Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 25 for “"dehydroxylation"”.
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ENZYMOLOGY AND MOLECULAR BIOLOGY OF BILE ACID 7alpha- AND 7beta- DEHYDROXYLATION BY THE INTESTINAL BACTERIA CLOSTRIDIUM SCINDENS AND CLOSTRIDIUM HYLEMONAE
… bile acids. The products of microbial 7alpha-dehydroxylation, secondary bile acids, are suggested by numerous lines of evidence to be involved in promoting colon carcinogenesis. 7alpha-dehydroxylating activity is a multi-step pathway, genes of which have only been identified in a small number …
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The 21-dehydroxylation of corticosteroids: evidence for an enol intermediate and the hydroxylation of steroids by fungal cyto-chrome P450: evidence for a stepwise mechanism
Two enzyme mechanisms were examined: the 21-dehydroxylation of corticosteroids by the anaerobe Eubacterium l en tum, and the hydroxylation of steroids by fungal cytochrome P450. Deuterium labelling techniques were used to study the enzymic dehydroxylation. Corticosteroids doubly labelled (2H) at …
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Untersuchungen zur Dehydroxilierung dioktaedrischer Smectite
… in smectites. The main focus of this work is the dehydroxylation process of dioctahedral semctites. In a first chapter the seven utilised bentonites, as well as the extracted smectites were investigated by conventional methods. Accordingly they were characterised as different types of dioctahedral …
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Studies of clay minerals and their decomposition products
… phase, the latter resulting from .the dehydroxylation of the clay minerals during ashing at 700 to 750 C. By using a combination of several physicochemical methods, different successive stages of dehydroxylation, structural consolidation, and recrystallisation of illite, montmorillonite …
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A iron-57 Moessbauer study on the thermal oxidation of iron in biotite mica.
… is in the range of measured barrier energies for dehydroxylation of layer silicates. This suggests that the bottleneck step may be local dehydroxylation: $\rm (OH\sp-\ \to O\sp{2-}\ + H\sp+).$ The persistent Fe$\sp{2+}$ can be understood from local crystal-chemical considerations. (Abstract …
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Studies of Sulfur Reduction of Taurine and Taurine-Conjugated Bile Acids by Bile acid 7α-Dehydroxylating Bacteria
… up to 20 unique bile acid metabolites. The 7α-dehydroxylation of the bile acids is the most physiologically important bile acid biotransformation. All known intestinal bacteria capable of bile acid 7α-dehydroxylation are anaerobic, gram-positive rods of the genera Clostridium and Eubcicterium. …
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Study of the baiE Gene in Bile Acid 7α-Dehydroxylating Bacteria
… encode the enzymes responsible for bile acid 7a-dehydroxylation. The baiE gene encodes a bile acid dehydratase activity in Eubacterium sp.V.P.I. 12708. Using the polymerase chain reaction assay we determined the presence or absence of baiE-like genes in five clostridial bile-acid …
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Study of the baiG Gene in Bile Acid 7α-Dehydroxylating Bacteria
… encode the enzymes responsible for bile acid 7α-dehydroxylation. The baiG gene encodes a bile acid transporter in Eubacterium sp. strain V.P.I. 12708. Utilizing the polymerase chain reaction I determined the presence or absence of baiG-like genes in six bile acid 7α-dehydroxylating strains: …
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Microbial metabolites and graft-versus-host disease in patients undergoing allogeneic hematopoietic cell transplant
… lower median diversity of bacterial bile acid 7α-dehydroxylation (bai) genes (p=0.0007 and FC < 0.05) in patients with GvHD, indicating that acute gut GvHD patients are deficient in microbial bai genes that make secondary bile acids. This work also covers the microbial metabolites short-chain …
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Adding Upstream Sequence and a Downstream Reporter to the Bile Acid Inducible Promoter of <I>CLOSTRIDIUM scindens</I> VPI 12708
… most significant of these modifications are 7α-dehydroxylations which form secondary bile acids (deoxycholate and lithocholate). Much research has illuminated the 7α-dehydroxylation pathway: of particular interest is the bile acid inducible operon, for which <i>Clostridium scindens </i>VPI 12708 …
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Novel Organic Transformations Arising from Gold(I) Chemistry
… our developed methods resulted in an efficient dehydroxylation protocol.
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The Effects of Iron Oxidation State on Surface Chemistry and Structure of Iron-Bearing Smectites: Cation Fixation and Selectivity, Structural Iron Environment, and Dissolution
… reduction of structural Fe(III) invokes partial dehydroxylation, protonation, and site translocation of Fe(II) to alter the crystal structure. The structural changes, therefore, influence their surface properties such as layer charge, cation-exchange capacity (CEC), and cation fixation and …
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Development of a Gene Transfer System in Clostridium Scindens VPI 12708
… patient. Many genes required for bile acid 7-a dehydroxylation are found on a large bile acid inducible operon (bai) that has been extensively studied. However the bai promoter, which directs expression of the bai operon, has yet to be characterized due, in part, to a lack of a functional …
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Selective Reduction of Laterite Ore
… talc, iron silicate and monoxide. At 600 °C, dehydroxylation of chlorite occurred. Chlorite was converted into olivine (forsterite) and enstatite at 600-800 °C. Olivine crystallised at temperatures above 810 °C. Ni-bearing phases after heat treatment at 800-850 °C were forsterite, enstatite, …
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Protective role of lignan-converting bacteria on chemically-induced breast cancer in gnotobiotic rats
… (SECO) followed by demethylation and dehydroxylation of SECO to enterodiol (ED). Finally, ED is dehydrogenated to enterolactone (EL). It is unclear whether the bacterial activation of SDG to ED and EL is crucial for the cancer preventing effects of dietary lignans. The possible …
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Characterising Adsorption and Mass Transfer in Porous Media
… measurements of the activation energy of dehydroxylation, thus establishing NMR relaxometry as a tool for directly probing the surface energetics of silica surfaces. This interpretation of T1/T2 ratios differs from that in conventional applications of the technique which typically present …
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The effect of oxygenates on the oligomerisation of propene over zeolite ZSM-5
… ketonic species. During acetic acid reaction dehydroxylation of the zeolite has been proposed as the cause of decreasing activity with time but this work has shown that the catalyst is regenerable and the acidity of the catalyst, as determined by ammonia TPD, remains unchanged after reaction …
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Desilicated ZSM-5 zeolite as catalyst for the dehydration of ethanol
… phase and are believed to be produced by dehydroxylation of BAS II which were generated by the "desilication-healing" phenomena. LAS II are distinguishable from LAS I since the latter are easily rehydrated back to the corresponding BAS I. The nature and strength of these different acidic …
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Gut microbiota-mediated bile acid metabolism: implications for oral drug absorption
… the effect of bile acid deconjugation and dehydroxylation on bile salt micelle solubilization capacity (Chapter II and III), supersaturated formulation stability (Chapter IV), drug-processing gene expression (Chapter V and VI), as well as passive and active transport mechanisms (Chapter III …
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Production and characterisation of hydroxyapatite/multi-walled carbon nanotube composites
… to sinter HA, yet water is necessary to prevent dehydroxylation and decomposition of the HA. Using 5 wt.% fCNT composite, fourteen sintering atmospheres were investigated to determine their effect on phase purity, hydroxylation, sintered density, and remaining CNT content after sintering. An …
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