline en réponse à l’hyperglycémie cérébrale. Enfin, la diminution de l’activation d’AKT suggère une résistance centrale à l’insuline. Ces résultats démontrent pour la première fois que l’altération hypothalamique de la signalisation ROS, de la fission et de la respiration mitochondriale, sont présent chez les rats exposés pendant 3 semaines à un régime HFHS. Ces défauts précoces hypothalamiques pourraient ainsi participer à un défaut primaire du contrôle de la sécrétion d’insuline, et finallement, à l’installation d’un phénotype diabétiqueThe hypothalamus participates in the control of energy homeostasis by detecting circulating nutrients, such as glucose. The mediobasal hypothalamus (MBH), in particular, senses hyperglycemia and initiates physiological responses, e.g., insulin secretion via the autonomous (vagal) nervous system. We have recently demonstrated that glucose sensing requires mitochondrial reactive oxygen species (mROS) signaling heavily dependant on mitochondrial fusion and fission (dynamics). Recently, genetic models have associated some of these dynamics within the MBH to their obesogenic susceptibility. The aims of my thesis were first to establish a model that only presents a hypothalamic glucose sensing defect induced by a high fat high sucrose (HFHS) feeding in rats. After caracterizing this model, our objectives were to determine whether modulating the diet affects mitochondrial dynamics, and thus, mROS signaling, through the mitochondrial respiratory function in the hypothalamus. We finally reversed some dysregulated metabolic signalings potentially involved in mitochondrial dynamics in order to reverse the phenotype observed in HFHS fed rats. Our results demonstrate that after 3 weeks of HFHS feeding, rats had a normal body weight despite an increase in the fat mass compared to control rats. HFHS fed rats displayed also a glucose intolerance, increased fasting glycemia but no modification of fasting insulinemia. Hypothalamic glucose sensing induced insulin secretion, measured after an intra-carotid glucose injection towards the brain that only increases brain glycemia without alteration in peripheral glycemia, was drastically decreased. However, glucose stimulated insulin secretion in isolated islets was not different compared to controls. These defects correlate with a decrease of MBH ROS production in response to glucose, with no modification in the redox status. Efficiency of hypothalamic mitochondrial respiration was evaluated using oxygraphy, and results showed mitochondrial respiratory deficiencies in HFHS fed rats. The fission protein DRP1 exhibited decreased mitochondrial translocation in the MBH in response to glucose, suggesting decreased mitochondrial fission. The increase of AMPK activation in the hypothalamus was not responsible for the alteration of hypothalamic glucose sensing since its reversal with an intracerebroventricular (ICV) injection of compound C failed to restore brain hyperglycemia induced insulin secretion. Likewise, an ICV injection of leptin that induced STAT3 activation also failed to restore brain hyperglycemia induced insulin secretion. Finally, the decrease in AKT activation suggested a central insulin resistance. These results demonstrate for the first time that hypothalamic alteration of mitochondrial ROS signaling, fission and respiration were present in rats exposed to a 3 weeks HFHS diet. Such hypothalamic glucose sensing defects are early events preceding those in islets. These early but drastic hypothalamic modifications could participate in a primary nervous defect of the control of insulin secretion, and finally, the etablishment of a diabetic phenotype
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Franconi, Jean-Michel. "Mise au point de sondes moleculaires pour l'etude par resonance magnetique nucleaire quantitative du fractionnement isotopique du deuterium accompagnant certaines reactions du metabolisme du glucose." Nantes, 1988. http://www.theses.fr/1988NANT2032.
Повний текст джерела
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Vieira, Thiago Antonio. "Síntese de C-glicosídeos e derivados a partir de fontes renováveis." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-03122018-170834/.
Повний текст джерелаАнотація:
Os carboidratos são componentes essenciais de muitos produtos naturais de grande importância medicinal. As porções carboidrato podem aumentar a solubilidade em água de drogas, diminuir a toxicidade e/ou contribuir para a bioatividade dos produtos naturais. A síntese de C-glicosídeos, a partir de D-glicose, é de grande interesse porque estes são úteis como blocos de construção para a síntese de vários tipos de moléculas com grande potencial de utilização em princípios ativos para tratamento de câncer, diabetes, HIV, como antivirais, entre outros. Os C-glicosídeos são essencialmente inertes à degradação porque o centro anomérico natural (um O- ou N-acetal instável) foi transformado hidroliticamente em ligação éter. Como resultado, uma atenção significativa tem sido dedicada para o desenvolvimento de novas vias sintéticas. A reação de Knoevenagel, descrita há mais de um século, consiste na condensação de aldeídos com moléculas contendo metileno ativo, tais como o ácido malônico ou o seu éster e dicetonas. Embora consista de uma desidratação, surpreendentemente, a reação é favorecida em meio aquoso, em alguns casos. A condensação de carboidratos desprotegidos com dicetonas tem atraído crescente interesse com a crescente cobrança da sociedade por tecnologias mais limpas (verdes). Nesse sentido, baseando-se no conceito de Química Verde e seus Doze princípios, buscou-se a redução ou troca de solventes orgânicos por outros mais verdes, adaptação dos sistemas de reação para operação em temperaturas mais brandas e substituição de matérias-primas por outras mais verdes. O objetivo principal consistiu na preparação da cetona-?-C-glicosídeo (CG) e seus derivados, a partir da D-glicose, com potencial aplicação como intermediários de fármacos. Nesse trabalho, foram preparados derivados do CG e da D-glicose: CG peracetilado, D-glicose peracetilada, CG perbenzoilado, D-glicose perbenzoilada, CG peracetilado clorado, CGAr1 ((E)-4-(4-metoxifenil)-1-(3,4,5-trihidroxi-6- (hidroximetil)-tetrahidro-2H-piran-2-il)but-3-en-2-ona), CGAr1 peracetilado e CGAr1 peracetilado bromado. O CG foi preparado em meio aquoso ou em EtOH-água 4:1, pH alcalino (35-80%). O CG peracetilado (2,3,4,6-tetracetil-1-C-(?-D-glicopiranosil)propan-2-ona) e a Dglicose peracetilada (1,2,3,4,6-pentacetil-1-C-(?-D-glicopiranosil)) foram preparados (71 e 77,5%) usando quatro metodologias: duas usando AcONa/Ac2O a 50-90 °C, uma com AcONa/py/DMAP a t.a. e uma com I2/Ac2O a 28 °C. O CG perbenzoilado (2,3,4,6-tetrabenzoil- 1-C-(?-D-glicopiranosil)propan-2-ona) e a D-glicose perbenzoilada (1,2,3,4,6-pentabenzoil-1-C- (?-D-glicopiranosil) foram preparados (31 e 83%), respectivamente, usando sete metodologias: duas em solução de NaOH a t.a., quatro com py e DCM e/ou tolueno como solvente a 65 °C, uma com py/DCM a 5 °C. O CG peracetilado clorado (2-(acetoximetil)-6-(3-cloro-2- oxopropil)tetrahidro-2H-piran-3,4,5-triil triacetato) foi preparado (19,6%) usando NH4Cl/oxone em MeOH sob refluxo. O CGAr1 foi preparado a partir do CG bruto com p-anisaldeído, L-prolina e TEA em MeOH a t.a (33,5%). O CGAr1 peracetilado ((E)-2-(acetoximetil)-6-(4-(4-metoxifenil)- 2-oxobut-3-en-1-il)-tetrahidro-2H-piran-3,4,5-triil triacetato) foi preparado (54%) usando três metodologias: Ac2O/AcONa a 50 °C, I2/Ac2O a 28 e a 50°C. O CGAr1 peracetilado bromado foi preparado (78%) usando Br2/CCl4 a t.a.Carbohydrates are essential components of many natural products of great medicinal importance. The carbohydrate portions may increase the water solubility of drugs, decrease toxicity and/or contribute to the bioactivity of the natural products. The synthesis of Cglycosides, from D-glucose, is of great interest because they are useful as building blocks for the synthesis of various types of molecules with great potential as active principles for the treatment of cancer, diabetes, HIV, as antivirals, among others. C-glycosides are essentially inert to degradation because their natural anomeric center (an unstable O- or N-acetal) has been hydrolytically transformed into an ether linkage. Thus, significant attention has been devoted to the development of new synthetic routes. The Knoevenagel reaction, described over a century ago, consists of the condensation of aldehydes with molecules containing active methylene, such as malonic acid or its ester and diketones. Although it consists of a dehydration, surprisingly, the reaction is favored in aqueous medium in some cases. The condensation of unprotected carbohydrates with diketones has attracted increasing interest with the growing society\'s demand for cleaner (green) technologies. Based on the concept of Green Chemistry and its Twelve Principles, the aim was to reduce or substitute organic solventes for greener ones, adapt reaction systems to operate at milder temperatures and substitute raw materials for greener ones. The main goal was to prepare ketone-?-C-glucoside (CG) and its derivatives, from D-glucose, with potential application as drug intermediates. In this work, CG and D-glucose derivatives were prepared: peracetylated CG, peracetylated D-glucose, perbenzoylated CG, perbenzoylated D-glucose, chlorinated peracetylated CG, CGAr1 ((E)-4-(4- methoxyphenyl)-1-(3,4,5-trihydroxy-6-(hydroxymethyl)-tetrahydro-2H-pyran-2-yl)but-3-en-2- one), peracetylated CGAr1 and brominated peracetylated CGAr1. CG was prepared (35-80%) in water or EtOH-water (4:1), alkaline pH. Peracetylated CG (2,3,4,6-tetraacetyl-1-C-(?-Dglucopyranosyl) propan-2-one) and peracetylated D-glucose (1,2,3,4,6-pentacetyl-1-C-(?-Dglucopyranosyl)) were prepared (71 and 77,5%), using four methodologies: two using AcONa/ Ac2O at 50-90 °C, one with AcONa/py/DMAP at rt and one with I2/Ac2O at 28 °C. The perbenzoylated CG (2,3,4,6-tetrabenzoyl-1-C-(?-D-glucopyranosyl)propan-2-one) and perbenzoylated D-glucose (1,2,3,4,6-pentabenzoyl-1-C-(?-D-glucopyranosyl) were prepared (31 and 83%) using seven methodologies: two in NaOH aqueous solution, four with py and DCM and/or toluene as solvent at 65 °C. Chlorinated peracetylated CG (2-(acetoxymethyl)-6-(3- chloro-2-oxopropyl)tetrahydro-2H-pyran-3,4,5-triyl triacetate) was prepared (19,6%) using NH4Cl/oxone in MeOH under reflux. CGAr1 was prepared from crude CG with p-anisaldehyde, L-proline and TEA in MeOH at rt (33,5%). The peracetylated CGAr1 ((E)-2-(acetoxymethyl)-6- (4-(4-methoxyphenyl)-2-oxobut-3-en-1-yl)-tetrahydro-2H-pyran-3,4,5-triyl triacetate) was prepared (54%) using three methodologies: Ac2O/AcONa at 50 °C, I2/Ac2O at 28 and at 50 °C. Brominated peracetylated CGAr1 was prepared (78%) using Br2/CCl4 at rt.
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Carneiro, Lionel. "Détection hypothalamique de l'hyperglycémie : rôle de la dynamique mitochondriale dans la signalisation par les espèces actives de l'oxygène." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00689166.
Повний текст джерелаАнотація:
L'homéostasie énergétique se définit comme le maintien de l'équilibre entre les apports et les dépenses d'énergie. La régulation nerveuse de cet équilibre est principalement assurée par l'hypothalamus. Il existe dans cette structure des neurones spécialisés dont l'activité électrique est modifiée par des signaux nerveux, métaboliques et hormonaux.Nous avons travaillé sur la détection du glucose dans cette structure, qui permet l'élaboration d'une réponse adaptée en termes de prise alimentaire et de contrôle du métabolisme. Lors de cette détection, l'utilisation du glucose conduit à la formation d'Espèces Actives de l'Oxygène d'origine mitochondriale (mEAOs) par la chaîne respiratoire mitochondriale (CRM), constituant une signalisation redox indispensable aux réponses physiologiques. De récentes études in vitro (cultures de myoblastes, hépatocytes) ont par ailleurs mis en évidence le rôle de la dynamique mitochondriale, qui contrôle la morphologie des mitochondries par des mécanismes de fission et de fusion, sur la production de mEAOs induite par une hyperglycémie. Cette dernière déclenche la fission des mitochondries de façon concomitante à la production de mEAOs. En revanche, le blocage de la fission empêche la production de mEAOs lors de l'hyperglycémie dans ces cultures. Ces études suggéraient donc que la fission soit déclenchée par l'hyperglycémie et permette alors la production de mEAOs. Mon projet de thèse a consisté à déterminer l'implication de la dynamique mitochondriale dans la signalisation mEAOs lors de la détection hypothalamique du glucose. Nos résultats nous ont permis de mettre en évidence, dans un premier temps, un adressage de la protéine de fission DRP1 à la mitochondrie dans l'hypothalamus lors d'une hyperglycémie cérébrale, évènement nécessaire au déclenchement de la fragmentation des mitochondries. Cette fragmentation est confirmée en imagerie où l'analyse morphologique montre des mitochondries plus petites, plus sphériques et moins allongées que celles des témoins. Dans un deuxième temps, nous avons déterminé l'implication de cette fission mitochondriale dans la détection hypothalamique du glucose. Son importance a pu être évaluée en bloquant la fission des mitochondries par l'inhibition de l'expression de la protéine de fission DRP1 spécifiquement dans le VMH, par interférence ARN. Cette stratégie nous a permis d'obtenir une inhibition de l'expression de DRP1 de près de 80%, 72h après l'injection. Cette inhibition est localisée au VMH et a pour conséquence une élongation des mitochondries qui présente un réseau mitochondrial plus filamenteux. L'étude du phénotype des animaux a mis en évidence une hyperphagie associée à l'inhibition de la fission mitochondriale dans le VMH. Cette hyperphagie n'entraine cependant aucune modification du poids corporel. Ceci suggère une augmentation des dépenses énergétiques chez ces animaux. De plus, ils présentent une perte de sensibilité hypothalamique au glucose qui conduit à un défaut du contrôle nerveux de la sécrétion d'insuline, ainsi qu'à une perte de l'effet satiétogène du glucose lors d'un test de réalimentation. Nous montrons que cette perte de sensibilité au glucose est due à un défaut de production hypothalamique des mEAOs en réponse au glucose, production qui est nécessaire à la signalisation responsable des réponses effectrices. Ce défaut de production de mEAOs est associé à un dysfonctionnement de la CRM. L'ensemble de ce travail permet donc de montrer pour la première fois, in vivo, que la fission mitochondriale est indispensable à la production hypothalamique de mEAOs lors d'une hyperglycémie cérébrale. Cette production est nécessaire au déclenchement du contrôle nerveux permettant d'une part la sécrétion d'insuline et d'autre part le rassasiement induit par le glucose intra-hypothalamique.
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Junior, Fadi Antoine Taraboulsi. "Enzimas microbianas na conversão da sacarose em frutose e ácido glicônico usando reatores descontínuo-alimentado e contínuo com membrana." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/9/9134/tde-28072010-113005/.
Повний текст джерелаАнотація:
A sacarose é uma matéria-prima em franca expansão de produção no Brasil, seu maior produtor e exportador. Essa molécula pode ser convertida, através de um processo multienzimático, em produtos de maior valor agregado: frutose e ácido glicônico, os quais são importados pelo país, e amplamente utilizados em indústrias químicas, de produção de fármacos e setores alimentícios. Neste estudo, avaliou-se a hidrólise da sacarose pela invertase assim como a conversão da glicose em ácido glicônico, pela ação da glicose oxidase, ambas em processo descontínuo-alimentado. A solução de substrato (64g/L-sacarose; 32g/L-glicose) foi adicionada segundo as seguintes leis: constante, linear crescente, linear decrescente, exponencial crescente e exponencial decrescente. No caso da glicose, foi necessária a utilização de enzima auxiliar, a catalase, para degradar a água oxigenada formada durante a conversão da glicose. Mediante os resultados dos testes com os dois substratos, realizou-se teste de conversão direta da sacarose em frutose e ácido glicônico, utilizando-se invertase, glicose oxidase e catalase em regime descontínuo-alimentado, com alimentação linear decrescente (melhor resultado para ambos os substratos). No procedimento contínuo, alvo principal do trabalho, utilizou-se reator com membrana, da marca MILLIPORE ®, integrando em uma única etapa a conversão catalítica, a separação/concentração do produto e a recuperação do biocatalisador. A temperatura foi controlada por circulação de água, tendo acoplado uma bomba peristáltica (para controlar a vazão de alimentação do substrato) e um sistema de pressurização. O reator operou com membrana de ultrafiltração (corte molecular = 100 kDa) e foi mantido sob agitação constante. Os parâmetros de partida foram, a princípio, fixados de acordo com os valores otimizados no reator descontínuo-alimentado com o emprego simultâneo das enzimas.Sucrose is a commodity largely produced in Brazil and one of the most used and commercialized product in food industry. It can be converted through a multienzyme process in fructose and gluconic acid, which have commercial values higher than sucrose. Both products are imported by Brazil, being largely employed in the chemical, food and pharmaceutical industry. This work dealt with the hydrolysis of sucrose by invertase into fructose and glucose, and the oxidation of glucose to gluconic acid by glucose oxidase and catalase. Catalase was added in order to decompose the hydrogen peroxide an inhibitor of glucose oxidase formed as by-product of the oxidation. Two processes were employed. Fed-batch in which the hydrolysis and oxidation reactions were carried out separately by adding invertase followed by glucose oxidase and catalase was conducted by adding the solution of substrate according to a constant, increasing linear, decreasing linear, increasing exponential or decreasing exponential mode. The best fed-batch performance was attained through the decreasing linear addition of sucrose (64g/L) and glucose (32g/L). Setting this kind of addition and using all enzymes simultaneously, the direct conversion of sucrose to fructose and gluconic acid occurred at a yield of 72%. The continuous process was carried out in a cell-type membrane reactor (membrane cut off = 100 kDa), in which the sucrose conversion was made by using all enzymes simultaneously, leading to a final yield of about 76%
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Benhaddou, Rachida. "Arylation de doubles liaisons catalyses par le palladium : influence de differents facteurs sur la cinetique de la reaction, etude de nouvelles syntheses d'aryl-c-glycosides." Paris 6, 1988. http://www.theses.fr/1988PA066065.
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Valle, Maíra Mello Rezende. "Alterações na homeostase redox das células beta pancreáticas em resposta à glicose." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-19022015-163014/.
Повний текст джерелаАнотація:
As espécies reativas de oxigênio são capazes de influenciar a secreção de insulina, porém ainda não está clara a influência da glicose, principal secretagogo deste hormônio, sobre a homeostase redox das células beta pancreáticas. Incubações por 1 e 48 horas com diferentes concentrações de glicose (2,8; 5,6; 8,3; 11,1; 16,7 e 20 mM) demonstraram que esta é capaz de alterar não só o conteúdo de superóxido, produzido pela mitocôndria e NADPH oxidase, mas também o sistema antioxidante, alterando a concentração de GSH e a expressão das enzimas antioxidantes. Além disso, aumenta a interação Rac1/Sod1, que mantém a NADPH oxidase ativa. Porém, não apresenta endossomas de sinalização redox, os redoxossomas, em resposta a glicose. Estas alterações podem afetar eventos chave para este tecido endócrino, como a secreção de insulina e a morte celular.ROS production in pancreatic beta cells has been associated with the insulin secretion process but the mechanism by which glucose affects the redox state in these cells remains unknown. In order to address this issue, we evaluated the effect of 1 or 48 hours incubation of pancreatic beta cells with various glucose concentrations (2.8, 5.6, 8.3, 11.1, 16.7 and 20 mM). Glucose loading induced superoxide production by mitochondria and NADPH oxidase complex, and enhanced the antioxidant capacity by increasing GSH content and modulate expression of antioxidant enzymes. Glucose also promoted Rac1/Sod1 interaction that maintains NADPH oxidase activated. These cells however did not present redox endosomes, the redoxosomes, in response to glucose loading. These effects might be associated with the process of insulin secretion and pancreatic beta cell death.
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Lebeau, Thierry. "Fermentation alcoolique de mélanges glucose-xylose par les levures Candida shehatae et Saccharomyces cerevisiae co-immobilisées dans un nouveau type de bioréacteur à membrane." Rouen, 1997. http://www.theses.fr/1997ROUES014.
Повний текст джерелаАнотація:
Ce travail étudie la fermentation alcoolique d'un mélange de glucose (35 g/l) et de xylose (15 g/l) par Candida shehatae et Saccharomyces cerevisiae co-immobilisées dans une structure membranaire composite constituée d'une couche plane d'agar enserree entre deux membranes microporeuses. L'utilisation d'un bioréacteur à double chambre a permis une alimentation dissymétrique en substrats et en dioxygène de la structure immobilisatrice et de répondre ainsi aux exigences de culture de chacune des deux espèces. Lors de fermentations discontinues, nous avons montré que les levures consommaient totalement le glucose mais seulement 25% a 40% du xylose. Afin de comprendre les raisons de la faible conversion du xylose par les levures immobilisées, nous avons évalué la résistance opposée par la structure biocatalytique à la diffusion des divers solutés (glucose, xylose, éthanol et xylitol). Cette résistance double au cours de l'incubation : une augmentation de cet ordre ne peut expliquer à elle seule le blocage du système. Une étude des capacités fermentaires des cellules extraites de la structure immobilisatrice a montré que les levures localisées près de la source de substrats carbonés subissaient un fort stress, probablement du à l'accumulation de co-métabolites toxiques dans le milieu de culture. Nous avons enfin effectué des fermentations en continu dans un prototype de bioréacteur à double chambre possédant une surface d'échange élargie. Un taux de conversion du xylose de 73% (et de 100% pour le glucose) a pu être atteint pour un taux de dilution D de 0,04 h(-1), bien que la charge microbienne initiale du gel d'agar fut relativement faible (2,5 g/l de Candida shehatae + 2,5 g/l de Saccharomyces cerevisiae).
42
Marklund, Niklas. "The role of reactive oxygen species in traumatic brain injury : Experimental studies in the rat." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5053-9/.
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Wu, Liya [Verfasser], and Klaus [Akademischer Betreuer] Parhofer. "The effect of walnut consumption on lipid and glucose metabolism, adipokines, C-reactive protein, endothelial function, body weight and blood pressure in healthy men and healthy postmenopausal women / Liya Wu. Betreuer: Klaus Parhofer." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1111505276/34.
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Menéndez, Aguirre Orquídea de María Pastora. "Stability of microbial transglutaminase and its reactions with individual caseins under atmospheric and high pressure." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1161695264565-75969.
Повний текст джерелаАнотація:
Kinetic inactivation of factor XIIIa and MTG were performed in a pressure range from 0.1 to 400 MPa at 40°C within a time from 0 to 60 min in a TRIS-acetate buffer at pH 6.0. The inactivation of both enzymes at these conditions followed a first order reaction model. The high inactivation rate constant of 26.6 x10-3/min-1 for factor XIIIa at low pressure (50 MP) indicated that this enzyme is much easier to inactivate than MTG, which achieved an inactivation rate constant value of 9.7 x10-3/min at higher pressure (200 MPa). An inactivation volume of –10.17±0.5 cm3/mol confirmed that MTG is very stable under high pressure. The stability of MTG under high pressure and thermal treatment was related to its conformational changes. Enzyme inactivation was accompanied by secondary and tertiary structure changes until an irreversible protein precipitation is achieved. The tertiary structure, represented by circular dichroism spectra in the aromatic region showed differences among native and MTG samples treated under high pressure, as well as at elevated temperature. Tyrosine bands, indicating protein unfolding, increased proportionally with increasing pressure treatment above 400 MPa. Nevertheless, compared to pressure, a maximal enhancement could be observed after thermal treatment at 0.1 MPa at 80°C. That demonstrated the exposure of hydrophobic groups to the protein surface with a concomitant protein unfolding. The spectra in the far ultraviolet region showed that increasing high pressure and high temperature lead to alterations in the secondary structure. The mathematical algorithms CONTIN used to calculate secondary structures stated that the 24.5% of alpha-helix of native MTG decreased to 17.2% after a treatment at 400 MPa at 40°C for 60 min and to 6.5% after a treatment at 0.1 MPa at 80°C for 2 min. However, beta-strand structures remained relatively stable after these several treatments. MTG is arranged in a way that the active site is located between beta-strand domains that are surrounded by alpha-helices, the results of this investigation suggested that MTG activity is related with the relative stability of alpha-helix and the outstanding stability of the central beta-strand structure. The irreversible precipitated protein observed at 600 MPa at 40°C for 60 min and 0.1 MPa at 80°C for 2 min was caused principally by the formation of disulfides bonds, because high pressure and high thermal treatment lead to the exposition of the Cys64 residue towards the solvent with the subsequent ability to react with neighbouring cysteine residues. Furthermore, the reaction between protein and reducing sugars resulted in the formation of Maillard products. Furosine, as an indicator of the early stages of Maillard reaction was measured. Concentration values of 261.0 mg/g protein from samples treated at 600 MPa and 40°C and 238.5 mg/g protein from samples treated at and 0.1 MPa and 80°C for 2 min were obtained. Pentosidine a subsequent product observed in the advanced Maillard reaction was also present. Concentrations of 13.7 and 6.7 mg/g protein were obtained in the samples treated at 600 MPa and 40°C for 60 min and 0.1 MPa and 80°C for 2 min, respectively. Kinetic inactivation studies of MTG in a pressure range from 0.1 to 600 MPa at 10, 30, 40, and 50°C within a long time range from 0 to 140 h were performed in order to study MTG stability under the simultaneous effect of pressure and temperature. The inactivation kinetic showed a first and very fast step and a second very slow step suggesting irreversible inactivation behaviour. Activation energy and entropy difference decreased with increasing pressure. Thereby, the inactivation rate constants of enzyme were less temperature dependent at high pressure. The effect of pressure and temperature on MTG inactivation had a synergistic behaviour. At temperatures of 10, 30, and 40°C, increasing pressure leads to increasing inactivation rate constants. However at 50°C a tendency change occurred. Negative activation volumes of –16.2±0.5, -13.6±0.1, -11.2±0.3 cm3/mol were obtained for 10, 30 and 40°C respectively and for treatment at 50°C a positive value of about +3.0±2.0 cm3/mol in a pressure range from 0.1 to 300 and a negative volume of –11.0±0.4 cm3/mol MPa from 300 to 600 MPa were calculated. A pressure/temperature diagram from inactivation rate constants was performed to represent MTG stability. The diagram shows that in a pressure and temperature range from 0.1 to 550 MPa and 10 to 40°C, pressure induces MTG stabilization against heat denaturation. At 50°C in range from 0.1 to 300 MPa, pressure induces also enzyme stabilization again heat denaturation, but at the same temperature and above 300 MPa the enzyme was inactivated. After MTG stability analysis, reaction kinetics from MTG with individual caseins in a TRIS-acetate buffer pH 6.0 were performed under atmospheric pressure (0.1 MPa) and high pressure (400 MPa) at 40°C. The reaction was monitored by gel permeation chromatography under in three assumptions: 1) The initial velocity kinetics was obtained from a non-progressive enzymatic reactions with the products. 2) The substrate concentration exceeded enzyme concentration. 3) The sum of the individual catalytic constants of the reactive glutamine residues inside caseins are represented by a single MTG-monomeric casein complex. Enzyme reaction kinetics of MTG with the individual caseins carried out at 0.1 MPa at 40°C showed Michaelis-Menten-Henri behaviour with maximal velocities of 2.7 x 10-3, 0.8 x 10-3, and 1.3 x 10-3 mmol/L∙min and Km values of 59 x 10-3, 64 x 10-3 and 50 x 10-3 mmol/L of beta-, alpha-s1-, and whole-casein, respectively. This suggested that MTG achieved a maximal velocity with ß-casein, but had the best affinity with acid casein followed by beta- casein and finally alpha-s1-casein. Enzyme reaction kinetics of beta-casein carried out at 400 MPa and 40°C also showed a Michaelis-Menten-Henri behaviour with a similar maximal velocity of 2.6 x 10-3 mmol/L×min, but the Km value of 144 x 10-3 mmol/L showing kinetical similarity to a non-competitive inhibition. The reaction of MTG with alpha-s1-casein under high pressure did not fit in to Henri-Michaelis-Menten kinetics. Kinetic parameters showed that the affinity of MTG to beta- and alpha-s1-casein under atmospheric pressure is higher than the affinity of MTG to these caseins under high pressure. This loss of affinity can be explained by a constant number of reactive glutamine residues of casein, although the protein is unfolding at high pressure, a decrease of enzyme activity of MTG to 74% after treatment at 400 MPa at 40°C for 15 min and self association of casein under thermal and high pressure treatment. Fur technological application, the formation of acid milk gels was studied under the influence of MTG within its range of pH stability. Simultaneous addition of MTG and different concentrations of glucono-delta-lactone (Gdl) to casein solutions (5% w/v) at 40°C was analysed. Gels firmness was accessed by oscillation rheometry and gel permeation chromatography. Oscillation rheometry data showed that the time of gelation decreased with an increasing Gdl concentration added to the system, however higher concentrations of Gdl caused the formation of weaker gels. Addition of 1 g Gdl/g protein without MTG caused gelation within 5 min and a storage module value G´ of 48.9 Pa. With the simultaneous addition of 1 g Gdl/g protein and 6 U MTG/ g protein the gelation time was 4 min and the reached storage modulus was 63.7 Pa. However, the addition of 0.21 g Gdl/g protein and 6 U/g protein MTG increase the gelation time to about 69 min, but, a higher module value G´ of 111.0 Pa was achieved. Addition of high Gdl concentration caused a rapid drop of pH below 5 leading to a fast enzyme inactivation. However addition of very low Gdl concentrations was also not optimal. The simultaneous influence of MTG and Gdl concentration on the gelation time and elastic properties was evaluated by a central composite rotatable design (CCRD). The resulting quadratic storage modulus model showed that, MTG concentration had a significant influence on storage modulus G´ and, that the firmness of the gels increase in direct proportion with MTG activity with the existence of a optimum Gdl concentration, whereas the resulting linear model of the gelation time stated that Gdl concentration has a significant influence on the gelation time, while it is independent of the MTG activity. A maximal firmness of 136 ± 2 Pa was reached between a range of 0.24 - 0.27 g Gdl/g protein and 5.8 U MTG/g within a time from 49 to 59 min. Gel permeation chromatography analysis demonstrated that acid gels induced by Gdl were formed by reversible cross-linking like electrostatic interactions and hydrogen bonds as well as disulfide bonds caused by temperature treatment. Whereas, the addition of MTG proved the formation of non-reversible cross-linking like oligomers based on Ne-(g-glutamyl)- lysine, which gave more firmness and stabilization on the casein gel network.
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Lefrançois, Pauline. "Développement d’un microréacteur biomimétique pour l'analyse in situ d'activités enzymatiques par couplage de l’électrochimie et de la microscopie de fluorescence." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0759/document.
Повний текст джерелаАнотація:
De nombreuses réactions enzymatiques sont à l’origine de processus physiologiques au sein des organismes vivants. Ces réactions sont basées sur des transferts de protons et d’électrons et con-duisent souvent à la production d’espèces secondaires. Parmi elles, les espèces réactives de l’oxygène et de l’azote (ROS, RNS) présentent un intérêt particulier puisqu’elles jouent un double rôle : d’une part en permettant à l’organisme de réagir à un stress par l’activation de voie de signalisation redox, et d’autre part ces ROS et RNS peuvent causer des dommages tissulaires et être à l’origine de dys-fonctionnement (stress oxydant) au sein de l’organisme. La haute réactivité de ces espèces induit leurs faibles durées de vie (ns-min) et rend l’étude de certaines réactions enzymatiques difficiles en solu-tion. Ce projet de thèse a pour objectif de développer un microréacteur biomimétique pour l’étude d’activités enzymatiques produisant des ROS/RNS. En effet, en confinant une réaction au sein d’un compartiment de taille équivalente à celle d’une cellule (20-100 μm de diamètre), les espèces générées (H2O2, NO•, NO2-) doivent pouvoir être sondées in situ avec une résolution cinétique et quantitative. Des vésicules unilamellaires géantes sont formées en conditions physiologiques et servent de micro-réacteurs pour l’analyse des activités enzymatiques de la glucose oxydase et des NO-synthases. La microscopie de fluorescence permet l’observation des vésicules et le suivi du déclenchement de la réaction assuré par microinjection. Les espèces produites sont ensuite détectées en temps réel par électrochimie afin de déchiffrer à terme les différentes voies enzymatiques des NO-SynthasesEnzymatic reactions are involved in many physiological phenomena in living organisms. These reactions are based on protons and electrons transfers and can lead to the production of by-products. Among them, reactive oxygen and nitrogen species (ROS and RNS) are of great interest as they play a double role: on the one hand by allowing the organism to react to a stress by the activation of signaling redox pathways, and on the other hand, ROS and RNS can cause oxidative damages to tissues ensuing dysfunctions in the organism. The high reactivity of such species induce their short lifetimes (ns-min) and leads to uncertainties when it comes to the study of some enzymatic reactions in bulk. This PhD project aims to develop a biomimetic microreactor for the study of enzymatic ac-tivities producing ROS/RNS. Indeed, by confining a reaction within a cell-sized compartment (20-100 μm diameter), the generated species (H2O2, NO•, NO2-) could be analyzed in situ with a quantita-tive and kinetic resolution. Giant unilamellar vesicles are formed in physiological conditions and are used as microreactors for the monitoring of enzymatic activities of glucose oxidase and NO-synthases. Fluorescence microscopy allows individual vesicle observation and the monitoring of reactions trig-gered by microinjection. Then, released species are detected in real-time by electrochemistry in order to decipher the diverse enzymatic pathways of NO-Synthases
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Tolliver, Benjamin M., Devaiah P. Shivakumar, and Cecelia A. McIntosh. "Effects of Amino Acid Insertion on the Substrate and Regiospecificity of a Citrus paradisi Glucosyltransferase." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/345.
Повний текст джерелаАнотація:
Glucosyltransferases, or GTs, are enzymes which perform glucosylation reactions. These glucosylation reactions involve attaching a UDP-activated glucose molecule to acceptor molecules specific to the enzyme. The products of these reactions are observed to have a myriad of effects on metabolic processes, including stabilization of structures, solubility modification, and regulation of compound bioavailability. The enzyme which our lab focuses its research on is a flavonol-specific 3-O-GT found in Citrus paradisi, or grapefruit. This enzyme is part of the class of enzymes known as flavonoid GTs, which are responsible for, among other things, the formation of compounds which can affect the taste of citrus. Our lab focuses its research on performing site-directed mutagenesis on Citrus paradisi 3-O-GT in an attempt to modify its substrate specificity and regiospecificity. In this poster, we report our findings thus far concerning the addition of specific residues to the 3-O-GT's amino acid sequence based on an alignment with the sequence of a putative flavonoid GT found in Citrus sinensis.
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Tolliver, Benjamin M., Devaiah P. Shivakumar, and Cecelia A. McIntosh. "Effects of Amino Acid Sequence Insertion on the Substrate Preference of a Citrus Paradisi Glucosyltransferase." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etsu-works/347.
Повний текст джерелаАнотація:
Glucosyltransferases (GTs) are enzymes which perform glucosylation reactions, which involve attaching a UDP-activated glucose molecule to acceptor molecules specifi c to the enzyme. The enzyme which our lab focuses its research on is a fl avonol-specifi c 3-OGT found in Citrus paradisi, or grapefruit (Cp3GT). This enzyme is part of the class of enzymes known as fl avonoid GTs, which are responsible for, among other things, the formation of compounds which can affect the taste of citrus. Our lab focuses its research on performing site-directed mutagenesis on Cp3GT in an attempt to discover the residues important for substrate and regiospecifi city. In this study, we are testing the basis of substrate septicity of Cp3GT. We hypothesize that incorporation of fi ve amino acids specifi c to Citrus sinensis GT (CsGT) into Cp3GT at 308th position may facilitate mCp3GT to use anthocyanidins as one of the substrates. We report our fi ndings thus far concerning the addition of specifi c residues to the Cp3GT’s amino acid sequence based on an alignment with the sequence of a putative fl avonoid GT found in Citrus sinensis.
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Penn-Marshall, Michelle. "The Effects of Resistant Starch Intake in African-American Americans at Increased Risk for Type 2 Diabetes." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28104.
Повний текст джерелаАнотація:
Background: African-Americans are a vulnerable population group with disproportionately elevated rates of type 2 Diabetes Mellitus (DM). Resistant starch is a promising food ingredient that has the potential to reduce the risk factors involved in the development of type 2 DM. To date, there is a dearth of published research studies on the effect of resistant starch on African-Americans who are at increased risk for type 2 DM.
Objective: The major objective of this study was to determine if daily consumption of approximately twelve grams of high-maize™ 260 resistant starch (RS) added to bread improved glucose homeostasis by monitoring changes in fasting plasma glucose, fructosamine, hemoglobin A1c, insulin, glucagon-like peptide-1, C-reactive protein, homeostasis model assessment insulin resistant (HOMA- IR) and beta-cell function (HOMA-Beta), serum acetate, propionate, and butyrate levels.
Design: A fourteen-week, randomized, double-blind, within-subject crossover design feeding study was carried out in African-American males (n=8) and females (n=7) at increased risk for type 2 DM who resided in Southwest Virginia. All participants consumed bread containing added RS or control bread (no added RS) for six-weeks. RS and control bread feedings were separated by a two-week washout period.
Results: Fasting Plasma Glucose (FPG) levels were significantly lower (P = 0.0179) after six-week control bread feedings compared to baseline. FPG levels were also significantly lower (P < 0.0001) after two-week washout period than at baseline. FPG levels were significantly higher (P < 0.0001) after six-week resistant starch bread feeding than at washout. FPG levels due to consumption of resistant starch versus control bread approached significance (P = 0.0574). Fructosamine levels were significantly lower
(P = 0.0054) after control bread and resistant starch bread (P < 0.0012) consumption compared to baseline. No significant differences were found in fructosamine levels due to resistant bread intake versus control (P = 0.9692). Mean baseline HbA1c levels were 6.9% (n=15). This value was slightly lowered to 6.79% (n=14) at the end of the fourteen-week study, although statistical significance was not found. Mean ± standard errors for HbA1c values were 6.9% ± 0.18% and 6.9% ± 0.14% at baseline for the sequence groups, resistant starch first (n=7) and control treatment first (n=8) groups, respectively. Mean ± standard error HbA1c values were 6.7% ± 0.27% and 6.9% ± 0.27% at the conclusion of fourteen-week study for sequence groups, resistant starch first group (n=7) and control treatment first group, respectively. Baseline mean and standard errors
C-reactive Protein (CRP) levels for male and female combined results were 0.62 ± 0.16 mg/dL (n=15). Mean CRP levels were 0.53 ± 0.12 mg/dL for resistant starch bread and 0.64 ± 0.21 mg/dL for control bread feeding periods. No significant differences were found for treatment, gender, or sequence effects for C-reactive protein levels during the fourteen-week study (P > 0.05).
Mean HOMA-IR levels following six-week resistant starch and control bread consumption decreased to normal values (> 2.5), although no significant differences were found for treatment (P = 0.5923).
Conclusions: Eighty-seven grams of Hi- maize™ 260 Resistant Starch added to baked loaves of bread consumed by a free-living African-American population at increased risk for type 2 diabetes did not consistently show significance in all clinical indicators and biochemical markers assessed. On the basis of the evidence in this study we do not have evidence that this amount of resistant starch in this population's diet will prevent the onset of diabetes. However, results are suggestive that higher levels of resistant starch in a more controlled experiment could reduce clinical risk factors for type 2 diabetes.Ph. D.
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Miqueleto, Ana Paula. "Comportamento de reator anaeróbio operado em batelada seqüencial, contendo biomassa imobilizada e submetido a aumento progressivo da concentração de substrato de fácil degradação." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-02072009-085827/.
Повний текст джерелаАнотація:
Os objetivos deste trabalho foram avaliar o desempenho do reator anaeróbio operado em batelada seqüencial quando submetido ao aumento progressivo da concentração de glicose e estimar os parâmetros cinéticos da degradação da glicose. Inicialmente o reator foi operado com ciclos de 8 horas, tratando glicose nas concentrações, aproximadas, de 500, 1000 e 2000 mg/L. Não foi detectada glicose no efluente nas três condições. O reator operou de maneira estável, tratando aproximadamente 500 mg/L de glicose, com eficiência na remoção da DQO filtrada entre 93% e 97%. Na operação com concentrações de glicose no afluente próximas de 1000 mg/L e 2000 mg/L, observou-se instabilidade operacional, principalmente devido à produção de polímeros extracelulares (EPS) que comprometeram a hidrodinâmica e a transferência de massa no sistema. Os valores médios da concentrações de ácidos voláteis no efluente foram de 159 ± 72 mg/L e 374 ± 92 mg/L, respectivamente. Aos perfis de concentração de glicose foi ajustado modelo de primeira ordem, enquanto que um modelo modificado, contemplando concentração residual de matéria orgânica, foi ajustado aos perfis temporais de DQO. Para verificar a formação do EPS, operou-se o reator com 3 horas de ciclo nas concentrações, aproximadas, de 500 e 1000 mg/L. Esta fase teve como objetivo verificar a hipótese, segundo a qual, a produção de EPS seria resultado da exposição da biomassa a baixas concentrações de matéria orgânica por longo período. Dessa forma, reduzindo o tempo de ciclo, a exposição a baixas concentrações também seria reduzida. No entanto, embora o reator tenha operado com relativa estabilidade, verificou-se formação de grande quantidade de EPS logo na primeira condição operacional, com aproximadamente, 500 mg/L de glicose no afluente, indicando que a hipótese não estava correta.The main objectives of this study were to evaluate the performance of the anaerobic sequencing batch reactor when subjected to a progressive increasing of the influent glucose concentration and estimate the kinetic parameters of glucoses degradation. Initially the reactor was operated with 8-hour cycles, treating glucose at concentrations of 500, 1000 and 2000 mg/L. Glucose was not detected in the effluent in all these three conditions. The reactor showed operating stability treating glucose concentration of approximately 500mg/L, with efficiencies between 93% to 97% in the filtrated COD removal. In the operation with glucose concentrations of 1000 mg/L and 2000 mg/L, approximately, it could be noticed an operational instability, caused mainly by a production of extracellular polymers (EPS) leading to hydrodynamic and mass transfer problems in the reactor. The mean values of volatile acids concentration in the effluent were about 159 ± 72mg/L and 374 ± 92mg/L, respectively. A first order model was adjusted to glucose concentration profiles, and a modified model, including a residual concentration of substrate, was adjusted to COD temporal profiles. To verify the EPS formation, the reactor was operated with 3-hour cycle in the concentrations of 500 and 1000 mg/L This stage had the objective of verifying if the EPS production would result from the exposure of the biomass to low concentration of substrate for a long period of time. Thus, reducing the time cycle, the exposure to low concentrations would also be reduced. Nevertheless, even with the reactor operating with relative stability, the hypotheses could not be verified due the formation of a large amounts of EPS right in the first operational condition with approximately to 500 mg/L of glucose in the influent, showing that the hypothesis was not right.
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Neves, Luiz Carlos Martins das. "Emprego de reator com membrana na obtenção de frutose e ácido glicônico a partir da sacarose." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/9/9134/tde-11082017-170439/.
Повний текст джерелаАнотація:
Frutose e Ácido Glicônico são produtos importados empregados em diferentes setores nas áreas química, farmacêutica e alimentícia, representando um mercado de dois milhões de dólares (US$ 2,0 milhões) por ano. Por sua vez, a sacarose pode ser empregada como matéria-prima para a obtenção destes produtos através de conversão enzimátiva empregando invertase e glicose-oxidase. O uso de biorreatores com membrana (MBR) mostra-se interessante em processos enzimáticos, pois, ao serem empregados em processos contínuos permitem, simultaneamente, produção e separação dos produtos, reduzindo a formação de subprodutos e, eventual, inibição da enzima por excesso de substrato ou produtos. A sacarose é convertida em xarope de açúcar invertido (solução equimolar de frutose e glicose) pela invertase (Bioinvert®, enzima comercial), seguido pela oxidação da glicose em ácido glicônico pela ação da glicose oxidase (GO). O processo de conversão multi-enzimático da sacarose foi obtido através da alimentação de sacarose (50 mM) em reator com membrana (MBR) contendo invertase (24 U/mL), glicose-oxidase (0,5 U/mL) e catalase (470 U/mL) e operando com vazão específica de 6,0 h-1, 35ºC e pH 5,5. As condições operacionais otimizadas possibilitaram a conversão completa da sacarose (X = 100 %) e da glicose resultante (Y = 100%) com velocidades específicas de reação de 4,2 mmol/U.h, 0,60 mmol/U.h e 0,00062 mmol/U.h, respectivamente, para a invertase, glicose oxidase e catalase. A respeito da oxidação da glicose, a adição de catalase no meio reacional se fez necessária para minimizar os efeitos inibitórios sobre a GO através do peróxido de hidrogênio formado.The fructose and gluconic acid are products of great application in chemical, pharmaceutical and food industry. The actual Brazilian market for these compounds is about US$ 2 millions, here as the sucrose, the raw-material used for their production, represents about 2.4% of the Brazil\'s GNP. This conversion increases the value added to the sugarcane, usually marketed as a commodity, because the fructose and gluconic acid are more valuable products than sucrose. The use of membrane bioreactor (MBR), which operates under mild conditions regarding internal pressure, temperature and pH, has been growing along the years for enzyme catalyzed processes. Moreover, in the MBR the reaction and separation of the products occur simultaneously, avoiding the formation of by-products and the eventual inhibition of the enzyme caused by excess of substrate or products. The sucrose is converted to the inverted syrup (an equimolar solution of fructose and glucose) by invertase (in this work was employed Bioinvert®, a commercial invertase) followed by the oxidation of glucose in gluconic acid by the glucose oxidase (GO). The multi-enzymatic conversion of sucrose was attained when carried out under initial substrate of 50mM and invertase, glucose oxidase and catalase concentrations, respectively, of 24.0 U/mL, 0.5 U/mL and 470 U/mL in a membrane reactor utilizing a dilution rate of 6.0 h-1, 35ºC and pH 5.5. The optimized operational conditions led to a conversion yield of 100% for sucrose hydrolysis and glucose oxidation steps resulting in enzyme productivity of 4.2 mmol/U.h, 0.60 mmol/U.h and 0.00062 mmol/U.h, respectively, to invertase, glucose oxidase and catalase. In regard to the glucose oxidation, the addition of catalase in the reaction medium was necessary, in order to minimize the inhibition of the GO by the hydrogen peroxide formed.