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1
Boulter, Jonathan Michael. « Structural and functional studies of the erythrocyte anion exchanger, band 3 ». Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297079.
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Parker, Mark D. « Expression and anion transport studies on the human erythrocyte anion exchange protein (AE1, band 3) in the yeast Saccharomyces cerevisiae ». Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310589.
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Dayama, Parth Omprakash. « A Comparative Study of Electrodes and Membranes for Anion Exchange Membrane Water Electrolysis Systems ». Thesis, KTH, Tillämpad elektrokemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300182.
Texte intégralRésumé :
Vätgas kan framställas från förnybara energikällor genom vattenelektrolys med anjonbytande membran (AEMWE). AEMWE har vissa fördelar jämfört med traditionell alkalisk vattenelektrolys och elektrolysmed protonledande membran. Till exempel finns det möjlighet att använda alkalisk elektrolyt (även rent vatten) och billiga platinagruppsmetallfria katalysatorer tillsammans med ett anjonbytesmembran. Den största utmaningen med tekniken är att uppnå utmärkt och stabil prestanda för membran och elektroder. AemionTM anjonbytande membran (AEMs) av olika tjocklek, vattenupptag och kapacitet undersöktes i ett AEMWE system med 5 cm2 elektrodarea. Elektrokemisk prestanda hos dessa kommersiella AEM studerades med hjälp av porösa nickel elektroder. Bland de undersökta membranen visade AF2-HWP8-75-X stabil prestanda med en högfrekvent resistans (HFR) på 90 mΩ•cm2 och kunde nå en strömtäthet på 0,8 A/cm2 vid 2,38 V med 1 M KOH vid 60 ˚C. AEMWE med AF2-HWP8-75-X och olika elektrodkombinationer undersöktes under samma driftsförhållanden. En elektrodkombination med Raney-Ni och NiFeO som katod respektive anod visade bäst prestanda under utvärderingen och gav en strömtäthet på 1,06 och 3,08 A/cm2 vid 2,00 respektive 2,32 V. KOH-lösningens temperatur och koncentration sänktes till 45 ˚C respektive 0,1 M för att undersöka effekten av driftsparametrar på flödescellens prestanda. Flödescellen uppvisade god stabilitet under de nya driftsförhållandena, men dess prestanda minskade avsevärt. Den nådde en strömtäthet på 0,8 A/cm2 vid 2,25 V.Hydrogen can be produced from renewable energy sources using a novel anion exchange membrane water electrolysis (AEMWE) system. AEMWE has some benefits over the currently used state-of-the-art alkaline and proton exchange membrane water electrolysis systems. For instance, there is a possibility of using alkaline electrolytes (even pure water) and low-cost platinum-group-metal free catalysts together with an ion exchange membrane. However, the main challenge is that the AEMWE system should show excellent and stable performance, depending on the stability of the membrane and the electrodes. AemionTM anion exchange membranes (AEMs) of different thickness and water uptake capacity were investigated using a 5 cm2 AEMWE system. The electrochemical behaviour of these commercial AEMs was studied using nickel (Ni) felt electrodes. Among the investigated AEMs, the AF2-HWP8-75-X showed stable performance with a high frequency resistance (HFR) of 90 mΩ•cm2 and was able to reach a current density of 0.8 A/cm2 at 2.38 V using 1 M KOH at 60 ˚C. AEMWE systems based on AF2-HWP8-75-X and different electrode combinations were examined under the same operating conditions. An electrode combination with Raney-Ni and NiFeO as cathode and anode, respectively, showed the best performance during the degradation test and provided a current density of 1.06 and 3.08 A/cm2 at 2.00 and 2.32 V, respectively. The operating temperature and concentration of the KOH solution were reduced to 45 ˚C and 0.1 M, respectively, to study the effect of operating parameters on the flow cell performance. The flow cell showed good stability under the new operating conditions, but its performance was reduced significantly. It reached a current density of 0.8 A/cm2 at 2.25 V.
4
Crofts, Alan. « Anion efflux across the plasma membrane of Chara corallina ». Thesis, University of York, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358101.
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Santori, Pietro Giovanni. « Investigation of electrocatalysts for anion-exchange membrane fuel cells ». Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS129.
Texte intégralRésumé :
Cette thèse de doctorat étudie la synthèse, caractérisation structurale et activité pour la réaction de réduction de O2 (ORR) de catalyseurs Fe-N-C et de composites d’oxydes de manganèse supporté sur Fe-N-C, ainsi que leur utilisation en pile à combustible à membrane échangeuse d’anions (AEMFC). Tandis que les piles à membrane échangeuse de protons (PEMFC) requièrent aujourd’hui du platine dans ses catalyseurs pour atteindre des hautes performances, les piles AEMFC peuvent ouvrir la voie vers des piles sans métaux précieux. Si les catalyseurs Fe-N-C sont actuellement étudiés comme alternative au platine à la cathode des PEMFC, ils souffrent d’une faible activité et d’une durabilité limitée dans ce milieu. En revanche, on peut espérer que l’activité et la durabilité des catalyseurs Fe-N-C soient améliorées dans les AEMFC.Ce travail démontre la haute activité, stabilité et durabilité en milieu alcalin de catalyseurs Fe-N-C comprenant des sites FeNx à un atome de fer. Ils ont été préparés à partir de ZIF-8 et de sel de fer, pyrolysé sous Ar (Fe0.5-Ar) puis sous NH3 (Fe0.5-NH3). Leur activité a été mesurée en électrode à disque tournant (RDE) et en AEMFC, tandis que la stabilité a été mesurée en RDE et operando avec un spectromètre de masse (ICP-MS) en aval d’une cellule à flux (SFC), en électrolyte acide et alcalin. Le dispositif ICP-MS/SFC a été utilisé pour mesurer in operando la dissolution du fer. En électrolyte acide oxygéné, la vitesse de dissolution du fer du catalyseur le plus actif (Fe0.5-NH3) est 10 fois plus rapide que celle du catalyseur moins actif, Fe0.5-Ar. Ceci explique la faible stabilité des catalyseurs Fe-N-C pyrolysés sous NH3 en PEMFC. En revanche, en électrolyte alcalin, les vitesses de dissolution du fer sont faibles, même pour Fe0.5-NH3. Ces résultats vont de pair avec l’absence de changement d’activité en RDE après un test de dégradation accélérée. La nature des sites actifs a de plus été étudiée par spectroscopie d’absorption de rayons X en mode operando.Afin de réduire la quantité de peroxyde d’hydrogène sur Fe-N-C pendant l’ORR, plusieurs oxydes de manganèse ont été synthétisés et leur activité pour l’ORR et la réaction de réduction du peroxyde d’hydrogène (HPRR) évaluée. Il a été démontré par ICP-MS/SFC que même l’oxyde de manganèse le plus stable, Mn2O3, peut dissoudre une quantité importante de Mn pendant l’ORR en milieu alcalin. De plus, cette dissolution est due au peroxyde d’hydrogène produit pendant l’ORR. Des composites MnOx/Fe0.5-NH3 ont été étudiés pour les réactions ORR et HPRR. Tous ont montré une meilleure sélectivité pendant l’ORR que Fe0.5-NH3 seul, et l’effet le plus important fut avec Mn2O3.Avant d’étudier ces catalyseurs en AEMFC, une étude a été faite sur la compatibilité entre différents catalyseurs de l’ORR et/ou de l’oxydation de H2 (Pt/C, Fe0.5-NH3, PtRu/C, Pd-CeO2/C) et des ionomères échangeurs d’anion, en RDE dans 0.1 M KOH. Ceci a permis d’identifier certains problèmes entre les ionomères étudiés et les catalyseurs comprenant une faible quantité de métal (Fe0.5-NH3, Pd-CeO2/C).Les catalyseurs Fe0.5-NH3 et Mn2O3/Fe0.5-NH3 ont alors été étudiés en AEMFC avec un ionomère à base d’éthylène-tetrafluoroéthylène. Les deux catalyseurs atteignent une densité de courant de 80 mA cm-2 à 0.9 V, avec un chargement de 1.0-1.5 mg cm-2. Le pic de puissance sous H2/O2 est de 1 W cm-2 à 60°C, avec une AEM à base de polyéthylène basse densité, et de 1.4 W cm-2 à 65°C avec une AEM en polyéthylène haute densité. En comparaison, une densité de courant de 70 mA cm-2 à 0.9 V et un pic de puissance de 1.5 W cm-2 ont été obtenus avec 0.45 mgPt cm-2 à la cathode (40 wt% Pt/C) à 60°C, avec l’AEM en polyéthylène basse densité. Un test de durabilité de 100 h à 0.6 A cm-2 sous air a montré une bonne stabilité de Fe0.5-NH3.En conclusion, ce travail met en exergue l’application prometteuse des catalyseurs Fe-N-C à la cathode de piles AEMFC, afin de s’affranchir des catalyseurs à base de métaux précieuxThis PhD thesis investigates the synthesis, structural characterization and oxygen reduction reaction (ORR) activity of Fe-N-C catalysts and composites of Fe-N-C and manganese oxides, and their application at the cathode of anion exchange membrane fuel cells (AEMFCs). Compared to proton exchange membrane fuel cells (PEMFCs), where platinum is today needed to reach high performance, AEMFCs hold the promise to reach high performance without precious metals in their catalysts. While Fe-N-C catalysts are currently investigated as an alternative to Pt/C for PEMFC cathodes, they suffer from lower activity and lower durability in the acidic medium of PEMFCs. In contrast, both the ORR activity and stability of Fe-N-C catalysts can be expected to be significantly improved in AEMFC.This PhD work demonstrates the high activity, stability and durability in alkaline medium of Fe-N-C catalysts with atomically-dispersed FeNx sites. They were prepared from a mix of ZIF-8 and iron salt, pyrolyzed in argon (Fe0.5-Ar) and then ammonia (Fe0.5-NH3). The activity was measured in a rotating disk electrode (RDE) and in AEMFC, while the stability was measured in RDE and in operando with mass spectroscopy (ICP-MS) coupled with a scanning flow cell, in both acid and alkaline media. The latter setup was used to measure Fe dissolution in operando. It was evidenced that, in oxygenated acid electrolyte, the iron leaching rate of the most active Fe-N-C catalyst (Fe0.5-NH3) is 10 times faster compared to the less active Fe0.5-Ar. This explains the reduced stability of ammonia-treated Fe-N-C catalysts in operating PEMFC. In contrast, in alkaline medium, very little demetallation was observed even for Fe0.5-NH3. This was correlated with almost unchanged activity after load cycling in RDE. The nature of the active sites was investigated with X-ray absorption spectroscopy, including in operando measurements.Then, to minimize the amount of peroxide species during ORR on Fe-N-C, different manganese oxides were synthesized and their activity for ORR and hydrogen peroxide reduction reaction (HPRR) were evaluated, while operando manganese dissolution was investigated with ICP-MS. It was found that even the most stable Mn-oxide, Mn2O3, leached a significant amount of Mn during ORR in alkaline medium. It was further demonstrated that the Mn leaching is associated with hydrogen peroxide produced during ORR. Composites of Fe0.5-NH3 and Mn-oxides were then investigated for ORR and HPRR. Improved selectivity during ORR was observed for all composites relative to Fe0.5-NH3 alone, but the effect was strongest for Mn2O3.Before investigating such catalysts in AEMFC, a study on the compatibility between different ORR and/or hydrogen oxidation reaction catalysts (Pt/C, Fe0.5-NH3, PtRu/C, Pd-CeO2/C) and anion exchange ionomers was performed in RDE in 0.1 M KOH. The study identified issues between the investigated ionomers and catalysts having low metal contents on the carbon support (Fe0.5-NH3, Pd-CeO2/C).The catalyst Fe0.5-NH3 and its composite with Mn2O3 were then investigated in AEMFC with an ethylene-tetrafluoroethylene ionomer. Both cathode catalysts reached a current density of ca 80 mA cm-2 at 0.9 V, with relatively low loading of 1.0-1.5 mg catalyst·cm-2. The peak power density with H2/O2 reached 1 W cm-2 at 60°C with a low density polyethylene AEM and 1.4 W cm-2 with high density polyethylene AEM at 65°C. By comparison, a current density of ca 70 mA cm-2 at 0.9 V and peak power density of 1.5 W cm-2 was reached with 0.45 mgPt cm-2 at the cathode (40 wt% Pt/C) with low density polyethylene AEM at 60°C. A durability test of 100 h at 0.6 A cm-2 in air showed good stability of the Fe0.5-NH3 catalyst.In conclusion, this work highlights the promising application of Fe-N-C catalysts at the cathode of AEMFCs for replacing precious metal catalysts
6
Matsuoka, Koji. « Studies on direct alcohol fuel cells using anion-exchange membrane ». 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144928.
Texte intégralRésumé :
Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第11583号
工博第2529号
新制||工||1344(附属図書館)
23226
UT51-2005-D332
京都大学大学院工学研究科物質ｴﾈﾙｷﾞｰ化学専攻
(主査)教授 小久見 善八, 教授 垣内 隆, 教授 田中 功
学位規則第4条第1項該当
7
BONIZZONI, SIMONE. « Anion Conducting Polymers for Fuel Cell and Electrolyzer ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/382284.
Texte intégralRésumé :
The hydrogen, as energy vector, is considering one promising green, sustainable, low-cost alternative to hydrocarbon fuels. In the circular hydrogen economy, the fuel cell technologies play a crucial role of the energy conversion and, in particular, Anion Exchange Membrane Fuel Cell are retained to be very promising for the high-power delivery, the short waiting time before providing energy, the low working temperature.
My PhD is focus on synthesis and characterization of anionic conducting polymer for fuel cell and electrolyzer applications.
The first part of activities is focused on the study of new chemical modifications of polyfluorinated (Aquivion®), aliphatic polyketones, polystyrene polymer matrix to address the main drawbacks of the chemical and electrochemical stability and also the high cost. The synthesis methods involve the organic chemistry procedure for examples Pall-Knorr reaction, Baeyer-Villiger oxidation, methylation process.
The physical-chemical characterization part is aimed to the better understand the properties of the functionalized polymer matrix. The polymer structure is investigated by spectroscopes technique for example FTIR and solid-state NMR while, the thermal properties and their stability are determined by TGA and DSC measurements. For the promising work of Aquivion® modification, I also performed accelerated ageing treatment for testing the chemical and electrochemical stability and I used them in for water Electrolyzer application.
The functionalized polymers show interesting and promising properties for fuel cell and electrolyzer applications and, in particular, modified Aquivion® membranes show excellent stability in alkaline environmental and archive 130 mA cm-2 at 80°C. The results of Aquivion® modification are published on two international journals and the polyketones functionalization work is undergoing publication.The hydrogen, as energy vector, is considering one promising green, sustainable, low-cost alternative to hydrocarbon fuels. In the circular hydrogen economy, the fuel cell technologies play a crucial role of the energy conversion and, in particular, Anion Exchange Membrane Fuel Cell are retained to be very promising for the high-power delivery, the short waiting time before providing energy, the low working temperature. My PhD is focus on synthesis and characterization of anionic conducting polymer for fuel cell and electrolyzer applications. The first part of activities is focused on the study of new chemical modifications of polyfluorinated (Aquivion®), aliphatic polyketones, polystyrene polymer matrix to address the main drawbacks of the chemical and electrochemical stability and also the high cost. The synthesis methods involve the organic chemistry procedure for examples Pall-Knorr reaction, Baeyer-Villiger oxidation, methylation process. The physical-chemical characterization part is aimed to the better understand the properties of the functionalized polymer matrix. The polymer structure is investigated by spectroscopes technique for example FTIR and solid-state NMR while, the thermal properties and their stability are determined by TGA and DSC measurements. For the promising work of Aquivion® modification, I also performed accelerated ageing treatment for testing the chemical and electrochemical stability and I used them in for water Electrolyzer application. The functionalized polymers show interesting and promising properties for fuel cell and electrolyzer applications and, in particular, modified Aquivion® membranes show excellent stability in alkaline environmental and archive 130 mA cm-2 at 80°C. The results of Aquivion® modification are published on two international journals and the polyketones functionalization work is undergoing publication.
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Akanda, Nesar. « Voltage-dependent anion channels (VDAC) in the plasma membrane induces apoptosis / ». Linköping : Univ, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8240.
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Akanda, Nesar. « Voltage-dependent anion channels (VDAC) in the plasma membrane induce apoptosis ». Doctoral thesis, Linköpings universitet, Cellbiologi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8240.
Texte intégralRésumé :
Apoptosis, or programmed cell death, is essential for proper development and functioning of the body systems. During development, apoptosis plays a central role to sculpt the embryo, and in adults, to maintain tissue homeostasis by eliminating redundant, damaged or effete cells. Therefore, a tight regulation of this process is essential. Cell shrinkage associated efflux of K+ and Cl– through plasma membrane ion channels is an early event of apoptosis. However, little is known about these fluxes. The aim of this thesis was to investigate ion channels in the plasma membrane of neurons undergoing apoptosis. We studied differentiated (the mouse hippocampal cell line HT22, the human neuroblastoma cell line SK-N-MC, and rat primary hippocampal neurons) and undifferentiated (rat primary cortical neural stem cells cNSCs) cells with the patch-clamp technique. All cell types displayed a low electrical activity under control conditions. However, during apoptosis in differentiated neurons, we found an activation of a voltage-dependent anion channel. The conductance of the channel is 400 pS, the voltage dependence of the opening is bell shaped with respect to membrane voltage with a maximum open probability at 0 mV, and the Cl− to cation selectivity is >5:1. These biophysical properties remind about the voltage-dependent anion channel normally found in the outer mitochondrial membrane (VDACmt). Hence, we call our apoptosis-inducing plasma membrane channel VDACpl. The molecular identity of the channel was corroborated with the specific labelling of different anti-VDAC antibodies. Block of this channel either with antibodies or with sucrose prevented apoptosis, suggesting a critical role for VDACpl in the apoptotic process. VDACpl is a NADH (-ferricyanide) reductase in control cells. We found that the enzymatic activity is altered while the VDACpl channel is activated during apoptosis. Surprisingly, in cNSCs we did not find any activation of VDACpl, no VDACpl-specific labelling, no enzymatic activity, and no prevention of apoptosis with VDACpl-blocking strategies. Instead, we found an activation of a voltage-independent 37 pS ion channel, and that the Cl– channel blocker DIDS prevented apoptosis in cNSCs. Our finding that activation of VDACpl is critical for apoptosis in differentiated neurons hopefully can lead to new strategies in the treatment of several diseases related to apoptosis.
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Betaneli, Viktoria. « Voltage dependent anion channel : Interaction with lipid membranes ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-85742.
Texte intégralRésumé :
Evidence has accumulated that the voltage dependent anion channel (VDAC), located on the outer membrane of mitochondria, plays a central role in apoptosis. The involvement of VDAC oligomerization in apoptosis has been suggested in various studies. However, it still remains unknown how exactly VDAC supra-molecular assembly can be regulated in the membrane. Previous studies suggested the possible influence of various proteins on the formation of VDAC oligomers, but the important issue of the VDAC oligomeric state regulation by lipids has not been studied so far. Nevertheless, the effect of lipids on the oligomerization of several membrane proteins has been mentioned in the literature and in general, protein-lipid interactions are under extensive investigation.
In the present work, I addressed the influence of lipids on VDAC oligomerization experimentally by reconstituting the fluorescently labelled VDAC in giant unilamellar vesicles (GUVs)—a chemically well defined, cell-free minimal model system. Fluorescence cross-correlation spectroscopy was performed to determine the oligomeric state of VDAC. I investigated the effect of important for apoptosis anionic lipids, phosphatidylglycerol and cardiolipin, on VDAC oligomerization. I demonstrated that phosphatidylglycerol significantly enhances VDAC oligomerization in the membrane, whereas cardiolipin disrupts VDAC oligomers. These results suggest that up- or down- regulation of these lipids in mitochondria during apoptosis can tune VDAC oligomerization in the membrane.
Thus, this study sheds light on the role played by the above-mentioned lipids in the regulation of VDAC oligomerization during apoptosis and provides additional information on the molecular mechanisms of the programmed cell death.
Another objective of this work was to investigate the partitioning of VDAC into liquid disordered or liquid ordered lipid phases. The existence of lipid domains or the lipid rafts in mitochondria and VDAC enrichment in these rafts is still under debate. Additionally, mitochondrial VDAC was recently found in the plasma membrane. The role of this VDAC is not known, however, it was shown to be located in caveolae (specialized lipid rafts) and play an important role in neuronal apotosis and Alzheimer’s disease. Therefore, VDAC partitioning to the lipid rafts is an interesting question for investigation.
The possibility to reconstitute VDAC into minimal model systems–GUVs with phase separation, allowed to reveal the preferential partitioning of VDAC into liquid disordered lipid domain, which suggests either non-raft localization of VDAC or the requirement of the other factors for the recruitment of VDAC into lipid rafts.
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Park, Doh-Yeon. « Anion-conductive multiblock aromatic copolymer membranes : structure-property relationships ». Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52172.
Texte intégralRésumé :
Anion exchange membrane fuel cells (AEMFCs) are an alternative to proton exchange membrane fuel cells (PEMFCs) with potential benefits that include low cost (i.e., platinum-free), facile electro-kinetics, low fuel crossover, and use of CO-resistant metal catalysts. Despite these advantages, AEMFCs have not been widely used because they require more highly conductive anion exchange membranes (AEMs) that do not exhibit impaired physical properties. Therefore, the issues that this research is dealing with are to maximize conductivity and to improve chemical stability. As model materials for these studies, I synthesize a series of multiblock copolymers with which polymer structures and morphologies can be easily controlled. Chapter 2 presents the synthesis and the chemical structure determination of the multiblock copolymers.
With the objective of maximizing conductivity, an understanding of the impact of structural features such as organization, size, polarity and connectivity of ionic domains and channels within AEMs on ion/water transporting properties is necessary for the targeted and predictable design of an enhanced material. Chapters 3 to 5 describe three characterization techniques that reveal the role of these structural features in the transport process. Specifically, Chapter 3 demonstrates the possibility that the NMR relaxation times of water could be an indicator of the efficiency of ion channels. Low-temperature DSC measurements differentiate the state of water (i.e., bound water and free water) inside the membranes by measuring freezing temperature drop and enthalpy. Chapter 4 demonstrates that the number of water molecules in each state correlates with conductivity and suggests a major anion-conducting mechanism for the multiblock AEM systems. In Chapter 5, the measurement of the activation energy of diffusion characterizes ion transporting behavior that occurs on the sub-nanometer scale.
For the characterization of the chemical stability of the AEMs under high pH conditions, I employ automated 1H NMR measurements as a function of time as well as diffusion-ordered NMR spectroscopy (DOSY) as shown in Chapter 6. Finally, I demonstrate that new multiblock copolymers are successfully utilized as an ionomer for a hybrid cell in Chapter 7. The properties of the polymer strongly influence overall cell performance. I believe that the combination of the techniques presented in this thesis will provide insight into the ion/water transporting mechanism in a polymer ion conductor and guidance for improving conductivity and the chemical stability of the AEMs.
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Halle-Smith, Simon C. « A study of the inner membrane anion channel of rat liver mitochondria ». Thesis, University of East Anglia, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277348.
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Young, Mark. « Studies of the transmembrane domain of the human erythrocyte anion exchanger (band 3) ». Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340324.
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Pathak, Sudhir Kumar. « Treatment of Landfill leachates using anion exchange resins ». Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51812.
Texte intégralRésumé :
Landfill leachates are often discharged to wastewater treatment plants (WWTPs) but their highly varied composition makes their treatment in WWTPs difficult. Landfill leachates contain bio-refractory organic matter which easily passes the biological treatment processes at WWTPs and increases the organic matter in the effluent. Leachates also interfere with the UV disinfection process at treatment plants. Another concern is the presence of large amounts of bio-refractory organic nitrogen in the leachates which makes it difficult for WWTPs to meet the tightening total nitrogen requirements.
Studies were conducted to evaluate the applicability of anion exchange resins to remove organic matter, UV quenching substance and organic nitrogen from landfill leachates. Leachate samples based on varying age and treatment methods were utilized. The anion exchange resins were found to work effectively for all studied leachates. The resins were found to remove more bio-refractory UV absorbing substances as compared to total organic carbon (TOC), suggesting that anion exchange resins could be employed for removal of UV absorbing substances. Multiple regenerations of the resin showed slight loss in the capacity to remove UV and organic carbon. Fractionation of leachate samples showed effective removal of humic acid (HA) fraction which is responsible for most of UV quenching. The resin was also found to effectively remove the bio-refractory hydrophilic (Hpi) fraction which tends to persist even after HA fraction has bio-degraded. Membrane filtration (1000 Da and 3000 Da Molecular weight cut off) in conjunction with ion exchange resins achieved better removal of organic matter and UV254 absorbing substances. In addition, this also significantly improved the performance of resins. Significant removal of organic nitrogen was also observed using anion exchange though it was less than both UV and TOC. Around 80% removal of organic nitrogen associated with bio-refractory Hpi fraction was achieved using anion exchange suggesting ion exchange as a viable alternative for removing organic nitrogen.Master of Science
15
Suzuki, Shohei. « Studies on Direct Ammonia Fuel Cells Employing Anion Exchange Membranes ». 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215557.
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Wang, Lin. « Complementation and membrane assembly studies of human erythrocyte anion exchanger (AE1, band 3) ». Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388102.
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Holappa, K. (Katja). « Golgi-associated anion exchanger, AE2:identification, cell type specific targeting and structural role in the Golgi complex ». Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514273761.
Texte intégralRésumé :
Abstract
Anion exchanger 2 (AE2) is a member of the anion exchanger gene family, which includes three additional members, AE1, AE3, and AE4. They are also known as Na+-independent Cl-/HCO3- exchangers, and their major function is to regulate intracellular pH and chloride concentration. All four isoforms have several N-terminally truncated variants that are often expressed cell type specifically. Red blood cells express the full-length AE1 isoform that interacts with ankyrin, an adapter protein linking plasma membrane to the spectrin-based membrane skeleton. This membrane skeleton association is essential for maintaining the membrane integrity of red blood cells. AE3 variants are mainly found in the brain and heart, whereas AE4 is localized in the kidney.
Anion exchanger 2 is expressed in every cell line and tissue studied thus far, and it has been mainly localized to the plasma membrane. However, we found two types of localization/targeting of the AE2 protein in several of the cell lines studied. The protein was localized to either the plasma membrane or the Golgi complex, depending on the cell type. The AE2 variant expressed in these cells was identified as the full-length AE2 protein.
The determinants of differential intracellular targeting were assessed. We hypothesized that Golgi-AE2 is anchored to the Golgi membranes via its association with the Golgi membrane skeleton. We were able to show that the Golgi localization of AE2 correlated with the cell type specific expression of Ank195, a Golgi membrane skeletal protein. In cells where AE2 was targeted to the plasma membrane, Ank195 was not expressed. In addition, the detergent insolubility and co-redistribution properties of AE2 and Ank195 strongly suggested that these proteins interact with each other.
The Golgi membrane skeleton has been shown to be necessary for maintaining the Golgi structure. Our studies were consistent with these findings, showing that in cells in which AE2 expression was reduced by using AE2-specific antisense oligonucleotides, the Golgi complex was dispersed. The spectrin-based membrane skeleton was probably partially detached from the Golgi membranes leading to breakdown of the Golgi structure and disorganization of the microtubules associated with it.
The present findings suggest that the targeting of AE2 is cell type specific, and that Golgi-localized AE2 serves as a membrane association site for the spectrin-based Golgi membrane skeleton, thereby participating in the maintenance of the Golgi structure.
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Pereira, Clotilde Coppini. « Desenvolvimento de membranas aniônicas obtidas por enxertia via irradiação para aplicação em células a combustível alcalinas ». Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-12062017-093623/.
Texte intégralRésumé :
As membranas de troca aniônica são uma alternativa promissora para o desenvolvimento de eletrólitos mais eficientes para células a combustível alcalinas. Em geral, as membranas de troca aniônica são ionômeros capazes de conduzir íons hidroxila devido aos grupos quaternário de amônio e têm como característica elevado pH equivalente. Com o objetivo de desenvolver membranas aniônicas química e termicamente estáveis, com satisfatória condutividade iônica para aplicação em células a combustível alcalinas, as membranas aniônicas foram sintetizadas a partir de polímeros base de polietileno de baixa densidade (LDPE), polietileno de ultra alto peso molecular (PEUHMW), poli(etileno-co-tetrafluoroetileno) (PETFE) e poli(tetrafluoroetilleno-co-hexafluoroetileno) (PFEP) previamente irradiados nas fontes de radiação gama de 60Co ou com feixe de elétrons, para enxertia do monômero de estireno e funcionalizados com trimetilamina para incorporação dos grupos quaternário de amônio. As membranas resultantes foram caracterizadas por espectroscopia de ressonância paramagnética eletrônica (EPR), espectroscopia Raman, termogravimetria (TG), espectroscopia de impedância eletroquímica (EIS), além da determinação do grau de enxertia, capacidade de absorção de água por gravimetria e capacidade de troca iônica, por titulação. As membranas sintetizadas com os polímeros LDPE e UHMWPE pré-irradiados a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram resultados de condutividade iônica, quando na forma (OH-), de 29 mS.cm-1 e 14 mS.cm-1 a 65 °C, respectivamente. Os filmes de PFEP irradiados no processo simultâneo mostram níveis de enxertia insuficientes para a síntese de membranas aniônicas, necessitando maiores estudos para aperfeiçoar os processos de irradiação e enxertia. As membranas baseadas em PETFE, pré-irradiadas a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram maior condutividade iônica, quando na forma hidroxila (OH-), com valores de condutividade iônica entre 90 mS.cm-1 e 165 mS.cm-1 na faixa de temperatura entre 30 e 60 °C. Estes resultados mostraram que membranas de LDPE, UHMWPE e PETFE são eletrólitos promissores para a aplicação em células a combustível alcalinas.Anion Exchange Membranes (AEMs) are a promising alternative to the development of more efficient electrolytes for alkaline fuel cells. In general, the AEMs are ionomeric membranes able to conduct hydroxide ions (OH-) due to the quatermary ammonium groups, which confer high pH equivalent to the AEM. In order to develop alkaline membranes with high chemical and thermal stability, besides satisfactory ionic conductivity for alkaline fuel cells, membranes based on low density polyethylene (LDPE), ultrahigh weight molecular weight polyethylene (UHWHPE), poly(ethylene-co-tetrafluoroethylene) (PETFE) and poly(hexafluoropropylene-co-tetrafluoroethylene) (PFEP) previously irradiated by using 60Co gamma and electron beam sources, have been synthesized by styrene-grafting, and functionalized with trimethylamine to introduced quaternary ammonium groups. The resulting membranes were characterized by electron paramagnetic resonance (EPR), Raman spectroscopy, thermogravimetry (TG) and electrochemical impedance spectroscopy (EIS). The determination of the grafting degree and water uptake were conducted by gravimetry and ion exchange capacity, by titration. The membranes synthesized with PELD and PEUHMW polymers pre-irradiated at 70 kGy and stored at low temperature (-70 °C), up to 10 months, showed ionic conductivity results, in hydroxide form (OH-), of 29 mS.cm-1 and 14 mS.cm-1 at 65 °C, respectively. The PFEP polymers irradiated by the simultaneous process showed insufficient grating levels for the membrane synthesis, requiring more studies to improve the irradiation and grafting process. The styrene-grafted PETFE membranes, pre-irradiated at 70 kGy and stored at low temperature (-70 °C), up to 10 months, showed ionic conductivity results, in hydroxide form (OH-), of 90 mS.cm-1 to 165 mS.cm-1, in the temperature range 30 to 60 °C. Such results have demonstrated that LDPE, UHMWPE and PETFE based AEMs are promising electrolytes for alkaline fuel cell application.
19
Yu, Katayama. « Towards the realization of anion-exchange membrane fuel cell technology : potential of hydrogen-carrier utilization ». Kyoto University, 2017. http://hdl.handle.net/2433/227631.
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Ujwal, Rachma. « Structural and fuctional characterization of the outer mitochondrial membrane protein voltage-dependent anion channel 1/ ». Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1930281371&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Wyatt, Katrina. « Erythrocyte anion transporter : its interaction with cytoskeletal proteins and the effect of applying a membrane potential ». Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279408.
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22
Kim, Dohyun. « Micromachined chronocoulometric nitrate sensor and parallel-plate Donnan-dialytic sample-preparation system using anion-exchange membrane ». Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1785254321&sid=2&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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23
Espiritu, Richard. « Polyethylene-based anion exchange membrane for alkaline fuel cell and electrolyser application : synthesis, characterisation and degradation studies ». Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3702.
Texte intégralRésumé :
Alkaline anion exchange membranes (AAEM) have been fabricated using polyethylene as the base polymer offering a low cost AAEM for electrolyser and fuel cell applications. This study focused on the synthesis and characterisation of AAEM with controlled degree of grafting (DOG) and ion-exchange capacity (IEC) with the following parameters investigated: low density polyethylene (LDPE) film thickness 30-130 μm, gamma radiation dose and monomer concentration. The corresponding IEC, water uptake (WU) and degree of swelling (DS) are reported. The performance of 74.6% DOG membrane in a hydrogen fuel cell showed a high open circuit voltage of 1.06 V, with a peak power density of 608 mW cm-2 at 50 °C under oxygen. The use of a membrane with a high DOG does not impact fuel cross-over significantly and provides improved fuel cell performance due to its high conductivity, water transport and resilience to dehydration. The AAEMs showed long term stability, at 80 °C, exhibiting a conductivity of ca. 0.11 S cm-1 over a period of 3300 h under nitrogen. The membrane showed a degradation rate of 5.7 and 24.3 mS kh-1 under nitrogen and oxygen, respectively. With the membrane lifetime defined as the duration of fuel cell operation until the conductivity of the membrane has reduced to a cut-off value of 0.02 S cm-1, the estimated lifetime of the membrane is 2 years under nitrogen and 5 months under oxygen operating at 80 °C. The fabricated anion exchange membranes were subjected to degradation tests in deionised water for electrolyser/fuel cell operation. After the degradation test, the decrease in ion exchange capacity (IEC) of the AEM, hence decrease in ionic conductivity, was influenced by the applied gamma radiation dose rate. The use of a high radiation dose rate produced membranes with improved stability in terms of % IEC loss due to shorter, more uniformly distributed vinylbenzyl chloride (VBC) grafts. For LDPE-based AEMs, increasing the applied radiation dose rate during grafting from 30 to 2000 Gy h-1 significantly reduced AEM % IEC loss from 38 to 11%, respectively. Analyses of both the aged functionalised membranes and their resulting degradation products confirmed the loss of not only the functional group, but also the VBC group, which has not been reported previously in the literature. Investigation of other amine functional groups revealed similar degradation via the removal of both VBC and head group. Oxidation reactions iii taking place at pH close to neutral are the main contributor to the IEC loss, in contrast to the widely reported E2 or SN2 attack on the head group in high alkalinity solutions. A parallel degradation mechanism is proposed to explain head group loss of AEMs, that involves peroxide radicals which are more dominant in low alkalinity solutions. The investigation of the degradation of a commercially available AEM (A201, Tokuyama Corp.) was performed and compared with the fabricated LDPE AEMs. Using similar membrane thickness, results revealed that the fabricated AEM exhibited superior stability to the commercial A201 membrane in terms of % IEC loss and ionic conductivity, both in fuel cell and electrolyser modes. It is believed that the faster degradation rate of the A201 membrane could possibly be due to the attack of OH- ions on both the head group and on the polymer backbone, the latter of which was not observed on the fabricated AEMs.
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Pasquini, Luca. « Ion - conducting polymeric membranes for electrochemical energy devices ». Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4750.
Texte intégralRésumé :
La recherche vise à proposer des membranes pour des dispositifs électrochimiques capables d'atteindre le bon compromis en terme de conduction ionique, de stabilité et de longue durée de vie pour une haute efficacité.Nous avons réalisé des membranes échangeuses des protons, d'anions ou amphotères à base de polymères aromatiques stables fonctionnalisés. Des groupes sulfonique on été introduit sur la squelette du PEEK, des groupes d'ammonium sur le PEEK et le PSU ou le deux au même temps pour échanger ensemble des protons et des anions.L'optimisation continue des paramètres de synthèse, le choix des différents polymères et/ou des groupes de fonctionnalisation et l'amélioration des procédures et des traitements des membranes coulée, a conduit à de bons résultats en termes de conductivité ionique, sélectivité et stabilité.L'étude des principaux paramètres des membranes démontre une stabilité thermique entre 140 et 200 ° C selon la membrane sélectionnée, un comportement mécanique caractérisé par une résistance à la traction et un module d'élasticité élevée et un relativement faible ductilité, influencé par le niveau d’ hydratation de la membrane ou l éventuelle présence de cross-link. En optimisant le degré de fonctionnalisation et les types de groupes de fonctionnalisation, nous avons obtenu une accordable absorption d'eau, une conductivité ionique élevé pour différent ions (jusqu'à ≃ 3 mS / cm pour le polymère conducteurs des anions) et une perméabilité aux ions vanadium très faible (applications dans RFB) jusqu'à ≃ 10-10 cm2/min, ce qui est bien au-dessous des données typiques de la littérature et un paramètre très important pour applications technologiquesThe research aims to propose membranes for electrochemical devices alternative to the commercial ones able to reach the right compromise in term of good ionic conduction, stability and long life time for an high efficiency. We realized proton exchange, anion exchange and amphoteric membranes based on stable functionalized aromatic polymers (PEEK, PSU). We thus introduced sulfonic groups on a PEEK backbone to exchange protons or ammonium groups on PEEK and PSU to exchange anions. We also realized amphoteric membranes able to exchange at the same time both kinds of ions. The continuous optimization of synthesis parameters, the choice of different polymers and/or functionalization groups and the improvement of casting procedures and treatments of membranes, led to good results in terms of ionic conductivity, selectivity and stability.The study of the main parameters of the synthesized membranes demonstrates a thermal stability between 140 and 200°C depending on the selected membrane, a mechanical behavior characterized by a high elastic modulus and tensile strength and a relatively low ductility strongly influenced on the degree of hydration of the membrane as well as the eventual presence of cross-linking. Working on the degree of functionalization and the type of functionalizing groups, we obtained a tunable water uptake, an elevated ionic conductivity for different ions (up to ≃ 3 mS/cm for anionic conducting polymers) and a very low ion permeability (vanadium ions for RFB applications) down to ≃ 10-10 cm2/min, which is much below typical literature data for cation- and anion separation membranes and a challenge parameters for technological applications
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Ioup, Sarah E. « Water-Soluble Deep-Cavity Cavitands : Synthesis, Molecular Recognition, and Interactions with Phospholipid Membranes ». ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1572.
Texte intégralRésumé :
Water-soluble deep-cavity cavitands provide a rare opportunity to study self-assembly driven by the hydrophobic effect. These molecular hosts dimerize in the presence of certain guest molecules to form water-soluble molecular capsules. These systems have given rise to numerous novel chemical phenomena and have potential use in drug delivery. The host octaacid (OA) has been particularly well-characterized, but studies are limited to basic pH because of limited host solubility.
Herein we report an improved synthesis of OA and the syntheses of three new water-soluble deep-cavity cavitands. The new hosts are soluble at neutral pH, increasing relevance for biological studies. The new syntheses are versatile enough to apply to the synthesis of additional water- soluble cavitands in the future. We also describe preliminary characterization of the molecular recognition properties of the new hosts. Binding of organic guest molecules to form 1:1 host:guest complexes and 2:1 host:guest capsules was qualitatively similar to that of OA. However, binding of anions spanning the Hofmeister series revealed interesting new behavior. The new hosts bound a wider range of anions inside the hydrophobic pocket with much higher association constants. Moreover, external binding of several anions to the cavitand pendant feet was observed.
Looking towards biological applications, we desired to learn how these molecules interact with phospholipid membranes. Six water-soluble cavitands were tested for their ability to permeabilize liposomal POPC membranes. One host showed very high potency in permeabilizing membranes, while three other hosts showed moderate activity. Host binding of POPC was found to be at least one factor in host-induced permeabilization. A requenching assay to determine leakage mechanism strongly supported all-or-none leakage, whereby some vesicles lose all contents while others lose none. These results suggest that these cavitands induce partial transient leakage of vesicles by the formation of transient membrane pores. These findings show potential for the use of these hosts as drug delivery carriers, antimicrobial compounds, and tools in membrane alteration studies.
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Linares, Moya Douglas De Jesus. « Fundamental and applied studies on the development of an alkaline anion exchange membrane-based direct alcohol fuel cell ». Thesis, University of Newcastle upon Tyne, 2012. http://hdl.handle.net/10443/1367.
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Alameen, Omer Ahmed Omer. « Involvement of the putative anion transporter 1 (SLC26A6) in permeation of short chain fatty acids and their metabolites across the basolateral membrane of ovine ruminal epithelium ». Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213517.
Texte intégralRésumé :
Introduction: Microbial fermentation of carbohydrates in forestomach of ruminants produces large amounts of short-chain fatty acids (SCFA, mainly acetic acid, propionic acid, and n-butyric acid). The majority of these substrates is taken up directly across the ruminal wall. After luminal uptake into the epithelial cells, SCFA mainly occur in the dissociated form due to the intracellular pH of ~7.4. Moreover, a big portion of SCFA is metabolised within the cytosol. Main end products of epithelial SCFA metabolism are ketone bodies (D-3-hydroxybutyric acid and acetoacetic acid) and lactic acid. Both intact SCFA and ketone bodies and lactate need to be efficiently extruded from the ruminal epithelial cells to prevent a lethal drop of intracellular pH and counteract osmotic load of the cytosol. All these substances are less lipophilic in comparison to the undissociated form of SCFA. Thus, dissociated SCFA (SCFA-) and their metabolites need Protein mediated mechanisms for the extrusion across the basolateral side of ruminal epithelium. One mechanism suggested to be involved in the extrusion of SCFA- across basolateral membrane of the ruminal epithelium is the monocarboxylate transporter 1 (MCT1). Functionally, MCT1 was first assumed to operate as proton-coupled transporter for monocarboxylates including SCFA. Nonetheless, a recent study found a bicarbonate dependent anion exchange mechanism which turned out to be sensitive to MCT1 Inhibitors at the basolateral side of the ruminal epithelium pointing to the ability of MCT1 to act as an anion exchanger. However, in these experiments the inhibition of MCT1 abolished bicarbonate dependent transport only by half. This suggests the involvement of further anion exchanger(s) in the transport of SCFA across the basolateral membrane of ruminal epithelium. Promising candidates to underlie this exchange are the putative Anion exchanger 1 (PAT1) and a transport protein designated „down-regulated in adenoma“ (DRA).
Materials and Methods: Sheep rumen epithelium was mounted in Ussing Chambers under short-circuit conditions. Radioactively labelled acetate (ac) was added to the serosal side. Serosal to mucosal flux of ac (Jsm ac) was measured with or without anion Exchange inhibitors (50 mM NO3- or 1 mM DIDS) or the MCT1 inhibitor p-hydroxy mercuribenzoic
acid (pHMB; 1.5 mM) in the serosal buffer solution. The inhibitors were added alone or in combination with each other. Furthermore, mucosal to serosal flux of radioactivelly labelled ac or butyrate (bu) (Jms ac, bu) was measured in the presence or absence of SO42-, Cl- or NO3- (50 mM respectively) as exchange substrate in the serosal buffer solution. Immunohistochemical staining was conducted to locate PAT1 and DRA by use of commercially available antibodies.
Results: NO3- and pHMB significantly reduced Jsm ac by 57 % and 51 %, respectively. When pHMB was applied after pre-incubation with NO3- an additional inhibition of Jsm ac was observed. Vice versa, NO3- further inhibited Jsm ac when epithelia were pre-incubated with pHMB before. DIDS had no inhibitory effect on SCFA flux. Serosal presence of SO42- or Cl- enhanced Jms ac significantly. Regarding bu, Cl- or SO4 2- also enhanced Jms bu significantly. The different anions available in the serosal buffer solution numerically enhanced Jms in the order of SO4 2- > Cl- for both ac and bu, which corresponds to the known affinity sequence of PAT1 and DRA. Immunohistochemistry revealed localization of PAT 1 in the stratum basale, whereas DRA was not detectable using this method.
Conclusions: Basically, this study supports the suggestion that MCT1 works as an Anion exchanger in ruminal epithelium. In addition, it clearly shows that there is at least one further anion exchanger involved in the basolateral extrusion of SCFA and their metabolites. The functional and immunohistochemical findings suggest that PAT1 holds a significant role in this respect.
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Xu, Shaoyi. « SYNTHESIS OF PERFLUOROHETEROAROMATIC POLYMERS FOR ION-CONDUCTING MEMBRANE FUEL CELLS VIA FREE RADICAL-BASED REACTIONS AND SYNTHESIS OF DI-CATIONIC IONIC LIQUIDS AS EFFICIENT SO2 ABSORBENTS ». OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1160.
Texte intégralRésumé :
A novel free radical-based substitution reaction was developed for grafting aromatic/heteroaromatic compounds to perfluorosulfonic acid polymers (PFSAs). Two proton-exchange membranes perfluorobenzoic acid (PFBA) and perfluorobenzenesulfonic acid (PFBSA)—were synthesized for proton-exchange membrane fuel cells via the free radical-based reaction. The physical properties, in-plane ionic conductivities and fuel cell performance of two membranes were investigated. They exhibited different electrochemical and physical properties, possibly due to the formation of unique dimerized/trimerized structure of –CO2H groups in the PFBA membrane. A free radical-based thermolytic reaction under a high temperature (180 oC)/pressure (1000 psi) condition in the presence of TFA and hydrogen peroxide is first demonstrated. A novel perfluorotetrafluoroaniline (PFTFAn) polymer was synthesized from PFSA and 2,3,5,6-tetrafluoroaniline in one step via the thermolytic reaction. After doping H2SO4 in the PFTFAn polymer, a new conjugated acid membrane (H2SO4-doped PFTFAn) was obtained. The H2SO4-doped PFTFAn membrane displayed better chemical stability and mechanical properties than NafionTM due to the removal of –SO3H groups. The second part of this thesis deals with fluoropolymer-based anion-exchange membranes. A new class of coordinated metal/perfluoropolymer type composite membranes were synthesized and characterized for anion-exchange membrane fuel cells (AEMFCs). A membrane comprised of perfluoro(phenyl-2,2’:6’,2”-terpyridine) polymer, ZrO(ClO4)2 nanoclusters, and 2,2’:6’,2”-terpyridine displayed the highest conductivity of 23.1 mS/cm at 60 oC. The chemical stability test of composite membrane showed no conductivity loss after refluxing in 7 M KOH solution at 120 oC for 2,200 h. A H+ coordinated cage-shape molecule with a benzyl group (Bn-proton cage) was designed and synthesized as a base-stable anion-exchange group. By employing the free radical-based reaction, Bn-proton cage was grafted to a fluoropolymer to yield a stable anion-conductive membrane under alkaline conditions. The third part of this thesis is our design, synthesis and test of ionic liquids for reversible SO2 absorption. Novel di-cationic ionic liquids (DILs) were designed and synthesized for SO2 absorption. DILs were found to have better SO2 absorption capabilities than mono-cationic ionic liquids (MILs). A chloride-based DIL comprised of two N-methylimidazolium cations and a PEG9 (HO-(CH2CH2O)9-H) chain could reversibly uptake 3.710 mole SO2 per mole DIL under ambient conditions. The anion, temperature and water impact on SO2 absorption in DILs was investigated. Although replacing chloride with triflate or tosylate groups led to a reduced SO2 absorption for the DILs, a high selectivity against CO2 was observed in CO2 absorption test.
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Ouahid, Soumia. « Transport facilité du glucose à travers une membrane échangeuse d'anions avec l'ion borate comme transporteur ». Rouen, 1994. http://www.theses.fr/1994ROUES029.
Texte intégralRésumé :
Par couplage diffusion-réaction, le transport d'un substrat non ionique à travers une membrane échangeuse d'ions, peut être facilité en choisissant un contre-ion apte à réagir réversiblement avec le substrat. Dans ce travail, nous avons réalisé le transport facilité à travers une membrane échangeuse d'anions. L'ion borate était utilisé comme transporteur et sa teneur dans la membrane était fixée par l'activité de l'acide borique. Nous avons mené simultanément la modélisation et l'expérimentation du transport. Par des études d'équilibre et de conductivité, nous avons déterminé les paramètres physicochimiques, tels que le coefficient de stabilité du complexe glucose-borate et le coefficient de diffusion des différentes espèces présentes. Nous avons, de plus, mis en évidence en présence de glucose, deux aspects originaux: la variation de l'accessibilité des sites membranaires et la variation de leurs interactions avec certains contre-ions. Dans la majorité des cas, nous avons choisi une activité d'acide borique relativement faible afin que les polyborates soient minoritaires devant les autres contre-ions. Dans une première série de mesures, nous avons réalisé le transport facilité du glucose en fonction de son activité, en maintenant constante celle de l'acide borique. Dans une seconde série, le transport a été réalisé en fonction de l'activité du transporteur. A partir des paramètres préalablement déterminés, nous avons élaboré un modèle théorique qui permet de comparer les valeurs théoriques et expérimentales des flux du glucose. Nous parvenons à un bon accord lorsque le transport a été réalisé en imposant pour l'acide borique une activité pour laquelle les paramètres du modèle ont été caractérisés
30
García, Cruz Leticia. « Electroorganic synthesis using a Polymer Electrolyte Membrane Electrochemical Reactor : electrooxidation of primary alcohols in alkaline medium ». Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/61507.
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Souabni, Hager. « Modulation de l’activité du flavocytochrome b₅₅₈ : étude fonctionnelle ». Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112036/document.
Texte intégralRésumé :
Le complexe NADPH oxydase est un élément essentiel de l’immunité inné. Présent dans les cellules phagocytaires (neutrophile), sa fonction est de produire massivement, dans le phagosome, des anions superoxyde et générer ainsi des espèces encore plus réactives de l’oxygène qui vont détruire acides nucléiques, lipides et protéines des bactéries phagocytées. Le cœur membranaire catalytique du complexe NADPH oxydase est constitué d’un hétérodimère membranaire, le cytochrome b₅₅₈ (Cyt b₅₅₈). Après activation de celui-ci par les partenaires protéiques cytosoliques p47phox, p67phox, p40phox et Rac, une succession de réactions de transferts d’électron de part et d’autre de la membrane a lieu au sein du Cyt b₅₅₈ pour aboutir à la réduction du dioxygène de manière très contrôlée. Afin de mieux comprendre cette régulation, nous nous sommes d’abord intéressés aux stéreoisomères trans de l’acide arachidonique, activateur naturel de cet enzyme (cis), sur le fonctionnement de la NADPH oxydase et avons abordé cette étude parallèlement sur du Cytb₅₅₈ d’origine bovine présent dans des membranes de neutrophiles et dans des membranes de levures exprimant le Cytb₅₅₈ de manière hétérologue. Nous avons montré que la géométrie joue un rôle important sur l’activation du complexe enzymatique. Dans un deuxième temps, afin d’étudier le rôle de l’environnement membranaire sur le fonctionnement de la NADPH oxydase, nous avons déterminé les propriétés cinétiques et thermodynamiques de l’activité NADPH oxydase du Cytb₅₅₈ recombinant exprimé en levures, purifié, puis reconstitué en liposomes de composition lipidique variée. Après comparaison avec ces mêmes propriétés obtenues pour le Cytb₅₅₈ dans les membranes plasmiques et du réticulum endoplasmique de levures, nous avons montré que l’activité NADPH oxydase très sensible à la température peut être modulée par la composition et l’état physique de la membraneNADPH oxidase complex is a major actor of both antimicrobial host defense and inflammation by generating highly regulated superoxide anion, rapidly converted into reactive oxygen species (ROS). The NADPH oxidase complex consists of a heterodimeric integral membrane flavocytochrome b₅₅₈ and three cytosolic components p67phox, p47phox and p40phox, and the small GTP binding protein Rac. In response to a cellular stimulus, cytosolic proteins are recruited to the phagosomal membrane where they are assembled with the Cytb₅₅₈ to form the active NADPH oxidase. The aim of the work was to better understand the modulation of superoxide anion production by this enzyme. For this purpose, we performed experiments with both bovine neutrophil membranes and yeast membranes expressing the bovine recombinant Cytb₅₅₈. We first investigated the effect of the trans-isomerization of the cis-arachidonic acid, the activator of NADPH oxidase in vitro and showed that specific geometry of the activator plays an important role in the activation of the complex. We also studied the role of the membrane environment on the functioning of NADPH oxidase and determined the kinetics and thermodynamics of NADPH oxidase activity depending on the lipid composition of Cytb₅₅₈ proteoliposomes. Comparison with these properties obtained with recombinant Cytb₅₅₈ embedded into endoplasmic reticulum and plasma membranes, we showed that the NADPH oxidase activity is highly temperature dependent and can be modulated by the lipid environment and the physic state of the membrane
32
Lindegren, Klara. « Evaluation of the Removal Efficiency of Per- and Polyfluoroalkyl Substances in Drinking Water using Nanofiltration Membranes, Active Carbon and Anion Exchange ». Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-268448.
Texte intégralRésumé :
Per- and polyfluoroalkyl substances (PFASs) is a group of man-made, highly persistent chemicals. Due to the specific surface-active attributes of these molecules, applications are numerous and feed an economically important industry. During the last decade, PFASs have been detected globally in the environment, living organisms and tap water. The combination of toxic properties and high bioaccumulative potential, together with the discovery that conventional water treatment methods do not remove PFAS, renders further research on purification methods highly needed. Three techniques of purifying water from PFASs were examined. Nanofiltration technology (NF) is a membrane filtration technique, which produces a purified product (the permeate) by generating an effluent of high contaminant concentration (the reject water). To decontaminate the reject water, adsorption by granular activated carbon (GAC) or anion exchange (AE) have been proposed. The efficiency of these three technologies was studied at Bäcklösa drinking water treatment plant (DWTP) in Uppsala. A nanofiltration pilot with two 270NF membranes (Dow Filmtech™), connected in series, was used. A high removal efficiency (>90%) was found for all PFASs. Furthermore, it was confirmed that the concentration in the permeate water was a function of the concentration in the incoming raw water; increased PFAS raw water concentration resulted in increased PFAS permeate concentration. Size-exclusion and electrostatic repulsion were deemed important mechanisms. For the comparison of GAC (Filtrasorb 400®) and AE (Purolite® A-600), a column experiment was set up. The perfluoroalkane (-alkyl) sulfonic acids (PFSAs) and perfluorooctanesulfonamide (FOSA) had similar removal efficiencies using both GAC and AE, and the efficiency increased with increasing chain length. AE was found to have a higher average removal efficiency of perfluoroalkyl carboxylic acid (PFCAs) (62-95%) than GAC (49-81%). In conclusion, longer chain length PFASs were removed more effectively than shorter-chained, and the PFSAs and FOSA showed higher removal efficiency compared to the PFCAs. Furthermore, linear isomers were removed more effectively than branched for GAC and AE. In contrast, the opposite was found for the NF membrane, where branched isomers were better retained.Per- och polyfluorerade alkylsubstanser (PFAS) är en grupp syntetiska, ytterst persistenta kemikalier. På grund av deras ytaktiva egenskaper är de lämpliga för användning i många produkter och tillverkningsprocesser, och är således viktiga för en ekonomiskt betydande industri. Under det senaste årtiondet har PFAS påträffats i miljön, levande organismer och kranvatten världen över. Kombinationen av toxiska egenskaper, en hög bioackumuleringspotential och upptäckten att konventionella reningsmetoder inte avlägsnar substanserna från vatten, gör att vidare forskning av reningsmetoder för PFAS är mycket angelägen. Tre reningsteknikers förmåga att rena vatten från PFAS undersöktes. Nanofiltrering (NF) är en membranfiltreringsteknik som utöver den renade produkten, permeatet, även framställer en biprodukt av hög föroreningsgrad, rententatet. För att rena rententatet har adsorption till granulärt aktivt kol (GAC) eller jonbytarmassa (AE) föreslagits. Teknikerna utvärderades på Bäcklösa Vattenverk i Uppsala. Nanofiltreringen undersöktes i en pilotanläggning där två 270NF (Dow Filmtech™) membran var seriekopplade. En hög reningsgrad (>90%) konstaterades för alla typer av PFAS. Vidare visades PFAS-koncentrationen i permeatet vara en funktion av PFAS-koncentrationen i råvattnet; en ökad råvattenkoncentration gav en ökad permeatkoncentration. Storleksseparation och elektrostatisk repulsion befanns vara viktiga mekanismer som påverkade reningsgraden. För att undersöka de mekanismer som påverkar PFAS-adsorption jämfördes GAC (Filtrasorb 400®) och AE (Purolite® A-600) i ett kolonnexperiment. Reningsgraden för GAC och AE av perfluorerade sulfonsyror (PFSA) och perfluorooktan sulfonamider (FOSA) var lika hög och reningseffektiviteten ökade med ökande kolkedjelängd. AE återfanns ha en högre genomsnittlig reningsgrad av perfluorkarboxylsyror (PFCA) (62-95%) än GAC (49-81%). Sammanfattningsvis avlägsnades PFAS av längre kolkedjelängd mer effektivt än kortare kolkedjor, och PFAS med sulfonsyror och sulfonamider som funktionella grupper uppvisade en högre reningsgrad än karboxylsyrorna. Vidare renades linjära isomerer mer effektivt än grenade både genom GAC och AE. Däremot konstaterades det motsatta för NF-membranen, där grenade isomerer renades mer effektivt.
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Oktar, Doganay Ceren. « Separation Of Chromate And Borate Anions By Polymer Enhanced Ultrafiltration From Aqueous Solutions Employing Specifically Tailored Polymers ». Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12609178/index.pdf.
Texte intégralRésumé :
In this study two polychelatogens for borate and a polyelectrolyte for chromate retention (R) were designed for investigating the effect of pH and loading (g metal /g polymer) on the separation performances of the synthesized polymers using continuous polymer enhanced ultrafiltration.
Increase in pH increased the retention of borate for all of the synthesized polymers. Decrease in the loading resulted in an enhancement in boron retention with PNSM and PNSL. When COP was utilized, retentions remained almost constant after a certain loading, probably due to possible adverse effects of high polymer concentrations on polymer conformation in aqueous solutions.
Decrease in loading caused an increase in the retention of chromate until a loading of 0.01. After that a slight decrease was observed. Maximum Cr (VI) retention was obtained as 0.70 for a loading of 0.01 and a pH of 4. Effect of crowding on Cr(VI) retention was also investigated. It was observed that retention does not only depend on the loading but also on the concentrations of both Cr (VI) and PDAM. Effect of the presence of competing anions such as chloride and sulfate on the retention of chromate was investigated to see the effect of competing anion charge to the selectivity of the synthesized polyelectrolyte. Addition of both anions decreased the retention of Cr(VI) . Divalent sulfate decreased the retention more than monovalent chloride indicating that charge of the anion may be the predominant variable in the retention of chromate using PDAM.
Finally, dynamic and static light scattering measurements were performed to investigate the conformational changes in the structure of the synthesized polymers at different pH values as well as in the presence of boron in the solution.
In this study, it is shown that PEUF can be successfully applied to for boron and Cr (VI) retention with the synthesized polymers. Satisfactory retention values were obtained both for boron and Cr (VI). Even if the retention of Cr (VI) decreased with the addition of high amount of competing anions, significant Cr (VI) retentions could be obtained.
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Petri, Niclas. « Involvement of Membrane Transport Proteins in Intestinal Absorption and Hepatic Disposition of Drugs Using Fexofenadine as a Model Drug ». Doctoral thesis, Uppsala University, Department of Pharmacy, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5808.
Texte intégralRésumé :
The aims of this thesis were to study the in vivo relevance of membrane transporters for intestinal absorption and the hepatic disposition of drugs in humans and preclinical models. Fexofenadine is a substrate for ABCB1 (P-glycoprotein) and members of the organic anion transporting polypeptide (OATP/SLCO) family. It is marginally metabolised in humans.
The influence of known inhibitors of ABCB1 and OATPs on the membrane transport and pharmacokinetics of fexofenadine was investigated in Caco-2 and porcine models and in humans. The permeability of fexofenadine remained low, even when significantly altered by the addition of an inhibitor. Using the Loc-I-Gut® technique in vivo in humans, it was possible to see that the jejunal effective permeability of fexofenadine was unchanged when given with verapamil. However, the systemic exposure and apparent absorption rate of fexofenadine increased. This suggests that the first-pass liver extraction of fexofenadine was reduced by verapamil, probably through the inhibition of sinusoidal OATP-mediated and/or canalicular ABCB1-mediated secretion. The unchanged permeability can be explained by simultaneous inhibition of jejunal apical OATP-uptake and ABCB1-efflux, which would leave fexofenadine to be transported by passive trancellular diffusion. A Loc-I-Gut® perfusion in the porcine model enabling blood sampling in the portal and hepatic veins and bile collection revealed increased jejunal permeability, but no subsequent verapamil-induced elevation in the systemic exposure of fexofenadine. This indicates a species-related difference in the localisation of and/or the substrate specificity of fexofenadine for the transporters involved. The absence of an effect on the first-pass liver extraction in the porcine model might be caused by the observed lower liver exposure of verapamil.
Finally, a novel intubation technique enabling dosing of fexofenadine in the jejunum, ileum and the colon showed that fexofenadine was absorbed less along the length the intestine in agreement with the properties of a low permeability drug.
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Bertolotti, Bruno. « Élaboration de membranes échangeuses d’anions à architecture réseaux interpénétrés de polymères pour des batteries lithium-air ». Thesis, Cergy-Pontoise, 2013. http://www.theses.fr/2013CERG0676/document.
Texte intégralRésumé :
Ce travail porte sur la synthèse et la caractérisation de membranes polymères échangeuses d'anions, destinées à la protection de l'électrode à air dans une batterie lithium-air (en vue d'une application pour véhicule électrique). Ces matériaux à architecture de réseaux interpénétrés de polymères (RIP) associent un réseau polyélectrolyte cationique hydrocarboné, la poly(épichlorohydrine) (PECH), à un réseau de polymère neutre qui peut être soit hydrocarboné, soit fluoré. Tout d'abord, la synthèse du réseau polyélectrolyte et son assemblage sur l'électrode à air ont été optimisés. Une première série de RIP associant ce réseau PECH à un réseau de poly(méthacrylate d'hydroxyéthyle) a été synthétisée. Une seconde série de matériaux combinant ce même réseau PECH à un réseau de polymère fluoré a été développée. L'ensemble de ces matériaux a été caractérisé, et pour chaque série de RIP, la méthode de synthèse et la composition ont été optimisées. Les membranes RIP présentent des propriétés améliorées par rapport au réseau simple de PECH. L'électrode à air protégée par ces nouvelles membranes échangeuses d'anions présente une stabilité améliorée dans les conditions de fonctionnement de la batterie lithium-air. Plus précisément, une durée de vie de 1000 h est obtenue lorsque l'électrode à air a été modifiée avec un RIP fluoré, soit une augmentation d'un facteur 20 de la durée de vie de l'électrode non modifiéeThis work focuses on the synthesis and characterization of polymer membranes to be used as anion exchange membranes for protection on an air electrode in a new lithium–air battery for electric vehicle. In these materials showing interpenetrating polymer networks (IPN) architecture, a hydrogenated cationic polyelectrolyte network, the poly(epichlorohydrin) (PECH), is associated with a neutral network, which can be either hydrogenated or fluorinated. First, the synthesis of the polyelectrolyte network and the membrane/electrode assembly were optimized. Second, a first IPN series associating the PECH network with a poly(hydroxyethyl methacrylate) network was synthesized. Third, the same PECH network was associated with a fluorinated polymer network. All the materials were characterized, and optimal synthesis methods as well as an optimal composition were determined for each association. The IPNs show improved properties compared with the single PECH network. The air electrode protected by these new anion exchange membranes shows improved stability in the working conditions of the lithium-air battery. Specifically, a lifetime of 1000 h was obtained when the electrode was modified with a fluorinated IPN, a 20-fold increase in the lifetime of the non-modified electrode
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Alameen, Omer Ahmed Omer [Verfasser], Gotthold [Akademischer Betreuer] Gäbel, Gotthold [Gutachter] Gäbel et Holger [Gutachter] Martens. « Involvement of the putative anion transporter 1 (SLC26A6) in permeation of short chain fatty acids and their metabolites across the basolateral membrane of ovine ruminal epithelium : Involvement of the putative anion transporter 1 (SLC26A6) inpermeation of short chain fatty acids and their metabolites across thebasolateral membrane of ovine ruminal epithelium / Ahmed Omer Alameen Omer ; Gutachter : Gotthold Gäbel, Holger Martens ; Betreuer : Gotthold Gäbel ». Leipzig : Universitätsbibliothek Leipzig, 2016. http://d-nb.info/1240630549/34.
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Gomes, Ligia Ferreira. « Permeabilidade de membranas ao ânion radical superóxido (O2-) : estabelecimento de um método analítico para (O2- e estudo preliminar de permeabilidade em vesículas de anfifílico sintético ». Universidade de São Paulo, 1989. http://www.teses.usp.br/teses/disponiveis/9/9136/tde-27052008-134340/.
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Malewitz, Timothy. « Modeling Equilibrium Salt Partitioning in Neosepta AMX and Selemion AMV Antion Exchange Membranes ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1249342152.
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Dubouis, Michel. « Régénération de la soude à partir de solutions de carbonate de sodium par des procédés électromembranaires ». Grenoble INPG, 1993. http://www.theses.fr/1993INPG0051.
Texte intégralRésumé :
Differents procedes electromembranaires sont concus et etudies pour regenerer de la soude a partir de solutions de carbonate de sodium. En presence d'especes oxydables en faibles quantites, la regeneration s'effectue avec une cellule a une seule membrane permselective echangeuse de cations. Pour eviter l'oxydation de ces especes, par exemple le sulfure (na#2s) de la liqueur verte du procede kraft, le procede electromembranaire le plus adapte par sa simplicite et par sa capacite de fonctionnement sur le long terme, est constitue d'un electrolyseur a deux membranes echangeuses de cations, precede d'un reacteur d'acidification pour le degagement des gaz; dans la boucle reacteur-compartiment central de la cellule d'electrolyse, circule une solution de sulfate de sodium acidifiee. Une autre configuration de l'electrolyseur du procede est envisagee et testee avec une membrane echangeuse d'anions et une membrane echangeuse de cations suivant le procede classique d'electro-electrodialyse du sulfate de sodium. Ce procede est aussi compare a un electrolyseur a deux membranes echangeuses de cations avec introduction directe de la solution de carbonate et de sulfure de sodium dans le compartiment central ou se produit le degagement des gaz. Les membranes echangeuses de cations et plus particulierement les membranes echangeuses d'anions, separant le compartiment anodique du compartiment central de l'electrolyseur, sont etudiees par la methode des radiotraceurs et par spectrometrie raman. Ces procedes produisent de la soude qui peut etre aussi concentree que dans le procede chlore-soude a membrane et de l'hydrogene relativement pur dont l'utilisation par une anode a hydrogene est testee. Finalement, si les problemes d'environnement remettent en cause le procede bien etabli du four a chaux, la rentabilite de ces differents procedes devra etre reconsideree
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Van, Liefferinge François. « Molecular basis of the transport of small inorganic ions and thiamine pyrophosphate by the Voltage-Dependent Anion Channel and by a specific transporter of the mitochondrial inner membrane. Study by structure-guided simulations ». Doctoral thesis, Universite Libre de Bruxelles, 2021. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/331176.
Texte intégralRésumé :
The essential cellular functions of the mitochondrion require the exchange of a wide variety of molecules across its two membranes, which is carried out by different membrane proteins.The Voltage-Dependent Anion Channel (VDAC) located in the mitochondrial outer membrane (MOM) is responsible for the passage of various ions and small molecules to and from the intermembrane space. It is also involved in the regulation of cellular processes through its interactions with lipids or other proteins.At the MOM level, we studied the transport, through VDAC, of small inorganic ions and of thiamine pyrophosphate (TPP), an essential cofactor. Using different simulation methods such as Brownian dynamics (BD), All-Atom (AA) molecular dynamics (MD) and Coarse-Grained (CG) MD, we investigated the effect of two factors on the regulation of VDAC ion selectivity: ionic strength and membrane lipid composition. All simulation types show that VDAC becomes less selective towards anions with increasing salt concentration. The simulations further suggest that the selectivity mechanism occurs due to the filtering of some basic residues that point into the pore lumen. Furthermore, MD simulations show that the lipid composition of the membrane modulates the distribution of ions inside VDAC. In a comparison of POPE versus POPC bilayer, this regulation occurs through the more persistent interactions of some acidic residues located on both edges of the β-barrel with POPE head groups which, in turn, alters the electrostatic potential in the lumen which consequently affects the pore selectivity. CG MD simulations show that this mechanism also occurs in a mixed POPE/POPC bilayer by an enrichment of POPE on VDAC surface.In order to simulate the transport of the TPP, force field parameters have been developed and validated. Simulations of the translocation of TPP through VDAC show analogies with the mechanism used by other previously studied metabolites, in particular with ATP. At the mitochondrial inner membrane level, the mechanism of TPP transport by the specific thiamine pyrophosphate transporter (TPPT) shows significant similarities with the mechanism proposed for other members of the mitochondrial carrier family to which TPPT belongs. They mainly are the energetics arising from the alternating formation and disruption of two salt bridge networks, one on the matrix side and the other on the cytosolic side, and the interactions, of an ionic nature, formed by TPP during its binding in TPPT central cavity. Furthermore, the energy contribution provided by the cytosolic network establishes a weaker barrier than that of the matrix network, which may support the hypothesis of a uniport activity of TPPT.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Catonné, Jean-Claude. « Contribution à l'étude du défaut de sélectivité présenté par les membranes échangeuses d'anions, dans le cadre de leurs applications au traitement électrochimique de régénération des solutions aqueuses d'acides minéraux ». Paris 6, 1986. http://www.theses.fr/1986PA066030.
Texte intégralRésumé :
Essai d'identification de l'origine de la "fuite h+" et de celle des différentes sources susceptibles d'alimenter le mouvement d'eau au sein des membranes échangeuses d'anions, selon que le matériau est fortement ou non "élusterisé", puis d'établissement de l'existence d'une corrélation étroite entre l'intensité de fuite protonique et celle de la perméabilité osmotique des membranes (ainsi que le laisse prévoir la théorie de Gierke dans le cas des membranes échangeuses de cations). Et enfin, évaluation du rôle du champ électrique, ainsi que celui de la composition de l'électrolyte sur les résultats.
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Tomotani, Ester Junko. « Bioconversão de sacarose em ácido glicônico e frutose usando reator com membrana ». Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/9/9134/tde-16082017-123204/.
Texte intégralRésumé :
A conversão enzimática da sacarose pela ação sucessiva da invertase e da glicose oxidase (GOD), permite obter produtos de maior valor agregado, a saber, frutose e o ácido glicônico, dois produtos de amplo uso na indústria farmacêutica, alimentícia e química. Foi estudada a aplicação da invertase imobilizada em resinas aniônicas do tipo Dowex® (um copolímero de poliestireno-divinilbenzeno) sobre a hidrólise da sacarose bem como a oxidação da glicose pela glicose oxidase solúvel ou imobilizada no mesmo suporte em separado (sistema bifásico), utilizando-se um reator de membrana acoplado à membrana de ultrafiltração (100kDa) ou de microfiltração (5µm). Posteriormente, avaliou-se o desempenho de ambas as formas de enzimas, solúveis ou imobilizadas num sistema monofásico empregando o mesmo reator. A bioconversão executada em sistema bifásico permitiu a obtenção de xarope de frutose da ordem de 70% através da separação de glicose e frutose utilizando-se a resina catiônica 50W:8-100. O rendimento de 96,6% e 67,4% para as formas solúveis e imobilizadas respectivamente foram obtidas em sistema monofásico. O não desprendimento das enzimas dos suportes viabilizou o uso da membrana de microfiltração, trazendo vantagens à operação de biorreator com membrana.The enzymatic conversion of sucrose through a successive action of invertase and glucose oxidase (GOO) allows the obtainment of products with higher commercial value, fructose and gluconic acid, which are widely used in pharmaceutical, food and chemical industries. Invertase and GOO immobilized on Dowex® anionic resin (a polystyrene divinylbenzene copolymer) as well as soluble GOD were used in a membrane bioreactor (MS) for sucrose hydrolysis and glucose oxidation. The MB was coupled with a UF-membrane (100kDa) or a MF-membrane (5µm). The bioconversion was conducted in two steps (biphasic system) as well as in one step (monophasic system). The bioconversion operated in a biphasic system permitted obtaining a fructose syrup with a concentration of about 70% through a separation of glucose and fructose using a cationic resin, 50W:8-100. As for the monophasic system, the yield of 96.6% and 67.4% for soluble and immobilized forms were attained respectively. No leakage of the enzymes from the support allowed the use of a microfiltration membrane, adding advantages to the membrane bioreactor operation.
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Gholami, Sara [Verfasser]. « Association of neighboring β-Strands to form the β-barrel structure of the voltage-dependent anion channel, human isoform 1 (hVDAC1) precedes membrane insertion and is largely driven by polar interactions between basic and acidic amino acid side-chains / Sara Gholami ». Kassel : Universitätsbibliothek Kassel, 2020. http://d-nb.info/1232431893/34.
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Sivertsen, Edvard. « Membrane Separation of Anions in Concentrated Electrolytes ». Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2100.
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Taylor, Andrew Mark. « Biophysical studies on the human erythrocyte anion transporter, band 3 ». Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360571.
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Kizewski, Jamie P. « The development of novel radiation grafted alkaline anion-exchange membranes and alkaline ionomers ». Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557113.
Texte intégralRésumé :
Novel alkaline anion-exchange membranes (AAEMs) were successfully synthesised via radiation grafting of electron beamed films of poly( ethylene- co-tetra£luoroethylene), EB-ETFE. The resultant membranes were characterised, compared with previously developed AAEMs and evaluated in H2/O2 fuel cells. Limited statistically rigorous prior research, into the synthesis of previously developed (standard) trimethylamine (TMA) quaternised membranes, prompted an empirical investigation into the effects that the numerous synthesis parameters (variables) had on the final properties of the resultant AAEMs. Importantly, it was shown that EB-ETFE can be cold stored for at least 16 months at -36 ± 2°C and still produce AAEMs exhibiting fuel cell relevant ion-exchange capacities of 1.0 - 1.8 mmol g-l and ionic conductivities (through plane, fully hydrated) of 20 - 40 mS cm-1 at ambient temperature. In addition, quaternary head-groups that are alternative to the previously studied benzyltrimethylammonium were evaluated. This required the development of a new titration method for the determination of the chemical composition of the AAEMs (quaternary ammonium and tertiary amine contents). The alternative synthesis was achieved by replacement of the TMA quaternisation agent with the diamine 1,4-diazabicyclo[2.2.2]octane (DABCO). A 15 week investigation into the ex situ chemical stability of the novel AAEMs was conducted; stable ion-exchange capacities of 1.3 ± 0.3 mmol g-l were observed for both TMA and DABCO quaternised AAEMs when submerged at 60°C in water. The TMA and DABCO quaternised AAEMs (of similar hydrated thickness) exhibited hydrogen fuel cell performances of 120 mW cm-2 with the use of a previously developed alkaline ionomer (designated SION1). The use of a novel DAB CO-based ionomer (SION1.1) yielded improved performances of 200 mW cm-2 and decreased the membrane electrode assembly (MEA) internal ohmic resistances. This demonstrates the necessity of further alkaline ionomer optimisation and development. Through a greater understanding the amine head-group chemistry, the membrane synthesis process, and the ionomer interface, the economic outlay associated with AAEM synthesis may be reduced and the subsequent MEA performance and operational lifetime within a hydrogen fuel cell may be improved.
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Karagiannidis, Louise E. « Neutral receptors for the transport of anions across lipid membranes ». Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/374679/.
Texte intégralRésumé :
This report describes a novel method, using 33S NMR techniques, for the detection of sulfate transport across synthetic lipid membranes comprised of 1-palmitoyl-2 oleoylphosphatidylcholine. With this method it was possible to verify that tris(2 aminoethyl)amine based (thio)ureas and cyclic peptide based cryptands can promote the transmembrane transport of sulfate anions. This is a particularly notable accomplishment due to the highly hydrophilic nature of the sulfate anion, and the associated challenges with partitioning such a species into a hydrophobic lipid membrane. Furthermore, a series of bis(thio)urea compounds, based on the 1,2- bisaminocyclohexane scaffold are reported as ion transporters, capable of facilitating both chloride/nitrate and chloride/bicarbonate antiport transport processes. They have also been investigated for binding properties with a variety of anions, using 1H NMR techniques. The influence of stereochemistry on the anion binding and transport ability of the receptors is discussed in detail, with cis-stereoisomers being superior anion transporters to the transanalogues. Receptors based on the ortho-phenylenediamine bis-urea motif have been demonstrated as highly effective anion transporters and function by an antiport mechanism of anion transport. Modification of existing transporters, by adding fluorination at the central phenyl ring or by increasing fluorination at the peripheral phenyl groups, yielded highly potent anion transporters capable of surpassing the activity of the natural anion transporter prodigiosin, for chloride/bicarbonate exchange.
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Shi, Shengjing. « Influence of root exudates on soil microbial diversity and activity ». Lincoln University, 2009. http://hdl.handle.net/10182/1549.
Texte intégralRésumé :
Interactions between plant roots and soil microorganisms in the rhizosphere are critical for plant growth. However, understanding of precisely how root exudates influence the diversity and activity of rhizosphere microorganisms is limited. The main objective of this study was to investigate the effect of radiata pine (Pinus radiata) root exudates on rhizosphere soil microbial communities, with an emphasis on the role of low molecular weight organic anions. The study involved the development and validation of new methods for investigating rhizosphere processes in a purpose-built facility. This included development of an in situ sampling technique using an anion exchange membrane strip to collect a range of organic anions exuded from radiata pine roots grown in large-scale rhizotrons. These included tartarate, quinate, formate, malate, malonate, shikimate, lactate, acetate, maleate, citrate, succinate and fumarate. Soil microbial activity and diversity were determined using dehydrogenase activity and denaturing gradient gel electrophoresis. Links between organic anions in root exudates and rhizosphere soil microbial community structures were investigated by comparing wild type and genetically modified radiata pine trees which were grown in rhizotrons for 10 months. As expected, there was considerable temporal and spatial variability in the amounts and composition of organic anions collected, and there were no consistent or significant differences determined between the two tree lines. Significant differences in rhizosphere microbial communities were detected between wild type and genetically modified pine trees; however, they were inconsistent throughout the experiment. The shifts in microbial communities could have been related to changes in exudate production and composition. Based on results from the main rhizotron experiment, a microcosm study was carried out to investigate the influence of selected pine root exudate sugars (glucose, sucrose and fructose) and organic anions (quinate, lactate and maleate) on soil microbial activity and diversity. Soil microbial activity increased up to 3-fold in all of the sugar and organic anion treatments compared to the control, except for a mixture of sugars and maleate where it decreased. The corresponding impacts on soil microbial diversity were assessed using denaturing gradient gel electrophoresis and 16S rRNA phylochips. Addition of the exudate compounds had a dramatic impact on the composition and diversity of the soil microbial community. A large number of bacterial taxa (88 to 1043) responded positively to the presence of exudate compounds, although some taxa (12 to 24) responded negatively. Organic anions had a greater impact on microbial communities than sugars, which indicated that they may have important roles in rhizosphere ecology of radiata pine. In addition, a diverse range of potentially beneficial bacterial taxa were detected in soil amended with organic anions, indicating specific regulation of rhizosphere microbial communities by root exudates. This project highlighted the considerable challenges and difficulties involved in detailed investigation of in situ rhizosphere processes. Nonetheless, the findings of this study represent a significant contribution to advancing understanding of relationships between root exudates and soil microbial diversity, which will be further enhanced by refinement and application of the specific methodologies and techniques developed.
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Lam, Chak Sum. « Regulation of CFTR channels by bicarbonate-sensitive soluble adenylyl cyclase in human airway epithelial cells / ». View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202005%20LAM.
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LAKKIS, ZAHREDDINE ZEINAB. « Aspects thermodynamiques et cinetiques de l'extraction de metaux divalents par des acyl-4-pyrazolones-5 ». Strasbourg 1, 1986. http://www.theses.fr/1986STR13001.
Texte intégralRésumé :
Extraction de cd et zn a partir des milieux aqueux, perchlorate, nitrate et sulfate par des melanges de phenyl-1 methyl-3 benzoyl-4 pyrazolone-5 et de sels d'ammonium lipophiles. Le pyrazolonate de nh::(4) est l'agent reel de synergie. Mecanisme de transport de cuivre par des acyl-4 pyrazolones-5 a travers une membrane liquide epaisse