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1
Belford, Paul S. "Detoxification of organotin biocides." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38234.
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Черниш, Єлізавета Юріївна, Елизавета Юрьевна Черныш, and Yelyzaveta Yuriivna Chernysh. "The sewage sludge detoxification." Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/33561.
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Recycling of organic sewage sludge today is an urgent problem in the whole territory of Ukraine, which requires a solution. At the most of the municipal wastewater treatment plants, unfortunately, current removal, treatment and recycling of sewage sludge are not properly resolved. At present, the general part of sewage sludge is not carried out. Because it contains toxic chemicals, mainly heavy metals (HM) within the industrial waste water coming into the city sewer system after insufficient treatment or without treatment. As a result, sewage sludge is sent to the sludge pit and storage sites, which are assigned to the large land area. Therefore the process of HM removing from sewage sludge is of paramount importance to allow using sewage sludge as an organic fertilizer in agriculture.
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3
Ezzi, Mufaddal I. "Cyanide detoxification by soil microorganisms." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/842816/.
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Cyanides enter the environment through both natural and man-made sources. Natural sources include cyanogenesis by bacteria, fungi and plants. A number of cyanide catabolising microorganisms have also been reported in literature. This is the first reported instance of cyanide catabolism in Trichoderma harzianum. Four strains of T. harzianum, one of T. pseudokoningii were evaluated. An investigation was made into the occurrence and distribution of the cyanide catabolising enzymes. Three enzymes, cyanide hydratase, beta-cyanoalanine synthase and rhodanese, were studied. All the strains showed a high capacity to degrade cyanide via both the cyanide hydratase and rhodanese pathways, beta-cyanoalanine synthase activity, however, was not detected in any of the selected strains. In the studies on the kinetic characterization of the rhodanese enzyme, a broad pH optimum of 8.5 - 10.5 was obtained for all the strains and a broad temperature optimum of 35 - 55 °C was also observed. The KmCN and Vmax values ranged from 7-16 mM and from 0.069 - 0.093 betamoles. Min-1. mg protein-1, respectively, between the selected strains of Trichoderma. Strong evidence of cyanide biodegradation and co-metabolism emerged from studies with flask cultures where glucose was provided as a co-substrate. The rate of degradation of 2000 ppm CIST was enhanced almost three times in the presence of glucose. Plant microcosm studies carried out using pea and wheat seeds too gave further corroboration of the cyanide degrading and plant growth promotion capabilities of Trichoderma. Microcosms set-up with cyanide at 50 or 100 ppm CN, in the presence of Trichoderma, showed germination of both pea and wheat seeds. There was no seed germination in any of the controls in the absence of Trichoderma inoculation.
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MacLean, Morag. "Methylglyoxal detoxification in Escherichia coli." Thesis, University of Aberdeen, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287604.
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Methylglyoxal is a naturally occurring toxic electrophile which, in E. coli, can be detoxified by several routes. This study has focused on the glutathione-dependent glyoxalase system. The genes encoding glyoxalase I (gloA) and glyoxalase II (gloB) were identified in the E. coli genome and cloned into the multi-copy plasmid pHG165. A null mutant in glyoxalase I (ΔgloA::KanR) was also created. Cells overexpressing glyoxalase I exhibit elevated rates of detoxification and enhanced tolerance of methylglyoxal. Analysis of the ΔgloA mutant has revealed that growth and viability are quite normal, unless the cell is challenged with methylglyoxal either added exogenously or synthesized by the cells. The mutant strain has a low rate of detoxification of methylglyoxal; only 20 -30 % of the level of the detoxification compared to the parent strain. Thus, the glutathione-dependent glyoxalase system was shown to be the dominant pathway for the methylglyoxal detoxification in E. coli. Glyoxalase I mutant cells rapidly lose viability when exposed to methylglyoxal as cell viability parallels the rate of detoxification. Glyoxalase I is the rate determining step in this pathway as overexpression of glyoxalase II does not affect the overall rate of metabolism of methylglyoxal. Methylglyoxal-elicited potassium efflux via the E. coli potassium channel KefB is enhanced in strains overexpressing glyoxalase I. Activation of KefB is diminished in the absence of functional glyoxalase I or in a strain overexpressing glyoxalase II. S-lactoylglutathione is the product of glyoxalase I and the substrate for glyoxalase II. This glutathione adduct is the major activator of the KefB and KefC systems. The glyoxalase I substrate, hemithiolacetal, could partially activate KefB and KefC when they were overexpressed on a multi-copy plasmid.
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Pillai, Jitesh Kannan. "Mechanisms of Arsenic Detoxification and Resistance." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1699.
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Arsenic is a ubiquitous environmental toxic substance. As a consequence of continual exposure to arsenic, nearly every organism, from Escherichia coli to humans have evolved arsenic detoxification pathways. One of the pathways is extrusion of arsenic from inside the cells, thereby conferring resistance. The R773 arsRDABC operon in E. coli encodes an ArsAB efflux pump that confers resistance to arsenite. ArsA is the catalytic subunit of the pump, while ArsB forms the oxyanion conducting pathway. ArsD is an arsenite metallochaperone that binds arsenite and transfers it to ArsA. The interaction of ArsA and ArsD allows for resistance to As(III) at environmental concentrations.
The interaction between ArsA ATPase and ArsD metallochaperone was examined. A quadruple mutant in the arsD gene encoding a K2A/K37A/K62A/K104A ArsD is unable to interact with ArsA. An error-prone mutagenesis approach was used to generate random mutations in the arsA gene that restored interaction with the quadruple arsD mutant in yeast two-hybrid assays. Three such mutants encoding Q56R, F120I and D137V ArsA were able to restore interaction with the quadruple ArsD mutant. Structural models generated by in silico docking suggest that an electrostatic interface favors reversible interaction between ArsA and ArsD. Mutations in ArsA that propagate changes in hydrogen bonding and salt bridges to the ArsA-ArsD interface also affect their interactions.
The second objective was to examine the mechanism of arsenite resistance through methylation and subsequent volatilization. Microbial ArsM (As(III) S-adenosylmethyltransferase) catalyzes the formation of trimethylarsine as the volatile end product. The net result is loss of arsenic from cells. The gene for CrArsM from the eukaryotic green alga Chlamydomonas reinhardtii was chemically synthesized and expressed in E. coli. The purified protein catalyzed the methylation of arsenite into methyl-, dimethyl- and trimethyl products. Synthetic purified CrArsM was crystallized in an unliganded form. Biochemical and biophysical studies conducted on CrArsM sheds new light on the pathways of biomethylation. While in microbes ArsM detoxifies arsenic, the human homolog, hAS3MT, converts inorganic arsenic into more toxic and carcinogenic forms. An understanding of the enzymatic mechanism of ArsM will be critical in deciphering its parallel roles in arsenic detoxification and carcinogenesis.
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Hamel, Robert D. "Aluminum detoxification mechanisms in Pseudomonas fluorescens." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0025/MQ31433.pdf.
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Hou, Shurong. "HUMAN BUTYRYLCHOLINESTERASE MUTANTS FOR COCAINE DETOXIFICATION." UKnowledge, 2014. http://uknowledge.uky.edu/pharmacy_etds/38.
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Cocaine is one of the most reinforcing drugs of abuse and has caused serious medical and social problems. There is no FDA-approved medication specific for cocaine. It is of a high priority to develop an effective therapeutic treatment for cocaine abuse. Human butyrylcholinesterase (BChE) has been recognized as a promising candidate of enzyme therapy to metabolize cocaine into biologically inactive metabolites and prevent it from reaching central nervous system (CNS). However, the catalytic activity of wide-type human BChE against cocaine is not sufficiently high for treatment of cocaine abuse. Dr. Zhan’s lab has successfully designed and discovered a series of high-activity mutants of human BChE specific for cocaine metabolism.
This dissertation is mainly focused to address the possible concerns in further development of promising human BChE mutants for cocaine detoxification, including whether the administration of this exogenous enzyme will affect the cholinergic system, whether it can efficiently hydrolyze cocaine’s toxic metabolites, and whether the commonly used therapeutic agents will significantly affect the catalytic activity of the BChE mutants against cocaine when they are co-administered. According to the results obtained, all of the examined BChE mutants have a considerably improved catalytic efficiency against (-)-cocaine, without significantly improving the catalytic efficiency against any of the other examined substrates, including neurotransmitter acetylcholine. Two representative mutants (including E12-7) also have a considerably improved catalytic activity against cocaethylene (formed from combined use of cocaine and alcohol) compared to wild-type BChE, and E12-7 can rapidly metabolize cocaethylene, in addition to cocaine, in rats. Further evaluation of possible drug-drug interactions between E12-7 and some other commonly used therapeutic agents revealed that all of the examined agents, except some tricyclic antidepressants, do not significantly inhibit E12-7. In addition, an effort to discover new mutants with further improved activity against cocaine led to the discovery of a new BChE mutant, denoted as E20-7, according to both the in vitro and in vivo assays. The encouraging outcomes of the present investigation suggest that it is possible to develop a more effective enzyme therapy for cocaine abuse treatment using one of the most promising BChE mutants, such as E12-7 or E20-7.
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Brown, Stanley. "Heavy metal detoxification of sewage sludge." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302700.
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Zhang, Shiying. "Biological Detoxification of Mercury Contaminated Soil." DigitalCommons@USU, 1991. https://digitalcommons.usu.edu/etd/5384.
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This study examined biological mercury removal from soil using mercury-resistant bacteria in soil microcosms. Mercuric chloride was used to artificially contaminate Kidman soil to mercury concentrations of 5 ppm and 10 ppm. Soil moisture content was maintained at three levels, 20%, 30% and 50%. Mercury resistant-bacteria were added to soil samples and the mercury removal rate was compared to control samples without added bacteria. Mercury removal rate was initially enhanced by the addition of bacteria. After 30 days, no difference was observed between samples and controls with initial mercury concentration of 5 ppm when soil moisture content was 20%. At an initial mercury concentration of 10 ppm, soil samples had less mercury remaining than controls after 30 days. Autoclaved soil had a decreased mercury removal rate compared to soil not autoclaved. Addition of nutrient (sucrose) did not increase the mercury removal rate. A slurry-type bioreactor was found to be more efficient than a non-stir type. After 30 days of continuous stirring, 85-90% of the added mercury (10 ppm) was removed, while under the same conditions except no stirring, only around 60% of the mercury was removed.
Overall, biological detoxification of mercury from contaminated soil can be achieved by using a slurry-type bioreactor with additon of mercury-resistant bacteria.
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Lawson, Kathryn René. "Catabolism as a mechanism of polyamine detoxification." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288919.
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Maintenance of optimal polyamine pool levels is critical for cell survival. Intracellular polyamine depletion is usually cytostatic, whereas unregulated polyamine accumulation can result in cytotoxicity. The purpose of this work was to examine the importance of polyamine depletion in cell survival, either through increased polyamine catabolism or decreased polyamine synthesis. The polyamine analogue CHENSpm, which induces apoptosis in several cell lines, was used to examine the role of polyamine catabolism in cell survival. The susceptibility of Chinese hamster ovary cells and HCT 116 human colon cells to CHENSpm-mediated toxicity was inversely correlated with the level of polyamine oxidase (PAO) activity present in each cell type. Chinese hamster ovary cells (CHO), which contained high levels of PAO, were not growth inhibited by CBENSpm, however concomitant PAO inhibition led to a moderate growth suppression. The inhibition of the diamine exporter (DAX) in addition to PAO led to a CHENSpm-mediated cytotoxic response that was manifested as apoptosis induction. HPLC analysis of CHENSpm- treated CHO cell extracts revealed the presence of an unidentified amine that was not present when PAO was inhibited. This suggests that PAO is able to utilize CHENSpm as a substrate, and that this metabolism protects cells from CHENSpm-mediated cytotoxicity. The effect of polyamine depletion in apoptosis induced by the non-steroidal anti-inflammatory drug (NSAID) sulindac was examined in cells harboring an activated Ki-ras. Cells overexpressing Ki-ras underwent an accelerated apoptosis induction with either metabolite of sulindac, however overall toxicity was unaffected in long-term survival assays. DFMO did not affect apoptosis induction by sulindac sulfone, nor did it increase sulindac sulfone toxicity in long-term survival studies. DFMO alone was selectively cytotoxic to Ki-ras transfected clones in a dose-dependent manner. Ki-ras transfection increased c-myc expression, but had no effect on ODC steady-state mRNA levels. The downregulation of N1-spermidine/spermine acetyltransferase (SSAT) seen in Ki-ras transfected cells suggests polyamine, catabolism may protect cells from DFMO-induced cytotoxicity. These studies demonstrate that polyamine, catabolism may play an important role in cell survival under conditions of suboptimal polyamine levels.
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Carter, Ben. "Constructs for the detoxification of organophosphorous compounds." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/80feadcd-506d-4f38-ad98-50050e58a23b.
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Organophosphorous compounds (OPs) form the basis of many biocides and nerve agents, affecting millions of people each year. Current treatments for acute OP poisoning use atropine to prevent neurotransmitter overaccumulation, and oximes for rescuing phosphorylated acetylcholinesterase (AChE) prior to an irreversible ageing event, but medical care may be required for weeks. Hydrolysis of the OP phosphoester bond prevents the inhibitive phosphorylation of AchE, thus enzymes are an obvious candidate for novel treatments. Enzyme-based therapies for OP poisoning have been shown to delay mortality, but leaching of lipophilic OPs from fat deposits leads to prolonged toxicity, superseding the detoxifying effects of the enzyme due to systemic clearance. Furthermore, these same enzymes may be used for the bioremediation of waterways affected by OP pesticide runoff from crops. Here, an artificial membrane-binding protein from the OP-degrading enzyme OpdA is produced that spontaneously partitions into membranes to enhance enzyme-based therapies for OP poisoning. OpdA was expressed in Escherichia coli with high yields, and cationised with high efficiency to homogenise the surface charge for subsequent anionic surfactant engraftment, giving a supercationic enzyme, cOpdA, which maintained structure and activity, but rapidly penetrated cells, resulting in cytotoxicity. Electrostatic engraftment of an anionic polymer surfactant to the surface of the cOpdA mitigated the cytotoxicity, and the constructs were shown to remain active at the cell surface for 5 days. Crucially, the surfactant conjugation has no deleterious effects on the enzyme, and surprisingly causes a significant increase in its turnover rate and substrate affinity. Small angle X-ray scattering and molecular dynamics simulations show that the surfactant forms a highly-dynamic compact corona surrounding the enzyme. Finally, the high-yield expression system for OpdA by Escherichia coli is used in conjunction with a new bioprinting methodology to produce a 3D bacterial microreactor for OP degradation. The novel cell-laden bioink is printable at high resolutions, is not cytotoxic, and maintains its structure over several weeks. Crucially, the printed structures maintain OP-degrading activity.
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Jäger, Timo. "Novel routes of hydroperoxide detoxification in Mycobacterium tuberculosis." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969199252.
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Choudhury, Hassanul Ghani. "Structural and functional studies of bacterial detoxification mechanisms." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39387.
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Bacterial multidrug resistance is a prominent issue with an ever-increasing amount of drugs becoming ineffective in treating bacterial infections. The elucidation of the 3D structure of bacterial resistance proteins has become extremely important in the development of new antimicrobials. Bacteria can sense external stimuli and regulate the expression of genes that can confer antibiotic resistance. Response regulators are capable of binding DNA both in their phosphorylated and unphosphorylated states, upregulating gene expression. The crystal structure of the unphosphorylated dimeric Escherichia coli BaeR in an intermediate state has been determined. One subunit of the dimer is in an 'active-like' conformation and the other in an inactive conformation. The dimer is formed by a domain swap, which is supported by our small angle X-ray scattering data. This structure provides a possible mechanism on how an unphosphorylated response regulator is capable of binding DNA. Bacteria can detoxify toxic chalcogens, selenium and tellurium, by methylation. The structure of the Escherichia coli TehB has been determined. From our functional analysis, TehB is capable of methylating different chalcogen oxyanions, making it a powerful detoxifying protein. Based on the structure, mutagenesis and kinetic data, we proposed a reaction mechanism for chalcogen detoxification. This data provides the first molecular understanding of the detoxification process of chalcogens by bacteria. In order to survive, certain bacteria under nutrient starved conditions produce antimicrobial peptides (e.g. bacteriocins and microcins) that target closely related species. They have dedicated ABC transporters to export the toxins out of the cells producing them. The crystal structure of the microcin J25 ABC exporter McjD has been determined. Our biochemical data show McjD has a high specificity towards its substrate. In addition, McjD adopts a new 'nucleotide-bound outward-occluded' conformation. Comparison with other ABC exporters has allowed us to propose an intermediate step in ABC exporter mechanism.
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Eshelli, Manal Suleiman. "Bio-detoxification of secondary metabolites of filamentous fungi." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=15342.
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McCracken, Nigel William. "Role of esterases in the detoxification of pesticides." Thesis, University of Newcastle Upon Tyne, 1991. http://hdl.handle.net/10443/550.
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Occupational exposure of pesticides occurs via inhalation through the lungs or by absorption through the skin. The assessment of the possible importance of these extrahepatic tissues in the hydrolysis of pesticides is important. Although the liver has been shown to be the most metabolically active tissue, both the skin and lung have the ability to metabolise pesticides. Therefore, the possibility exists that pesticides which are absorbed through the lung and skin may undergo first pass metabolism in these tissues. In the study, the esterase enzymes responsible for the hydrolysis and subsequent detoxification of a number of pesticide substrates were identified and quantified. Esterases which hydrolysed the pesticides fluazifop-butyl and carbaryl and phenylacetate, a marker substrate for esterase activity, were found to be distributed in the microsomal fraction of the liver and lung and in the blood. In vitro studies in the rat show that lung, skin and plasma have an important role to play in the first pass metabolism of the pesticides fluazifop-butyl and carbaryl. In paraoxon hydrolysis, the plasma plays an important role in first pass metabolism, whereas the lung and skin have little effect. With the use of inhibitors and inducers these esterase enzymes were characterised as `A' or `B' esterases. Fluazifop-butyl and carbaryl were hydrolysed by carboxylesterase, a `B' esterase, whereas paraoxon was hydrolysed by paraoxonase, an `A' esterase. Phenylacetate was found to be hydrolysed by both `A' and `B' esterases. Parallel studies were carried out in human liver and blood to establish whether the rat was an appropriate model for study of the detoxification of pesticides by esterases. Studies have shown that there is considerable similarity in the nature of human and rat esterase enzymes, although there are significant differences in absolute activities.
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Boucher, Ian. "Structural studies of enzymes involved in cell detoxification." Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437619.
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Romão, Susana de Freitas. "The cytosolic hydroperoxide detoxification system of Leishmania infantum." Doctoral thesis, Instituto de Ciências Biomédicas Abel Salazar, 2008. http://hdl.handle.net/10216/16148.
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Romão, Susana de Freitas. "The cytosolic hydroperoxide detoxification system of Leishmania infantum." Tese, Instituto de Ciências Biomédicas Abel Salazar, 2008. http://hdl.handle.net/10216/16148.
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Hanumanth, Rao C. "Semiconductor Photocatalysts For The Detoxification Of Water Pollutants." Thesis, Indian Institute of Science, 2000. http://etd.iisc.ac.in/handle/2005/216.
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Water pollution is a major concern in vast countries such as India and other developing nations. Several methods of water purification have been practiced since many decades, Semiconductor photocatalysis is a promising technique, for photodegradation of various hazardous chemicals that are encountered in waste waters. The great significance of this technique is that, it can degrade (detoxify) various complex organic chemicals, which has not been addressed by several other methods of purification. This unique advantage made this field of research to attract many investigators particularly in latter eighties and after.
This thesis incorporates the studies on the various semiconductor photocatalysts that have been employed for the detoxification purposes. The fundamental principles involved in the photoelectrochemistry, reactions at the interface (solid - liquid or solid - gas) and photocatalytic reactions on fine particles are briefed. General nature and size quantization in semiconductor particles, photocatalytically active semiconductors, TiCh and ABO3 systems, chemical systems and modifications for solar energy conversions are brought out in the introduction chapter besides giving brief description about photocatalytic mineralization of water pollutants with mechanism involved, formation of reactive species and the factors influencing photomineralization reactions. Scope of the present work is given at the end of the first chapter.
Second chapter deals with the materials used for the preparation of photocatalyst, preparative techniques, methods of analysis, instruments employed for the photodegradation experiments and a brief description of material characterization methods such as X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential thermal analysis, optical absorption spectro photometry, Electron paramagnetic resonance (EPR), and gas chromatograph - mass spectroscopy (GC - MS). Various preparative routes such as wet chemical and hydrothermal methods for obtaining TiO2 (both rutile and anatase forms), BaTiOs and SrTiO3 fine particles and the chemical analysis of their constituents have been described in brief.
Third chapter presents the results of materials characterization. T1O2 (rutile and anatase), BaTiO3 and SrTiO3 have been characterized separately using various techniques. Different routes of obtaining the photocatalyst fine particles, heat treatment at various temperature ranges, experimental procedures and the results of characterization are brought out in this chapter.
Fourth and fifth chapters present the details of degradation studies carried out on the photomineralization of chlorophenol, trichloroethylene and formaldehyde. Studies include photodegradation of the pollutants with different catalysts varying experimental conditions to check the effects of change in
concentration of pollutants, oxidizer, pH, surface hydroxylation, etc. The most favorable conditions for the complete mineralization of the
pollutants have been studied. In case of TiO2, anatase form has shown greater photoactivity when compared to rutile and complete mineralization of chlorophenols has been achieved at low pollutant
concentrations, neutral pH, with H2O2 and UV illumination. Retarding effects of surface hydroxylation and the formation of peroxotitanium species during photodegradation have been presented. TCE and HCHO degradation with BaTiO3/SrTiO3 has been studied. Photocatalyst heat-treated at 1100°G-1300°C is found to be highly active in combination with H2O2 as electron scavenger. HCHO is not getting degraded to its completeness in aqueous conditions owing to the strong competition in surface adsorption posed by H2O molecules. Vapour-solid phase reaction however gave good results in the detoxification of HCHO via disproportionation. Summary and conclusions are given at the end of the thesis.
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Hanumanth, Rao C. "Semiconductor Photocatalysts For The Detoxification Of Water Pollutants." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/216.
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Water pollution is a major concern in vast countries such as India and other developing nations. Several methods of water purification have been practiced since many decades, Semiconductor photocatalysis is a promising technique, for photodegradation of various hazardous chemicals that are encountered in waste waters. The great significance of this technique is that, it can degrade (detoxify) various complex organic chemicals, which has not been addressed by several other methods of purification. This unique advantage made this field of research to attract many investigators particularly in latter eighties and after.
This thesis incorporates the studies on the various semiconductor photocatalysts that have been employed for the detoxification purposes. The fundamental principles involved in the photoelectrochemistry, reactions at the interface (solid - liquid or solid - gas) and photocatalytic reactions on fine particles are briefed. General nature and size quantization in semiconductor particles, photocatalytically active semiconductors, TiCh and ABO3 systems, chemical systems and modifications for solar energy conversions are brought out in the introduction chapter besides giving brief description about photocatalytic mineralization of water pollutants with mechanism involved, formation of reactive species and the factors influencing photomineralization reactions. Scope of the present work is given at the end of the first chapter.
Second chapter deals with the materials used for the preparation of photocatalyst, preparative techniques, methods of analysis, instruments employed for the photodegradation experiments and a brief description of material characterization methods such as X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential thermal analysis, optical absorption spectro photometry, Electron paramagnetic resonance (EPR), and gas chromatograph - mass spectroscopy (GC - MS). Various preparative routes such as wet chemical and hydrothermal methods for obtaining TiO2 (both rutile and anatase forms), BaTiOs and SrTiO3 fine particles and the chemical analysis of their constituents have been described in brief.
Third chapter presents the results of materials characterization. T1O2 (rutile and anatase), BaTiO3 and SrTiO3 have been characterized separately using various techniques. Different routes of obtaining the photocatalyst fine particles, heat treatment at various temperature ranges, experimental procedures and the results of characterization are brought out in this chapter.
Fourth and fifth chapters present the details of degradation studies carried out on the photomineralization of chlorophenol, trichloroethylene and formaldehyde. Studies include photodegradation of the pollutants with different catalysts varying experimental conditions to check the effects of change in
concentration of pollutants, oxidizer, pH, surface hydroxylation, etc. The most favorable conditions for the complete mineralization of the
pollutants have been studied. In case of TiO2, anatase form has shown greater photoactivity when compared to rutile and complete mineralization of chlorophenols has been achieved at low pollutant
concentrations, neutral pH, with H2O2 and UV illumination. Retarding effects of surface hydroxylation and the formation of peroxotitanium species during photodegradation have been presented. TCE and HCHO degradation with BaTiO3/SrTiO3 has been studied. Photocatalyst heat-treated at 1100°G-1300°C is found to be highly active in combination with H2O2 as electron scavenger. HCHO is not getting degraded to its completeness in aqueous conditions owing to the strong competition in surface adsorption posed by H2O molecules. Vapour-solid phase reaction however gave good results in the detoxification of HCHO via disproportionation. Summary and conclusions are given at the end of the thesis.
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Simmons, Jane. "The structure and function of amorphous calcium phosphate biominerals." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339520.
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Ekevall, Elizabeth. "Development of membrane bioreactors for liver failure therapy." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248546.
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Clarke, Stephen Edward. "Characterisation of housefly cytochrome P-450." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/847312/.
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The cytochrome P-450 dependent monooxygenase activity in a 'wild type' susceptible strain of housefly was studied. Catalytic activities were identified that demonstrated that the housefly cytochrome P-450 was capable of similar catalytic functions as those described for higher animals. Although several specific activities were lower than in mammalian species, benzphetamine N-demethylation was comparable and there was higher constitutive activity toward lauric acid than is observed in rat hepatic microsomes. The inducing agent phenobarbital increased both total cytochrome P-450 content and the benzphetamine N-demethylase specific activity. The high constitutive activity for fatty acids was induced by the hypolipidaemic drug clofibrate, specifically inducing the w-hydroxylase activity. The substrate specificity toward lauric acid extended equally to myristic and palmitic acid. Housefly microsomal cytochrome P-450 also metabolised the unsaturated fatty acid, arachidonic acid, the w-hydroxy-lation again inducible by clofibrate pretreatment. The w-hydroxylation of these fatty acids appeared to be a well-coupled reaction, a property that also appeared to be exhibited by the rat hepatic w-hydroxylase. The housefly fatty acid hydroxylation showed certain similarities to that in the rat, both in the specificity for w-hydroxylation and in the result of induction by clofibrate. Structural comparison to cytochrome P-450IVA1, IIB1 and IA1 was made by Western blot analysis with polyclonal antibodies raised to these rat hepatic isoenzymes. Housefly cytochrome P-450 shared few, if any, common epitopes with these rat isoenzymes, nor did these antibodies inhibit housefly cytochrome P-450 dependent monooxygenase activity. Cytochrome P-450 from clofibrate-pretreated housefly microsomes was partially purified by affinity chromatography. The cytochrome P-450 had a specific content of 5. 7nmol.mg-1 and a monomeric molecular weight of 52,000 daltons and a reduced carbon monoxide difference spectrum absorbance maxima at 448nm. In a reconstituted system, this preparation exhibited activity toward lauric acid and to a lesser extent arachidonic acid in each case w-hydroxylated products predominated. This is the first example of a purification of an insect cytochrome P-450 multiple form with a defined product reaction.
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Ronseaux, S. "Systemic detoxification of plant secondary metabolites by ruminant herbivores." Thesis, University of Aberdeen, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590983.
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The effect of xenobiotic compounds on drug metabolising enzymes was assessed in ruminants; the development of an in vivo approach using a drug cocktail to measure specific enzyme families of phase I and II metabolism has been developed. Predictive clearances based on in vitro data from tolbutamide, phenacetin, chlorzoxazone, midazolam and oxazepam incubations were correlated with clearance determined in vivo (R2= 0.695). A drug cocktail approach was used to assess the effect of plant secondary compounds on phase I and II enzymatic activities. This approach showed that phase I enzymes, e.g. CYP3A, can be affected by plant compounds, such as α-pinene or pyrrolizidine alkaloids. Additionally, due to carry over from one treatment period to the next, this experiment showed that interaction between plant secondary compounds can alter the overall effect of a single compound. Subsequently, in vitro experiments with hepatocytes or rumen microorganisms from sheep or goats, showed that pyrrolizidine alkaloids were not completely degraded in rumen fluid after 48h. Dose- and time-dependent toxicity of pyrrolizidine alkaloids to hepatocytes were observed. The magnitude of toxicity measured in goat and sheep hepatocytes was compatible with in vivo observations. Interaction between plant compounds observed in vivo was confirmed by in vitro assays. This concept of interaction between plant compounds was used to decrease the toxicity of pyrrolizidine alkaloids to hepatocytes. Exposure to certain plant compounds prior to the potentially toxic compounds could decrease pyrrolizidine alkaloid toxicity by acting on phase I or II enzymes. The mechanism of protection appears to be different between sheep and goats.
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Lao, Si-houy. "Detoxification of 3,4-dichloroaniline in soybean by n-malonylation." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3035/.
Full textAbstract:
3,4-Dichloroaniline (DCA), the degradation product of certain herbicides, is not readily degraded by micro-organisms and, due to its persistence in the environment, is considered to be a reference xenobiotic. Here, the metabolic fate of [UL-(^14)C]-3,4-DCA was investigated in soybean (Glycine max var. Chapman) plants over a 48 h period following treatment via the root media. DCA was rapidly taken up and metabolised to 7V-malonyl-DCA. Synthesis occurred in the roots and the conjugate was largely exported into the culture medium, a smaller proportion being retained within the plant tissue. Once exported, the DCA metabolites present in the medium were not readily taken up by soybean roots. Conjugation and export of DCA therefore constitute an effective detoxification mechanism for the plant. A radiometric assay for DCA-N-malonyltransferase (E.C.2.3.1.114; DCA-N-MT) was developed and used to follow DCA-N-MT activity through a four-step protocol, in which DCA-N-MT was purified 400-fold from soybean roots. SDS- PAGE analysis and gel filtration chromatography suggested that DCA-N-MT is a 52 ± 2 kDa protein. Following treatments with 100 μM DCA for 24 h, DCA-N-MT activity in soybean roots increased from 44.6 ± 8.1 nkatg(^1) to 104 ± 4.9 nkatg(^1) but did not vary significantly in suspension-cultured cells (332.9 ± 38.9 nkat.g(^1)). Kinetic studies suggested that this increase in activity could be due to de novo protein synthesis. Partially-purified DCA-N-MT was therefore subjected to differential gel electrophoresis (DiGE) analysis to identify proteins which increased in abundance in response to DCA pre-treatment. Although a clear candidate for DCA-N-MT was not detected, five differentially expressed proteins were identified by mass spectrometry.
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Hatton, Pamela J. "Role of glutathione transferases in herbicide detoxification in weeds." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5443/.
Full textAbstract:
Glutathione transferases (GSTs) catalyse the conjugation of the electrophilic herbicides atrazine, metolachlor, alachlor and fluorodifen with the tripeptide glutathione (GSH). Maize (Zea mays L), contains multiple GSTs with differing substrate specificities which confer tolerance to a variety of herbicides. In contrast far less is known regarding the GSTs in competing weed species. In vivo metabolism studies using seedlings of maize and the weeds Panicum miliaceum. Digitaria sanguinalis, Sorghum bicolor. Setaria faberi. Abutilon theophrasti and Echinochloa crus-galli demonstrated that all species were capable of metabolising radiolabelled atrazine to GSH conjugates and the relative rates of metabolism related well to GST activities. Similarly, GST activities toward atrazine, metolachlor and alachlor correlated well with herbicide tolerance, with GSH availability being less important. GST activities towards metolachlor, alachlor and atrazine were highest in young maize plants and decreased with age, whilst GST activities in S.faberi remained unchanged. At 35 days GST activities were similar in the two species and the atrazine selectivity was lost. GSH content decreased with age in both species. Protein purification studies showed that S.faberi contains 4 GST isoenzymes with differing substrate specificities. The major GST was estimated to account for 0.1 % of die total soluble protein in S.faberi. PCR-amplification of a cDNA prepared from mRNA showed that S.faberi contains a GST with 88% identity to GST I from maize at the nucleotide level and 82% identity at the amino acid level. Similarly antibodies raised to maize and wheat GSTs recognised GSTs in S.faberi. It is concluded that GSTs determine the relative tolerance to chloroacetanilides and atrazine in weed seedlings but may be less important in older plants. The GSTs in S.faberi are similar in complexity to those determined in maize but are expressed at lower levels.
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Ordway, Fiona Elizabeth Anne. "Heavy metal detoxification by yeast to produce quantum semiconductors." Thesis, University of Huddersfield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438056.
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Al, Hawani Israa. "Studies on bacterial detoxification systems for NO and CO." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19295/.
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Li, Guiying. "A Tio2 Photoelectrocatalytic System for Wastewater Detoxification and Disinfection." Thesis, Griffith University, 2010. http://hdl.handle.net/10072/367000.
Full textAbstract:
This work systematically investigate the nanoparticulate TiO2 photocatalysis and
photoelectrocatalysis based methods for decomposition, detoxification and disinfection of
a series of biological contaminants ranged from small biological compounds such as
amino acids and nucleotide bases, to large biological compounds including protein, lipid
and DNA, to living microorganisms such as bacteria and virus. The small biological
compounds (e.g., amino acids and nucleotide bases) are the basic building blocks of the
large biological compounds (e.g., proteins and DNA), and the large biological compounds
are the building blocks of the living microorganisms (e.g., bacteria and viruses). Due to
the complicity involved, in order to understand the full spectrum of the decomposition,
detoxification and disinfection mechanisms of living microorganisms, a bottom-up
strategy was employed in this study. The photocatalytic and photoelectrocatalytic
degradation of small biological compounds were firstly investigated to gain the necessary
information for a better understanding of degradation mechanisms of large biological
compounds. The photocatalytic and photoelectrocatalytic degradation of large biological
compounds were then investigated to gain the necessary information for a better
understanding of decomposition/disinfection mechanisms of living microorganisms. This
was followed by the investigation of photocatalytic and photoelectrocatalytic
decomposition/detoxification/disinfection of living microorganisms.
Chapter 1 of the thesis provides comprehensive literature reviews of the present status
of research developments relevant to this work and the justification for the research topic.
Nanoparticulate TiO2 photoanode is a key element of the proposed research. Chapter
2 describes the fabrication and characterisation of the nanoparticulate TiO2 photoanode.
The nanoparticulate TiO2 photoanode was successfully fabricated using a sol-gel method.
The photoelectrocatalytic properties of the resultant TiO2 photoanodes were systematically
evaluated using water, as well as organic model compounds in both bulk and thin-layer
photoelectrochemical cells. The results indicated that the resultant photoanodes possess
high photocatalytic activity. The measured net charge under the exhaustive conditions in
a thin-layer photoelectrochemical cell is essentially the same as the theoretically required
charge, demonstrating a superior oxidation power and 100% electron collection efficiency.
Photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of small biological
compounds such as amino acids and nucleotide bases were carried out in Chapters 3 and 4.
These small biological compounds were found to be photocatalytically and
photoelectrocatalytically degradable. The degradation efficiency of PEC method was
found to be higher than that of PC method for all compounds investigated. The organic
nitrogens in the original compounds can be oxidised to either NH3/NH4 + or NO3- or both,
depending the chemical structures of the original compounds and the degradation methods
used. Both experimental results and the theoretically calculated frontier electron densities
values of (2FEDHOMO)2 and (FEDHOMO)2+(FEDLUMO)2 demonstrated that the reaction
mechanisms/pathways of PEC processes differed remarkably from that of PC processes.
As a part of the proposed “bottom-up” strategy, PC and PEC degradation of large
biological compounds such as bovine serum albumin (BSA), lecithin and bacteria
genomic DNA were performed in Chapter 5. A new method for estimating the theoretical
charge required to mineralise these large biological compounds with unknown chemical
formula was firstly developed and experimentally validated. The degradation efficiency
of PEC method was found to be higher than that of PC method for all large biological
compounds investigated.
In Chapter 6, a bactericidal technique (PEC-Br) utilising in situ photoelectrocatalytically generated photohole (h+), Br2•- and active oxygen species (AOS) for instant inactivation and rapid decomposition of Gram-negative bacteria such as E. coli was proposed and experimentally validated. The method is capable of inactivating 99.90% and 100% of 9×106 CFU/mL E. coli within 0.40 s and 1.57 s, respectively. To achieve the same inactivation effect, the PEC-Br method is 358 and 199 times faster than that of the PEC method, and 2250 and 764 times faster than that of the PC method.
The Chapter 7 demonstrated the bactericidal technique developed in Chapter 6 can
also be applied as a virucidal technique for rapid inactivation of viruses such as
replication-deficient recombinant adenovirus (RDRADS). The PEC-Br method is capable
of deactivating 99.77% and 100% of RDRADS within 14.32 s and 31.65 s, respectively.
The final chapter of the thesis (Chapter 8) summarises the outcomes of this study and
future work.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Bretschneider, Anne [Verfasser], David G. Gutachter] Heckel, Ping [Gutachter] [Wang, and Stefan H. [Gutachter] Heinemann. "ABC transporters in insect detoxification pathways : ABC transporters in insect detoxification pathways / Anne Bretschneider ; Gutachter: David G. Heckel, Ping Wang, Stefan H. Heinemann." Jena : Friedrich-Schiller-Universität Jena, 2016. http://d-nb.info/1177609010/34.
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Navarro, Roldán Miguel Ángel. "Detoxification and sublethal effects of neurotoxic insecticides in tortricid moths." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/462995.
Full textAbstract:
El coneixement bàsic dels efectes letals i subletals que els insecticides poden generar en els insectes
plaga resulta particularment important per l’optimització i millora de les estratègies de Control Integrat
de Plagues (C.I.P), especialment quan l’ús d’insecticides és la principal eina de control. Al llarg de la
present tesi s’ha realitzat una feina molt exhaustiva que dóna com a resultat unes corbes de mortalitat
dosi-resposta per a tres insecticides neurotòxics amb diferents maneres d’acció [clorpirifòs (un
organofosforat inhibidor de l’acetilcolinesterasa (AChE)), λ-cihalothrín (un piretroide modulador dels
canals de sodi), i tiacloprid (un neonicotinoide agonista dels receptors nicotínics de l’AChE)] sobre tres
espècies d’arnes que són importants plagues fruiteres [Cydia pomonella (L.), Grapholita molesta
(Busck), i Lobesia botrana (Denis & Schiffermüller)]. Tot seguit, es van analitzar els mecanismes de
detoxificació de les tres espècies pels tres insecticides mitjançant l’estudi de les principals famílies
enzimàtiques involucrades en la detoxificació [carboxil-esterases (EST), glutatió-S-transferases
(GST), i multi-funció oxidases (MFO)]. Finalment, es va explorar si dosis subletals de l’insecticida
tiacloprid, estimades en la primera part de la tesi, tenien un efecte sobre el sistema de comunicació
mitjançant feromones sexuals en les tres espècies. Un aspecte característic d’aquesta tesi és que se
centra en l’insecte adult, el qual està vagament representat dins la literatura científica de l’àrea de la
toxicologia en Lepidòpters, probablement degut que la gran majoria dels insecticides tenen als ous o a
diferents estadis larvaris com a element diana. No obstant, l’ús d’adults en aquest estudi ens reportarà
una sèrie de descobriments insospitats que s’explicaran a continuació.El conocimiento básico de los efectos letales y subletales que los insecticidas pueden generar en los insectos plaga resulta particularmente importante para la optimización y mejora de las estrategias de Control Integrado de Plagas (C.I.P), especialmente cuando el uso de insecticidas es la principal herramienta de control. El exhaustivo trabajo realizado a lo largo de la presente tesis da como resultado unas curvas de mortalidad dosis-respuesta para tres insecticidas neurotóxicos con diferentes modos de acción [clorpirifós (un organofosforado inhibidor de la acetilcolinesterasa (AChE)), λ-cihalothrín (un piretroide modulador de los canales de sodio), y tiacloprid (un neonicotinoide agonista de los receptores nicotínicos de la AChE)] sobre tres especies de polillas que son importantes plagas frutales [Cydia pomonella (L.), Grapholita molesta (Busck), y Lobesia botrana (Denis & Schiffermüller)]. Acto seguido, se analizaron los mecanismos de detoxificación de las tres especies para los tres insecticidas mediante el estudio de las principales familias enzimáticas involucradas en la detoxificación [carboxilesterasas (EST), glutatión-S-transferasas (GST), y multifunción oxidasas (MFO)]. Finalmente, se exploró si dosis subletales del insecticida tiacloprid, estimadas en la primera parte de la tesis, tenían un efecto sobre el sistema de comunicación mediante feromonas sexuales en las tres especies. Un aspecto característico de esta tesis es que se centra en el insecto adulto, el cual está muy poco representado en la literatura científica del área de la toxicología en Lepidópteros, probablemente debido a que la gran mayoría de los insecticidas tienen a los huevos o a diferentes estadios de la larva como elemento diana. Sin embargo, el uso de adultos en este estudio nos reportará una serie de hallazgos inesperados que se explicarán a continuación.
Basic knowledge on lethal and sublethal insecticide effects on pest insects is particularly important for optimization and continuous improvement of IPM strategies, especially when insecticides are used as the main crop-protection strategy. The work that I carried out in my Ph.D. thesis provides thorough dose-mortality curves for three neurotoxic insecticides with different modes of action [chlorpyrifos (organophosphate, acetylcholinesterase inhibitor), λ-cyhalothrin (pyrethroid, sodium channel modulator), and thiacloprid (neonicotinoid, nicotinic acetylcholinesterase receptor agonist)] on three key fruit pest species [Cydia pomonella (L.), Grapholita molesta (Busck), and Lobesia botrana (Denis & Schiffermüller)]. Subsequently I analyzed the detoxification mechanisms of the three species against the three insecticides by studying the most common enzymatic detoxification groups [carboxylesterases (EST), glutathione-S-transferases (GST), and mixed-function oxidases (MFO)]. Finally, I explored if the sublethal doses of thiacloprid estimated in the first part of the thesis affect the sex-pheromone communication system of these species. A singular aspect of my thesis is that I focused on the adult stage, which is poorly represented in the toxicological scientific literature of Lepidoptera, probably because most insecticides are mainly designed to kill egg or larval stages. However, this choice ultimately led to some unexpected findings that I explain next.
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Patel, Vishal M. "Synthesis of calcium carbonate coated emulsion droplets for drug detoxification." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001175.
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Alriksson, Björn. "Ethanol from lignocellulose : Alkali detoxification of dilute-acid spruce hydrolysates." Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-2632.
Full textAbstract:
Detoxification of dilute-acid lignocellulose hydrolysates by treatment with Ca(OH)2 (overliming) efficiently improves the production of fuel ethanol, but is associated with drawbacks like sugar degradation and CaSO4 precipitation. In factorial designed experiments, in which pH and temperature were varied, dilute-acid spruce hydrolysates were treated with Ca(OH)2, NH4OH or NaOH. The concentrations of sugars and inhibitory compounds were measured before and after the treatments. The fermentability was examined using the yeast Saccharomyces cerevisiae and compared with reference fermentations of synthetic medium without inhibitors. The treatment conditions were evaluated by comparing the balanced ethanol yield, which takes both the degradation of sugars and the ethanol production into account. Treatment conditions resulting in excellent fermentability and minimal sugar degradation were possible to find regardless of whether Ca(OH)2, NH4OH or NaOH was used. Balanced ethanol yields higher than those of the reference fermentations were achieved for hydrolysates treated with all three types of alkali. As expected, treatment with Ca(OH)2 gave rise to precipitated CaSO4. The NH4OH treatments gave rise to a brownish precipitate but the amounts of precipitate formed were relatively small. No precipitate was observed in treatments with NaOH. The possibility that the ammonium ions from the NH4OH treatments gave a positive effect as an extra source of nitrogen during the fermentations was excluded after experiments in which NH4Cl was added to the medium. The findings presented can be used to improve the effectiveness of alkali detoxification of lignocellulose hydrolysates and to minimize problems with sugar degradation and formation of precipitates.
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Fletcher, Kelly Elizabeth. "New insights into reductive detoxification of chlorinated solvents and radionuclides." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37244.
Full textAbstract:
Naturally occurring bacterial populations are capable of detoxifying chlorinated compounds and immobilizing the radionuclide uranium via reductive processes. This study addressed the following three knowledge gaps in the fields of chlorinated solvent and uranium bioremediation, 1) the risks and benefits of coupling bioremediation with thermal treatment for clean-up of chlorinated ethene-contaminated sites, 2) the accuracy of available techniques for the monitoring of chlorinated solvent bioremediation, and 3) the role of gram positive Desulfitobacterium spp. in uranium immobilization. Experiments demonstrated that thermal treatment increases electron donor availability, but the increased electron donor was not used to fuel reductive dechlorination and was actually consumed for methanogenesis. Two approaches for monitoring chlorinated solvent bioremediation were investigated, molecular techniques and compound-specific isotope analysis (CSIA). Results demonstrated that while Dehalococcoides (Dhc) gene expression was up-regulated under conditions inhibitory to dechlorination, the isotope effects associated with dechlorination reactions catalayzed by Dhc populations in consortia and in pure cultures were similar. U(VI) reduction by multiple Desulfitobacterium isolates was demonstrated. Interestingly, while almost all U(VI)-reducing populations have been reported to produce uraninite (UO2), the product of U(VI) reduction by Desulfitobacterium isolates was a unique form of insoluble mononuclear U(IV).
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Gamage, McEvoy Joanne. "Carbon-enhanced Photocatalysts for Visible Light Induced Detoxification and Disinfection." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31099.
Full textAbstract:
Photocatalysis is an advanced oxidation process for the purification and remediation of contaminated waters and wastewaters, and is advantageous over conventional treatment technologies due to its ability to degrade emerging and recalcitrant pollutants. In addition, photocatalytic disinfection is less chemical-intensive than other methods such as chlorination, and can inactivate even highly resistant microorganisms with good efficacy. Process sustainability and cost-effectiveness may be improved by utilizing solar irradiation as the source of necessary photons for photocatalyst excitation. However, solar-induced activity of the traditionally-used titania is poor due to its inefficient visible light absorption, and recombination of photo-excited species is problematic. Additionally, mass transfer limitations and difficulties separating the catalyst from the post-treatment slurry hinder conversions and efficiencies obtainable in practice. In this research, various strategies were explored to address these issues using novel visible light active photocatalysts. Two classes of carbon-enhanced photocatalytic materials were studied: activated carbon adsorbent photocatalyst composites, and carbon-doped TiO2. Adsorbent photocatalyst composites based on activated carbon and plasmonic silver/silver chloride structures were synthesized, characterized, and experimentally investigated for their photocatalytic activity towards the degradation of model organic pollutants (methyl orange dye, phenol) and the inactivation of a model microorganism (Escherichia coli K-12) under visible light. The adsorptive behaviour of the composites towards methyl orange dye was also studied and described according to appropriate models. Photocatalytic bacterial inactivation induced by the prepared composites was investigated, and the inactivation mechanisms and roles of incorporated antimicrobial silver on disinfection were probed and discussed. These composites were extended towards magnetic removal strategies for post-use separation through the incorporation of magnetic nanoparticles to prepare Ag/AgCl-magnetic activated carbon composites, and the effect of nanoparticles addition on the properties and photoactivities of the resulting materials was explored. Another silver/silver halide adsorbent photocatalyst composite based on activated carbon and Ag/AgBr exhibiting visible light absorption due to both localized surface plasmon resonance and optical band gap absorption was synthesized and its photocatalytic activity towards organics degradation and microbial inactivation was studied. Carbon-doped mixed-phase titania was also prepared and experimentally investigated.
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Chalmers, D. "Chemical carcinogenesis : Studies on detoxification enzymes in somatic cell hybrids." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371997.
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Chen, Liyan. "Detoxification and nutritional enhancement of soy meal via microbial bioprocessing." Diss., Kansas State University, 2013. http://hdl.handle.net/2097/15623.
Full textAbstract:
Doctor of PhilosophyDepartment of Grain Science and Industry
Praveen V. Vadlani
Soy meal (SM) is the main protein source for monogastric animals. Anti-nutritional factors in SM limited its usage for young monogastric animals. Aspergillus was investigated to degrade these factors and to enhance its nutritional value via solid state fermentation. Galacto-oligosaccharides were totally degraded from the initial 9.48 mmol/100 g, and trypsin inhibitor decreased from 10.7 TIU/mg to a non-detectable level after 36 hr fermentation. Structural polysaccharides decreased by 59% (w/w) and the degree of hydrolysis of SM protein increased from 0.9% to 7% (w/w) through the 7 d fermentation. Fermentation also modified nutritional factors. Protein content increased from 50.47% (w/w) to 58.93% (w/w) after 36 hr fermentation. Amino acid profile was significantly enhanced. Two - stage temperature-induced fermentation protocol was developed to increase the degradation rate of phytic acid by A. oryzae (ATCC 9362) and by A. ficuum (ATCC 66876). The first stage maximized phytase production with fermentation parameters obtained by central composite design. The second stage achieved maximum enzymatic degradation with parameters obtained by studying the phytase temperature characteristics. While using A. oryzae, 57% of phytic acid in SM was degraded by the two stage protocol compared to 39% degradation from single stage fermentation. For A. ficuum, the two-stage temperature fermentation protocol achieved a 98% degradation level of phytic acid degradation compared with the single stage process. Two-stage temperature-induced co-fermentation of A. oryzae and A. ficuum was investigated to simultaneously degrade phytic acid and soy protein with high efficiency. Co-fermentation of A. oryzae and A. ficuum resulted in higher phytic acid degradation than A. oryzae fermentation and superior protein hydrolysis compared to A. ficuum fermentation. Sterilization distorted the results of fermentation effect on soy allergens and soy protein degradation. Virginiamycin is a kind of bacterisin. It was added to A. oryzae solid state fermentation, to exclude the necessity of SM sterilization. Nonsterile, solid state fermentation using A. oryzae and virginiamycin showed the complete degradation of α and α’ subunits of β-conglycinin and decreased immunoreactivity of soy protein. The modified SM after microbial bioprocessing created an innovative product with enhanced characteristics with potential wider applications for feed industry.
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Sparrow, Helen. "The role of glutathione transferases in the detoxification of TNT." Thesis, University of York, 2010. http://etheses.whiterose.ac.uk/1470/.
Full textAbstract:
Manufacture, use, storage and improper disposal of the explosive 2,4,6-trinitrotoluene (TNT) have led to widespread, global contamination of soil and groundwater. TNT is highly toxic and recalcitrant to degradation resulting in environmental build-up with far reaching ecological and health implications. It is therefore a priority to remove contaminating TNT from the environment. Phytoremediation is a promising solution; suitable plants possess some natural ability to transform TNT, high biomass, deep root systems, requirement for minimal nutrient input and ability to reduce contamination spread by wind or water erosion; making them an attractive remediation system. Key genes involved in the detoxification of TNT by plants have been recently identified by expression studies and the encoded enzymes characterised. This has lead to the thorough investigation of the enzymes in the pathway of TNT detoxification; Phase I transformation includes oxophytodienoate reductases, with uridine diphosphate (UDP) glycosyltransferases (UGTs) playing a role in the Phase II conjugation step. The expression studies identified additional enzymes also likely to be involved in these phases including glutathione transferases (GSTs). GSTs are known to detoxify compounds by conjugation to glutathione (GSH), and like UGTs are Phase II detoxification enzymes. This thesis presents an investigation into whether plant GSTs play a role in the detoxification of TNT. In vitro analysis of recombinant GSTs was performed to elucidate the activity of GSTs towards TNT. Seven GSTs were cloned, expressed and purified from Escherichia coli. TNT assays performed with pure enzyme indicated that at least two of the GSTs were able to transform TNT. Analysis of the reaction product by mass spectrometry showed that TNT was conjugated to glutathione through substitution of a nitro-group, a highly desirable reaction as the removal of a nitro group from TNT is likely to increase the likelihood of subsequent mineralisation of the pollutant. This is the first identification of enzymes capable of this transformation. The two GSTs which exhibited activity towards TNT were overexpressed in Arabidopsis to clarify if the conjugating activity observed in vitro was able to confer increased tolerance to TNT to the transformed plants. Transgenic lines showed no enhanced growth compared to wild type plants on TNT amended media, root lengths appeared slightly shorter while TNT uptake and biomass were reduced. The role of GSTs in the detoxification of TNT remains unresolved however it is likely that GSTs do not play an integral role in TNT detoxification in plants. Nonetheless, the two GSTs characterised in the project are the first examples of plant enzymes which are able to catalyse the removal of nitro groups from TNT. Engineering these GSTs to improve their ability to transform TNT could offer an opportunity for effective environmental remediation.
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Harrison, Laura. "Nitric oxide detoxification systems and cellular pathogenesis of Neisseria meningitidis." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/6632/.
Full textAbstract:
Nitric oxide is an important biological mediator of a variety of physiological processes and S nitrosylation, the addition of an NO moiety to the cysteine residue of a protein, is an established post-translational modification known to be involved in the regulation of a growing number of cellular pathways. The gram-negative bacteria, Neisseria meningitidis is capable of expressing a number of enzymes involved in partial denitrification including the nitric oxide reductase, NorB. This not only allows the bacteria to supplement their growth in the oxygen limited conditions associated with the nasopharnyx, but it also protects them from the antimicrobial effects associated with NO. Bacterial expression of NorB has a variety of consequences including enhanced bacterial survival in a macrophage cell model along with a reduction in total and nuclear levels of S nitrosothiol in an activated murine macrophage model. The work presented in this thesis was undertaken with the aim of establishing if the ability of the bacteria to detoxify NO and remove or prevent formation of S nitrosothiol would have physiological consequences with emphasis on cellular targets known to be regulated by S nitrosylation. A pre-stimulated murine macrophage model was established and the impact of bacterial infection on caspase-3 activity and cell death was investigated. Infection with wild-type bacteria led to a more rapid cell death, in the absence of caspase-3 activation, compared to cells infected with a ΔnorB mutant derivative. The transcription factor NFκB has been suggested to be regulated by S nitrosylation, and indeed the binding activity of the p65 subunit was shown to be negatively regulated in an iNOS and S nitrosylation dependent manner in a murine macrophage model in response to LPS and interferonγ (IFNγ) stimulation. Conversely, following an infection, modulation of NFκB binding activity appeared to be iNOS independent despite S-nitrosylation of NFκB occurring, suggesting an alternative mechanism of modulation that renders S nitrosylation superfluous. The ability of the bacteria to express NorB had no apparent impact on NFκB binding activity. The ubiquitous protein GAPDH was also investigated and its nuclear translocation was shown to be regulated by S nitrosylation. Infection with N. meningitidis was associated with a reduction in nuclear GAPDH translocation when compared to cells stimulated with LPS and IFNγ alone. Work was also commenced to establish if a reduction in total S-nitrosothiol as a result of bacterial NO detoxification could be observed in an in vivo mouse model. Total levels of S nitrosothiol and tri-iodide reactive species were unaffected by infection with Neisseria meningitidis either in the presence or absence of the norB gene at 4h post infection.
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Dixon, David Peter. "Glutathione transferases in maize (Zea mays)." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4788/.
Full textAbstract:
The glutathione transferases (GSTs) of maize have been the most studied GSTs in plants, however much is still not known about these enzymes. In the course of the current study six GST subunits (Zm GSTs I, II and III, which have been reported previously, and Zm GSTs V, VI and VII, which have not been previously reported) have been identified in the dimers Zm GST I-I, I-II, I-III, V-V, V-VI and V-VII. Maize GSTs are known to be important in herbicide detoxification and the purified maize enzymes were each found to have differing activities toward a number of herbicides, and also a range of other potential GST substrates. Additionally, Zm GST I II and Zm GST V-V possessed glutathione peroxidase activity. The developmental regulation and chemical inducibility of maize GSTs were studied in maize seedlings using western blotting, with different subunits showing markedly different responses. Zm GST I was constitutively present in all plant parts and unaffected by chemical treatment, Zm GST II was only detected in young roots but was induced in roots and shoots by many different chemical treatments, and Zm GST V was present at low levels throughout maize plants, with levels enhanced greatly by treatment with the safener dichlormid but not by other chemicals tested. cDNA clones corresponding to Zm GST subunits I, III, V, VI and VII were isolated by library screening using antibody or DNA probes. The cDNA sequences for Zm GST subunits V, VI and VH were different from those of previously cloned type I (theta class) maize GSTs and were most similar to the auxin-regulated GST family (type III or tau class GSTs) previously only identified in dicotyledonous species. The cloned GSTs were expressed as recombinant proteins in E. coli, allowing further characterisation, including detailed kinetic analysis for recombinant Zm GST I-I and Zm GST V-V.
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Le, Juez Valérie. "Obtention détection et détoxification des endotoxines bactériennes : étude de différentes interactions." Paris 5, 1991. http://www.theses.fr/1991PA05P609.
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Bartu, Anne E. "A grounded study of the experience of detoxification from psychoactive drugs." Curtin University of Technology, School of Nursing, 1998. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12124.
Full textAbstract:
The main objective of this thesis was to develop a substantive theory that explained the phenomenon of detoxification from psychoactive drugs such as alcohol, tranquillisers, opioids, and amphetamines in a medical treatment unit for licit and illicit drug users. The other objectives were to (a) determine if the differences reported in earlier studies between licit and illicit drug users in terms of socio-demographic and drug use variables remain extant, and (b) assess the extent of minor psychiatric morbidity among the participants. Both grounded theory and quantitative methods of data collection and analysis were used in the study.The findings of the quantitative component of the study indicated that there were significant differences between licit and illicit drug users in regard to age, drug use characteristics, and completing the treatment program. That is, illicit drug users were younger than licit drug users, more likely to be poly drug users, and drop out of the program. The prevalence of minor psychiatric morbidity among the participants was 93.6%, and was largely independent of socio-demographic and drug use variables. The high prevalence of minor psychiatric morbidity suggests that the majority of participants warranted further follow-up support in the community after they left the treatment unit. The uptake of referrals for follow-up support, however, was 55.9%.The basic or core social psychological problem identified by the constant comparative method of grounded theory was found to have two parts, both of which were interpreted as forms of disequilibrium. The first part of disequilibrium, which was a precursor to treatment, was conceptualised as Hitting the Wall. The events associated with the symbolic "wall" interrupted the participants' drug focussed lifestyles and induced them to enter treatment. These events and problems were not resolved whilst in ++treatment, they lingered with the participants while they were in the unit, and remained to be addressed when they left. Whilst undergoing detoxification the participants encountered the second part of disequilibrium which was categorised as Incompatibility. The problem of Incompatibility was related to the heterogeneity of the participants and the structure of the treatment program that in many cases was unable to accommodate individual differences and needs.The core or basic social psychological process was conceptualised as Seeking Balance through Hanging In. The participants engaged in this process to deal with the disequilibrium of the precursor problem of Hitting the Wall and the problem of Incompatibility encountered in the unit. Seeking Balance through Hanging In was found to have four phases. The phases were Making the Break, Submitting to Cleansing, Fitting In, and Moving On. The process was linear in that the phases were sequential, and failure to complete a phase meant dropping out of the detoxification program. The experience of detoxification was modified by several contextual conditions. These were the physical enviroment, the participants' expectations of withdrawal symptoms, and the workload of the staff.The substantive theory, Seeking Balance through Hanging In, integrated all emergent categories, and explained the experience of the phenomenon of withdrawal from psychoactive drugs in a particular context. Recommendations for further research include testing the described phases and relationships of the substantive theory in similar environments, exploring the importance of the modifying conditions on client outcomes, and undertaking follow-up studies to determine the outcomes of those who completed the program as compared to the outcomes of those who dropped out. In addition, further studies are recommended to assess the transientness of the level ++
of minor psychiatric morbidity detected among the participants in this study.The findings of this study make an important contribution to understanding the experience of detoxification from the perspective of the participants. The substantive theory has implications for clinical practice, professional education, management, and further research.
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Bartu, Anne. "A grounded study of the experience of detoxification from psychoactive drugs." Thesis, Curtin University, 1998. http://hdl.handle.net/20.500.11937/1748.
Full textAbstract:
The main objective of this thesis was to develop a substantive theory that explained the phenomenon of detoxification from psychoactive drugs such as alcohol, tranquillisers, opioids, and amphetamines in a medical treatment unit for licit and illicit drug users. The other objectives were to (a) determine if the differences reported in earlier studies between licit and illicit drug users in terms of socio-demographic and drug use variables remain extant, and (b) assess the extent of minor psychiatric morbidity among the participants. Both grounded theory and quantitative methods of data collection and analysis were used in the study.The findings of the quantitative component of the study indicated that there were significant differences between licit and illicit drug users in regard to age, drug use characteristics, and completing the treatment program. That is, illicit drug users were younger than licit drug users, more likely to be poly drug users, and drop out of the program. The prevalence of minor psychiatric morbidity among the participants was 93.6%, and was largely independent of socio-demographic and drug use variables. The high prevalence of minor psychiatric morbidity suggests that the majority of participants warranted further follow-up support in the community after they left the treatment unit. The uptake of referrals for follow-up support, however, was 55.9%.The basic or core social psychological problem identified by the constant comparative method of grounded theory was found to have two parts, both of which were interpreted as forms of disequilibrium. The first part of disequilibrium, which was a precursor to treatment, was conceptualised as Hitting the Wall. The events associated with the symbolic "wall" interrupted the participants' drug focussed lifestyles and induced them to enter treatment. These events and problems were not resolved whilst in treatment, they lingered with the participants while they were in the unit, and remained to be addressed when they left. Whilst undergoing detoxification the participants encountered the second part of disequilibrium which was categorised as Incompatibility. The problem of Incompatibility was related to the heterogeneity of the participants and the structure of the treatment program that in many cases was unable to accommodate individual differences and needs.The core or basic social psychological process was conceptualised as Seeking Balance through Hanging In. The participants engaged in this process to deal with the disequilibrium of the precursor problem of Hitting the Wall and the problem of Incompatibility encountered in the unit. Seeking Balance through Hanging In was found to have four phases. The phases were Making the Break, Submitting to Cleansing, Fitting In, and Moving On. The process was linear in that the phases were sequential, and failure to complete a phase meant dropping out of the detoxification program. The experience of detoxification was modified by several contextual conditions. These were the physical enviroment, the participants' expectations of withdrawal symptoms, and the workload of the staff.The substantive theory, Seeking Balance through Hanging In, integrated all emergent categories, and explained the experience of the phenomenon of withdrawal from psychoactive drugs in a particular context. Recommendations for further research include testing the described phases and relationships of the substantive theory in similar environments, exploring the importance of the modifying conditions on client outcomes, and undertaking follow-up studies to determine the outcomes of those who completed the program as compared to the outcomes of those who dropped out. In addition, further studies are recommended to assess the transientness of the level of minor psychiatric morbidity detected among the participants in this study.The findings of this study make an important contribution to understanding the experience of detoxification from the perspective of the participants. The substantive theory has implications for clinical practice, professional education, management, and further research.
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Kern, Rory James. "Enzyme-based detoxification of organophosphorus neurotoxic pesticides and chemical warfare agents." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2118.
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Ozyamak, Ertan. "The analysis of methylglyoxal detoxification and stress responses in Escherichia coli." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until Nov. 20, 2011, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59008.
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Lee, Dong-Won. "Engineered chitosans for drug detoxification preparation, characterization, and drug uptake studies /." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004293.
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Cheung, Ka-hong. "Chromate toxicity assessment and detoxification by bacteria from the marine environment /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36249890.
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Ghanem, Eman Mohamed. "Directed evolution of phosphotriesterase for detoxification of the nerve agent VX." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4330.
Full textAbstract:
Phosphotriesterase (PTE) isolated from the soil bacterium Flavobacterium sp. is
a member of the amidohydrolase superfamily. PTE catalyzes the hydrolysis of a broad
spectrum of organophosphate triesters including the insecticide paraoxon, and the
chemical warfare agents; GF, sarin, and soman. In addition, PTE has been shown to
catalytically hydrolyze the lethal nerve agent, VX. However, the rate of VX hydrolysis
is significantly slower. PTE was subjected to directed evolution studies to identify
variants with enhanced activity towards VX hydrolysis. First generation libraries
targeted amino acid residues in the substrate binding site. The H254A mutation
displayed a 4-fold enhancement in kcat and a 2-fold enhancement in kcat/Km over wild
type PTE. The double mutant H254Q/H257F was isolated from the second generation
libraries and displayed a 10-fold enhancement in kcat and a 3-fold enhancement in
kcat/Km. In addition, H254Q/H257F displayed a 9-fold enhancement in kcat/Km for the
hydrolysis of the VX analog, demeton-S.
An in vivo selection approach utilizing organophosphate triesters as the sole
phosphorus source is discussed. The selection is based on co-expressing PTE with the
phosphodiesterase (GpdQ) from E. aerogenes. Substrate specificity of GpdQ was investigated using a small library of structurally diverse organophosphate diesters and
phosphonate monoesters. Results obtained from the in vivo growth assays showed that
GpdQ enabled E. coli to utilize various organophosphate diesters and phosphonate
monoesters as the sole phosphorus source. Cells co-expressing PTE and GpdQ were
tested for their ability to utilize two different organophosphate triesters as the sole
phosphorus source. The results from this experiment indicate that the growth rate is
limited by the phosphotriesterase activity.
Protein translocation to the periplasm was proven advantageous for in vivo
selection since it overcomes the limitation of intercellular delivery of the substrate of
interest. Translocation of PTE to the periplasmic space of E. coli was examined. Two
signal peptides were tested; the native leader peptide from Flavobacterium sp. and the
signal sequence of alkaline phosphatase. The results obtained from cellular fractionation
indicated that neither signal peptides were able to translocate PTE to the periplasm and
that the protein remained in the cytoplasm.
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Downs, Kerry. "The effect of selenium in the detoxification of the microcystin hepatotoxins." Thesis, University of Port Elizabeth, 2002. http://hdl.handle.net/10948/284.
Full textAbstract:
Blooms of cyanobacteria have been known to cause illness in humans and death in wild and domestic animals. One of the toxins produced by cyanobacteria is microcystin, which is a potent hepatotoxin. Microcystin is taken up by bile acid transporters in the intestine and transported into the liver. After exposure to acute doses of microcystin, severe haemorrhage has been observed along with apoptotic and necrotic hepatocytes. The cytoskeletal structure of the hepatocytes is disrupted and oxidative stress is induced. Selenium, a known anti-oxidant, has been shown to induce increased activity of glutathione peroxidase. Glutathione peroxidase removes peroxides from cells protecting them from oxidative stress. This study set out to determine if selenium could play a role in preventing the damage to mice livers due to microcystin toxin. The protective role of selenium was explored in three main studies: in the first study, the ability of selenium to increase the survival time of mice exposed to a lethal dose of toxin was determined. In the second study the mice were exposed to sublethal chronic doses of toxin over 30 days. The ability of selenium to minimise liver damage under these conditions was determined. The final study investigated the mechanism of the protective effect of selenium. The results of the first study suggested that selenium could extend survival time. In the second study the selenium supplemented mice showed a reduction in the extent of the increase in liver weight and a decrease in the amount of lipid peroxidation induced compared to the mice that received only toxin. The histology of the selenium supplemented mice also showed a decrease in the severity and amount of morphological changes in the liver. The third study indicated that the protection shown by selenium might be mediated by an increase in the glutathione peroxidase (GPX) activity in selenium supplemented mice. This increase in GPX activity would increase the removal of the lipid hydroperoxides and prevent the damage they would cause in the cell. A further result indicated an increase in glutathione S-transferase in only the toxin control mice when compared to the selenium supplemented and control mice. ii In conclusion selenium offers protection against microcystin but further studies need to be done to provide statistically valid results to clarify the level of protection.
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Butko, Emerald Claire. "Molecular mechanisms of cadmium detoxification and long distance transport in plants." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p1452831.
Full textAbstract:
Thesis (M.S.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed June 16, 2008). Available via ProQuest Digital Dissertations. Includes bibliographical references.