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1
Mettrick, Karla Adelle, et n/a. « Iron signalling pathways of Pseudomonas aeruginosa ». University of Otago. Department of Biochemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081128.143145.
Texte intégralRésumé :
The pathogenic bacterium Pseudomonas aeruginosa uses a variety of highly efficient chelating compounds (siderophores) to acquire sufficient iron for growth and virulence. These siderophores can either be endogenous or acquired from exogenous sources such as other bacteria or fungi. The transport of the endogenous siderophore pyoverdine activates a signal-transduction pathway that increases the synthesis of both the ferripyoverdine receptor protein (FpvA) and pyoverdine itself. Signal-transduction systems similar to this have three specific proteins involved: a receptor protein specific for one siderophore in the outer membrane, an anti-sigma factor in the cytoplasmic membrane and a sigma factor that activates gene expression in the cytoplasm.
The aim of the research presented in this thesis was to study the roles of the proteins in three different iron uptake and signalling pathways of P. aeruginosa. The substrates for each receptor protein were confirmed and the roles of each protein in the pathways were compared to the P. aeruginosa pyoverdine signalling pathway. The pyoverdine, desferrioxamine and ferrichrome transport pathways were studied to find whether interactions occur between them and if so, the mechanism(s) for that interaction. Furthermore, a technique for analysing gene expression of P. aeruginosa in sputum from the cystic fibrosis (CF) lung was developed. This technique was subsequently used to study the levels of iron responsive gene expression.
The receptor, sigma factor and anti-sigma factors were all found to have a role in the siderophore-induced expression of their own signalling pathway. The experimental data provide evidence of similarities in the roles of the sigma and receptor proteins within each pathway but different roles for the anti-sigma factors. In the absence of the cognate sigma factor or anti-sigma factor the expression of the desferrioxamine and ferrichrome receptors could not be upregulated. Without its cognate sigma factor fpvA could no longer be upregulated in the presence of pyoverdine. However, unlike the other systems, in the absence of the cognate anti-sigma factor, expression of fpvA was always observed. This is consistent with the anti-sigma factors being required for the activity of the cognate sigma factor in the ferrichrome and desferrioxamine signalling pathways but not the pyoverdine signalling pathway.
The siderophore signalling pathways were found to be upregulated in the presence of multiple siderophores, but generally to a lesser extent than if only one siderophore was available. This suggests that in the presence of multiple siderophores, P. aeruginosa uses all available iron chelators. The study of the role of the receptor, sigma factor and anti-sigma factor into these effects indicate sigma factor competition for RNA polymerase has a major role in the effects of multiple siderophores on pathways upregulation.
The gene expression studies of P. aeruginosa in sputum from the lungs of CF patients provided support for the hypothesis that the bacteria were growing in an environment where iron levels were sufficient for bacterial growth, but not storage of iron. The expression of the sigma factor gene pvdS that is required for pyoverdine synthesis was studied because expression of this gene is a sensitive reporter of intracellular iron levels. It was found to be downregulated in bacteria in sputum compared to laboratory grown bacteria. This result suggests the bacteria are inhabiting a more iron-replete environment within the lung. This finding advances our understanding of the CF lung environment and the impact it has on P. aeruginosa infection. This knowledge has medical implications for the development of novel therapies to combat P. aeruginosa infection.
2
Gomez, Perez Laura. « Alternative electron transfer pathways in iron-metabolising bacteria ». Thesis, University of East Anglia, 2018. https://ueaeprints.uea.ac.uk/69911/.
Texte intégralRésumé :
Ferric iron (Fe3+) can be used as a terminal electron acceptor by iron-reducing microorganisms to facilitate cellular respiration under anoxic conditions. In contrast, ferrous iron (Fe2+) is used as an electron donor by iron-oxidising microorganisms. The presence of dissimilatory pathways in iron metabolisers maintain bioavailable iron in the environment for other organisms. Redox reactions between gram-negative bacteria and iron usually occur through an extracellular electron transport (EET) pathway that allows electrons to cross from the inner membrane to the extracellular environment or vice versa. The study of the redox pathway has been thoroughly studied in the iron reducer Shewanella oneidensis, however, there is little information about the metabolic pathways used by other iron metabolisers. In this thesis, the environmental isolates Acinetobacter and Citrobacter have been described as novel iron reducing bacteria by using a combination of techniques including ferrozine assays, cytochrome identification methods and transcriptomic analysis. Results in this thesis suggest that Acinetobacter (previously described as a strict aerobic microorganism) in fact is capable of respiring using iron when oxygen is not available. In contrast, Citrobacter's iron reduction pathway seems to involve fermentative processes. These results point out that extracellular electron transport is not the only mechanism in dissimilatory iron metabolism. Moreover, these results suggest that anaerobic environments could be a reservoir for pathogenic strains of Acinetobacter, as it has been shown that this species do not require oxygen to survive. In addition to the study of new iron reducers, an overexpression system has been developed to study proteins involved in metal oxidation pathways without the need of culturing the notoriously slow-growing iron oxidising bacteria. The genes cyc2 and cyc2PV-1, which encode outer membranes cytochromes from Acidithiobacillus ferrooxidans and Mariprofundus ferrooxydans respectively, have been transformed into the iron reducer Shewanella oneidensis for protein expression optimization. The optimization of this process offers great possibility for the future study and applications of metal oxidation pathways.
3
Gabrielli, Natalia 1978. « Cross-talk between iron starvation and H202 signaling pathways in Schizosaccharomyces pombe ». Doctoral thesis, Universitat Pompeu Fabra, 2012. http://hdl.handle.net/10803/108037.
Texte intégralRésumé :
Hydrogen peroxide (H2O2), a reactive oxygen species (ROS), is involved in both oxidative stress and signaling cascades in a dosage dependent manner. Its toxicity is partially explained through reactivity with iron via the Fenton reaction. Iron, indispensible for many cellular processes, is thus tightly regulated to balance between need and toxicity. Using fission yeast as a model system, we explored the relationship between H2O2 and the iron starvation response system, specifically whether cross-talk allowed mutual regulation that could prevent synergistic toxicity of ROS via diminishing iron quantity. We screened around of 2700 haploid Schizosaccharomyces pombe deletion mutants in different oxidative stress agents, identifying new genes amongst which fep1, pcl1 and sib2 are involved in iron homeostasis. H2O2, unexpectedly, triggers transcriptional iron starvation response, including enhanced iron import and decreased iron consumption. Over-expression of several antioxidant proteins, in particular heme-containing catalase, causes strong iron consumption within the cell, triggering the iron starvation pathway accidentally. Furthermore, glutaredoxin Grx4 contains an iron-sulfur cluster (ISC) involved in iron sensing, underpinning regulation of the iron starvation response. Finally, we identify and characterize the frataxin homolog gene in S. pombe, pfh1. Deficiencies in frataxin provoke a neurodegenerative disease called Friedreich ataxia; the function of this protein remains controversial. We create ∆pfh1 strain as a new model system to elucidate the molecular events leading to the disease.El peróxido de hidrógeno (H2O2) es un agente oxidante que además de participar en cascadas de señalización produce toxicidad por daño oxidativo. Parte de su toxicidad se explica por su reactividad con hierro. Así, las concentraciones de hierro en el interior celular han de estar estrictamente reguladas. Usando la levadura de fisión, Schizosaccharomyces pombe, como un sistema modelo, estudiamos las relaciones entre H2O2 y el sistema de respuesta a déficit de hierro. Genes como fep1, pcl1 y sib2, importantes para mantener su homeostasis, fueron encontrados en un análisis de 2700 mutantes de S. pombe, tras tratamiento con diferentes agentes oxidantes. Inesperadamente encontramos que H2O2 desencadena una respuesta transcripcional de déficit de hierro, incluyendo aumento de su entrada y disminución de su consumo. Ésta es una respuesta accidental debido a la sobreexpresión de proteínas como catalasa, una hemoproteína, consumidoras masivas de hierro. Encontramos además que la glutaredoxina Grx4 contiene un clúster de hierro-azufre implicado en sensar hierro. Finalmente, identificamos, caracterizamos y delecionamos el homólogo de frataxina en S. pombe, pfh1. Deficiencias en frataxina provocan ataxia de Friedreich. Los mecanismos por los cuales se desencadena esta enfermedad están todavía por elucidar, pero S. pombe es un buen sistema modelo para su estudio.
4
Birmingham, Ryan W. « TRANSPORT PATHWAYS OF SHELF SOURCE MICRONUTRIENTS TO THE SOUTHERN OCEAN ». Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53728.
Texte intégralRésumé :
We use a numerical ocean model to evaluate the hypothesis that the continental shelves are significant sources of dissolved iron to the Southern Ocean. We simulate the distribution of passive tracers released from the 18 different continental shelf regions of the extra-tropical southern hemisphere oceans using an offline, eddy-permitting transport model. The circulation fields are taken from the Southern Ocean State Estimate, and we only simulate the transport of inert tracers focusing on the physical transport pathways. The resulting tracer fields are then compared with the remotely sensed ocean color data, revealing a remarkable resemblance between the distributions of shelf-source tracers and the climatological surface chlorophyll-a concentrations. We further analyze the spatial pattern of simulated tracer fields in relation to satellite ocean color data. Dynamic ocean features such as the Southern Ocean fronts and coastal waters are reflected in both the tracer model and the observed biological productivity. Our results support the overall importance of continental shelves as a potential source region for dissolved iron. The relative importance of different shelf regions is found to vary significantly depending on the relevant circulation features.
5
Neate, Peter Gregory Nigel. « Pathways to sustainable catalysis : from novel catalysts to mechanistic understanding ». Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25441.
Texte intégralRésumé :
Catalysis allows for the controlled formation of new bonds, whilst reducing both time and energy expenditure in the process. Catalysis has traditionally been the realm of precious metals, which have been used to carry out a bewildering array of reactions. However, there is an ever-increasing drive for the development of catalytic methodology employing sustainable and environmentally benign catalysts. Two such candidates are organocatalysis, omitting the need for metals where possible, or the use of iron catalysis. Two key areas to the advancement of the of field catalysis are the identification and development of new catalysts as well as an understanding of the mechanisms of established catalytic processes. Novel catalysts can provide many benefits such as enhanced or even novel reactivity, access to new classes of substrates or simply be more readily accessible compared with previously developed catalysts. To this end, the first example of Lewis-base-catalysis using the recently developed cyclopropenimine motif is reported. This was exploited in the trifluoromethylation of aldehydes and ketones using the Rupert-Prakash reagent (Scheme A-1). Scheme A-1 Cyclopropenimine-catalysed trifluoromethylation of aldehydes and ketones Developing an understanding of catalytic methodologies in the terms of their mechanism and active species is also a key area in catalysis. Insight into these can direct the expansion of these systems in terms of both more effective catalysts and tailoring reaction conditions as examples. The iron-catalysed hydromagnesiation of styrene derivatives was studied in detail. This culminated in a proposed mechanism, involving a novel hydride transfer process (Scheme A-2). Studies were carried out using a combination of kinetic analysis and in situ Mössbauer spectroscopy, as well as successfully isolating and studying the reactivity of a catalytically-relevant, formal iron(0)-species.
6
Gonska, Nathalie. « Proton pathways in energy conversion : K-pathway analogs in O2- and NO-reductases ». Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147267.
Texte intégralRésumé :
Oxygen and nitric oxide reductases are enzymes found in aerobic and anaerobic respiration, respectively. Both enzyme groups belong to the superfamily of Heme-Copper Oxidases, which is further divided into several subgroups: oxygen-reducing enzymes into A-, B- and C-type and nitric oxide reductases into qNORs and cNORs. Oxygen reducing enzymes use the energy released from oxygen reduction to take up electrons and protons from different sides of the membrane. Additionally, protons are pumped. These processes produce a membrane potential, which is used by the ATP-synthase to produce ATP, the universal energy currency of the cell. Nitric oxide reductases are not known to conserve the energy from nitric oxide reduction, although the reaction is highly exergonic. Here, the detailed mechanism of a B-type oxidase is studied with special interest in an element involved in proton pumping (proton loading site, PLS). The study supports the hypothesis that the PLS is protonated in one and deprotonated in the consecutive step of the oxidative catalytic cycle, and that a proton is pumped during the final oxidation phase. It further strengthens the previous suggestion that the PLS is a cluster instead of a single residue or heme propionate. Additionally, it is proposed that the residue Asp372, which is in vicinity of the heme a3 propionates previously suggested as PLS, is part of this cluster. In another study, we show that the Glu15II at the entry of the proton pathway in the B-type oxidase is the only crucial residue for proton uptake, while Tyr248 is or is close to the internal proton donor responsible for coupling proton pumping to oxygen reduction. The thesis also includes studies on the mechanism and electrogenicity of qNOR. We show that there is a difference in the proton-uptake reaction between qNOR and the non-electrogenic homolog cNOR, hinting at a different reaction mechanism. Further, studies on a qNOR from a different host showed that qNOR is indeed electrogenic. This surprising result opens up new discussions on the evolution of oxygen and nitric oxide reductases, and about how energy conservation can be achieved.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.
7
Kirby, Shane Douglas. « Ferric binding proteins, identification and role in the iron acquisition pathways of the Pasteurellaceae and Neisseriaceae ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0008/NQ49508.pdf.
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8
Diekrup, David. « Depositional Pathways and the Post-Depositional History of the Neoarchean Algoma-Type BIF in Temagami, ON ». Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39875.
Texte intégralRésumé :
Algoma-type banded iron formation is common in Neoarchean greenstone belts, and many of its distinctive features such as the banding of iron-rich and silica-rich material and deposition in volcanic terranes have been ascribed to their deposition related to volcanic-hydrothermal activity and cyclic variability in depositional pathways. The work presented in this thesis tests these assumptions and presents a model for the deposition and post-depositional processes now represented by the petrography and geochemistry of a 2.73 Ga type-locality of Algoma-type BIF in Temagami, ON. Adsorption of components onto the surface of Fe-oxyhydroxides forming in the anoxic Neoarchean water column is the most likely process capable of transferring silica, as well as trace quantities of transition metals, rare earth elements, Ge, P, U and other components to the sediment. The petrogenesis of the Temagami BIF lithologies suggests ongoing recrystallization processes and volume loss reactions leading to the formation of magnetite layers, while jasper is identified as the most pristine lithology best representative of the initially deposited Fe-oxyhydroxide-silica gel. Recrystallization and volume loss reactions are controlled by the ongoing dewatering during compaction and diagenesis, without the influence of external hydrothermal or metamorphic fluids. When corrected for the volume loss and small amounts of clastic contamination, little residual variability can be observed in the composition of jasper and magnetite layers, indicative of an originally homogenous primary precipitate instead of sorted and layered material deposited on the seafloor. This model is in stark contrast to previous interpretations of seasonal variability in biologic activity, cyclical seasonal or hydrothermal events responsible for primary layering in BIF. Instead, very little direct input of hydrothermal components is recorded in the chemistry of the Temagami BIF, and elements abundant in high-temperature hydrothermal fluids such as sulfur are instead sourced from atmospheric sources and deposited by bacterial pathways. Lack of primary chemical variability and non-hydrothermally sourced components captured in BIF argue against a genetic link to local hydrothermal venting, but rather an open ocean depositional setting. As such, the Temagami BIF does not represent a marker horizon related to local or regional hydrothermal venting and potential formation of associated massive sulfide deposits but reflects processes and the chemistry of the open Neoarchean ocean.
9
Parkin, David. « Decomposition pathways of an S-nitroso sugar, S-nitroso dithiols and the reaction of S-nitrosothiols with iron complexes ». Thesis, Durham University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251214.
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10
Ruegg, Evonne Teresa Nicole. « Investigating the porphyrias through analysis of biochemical pathways ». Thesis, University of Canterbury. Biochemistry, 2014. http://hdl.handle.net/10092/10257.
Texte intégralRésumé :
ABSTRACT
The porphyrias are a diverse group of metabolic disorders arising from diminished
activity of enzymes in the heme biosynthetic pathway. They can present with acute
neurovisceral symptoms, cutaneous symptoms, or both. The complexity of these
disorders is demonstrated by the fact that some acute porphyria patients with the
underlying genetic defect(s) are latent and asymptomatic while others present with
severe symptoms. This indicates that there is at least one other risk factor required in
addition to the genetic defect for symptom manifestation. A systematic review of the
heme biosynthetic pathway highlighted the involvement of a number of micronutrient
cofactors. An exhaustive review of the medical literature uncovered numerous reports
of micronutrient deficiencies in the porphyrias as well as successful case reports of
treatments with micronutrients. Many micronutrient deficiencies present with
symptoms similar to those in porphyria, in particular vitamin B6. It is hypothesized
that a vitamin B6 deficiency and related micronutrient deficiencies may play a major
role in the pathogenesis of the acute porphyrias. In order to further investigate the
porphyrias, a computational model of the heme biosynthetic pathway was developed
based on kinetic parameters derived from a careful analysis of the literature. This
model demonstrated aspects of normal heme biosynthesis and illustrated some of the
disordered biochemistry of acute intermittent porphyria (AIP). The testing of this
model highlighted the modifications necessary to develop a more comprehensive
model with the potential to investigated hypotheses of the disordered biochemistry of
the porphyrias as well as the discovery of new methods of treatment and symptom
control. It is concluded that vitamin B6 deficiency might be the risk factor necessary
in conjunction with the genetic defect to trigger porphyria symptoms.
11
Albarouki, Emad Verfasser], Holger B. [Akademischer Betreuer] Deising, Nicolaus von [Akademischer Betreuer] [Wirén et Uwe [Akademischer Betreuer] Conrath. « High affinity iron uptake pathways are indispensable for virulence of the maize pathogen Colletotrichum graminicola / Emad Albarouki. Betreuer : Holger B. Deising ; Nicolaus, von Wirén ; Uwe Conrath ». Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2013. http://d-nb.info/1046312758/34.
Texte intégral
12
Bilton, Paul. « Investigations on an iron transport pathway ». Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/10813.
Texte intégralRésumé :
In this study, an iron-uptake ATP-binding cassette (ABC) transporter, FbpABC, from the Gram-negative human pathogen Neisseria gonorrhoeae has been investigated. The periplasmic binding protein, FbpA, has been mutated to facilitate investigation of complex formation with the two other components of the transporter, FbpB and FbpC. FbpBC was PCR-amplified from N. gonorrhoeae genomic DNA, co-expressed in E. coli cells, and its purification optimised. FbpA residues R48 and V272 have been mutated to allow covalent modification with a linker molecule to allow attachment to a sensor surface and used as bait to pull-down the purified FbpBC complex, using surface plasmon resonance. This is the first report of the purification of FbpB, and the first demonstration of FbpABC association in vitro. A radioactive iron-uptake assay revealed that E. coli cells expressing the N. gonorrhoeae FbpABC operon take-up more iron than control cells. The FbpC gene was cloned using recombinant DNA technology and over-expressed in E. coli to perform biochemical characterisation of the enzyme. The expression and purification of selenomethionine-labelled FbpC allowed determination of the X-ray crystal structure of FbpC at Imperial College, London. Crystals of FbpC diffracted to a resolution of 2.7 Å, and the structure is currently being solved. Metal-free apo-FbpA was reloaded with ruthenium(III) and osmium(III) salts and characterised by various techniques. Chromatography and ICP-OES analysis of Ru- and Os-FbpA showed that there were two main species formed with each metal. Both species have four metal atoms bound and differ in that one species may be capped by a single phosphate anion, and the other by two phosphate anions. EXAFS was also performed on the ruthenium bound species.
13
Geiser, Dawn Lynn. « Elucidating the Role of Ferritin in the Iron Metabolic Pathway of Aedes aegypti ». Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/195863.
Texte intégralRésumé :
Female mosquitoes of the species, Aedes aegypti (yellow fever mosquito, Diptera), blood feed for oogenesis. Therefore, mosquitoes are exposed to high iron loads and possibly blood-borne pathogens. We are interested in studying iron metabolism in A. aegypti to find methods for controlling mosquito populations, and thereby reduce human exposure to these pathogens. First, we found that the expression of the Aedes ferritin light chain homologue (LCH) is up-regulated by blood feeding. Ferritin LCH and heavy chain homologue (HCH) genes are closely clustered together and both mRNA transcripts increase with iron and oxidative stress (H2O2 and hemin). Second, we show A. aegypti larval cells synthesize and secrete ferritin in response to iron. Cytoplasmic ferritin is maximal at low levels of iron, consists of a specific subunit composition and reflects cytoplasmic iron levels. Secreted ferritin increases in linear relationship to increasing iron dose and is composed of different subunits than cytoplasmic ferritin. HCH and LCH transcripts increase with increasing cytoplasmic iron suggesting transcriptional control of ferritin synthesis. We previously reported that the mosquito HCH mRNA has an iron responsive element (IRE), but LCH mRNA does not have a canonical IRE. We show that iron regulatory protein 1 (IRP1)/IRE binding activity declines in response to increasing cytoplasmic iron levels. These data would indicate that HCH synthesis is controlled at transcription and translation. Third, we report that A. aegypti larval cell cytoplasmic iron concentration does not change temporally with iron treatment. However, membrane iron levels increase with iron over time. Iron temporally up-regulates both HCH and LCH mRNA. Ferritin secretion increases with time in response to iron and reflects that most of the intracellular ferritin is found in the membrane fraction. Membrane ferritin has the same subunit composition as cytoplasmic ferritin. Finally, membrane ferritin is found in both non-iron and iron-treated cells. This suggests a mechanism to store iron from a blood meal in membrane ferritin. These results indicate Aedes ferritin could act as an antioxidant and holoferritin secretion is likely the mechanism whereby mosquito cells protect against iron overload and, thus reduce the intracellular potential for iron-mediated oxidative stress during blood feeding.
14
Strickland, Natalie Judith. « In silico and functional analyses of the iron metabolism pathway ». Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/79871.
Texte intégralRésumé :
Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Iron is an essential micronutrient that is an absolute requirement for correct cellular function in all eukaryotic organisms. However, ferrous iron has the ability to catalyze the formation of potentially toxic reactive oxygen species and regulation of iron metabolism is therefore of critical importance. Currently, there is little known about the co-ordinated regulation of the plethora of genes coding for proteins involved in this biochemical pathway, with the exception of the well characterized post-transcriptional IRE/IRP system. Regulation of gene expression in eukaryotic organisms is a highly intricate process. Transcriptional regulation is the first step and is controlled by the presence of specific cis-regulatory regions (cis-motifs), residing within the promoter region of genes, and the functional interactions between the products of specific regulatory genes (transcription factors) and these cismotifs. A combinatorial bioinformatic and functional approach was designed and utilized in this study for the analysis of the promoter architecture of genes of the iron metabolic pathway. The upstream non-coding region (~2 kb) of 18 genes (ACO1, CP, CYBRD1, FTH1, FTL, HAMP, HEPH, HFE, HFE2, HMOX1, IREB2, LTF, SLC11A2, SLC40A1, STEAP3, TF, TFRC, TFR2), known to be involved in the iron metabolism pathway, was subjected to computational analyses to identify regions of conserved nucleotide identity utilizing specific software tools. A subset of nine (CYBRD1, FTH1, HAMP, HFE, HFE2, HMOX1, IREB2, LTF, TFRC) of the genes were found to contain a genomic region that demonstrated over 75% sequence identity between the genes of interest. This conserved region (CR) is approximately 140 bp in size and was identified in each of the promoters of the nine genes. The CR was subjected to further detailed examination with comparative algorithms from different software for motif detection. Four specific cis-motifs were discovered within the CR, which were found to be in the same genomic position and orientation in each of the CR-containing genes. In silico prediction of putative transcription factor binding sites revealed the presence of numerous binding motifs of interest that could credibly be associated with a biological function in this pathway, including a novel MTF-1 binding site in five of the genes of interest. Validation of the bioinformatic predictions was performed in order to fully assess the relevance of the results in an in vitro setting. Luciferase reporter constructs for the nine CRcontaining genes were designed containing: 1) the 2 kb promoter, 2) a 1.86 kb promoter with the CR removed and 3) the 140 bp CR element. The expression levels of these three reporter gene constructs were monitored with a dual-luciferase reporter assay under standard culture conditions and simulated iron overload conditions in two different mammalian cell lines. Results of the luciferase assays indicate that the CR promoter constructs displayed statistically significant variation in expression values when compared to the untreated control constructs. Further, the CR appears to mediate transcriptional regulatory effects via an iron-independent mechanism. It is therefore apparent that the bioinformatic predictions were shown to be functionally relevant in this study and warrant further investigation. Results of these experiments represent a unique and comprehensive overview of novel transcriptional control elements of the iron metabolic pathway. The findings of this study strengthen the hypothesis that genes with similar promoter architecture, and involved in a common pathway, may be co-regulated. In addition, the combinatorial strategy employed in this study has applications in alternate pathways, and could serve as a refined approach for the prediction and study of regulatory targets in non-coding genomic DNA.
AFRIKAANSE OPSOMMING: Yster is ‘n noodsaaklike mikrovoedingstof wat ‘n vereiste is vir korrekte sellulêre funksie in alle eukariotiese organismes. Yster (II) of Fe2+ het egter die vermoë om die vorming van potensiële toksies reaktiewe suurstof spesies te kataliseer en dus is die regulasie van die yster metaboliese padweg van kardinale belang. Tans is daar beperkte inligting oor koördineerde regulasie van die gene, en dus proteïene waarvoor dit kodeer, in hierdie padweg. ‘n Uitsondering is die goed gekarakteriseerde na-transkripsionele “IRE/IRP” sisteem. Regulasie van geenuitdrukking in eukariotiese organismes is ‘n ingewikkelde proses. Transkripsionele regulasie is die eerste stap en word beheer deur die teenwoordigheid van spesefieke cis-regulatoriese elemente (cis-motiewe), geleë in die promotor area van gene, en die funksionele interaksies wat plaasvind tussen die produkte van spesifieke regulatoriese faktore (of transkripsie faktore) en hierdie cis-motiewe. ‘n Gekombineerde bioinformatiese en funksionele benadering was ontwerp en daarna gebruik in dié studie vir die analise van die promotor argitektuur van gene wat ‘n rol speel in die yster metaboliese padweg. Die stroomop nie-koderende streek (~2 kb) van 18 gene (ACO1, CP, CYBRD1, FTH1, FTL, HAMP, HEPH, HFE, HFE2, HMOX1, IREB2, LTF, SCL11A2, SLC40A1, STEAP3, TF, TFRC, TFR2), bekend vir hul betrokkenheid in die yster metabolisme padweg, was bloodgestel aan bioinformatiese analises om die streke van konservering te identifiseer met die hulp van spesifieke sagteware. Slegs nege (CYBRD1, FTH1, HAMP, HFE, HFE2, HMOX1, IREB2, LTF, TFRC) van die geanaliseerde gene het ‘n genomiese area bevat wat meer as 75% konservering getoon het. Hierdie gekonserveerde area (GA) is 140 bp in lengte en is geïdentifiseer in elk van die promotors van die nege gene. Die GA was verder bloodgestel aan analises, met die hulp van spesifieke sgateware, wat gebruik maak van vergelykende algoritmes vir motief karakterisering. Vier cis-motiewe is identifiseer en kom voor in dieselfde volgorde en oriëntasie in elk van die gene. In silico voorspelling van moontlike transkripsie faktor bindingsplekke het getoon dat daar talle bindingsmotiewe van belang teenwoordig is en dié motiewe kan gekoppel word aan biologiese funksies in hierdie padweg, insluitend ‘n nuwe MTF-1 bindingsplek in vyf van die gene van belang. Die bioinformatiese analises is verder gevalideer om die relevansie van die resultate in ‘n in vitro sisteem ten volle te assesseer. Luciferase rapporteerder konstrukte is vir die nege gene ontwerp wat die volgende bevat: 1) die 2 kb promotor, 2) ‘n 1.86 kb promotor met die GA verwyder en 3) die 140 bp GA element. Die vlakke van uitdrukking van hierdie drie rapporteerder konstrukte was genormaliseer met ‘n dubbele-luciferase rapporteerder assay onder standaard kultuur kondisies en gesimuleerde ysteroorlading kondisies in twee verskillende soogdier sellyne. Resultate van die luciferase assays dui aan dat die GA promotor konstrukte statisties betekenisvolle variasie toon in vergelyking met die onbehandelde kontrole konstrukte. Verder, die GA blyk om transkipsionele regulatoriese effekte te medieer via ‘n yster-onafhanklike meganisme. Dit blyk duidelik dat die bioinformatiese voorspellings ook funksioneel getoon kon word en was dus relevant in dié studie en regverdig verdere ondersoek. Hierdie eksperimentele ontwerp verteenwoordig ‘n unieke en omvattende oorsig van nuwe transkripsionele beheer elemente wat voorkom in die yster metaboliese padweg. Die resultate van dié studie versterk die hipotese dat gene met soortgelyke promotor argitektuur en wat betrokke is in ‘n gemene padweg saam gereguleer kan word. Daarbenewens, die gekombineerde strategie wat in hierdie studie gebruik is het toepassings in alternatiewe metaboliese paaie, en kan dien as ‘n verfynde benadering vir die voorspelling en studie van die regulerende teikens in nie-koderende genomiese DNS.
National Research Foundation (Thuthuka)
Stellenbosch University
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Tandy, Sarah Rosamunde. « Characterisation of the iron uptake pathway in human intestinal Caco-2 cells ». Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393138.
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Farooq, Muhammad Ali. « Iron Citrate Toxicity Causes aco1Δ-induced mtDNA Loss in Saccharomyces cerevisiae ». ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/honors_theses/34.
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Aconitase is an enzyme of the Krebs cycle that catalyzes the isomerization of citrate to isocitrate. In addition to its enzymatic activity, Aco1 has been reported to bind to mitochondrial DNA (mtDNA) and mediate its maintenance in the budding yeast S. cerevisiae. In the absence of Aco1, cells rapidly lose mtDNA and become “petite” mutants. The purpose of this study is to uncover the mechanism behind mtDNA loss due to an aco1 deletion mutation. We found that an aco1 mutation activates the mitochondria-to-nucleus retrograde (RTG) signaling pathway, resulting in increased expression of citrate synthases (CIT) through the activation of two transcription factors Rtg1 and Rtg3. Increased activity of CIT leads to increased iron accumulation in cells, which is known to raise reactive oxygen species (ROS). By deleting RTG1, RTG3, genes encoding citrate synthases, orMRS3 and MRS4, encoding two irontransporters in the mitochondrial inner membranes, mtDNA loss can be prevented in aco1 deletion mutant cells. We further show that the loss of SOD1, encoding the cytoplasmic isoform of superoxide dismutase, but not SOD2, encoding the mitochondrial isoform of superoxide dismutase, prevents mtDNA loss in aco1 mutant cells. Altogether, our data suggest that mtDNA loss in aco1 mutant cells is caused by the activation of the RTG pathway and subsequent iron accumulation and toxicity in the mitochondria.
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Tang, Wai-ho Jack. « Polyol pathway contributes to iron-induced oxidative damage in ischemia-reperfused rat hearts ». Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558022.
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鄧偉豪 et Wai-ho Jack Tang. « Polyol pathway contributes to iron-induced oxidative damage in ischemia-reperfused rat hearts ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558022.
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Maxwell, Deborah Bolin. « Iron Molybdenum Cofactor : Catalyst in Dihydrogen Production and NifEN's Role in the FeMo-co Biosynthetic Pathway ». Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5432.
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Humankind's tremendous industrial and technological progress over the last two centuries has been driven by the natural abundance and availability of fossil fuels. As those reserves deplete, the prudent course of action would be to develop other readily available fuel sources. Some research efforts using biomolecules involve the hydrogenases and nitrogenases with the goal of evolving dihydrogen. At the nitrogenase active site, the iron-molybdenum cofactor (FeMo-co) catalyzes the reduction of dinitrogen and protons to form ammonia and dihydrogen. Toward the goal of producing dihydrogen passively as an alternative fuel, a novel advanced material has been developed. CdSe nanoparticles complexed with FeMo-co, in both aqueous and organic solvent systems showed complex formation. When the system was interrogated by EPR spectroscopy, evidence of electron transfer was observed. The CdSe-MSA?NafY?FeMo-co system when illuminated with visible light evolved dihydrogen consistently in four different experimental sets under the same reaction conditions. NifEN protein plays an important role in the biosynthesis of FeMo-co in addition to the involvement of NifU, NifS, NifB, NifX, NifH and NafY. After NifB synthesizes a FeMo-co precursor, 6-Fe NifB-co, NifEN further incorporates additional Fe, S, Mo, and (R)-homocitrate to complete the synthesis of FeMo-co. Molybdenum is provided to NifEN as its oxoanion, Mo(VI)O42-; however, in FeMo-co molybdenum is in the oxidation state of Mo(IV). EPR spectroscopic investigation of NifEN turnover samples showed a signal at g = 2.00 that was dependent on molybdate concentration. Power and temperature profiles gave evidence that the g = 2.00 EPR signal was distinct from the Fe-S clusters in NifEN. The species observed at g = 2.00 was assigned to the reduction of Mo(VI) to Mo(V). How to utilize the effectiveness of FeMo-co and complex it to photoactive materials for the purpose of evolving dihyrogen upon illumination, thus providing a sustainable alternative energy source is one subject of this dissertation. A related subject is to gain an understanding of the biosynthetic pathway of FeMo-co by investigation of NifEN turnover experiments. This understanding should contribute towards the development of improved catalysts for meeting future energy demands.Ph.D.
Doctorate
Chemistry
Sciences
Chemistry
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Wilkinson, Nicole. « Regulation of murine erythropoiesis and metabolism by the iron regulatory protein1/hypoxia inducible factor 2 alpha pathway ». Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121348.
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Iron is an essential nutrient for many biochemical functions within the body. However, its flexible redox potential is a "double edged" sword that makes it both essential for life but also renders it potentially toxic. As iron excretion is limited, iron absorption is tightly regulated. Systemic iron homeostasis is controlled through the hepatic hormone hepcidin. Iron and other stimuli control hepcidin transcription. When produced hepcidin circulates through out the body and binds to the cellular iron exporter ferroportin (FPN1) expressed on duodenal enterocytes, macrophages, and hepatocytes causing FPN1's subsequent internalization and degradation. Ergo hepcidin function to control the efflux of iron from duodenal enterocytes, hepatocytes, and macrophages in to the blood stream. Cellular iron metabolism is controlled through iron regulatory proteins 1 and 2 (IRP1 and IRP2). IRPs repress or stabilize translation of mRNAs, encoding proteins of iron uptake, utilization, and storage, which contain iron responsive elements (IRESs) within their untranslated regions.This work examines in vivo regulation of hypoxia inducible factor 2 alpha (HIF2α) by IRP1. HIF2α is a transcription factor involved in the transcription of many genes involved in the body's response to hypoxic stress including, most notable, erythropoietin the hormone responsible for erythropoiesis. In chapter II it is hypothesized that translational de-repression of HIF2α mRNA by the absence of IRP1 leads to polycythemia through the induction of erythropoietin. Here it is demonstrated that IRP1 but not IRP2 is involved in the translational de-repression of HIF2α which subsequently leads to an accumulation of HIF2α protein in the kidneys of IRP1-/- mice. It is further demonstrated that the accumulation of HIF2α protein in the kidneys leads to an increase serum erythropoietin and subsequent polycythemia in IRP1-/- mice. In chapter III it is hypothesized that IRP1-/- mice will demonstrate a metabolic phenotype. Here it is demonstrated that IRP1-/- mice exhibit hypoglycaemia. Through the global knock out of IRP1 couple with the hepatocyte specific deletion of HIF2α we observe a partial rescue of the hypoglycaemic phenotype seen in IRP1-/- mice.Le fer est un nutriment essentiel à de nombreuses fonctions biochimiques du corps. Cependant, son potentiel redox flexible est une épée à double tranchant qui rend le fer à la fois essentiel à la vie mais aussi potentiellement toxique. Alors que l'excrétion du fer est limitée, son absorption est amplement régulée. L'homéostasie systémique du fer est contrôlée par l'hormone hépatique hepcidine. Le fer et d'autres stimuli contrôlent la transcription de l'hepcidine. Une fois produite, l'hepcidine circule dans l'organisme et se fixe à la ferroportine, exporteur cellulaire du fer, qui est exprimé à la surface des entérocytes duodénaux, des macrophages et des hépatocytes causant son internalisation et ensuite sa dégradation. En conséquence, l'hepcidine fonctionne pour contrôler l'efflux du fer de ces cellules dans la circulation sanguine. Le métabolisme cellulaire du fer est contrôlé par les protéines de régulation du fer 1 et 2 (IRP1 et IRP2). Les IRP répriment ou stabilisent la traduction d'ARNm codant les protéines responsables de la capture, l'utilisation, et le stockage du fer, lesquels contiennent des éléments de réponse au fer (IRE) dans leurs régions non traduites. Ce travail examine la régulation in vivo du facteur inductible de l'hypoxie 2 alpha (HIF2α) par IRP1. HIF2a est un facteur de transcription impliqué dans la transcription de nombreux gènes incluant, le plus notable, l'érythropoïétine l'hormone responsable de l'érythropoïèse. Dans le chapitre II, l'hypothèse est que la dérépression traductionnelle de l'ARNm de HIF2α par l'absence de IRP1 conduit à la polyglobulie à travers l'induction de l'érythropoïétine. Ici il est démontré que IRP1, et non IRP2, est impliqué dans la dérépression traductionnelle de HIF2α qui mène à l'accumulation de la protéine HIF2α dans les reins des souris IRP1-/-, aboutissant à l'augmentation de l'érythropoïétine dans le sérum et conséquemment à la polyglobulie dans ces souris. Dans le chapitre III, L'hypothèse est que les souris IRP1-/- exhibent des anomalies métaboliques. Ici nous établissons que les souris IRP1-/- présentent un phénotype d'hypoglycémie. Il est ensuite observé que ce phénotype est partiellement secouru à travers l'élimination globale de IRP1 couplée à la délétion spécifique de HIF2α dans les hépatocytes.
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Hai, Jun. « Antibiotics and nanoparticles targeting via the iron acquisition pathway : The case of cells infected or not Chlamydia trachomatis ». Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC165.
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La faible pénétration des antibiotiques ou d'autres drogues dans lés cellules rend certaines infections ou d'autres maladies telles que les cancers difficiles à traiter. La stratégie d'un cheval de Troie pour acheminer les médicaments directement vers sa cible dans les cellules est parmi les voies possibles pouvant améliorer l'efficacité thérapeutique. Dans ce travail, nous nous sommes intéressés à Chlamydia Trachomatis pour l'antibiothérapie et aux cellules cancéreuses en utilisant des nanoparticules magnétiques à visée thérapeutique. Dans les deux cas, la transferrine, la protéine majeure impliquée dans l'acquisition de fer, a été utilisée comme cheval de Troie pour cibler les cellules avec des antibiotiques et/ou des nanoparticules magnétiques. Dans le premier cas, l'amoxicilline a été greffée sur la transferrine et le système Amox¬transferrine a été testé in vitro et sur des cellules HeLa infectées par Chlamydia. Il est 10 fois plus efficace que l'amoxicilline seule, ce qui peut éventuellement impliquer la transferrine dans le système d'acquisition du fer de Chlamydia. Dans le second cas une série de trois nanomatériaux hybrides constitués de nanoparticules superparamagnétiques de maghémite portant des transferrines ont été synthétisés et caractérisés. Les 3 nanomatériaux sont internalisés dans les cellules HeLa et Lymphocyte par endocytose du récepteur de la transferrine. Ces résultats peuvent ouvrir de nombreuses possibilités dans le domaine de l'antibiothérapie pour les systèmes type transferrine-antibiotique ainsi que dans l'imagerie IRM, l'hyperthermie magnétique et la chimiothérapie pour les nanohybridesThe poor intracellular penetration of the most commonly used antibiotics or other drugs renders intracellular infections and/or other diseases, such as cancers difficult to treat. The strategy of a Trojan horse delivering the drug into the required spot is among the interesting routes exploited to overturn this therapeutic deficiency. Among these two are of interest, the first concerns Chlamydia trachomatis response to antibiotherapy and the second concerns the delivery of therapeutic nanoparticles to specific cells such as cancerous. In this work, transferrin, the major protein implied in the acquisition of iron, was used as a Trojan horse to deliver antibiotics and/or nanohybrid constructs. In the first case amoxicillin was grafted onto transferrin and the system tested in vitro and in HeLa cells infected with Chlamydia. It showed to be at least ten times more efficient that amoxicillin which may implicate transferrin in iron acquisition by Chlamydia. In the second case, a series of three nanoconstructs of superparamagnetic maghemite nanoparticles canying transferrin were synthesized and characterized. The three nanoconstructs are internalized in HeLa cells by the transferrin-receptor mediated endocytosis. These promising results are of interest in antibiotherapy for the antibiotic-transferrin constructs as well as in imagery, magnetic hyperthermia and chemotherapy for the nanoconstructs
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Wahedi, Mastura, Aaron M. Wortham, Mark D. Kleven, Ningning Zhao, Shall Jue, Caroline A. Enns et An-Sheng Zhang. « Matriptase-2 suppresses hepcidin expression by cleaving multiple components of the hepcidin induction pathway ». AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2017. http://hdl.handle.net/10150/626185.
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Systemic iron homeostasis is maintained by regulation of iron absorption in the duodenum, iron recycling from erythrocytes, and iron mobilization from the liver and is controlled by the hepatic hormone hepcidin. Hepcidin expression is induced via the bone morphogenetic protein (BMP) signaling pathway that preferentially uses two type I (ALK2 and ALK3) and two type II (ActRIIA and BMPR2) BMP receptors. Hemojuvelin (HJV), HFE, and transferrin receptor-2 (TfR2) facilitate this process presumably by forming a plasma membrane complex with BMP receptors. Matriptase-2 (MT2) is a protease and key suppressor of hepatic hepcidin expression and cleaves HJV. Previous studies have therefore suggested that MT2 exerts its inhibitory effect by inactivating HJV. Here, we report that MT2 suppresses hepcidin expression independently of HJV. In Hjv(-/-) mice, increased expression of exogenous MT2 in the liver significantly reduced hepcidin expression similarly as observed in wild-type mice. Exogenous MT2 could fully correct abnormally high hepcidin expression and iron deficiency in MT2(-/-) mice. In contrast to MT2, increased Hjv expression caused no significant changes in wild-type mice, suggesting that Hjv is not a limiting factor for hepcidin expression. Further studies revealed that MT2 cleaves ALK2, ALK3, ActRIIA, Bmpr2, Hfe, and, to a lesser extent, Hjv and Tfr2. MT2-mediated Tfr2 cleavage was also observed in HepG2 cells endogenously expressing MT2 and TfR2. Moreover, iron-loaded transferrin blocked MT2-mediated Tfr2 cleavage, providing further insights into the mechanism of Tfr2's regulation by transferrin. Together, these observations indicate that MT2 suppresses hepcidin expression by cleaving multiple components of the hepcidin induction pathway.
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Wan, Moli [Verfasser], et Stefan [Akademischer Betreuer] Peiffer. « Interaction between ferric hydroxides and dissolved sulfide in anoxic aquifers : Pathway and kinetics of iron and sulfur products formation / Moli Wan. Betreuer : Stefan Peiffer ». Bayreuth : Universität Bayreuth, 2015. http://d-nb.info/1076319505/34.
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Matsubayashi, Keiko. « Contribution of cytochrome P450 3A pathway to bromocriptine metabolism and effects of ferrous iron and hypoxia-reoxygenation on its elimination in the perfused rat liver ». Kyoto University, 1997. http://hdl.handle.net/2433/202219.
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Ballaminut, Nara. « Caracterização do processo de descoloração de corante reativo diazo por basidiomicetos tropicais ». Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-23032017-164405/.
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Corantes reativos têxteis podem ser degradados por basidiomicetos, por meio de enzimas oxidativas e hidrolíticas, e compostos de baixa massa molar. Foi avaliada a descoloração de CI Reactive Blue 222 por Peniophora cinerea, Pleurotus ostreatus e Trametes villosa, selecionando condições ótimas para o processo e diferentes vias metabólicas foram observadas. A degradação foi confirmada por cromatografia de camada delgada. Foi sugerido que lacases de P. ostreatus oxidam o grupo cromóforo azo, ligado ao fenol, nas primeiras 24 horas, conjuntamente hidroxilização não enzimática. Lacases de P. cinerea oxidam Mn+2 e quinona, possibilitando a via de Fenton e hidroxilizando assim a molécula do corante, paulatinamente, a partir das ligações mais vulneráveis. T. villosa faz uso prioritariamente da via de Fenton, hidroxilizando gradativamente a molécula do corante. Dessa forma, embora a maioria de estudos associem a produção enzimática à descoloração, a participação dos compostos de baixa massa molar não pode ser negligenciada.Reactive textile dyes can be degraded by basidiomycetes, by means of hydrolytic and oxidative enzymes, and low molecular weight compounds. Was evaluated the CI Reactive Blue 222 decolorization by Peniophora cinerea, Pleurotus ostreatus, and Trametes villosa, selecting optimal conditions for the process and different metabolic pathways were observed. The degradation was confirmed by thin layer chromatography. It was suggested that P. ostreatus laccases oxidize azo chromophore group attached to the phenol, within 24 hours, together nonenzymatic hydroxylizating. P. cinerea laccases oxidize Mn+2 and quinone, enabling via Fenton and so hidroxylizing the dye molecule, gradually, from the most vulnerable links. T. villosa uses primarily via Fenton, gradually hidroxylizing the dye molecule. Thus, although most studies have linked enzyme production with the decolorization, the share of low molecular weight compounds can not be neglected.
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Miles, Anna Louise. « V-ATPase regulation of Hypoxia Inducible transcription Factors ». Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283217.
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Metazoans have evolved conserved mechanisms to promote cell survival under low oxygen tensions by initiating a transcriptional cascade centered on the action of Hypoxia Inducible transcription Factors (HIFs). In aerobic conditions, HIFs are inactivated by ubiquitin-proteasome-mediated degradation of their a subunit, which is dependent on prolyl hydroxylation by 2-oxoglutarate (2-OG) and Fe(II)-dependent prolyl hydroxylases (PHDs). In hypoxia, HIF-$\alpha$ is no longer hydroxylated and is therefore stabilised, activating a global transcriptional response to ensure cell survival. Interestingly, HIFs can also be activated in aerobic conditions, however the mechanisms of this oxygen-independent regulation are poorly understood. Here, I have explored the role of the vacuolar H+-ATPase (V-ATPase), the major proton pump for acidifying intracellular vesicles and facilitating lysosomal degradation, in regulating HIF-$\alpha$ turnover. Unbiased forward genetic screens in near-haploid human cells identified that disruption of the V-ATPase leads to activation of HIFs in aerobic conditions. Rather than preventing the lysosomal degradation of HIF-$\alpha$, I found that V-ATPase inhibition indirectly affects the canonical proteasome-mediated degradation of HIF-$\alpha$ isoforms by altering the intracellular iron pool and preventing HIF-$\alpha$ prolyl hydroxylation. In parallel, I characterised two putative mammalian V-ATPase assembly proteins, TMEM199 and CCDC115, identified by the forward genetic screen and subsequent mass spectrometry analysis. I confirmed that both TMEM199 and CCDC115 are required for V-ATPase function, and established assays to determine how TMEM199 and CCDC115 associate with components of the core V-ATPase complex. Lastly, to measure how V-ATPase activity leads to changes in the labile iron pool, I developed an endogenous iron reporter using CRISPR-Cas9 knock-in technology. This approach confirmed that iron homeostasis is impaired during V-ATPase inhibition, and demonstrated that exogenous ferric iron can restore the labile iron pool in a transferrin-independent manner. Together my studies highlight a crucial link between V-ATPase activity, iron homeostasis, and the hypoxic response pathway.
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Vo, Chau Duy Tam. « Etude biochimique de trois nouvelles protéines impliquées dans la biosynthèse de l’ubiquinone en anaérobie chez Escherichia coli : UbiT, UbiU et UbiV A Soluble Metabolon Synthesizes the Isoprenoid Lipid Ubiquinone Ubiquinone Biosynthesis over the Entire O 2 Range : Characterization of a Conserved O 2-Independent Pathway ». Thesis, Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=http://theses-intra.upmc.fr/modules/resources/download/theses/2019SORUS401.pdf.
Texte intégralRésumé :
L’ubiquinone, ou coenzyme Q (CoQ ou UQ), est un lipide polyprénylé qui joue un rôle important dans le transport des électrons dans les chaînes respiratoires chez E. coli. La biosynthèse de l'UQ en aérobie chez E. coli nécessite huit réactions et implique au moins douze protéines (UbiA-UbiK et UbiX). Dans ce travail, nous démontrons que les protéines Ubi forment le complexe Ubi, un métabolon stable qui catalyse les six dernières réactions de la voie de biosynthèse. La structure tridimensionnelle du domaine SCP2 d’UbiJ forme une cavité hydrophobe étendue qui lie les intermédiaires de l’UQ à l'intérieur du complexe d’1-MDa. Le complexe Ubi est purifié à partir des extraits cytoplasmiques et la biosynthèse de l'UQ a lieu dans cette fraction, remettant en question l’hypothèse actuelle d'un processus de biosynthèse associé à la membrane. L’UQ est connue pour être synthétisée en aérobie et anaérobie. Nous caractérisons une nouvelle voie de biosynthèse de l’UQ indépendante de l'O2. Cette voie repose sur trois protéines, UbiT, UbiU et UbiV. UbiT possède un domaine de liaison aux lipides SCP2 et est probablement un facteur accessoire de la voie de biosynthèse, tandis qu’UbiU et UbiV (UbiU-UbiV) sont impliqués dans les réactions d'hydroxylation et représentent une nouvelle classe d'hydroxylases indépendantes de l’O2. Nous démontrons qu’UbiU-UbiV d’E.coli forme un hétérodimère, chaque protéine se lie à un centre [4Fe-4S] via des cystéines conservées essentielles à l'activité. De plus, nous montrons qu’UbiU purifié de P. aeruginosa est capable de lier de l’UQ, suggérant un rôle différent d’UbiU et d’UbiV. UbiU et UbiV appartiennent à la famille des peptidases U32, dont la fonction reste discutable. Nous démontrons, par des analyses bioinformatiques, que les protéines U32 sont caractérisées par quatre cystéines conservées très importantes pour leurs activités enzymatiques et par des outils biochimiques, nous confirmons que RlhA et TrhP, deux autres protéines de la famille U32, comme UbiU et UbiV, sont des protéines Fe-SUbiquinone (UQ) is a polyprenylated lipid that plays an important role in electron transport in the respiratory chains of E. coli. The aerobic biosynthesis of UQ in E. coli requires eight reactions and involves at least twelve proteins (UbiA-UbiK and UbiX). In this work, we demonstrate that seven Ubi proteins form the Ubi complex, a stable metabolon that catalyzes the last six reactions of the UQ biosynthetic pathway. The X-Ray structure of the SCP2 domain of UbiJ forms an extended hydrophobic cavity that could bind UQ intermediates inside the 1-MDa Ubi complex. The Ubi complex is purified from cytoplasmic extracts and UQ biosynthesis occurs in this fraction, challenging the current thinking of a membrane-associated biosynthetic process. UQ is reported to be biosynthesized under both anerobic and anaerobic conditions. We characterize a novel, O2-independent pathway for the biosynthesis of UQ. This pathway relies on three proteins, UbiT, UbiU, and UbiV. UbiT contains an SCP2 lipid-binding domain and is likely an accessory factor of the biosynthetic pathway, while UbiU and UbiV (UbiU-UbiV) are involved in hydroxylation reactions and represent a novel class of O2-independent hydroxylases. We demonstrate that UbiU-UbiV from E.coli form a heterodimer, wherein each protein binds a [4Fe-4S] cluster via conserved cysteines that are essential for activity. Moreover, we show that purified UbiU from P. aeruginosa is able to bind UQ, suggesting a different role of UbiU and UbiV. UbiU and UbiV belong to peptidase U32 family whose function remains questionable. By bioinformatic analyses, we demonstrated that U32 proteins were characterized by four conserved cysteines important for their enzymatic activities and by biochemical tools, we confirmed that RlhA and TrhP, two others U32 subfamilies, like UbiU and UbiV, are all Fe-S proteins
28
Pinder, Lorretta. « Influence of Sulphide on the Degradation Pathways for Chlorinated Ethenes ». Thesis, 2007. http://hdl.handle.net/10012/3070.
Texte intégralRésumé :
Although iron-based permeable reactive barriers are gaining importance in the treatment of groundwater contaminants, there have been field observations indicating that sulphide may affect the degradation rates of certain chlorinated ethenes. Previous observations suggest that sulphide has little effect on TCE degradation rates but can cause a significant decline in the rate of degradation of cis-DCE. This study was conducted to systematically test the effects of S2- on TCE, cis-DCE, trans-DCE, 1,1-DCE and VC. Two different concentrations of sulphide (5 and 50 mg/L) were used in the column experiments. The results showed that the rate of TCE degradation was only slightly reduce in the presence of sulphide, while there was substantial reduction in the rates of degradation of cis-DCE, 1,1-DCE and VC. Trans-DCE was affected by sulphide, however, not as severely as cis-DCE, 1,1-DCE and VC. Raman Spectra showed the presence of a small amount of sulphide precipitates, and corrosion potential measurements showed that sulphide shifted the corrosion potential of the iron to less negative values by approximately 70 mV, suggesting that the change in corrosion potential was not responsible for the preferential degradation of TCE relative cis-DCE and VC.
The dominant pathway for TCE degradation is β-elimination, while that for cis-DCE and VC is generally considered to be hydrogenolysis, though there is also evidence in the literature indicating that cis-DCE and VC can also degrade by catalytic hydrogenation. The results indicate that sulphide does not inhibit β-elimination but severely limits the hydrogenolysis/catalytic hydrogenation pathway. The fact that sulphide inhibited the conversion of ethene to ethane, a known catalytic reaction, indicated that sulphide is acting as a catalyst poison. It is therefore concluded that the primary mechanism for the transformation of cis-DCE to VC and for VC to ethene is catalytic hydrogenation, and that sulphide inhibits these transformations through its role as a catalyst poison.
29
CIAMBELLOTTI, SILVIA. « Human ferritin nanocages : from iron oxidation to drug delivery ». Doctoral thesis, 2016. http://hdl.handle.net/2158/1080397.
Texte intégralRésumé :
This thesis dealt with the study of the human ferritins family, the main iron storage proteins. It focused on the development of efficient methods for the heterologous expression in E.coli of different types of human ferritins. These samples have been used for the study of iron pathways in ferritin via structural approaches and to unreveal novel features of this class of nanocage proteins. This work permitted the identification of the key residues in the catalytic ferroxidase site of H-type ferritin, and of the nucleation site of ferroxidase-inactive L-type ferritin. The design, production and functional characterization of a number of mutants allowed to validate the mechanistic hypotheses suggested by the structural data. Thanks to its endogenous origin and its peculiar nanocage structure, ferritin has been exploited as a nanocarrier for the delivery of contrast agents and/or drugs. Following this interest, a study of the interaction between ferritin and some drug molecules has been also discussed.
30
Greenwald, Jessica Williams. « An In-depth Analysis of Iron and Pathogenicity Regulatory Pathways in Pseudomonas syringae pv. syringae B728a ». Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9882.
Texte intégralRésumé :
Pseudomonas syringae pv. syringae strain B728a (P.s.s. B728a) is an economically significant plant pathogen that is capable of successful epiphytic colonization of leaf surfaces. Although the virulence factors associated with this pathogen’s ability to cause disease have been well studied, the transition from epiphyte to pathogen is not well understood.
The research described in this dissertation utilizes high throughput sequencing transcriptome analyses to define an iron regulatory network that is predicted to be utilized during the epiphytic portion of the P.s.s. B728a lifecycle. This dissertation also describes a collaborative microarray analysis that analyzes the P.s.s. B728a transcriptome at a global level.
An iron associated sigma factor, AcsS, encoded within a peptide synthesis rich region of the P.s.s. B728a genome is shown to regulate the citrate siderophore achromobactin. RNA-seq transcriptome analysis reveals that this sigma factor regulates expression of genes predicted to be involved in functions that are important during the epiphytic stage of P.s.s. B728a, including genes involved in iron response, secretion, extracellular polysaccharide production, and cell motility.
As part of a collaboration, the transcriptomes of the P.s.s. B728a genome and nine deletion mutants in regulatory genes were analyzed by microarray analayses using seven treatment conditions, including epiphytic and in planta conditions. As part of these microarray analyses, results are described for the global regulator, GacS, and a downstream transcription factor, SalA. This study confirms the role of GacS and SalA in the regulation of major virulence components of P.s.s. B728a such as phytotoxin production and Type III secretion. This study also elucidates a role for GacS and SalA regulation of genes important for epiphytic survival and function, including the Type VI secretion system, iron acquisition, and EPS production.
31
Camponeschi, Francesca, Sabine Annemarie Elisabeth Heider, Simone Ciofi-Baffoni et Lucia Banci. « Characterization of pathways for the Fe-S protein biogenesis in the human cytoplasm ». Doctoral thesis, 2020. http://hdl.handle.net/2158/1217050.
Texte intégralRésumé :
Human cytosolic monothiolglutaredoxin-3 (GLRX3) is a protein essential for the maturation of cytosolic [4Fe−4S] proteins. We show here that dimeric cluster-bridged GLRX3 transfers its [2Fe−2S]2+ clusters to the human P-loop NTPase NUBP1, an essential early component of the cytosolic iron−sulfur
assembly (CIA) machinery. Specifically, we observed that [2Fe−2S]2+ clusters are transferred from GLRX3 to monomeric apo NUBP1 and reductively coupled to form [4Fe−4S]2+ clusters on both N-terminal CX13CX2CX5C and C-terminal CPXC motifs of NUBP1 in the presence of glutathione that acts as a reductant. In this process, cluster binding to the C-terminal motif of NUBP1 promotes protein dimerization, while cluster binding to the N-terminal motif does not affect the quaternary structure of NUBP1. The cluster transfer/assembly process is not complete on both N- and C-terminal motifs and indeed requires a reductant stronger than GSH to increase its efficiency. We also showed that the [4Fe−4S]2+ cluster formed at the N-terminal motif of NUBP1 is tightly bound, while the [4Fe−4S]2+ cluster bound at the C-terminal motif is labile. Our findings provide the first evidence for GLRX3 acting as a [2Fe−2S] cluster chaperone in the early stage of the CIA machinery. Iron-sulfur (Fe-S) clusters are among the most versatile cofactors in biology. Although Fe-S clusters formation can be achieved spontaneously in vitro with inorganic iron and sulfur sources, the in vivo behaviour is more complex and requires the so-called Fe-S biogenesis machineries. In the cytosol, the biogenesis of Fe-S proteins is assisted by the cytosolic Fe-S protein assembly machinery, which comprises at least thirteen known proteins, among which there are human ORAOV1 and YAE1. A hetero-complex formed by the two latter proteins facilitates Fe-S cluster insertion in the human ABC protein ABCE1 within a chain of binding events that are still not well understood. In the present work, ORAOV1 and the YAE1-ORAOV1 complex were produced and their structural and cluster binding properties spectroscopically investigated. It resulted that both ORAOV1 and the YAE1-ORAOV1 complex are characterized by well-structured alpha-helical regions and by unstructured, flexible regions, and are both able to bind a [4Fe-4S]2+ cluster. Bioinformatics and site-directed mutagenesis studies indicated that ORAOV1, and not YAE1, is the protein involved in [4Fe-4S]2+ cluster binding in the hetero-complex. ORAOV1 has indeed a conserved cluster-binding motif able to coordinate a [4Fe-4S] cluster. Overall, our data suggested that the YAE1-ORAOV1 complex might actively participate in the Fe-S cluster insertion into ABCE1 thanks to the [4Fe-4S]2+ cluster binding properties of ORAOV1.
32
Chang, Wan-Jou, et 張琬柔. « Unravelling Degradation Pathways of Arsenic by Nanoscale Zero-valent Iron in Aqueous Solution at Different Time Scales ». Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9b2y5a.
Texte intégralRésumé :
碩士國立臺灣大學
地質科學研究所
107
High levels of arsenic in groundwater influence millions of human health around the world. Nanoscale zero-valent iron (nZVI) has the function of transforming and immobilizing pollutants in aqueous solution, it’s widely recognized as a material with a high potential agent for environmental friendly treatment of groundwater. In this study, the batch experiments of different variables and in-situ experiments were carried out to explore the reaction mechanism between arsenic and nZVI in aqueous solution. Nano Zero-Valent Iron (nZVI) was syntesized by the reduction of ferric chloride with sodium borohydride, and which particle size ranges from 20 to 50 nm. nZVI is a spherical material having a core-shell structure. The batch experiment results show that the dosage is proportional to its ability to degrade arsenic solution. 0.1 g/L nZVI degrades 100 ppm As(III) solution at a removal efficiency of 60% at 24 hours, and the dosage of 0.5 g/L or more is better than 95%. nZVI is more reactive to As(III) than As(V). The efficiency of nZVI degradation in an anaerobic condition is better than that of aerobic condition due to the maintaince of core-shell structure of nZVI. 0.5 g/L nZVI reaches 90% degeadation in 30 minutes when the pH is in a neutral condition. The SEM and TEM images showed that some of the core-shell structure of nZVI reacting with arsenic solution were transformed to flakes, needles and clusters forms. In situ X-ray absorption spectroscopy results showed that the As(III) solution reacted with nZVI would oxidize to As(V). The Fe(0) signal of nZVI decreases with time, and the Fe(II) and Fe(III) signals are enhanced. The longer the reaction time, the more obvious the oxidation situation in the solid sample and the more the arsenic-oxygen bond number. Under the quick XAS analysis, As(III) on nZVI will be reduced to lower valence state in a very short time, which is in accordance with the results of batch experiments. It can be speculated that the excellent degradation efficiency is contributed to reduction ability. The higher the dosage, the stronger the reducing ability, and the better the degradation efficiency. The results of this study indicate that nZVI degrades arsenic in aqueous solution as a complex reaction involving oxidation, reduction, adsorption, coprecipitation, and chelation. It can be divided into three stages. The first stage, nZVI quickly removed arsenic from the aqueous solution and reacted with water to produce a reducing species in a very short time, which providing a powerful reducing ability. The second stage is that nZVI and its oxidate layer affected the transformation of arsenic both in the solid and liquid phases. The third stage was continuous slowly transform between nZVI and arsenic, nZVI was effectively immobilized arsenic in the aqueous solution on its particles and no longer released into the water.
33
Weber, S. « Insights into the formation of the Stuart Shelf iron-oxide-copper-gold (uranium) system from magnetotellurics ». Thesis, 2010. http://hdl.handle.net/2440/106281.
Texte intégralRésumé :
This item is only available electronically.The Gawler Craton, South Australia, is host to many economic ore resources. Of which, iron oxide copper-gold deposits, such as Olympic Dam, Carrapateena and Wirrda Well, stand out due to the quality and abundance of their ore resources. Understanding the mechanisms of their formation is vital for defining exploration models for future development. 166 stations of magnetotelluric data at periods between101-104 seconds have been used to produce three, 2D models that provide insight into the electrical conductivity of the sub-surface beneath the Stuart Shelf. Links between corresponding regions of conductivity across profiles are shown by faults. It is suggested here that the faults are the fluid flow pathways for the mineralizing hydrothermal fluids. These fluids have been derived from the mantle and the surface in two phases of fluid flow causing both deposition and destruction of graphite respectively.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2010
34
Min-YuLin et 林敏鈺. « Investigation on crystal Growth Pathways of Iron Sulfide Minerals by In-situ and Ex-situ X-ray Diffraction ». Thesis, 2017. http://ndltd.ncl.edu.tw/handle/53f36d.
Texte intégralRésumé :
碩士國立成功大學
地球科學系
105
Iron sulfide minerals spread wildly in sediments, including mackinawite, greigite and pyrite etc. Besides their brilliant properties in the field of material applications, the transformation sequence also plays a critical role on paleoenvironment and paleomagnetism. Most studies indicated the commonly known transformation pathway is mackinawite → greigite → pyrite and oxidants embarking transformation include hydrogen sulfide, polysulfide and oxygen. However, previous studies focused on single oxidant in solution system, the contribution of each one and whether transformation sequence always present as the intermediate phase: greigte; final phase: pyrite with existing two or more oxidants in system is less concerned and discussed. Therefore, co-precipitation was used to synthesize precursor (nanocrystalline FeS) first and prepared solution with three Fe/S values, representing “rich-sulfide” as well as “less-sulfide” conditions to observe the rate of transformation. Besides Fe/S value, oxygen was took into account by conducting experiment in anaerobic and aerobic environment, then altering pH to create the H2S system in each Fe/S condition to understand the contribution of hydrogen sulfide and oxygen to transformation. Moreover, in-situ X-ray diffraction analysis was used to obtain continuous transformation process. This study shows: the formation of greigite and the influence of oxygen in environment are limited in the abundant-H2S system where nucleation of pyrite became primary reaction. Due to synthesis method for in-situ experiment, only dropping a little amount of initial solution into capillary resulting in less amount of hydrogen sulfide in capillary, forbidding pyrite from nucleating in solution, therefore, the sequence of mackinawite → greigite → pyrite only can be observed at 80oC and 100oC from in-situ experiment. Without hydrogen sulfide and oxygen as oxidant, the formation of greigite by enhancing the molar value of iron is possible; however, goethite appeared instead not greigite as increasing oxygen concentration in environment.
35
Rutherford, Robert A(Robert Alexander). « Bounty Gold Mine : deformation history and the development of ore fluid pathways within an iron formation host, Western Australia ». Thesis, 1992. https://eprints.utas.edu.au/21462/1/whole_RutherfordRobertAlexander1993_thesis.pdf.
Texte intégralRésumé :
The Bounty orebody has a steep plunge and is bound within strata parallel shear zones
which are developed in an iron formation horizon. A footwall ultramafic volcanic
sequence and a hanging wall gabbro bound the mineralized iron formation which dips
steeply west. Shearing occurred during deformation event Dn and a peak contact
metamorphic grade of lower amphibolite fades.
Deformation in pre-Dn times was dominated by strong east-west directed
compression which resulted in complex, upright folding and thrusting of the
supracrustal sequence. With cessation or relaxation of the compression batholiths,
plutons and porphyritic stocks, dykes and sills of granite to granodiorite composition
intruded the folded greenstone sequence and broad contact metamorphic aureoles
were formed. A period of vertically oriented, maximum compressive stress (Dn)
succeeded the intrusive event. Resulting strain was focused along the footwall and
hanging wall boundaries of the iron formation and shear zones with a normal
movement sense developed. The hanging wall boundary of the iron formation, which
was locally rotated west of north during intrusion of a pre-Dn pluton, underwent down
dip or steep oblique shear movement with a normal sense. Sheared lithological
boundaries striking about 4° to 8° west of north were dilated, developing ore fluid
pathways with a steep plunge.
The ore fluid pathways are controlled by the rheological contrast and original shape of
the iron formations hanging wall boundary during Dn. The original shape was
influenced by intrusion of a pre-Dn pluton proximal to the deposit.
36
Wen, Pei-chen, et 溫珮辰. « An Understanding of the O2-Iron Protoporphyrin IX Binding in Human Serum Albumin and its Engineered Mutant from the O2 Diffusion Pathways and Escape Routes ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/48gm72.
Texte intégralRésumé :
碩士國立中央大學
化學學系
102
Human serum albumin (HSA) is the most prominent plasma protein in our circulatory system. Many studies have revealed that HSA is a versatile protein, which has a high binding constant for hemin to prevent it participates in Fenton’s reaction to produce hydroxyl radicals, highly toxic for our body. This strong affinity of HSA for hemin has stimulated efforts to develop albumin as an artificial hemoprotein which can mimic the O2 binding capability of Hb and myoglobin(Mb). Komatsu et al. have engineered three double mutants, which can reversibly bind and release O2 at room temperature. Among these mutants, HF (I142H/Y161F)-heme has the highest O2 binding affinity, which can be ascribed to the following reasons: (i) Ile-142 His mutation creating an axially coordinated to the central Fe2+ ion of the heme similar to that of hemoprotein and (ii) Tyr-161 Phe mutation making the sixth coordinate position of Fe2+ ion available. In this study, we investigate the O2 diffusion network (diffusion cavities and portals) of HSA and HF by employing temperature-controlled locally enhanced sampling (TLES) method to greatly enhance the simulation efficiency. We have identified the O2 diffusion cavities and portals of HSA and HF. The networks of O2 diffusion cavities of HSA and HF are distinct different. In the HF, the channels between all diffusion cavities are all allowed indicating the high probability of O2 molecules diffused to the distal diffusion cavity, the key cavity for heme- O2 binding. In the wild-type HSA, the channels of distal diffusion cavity and diffusion cavity I to diffusion cavity II are allowed, however, the channels of diffusion cavity II to distal diffusion cavity and diffusion cavity I are forbidden. These results indicate the diffusion cavity II in HSA plays a role like “O2 storage” leading to low probability of O2 molecules diffused to the distal diffusion cavity. These results support the experimental results of O2-heme binding affinities of HSA and HF in terms of the network of diffusion cavities.
37
Tu, Hsiu-Chuan, et 涂秀娟. « The Application of Nanoscale Zero-Valent Iron Slurry : Degradation Pathways and Efficiencies of Aqueous TCE under Different Atmospheres, and Transport Phenomena and Influence on Colony in Soil ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/50971598613346007888.
Texte intégralRésumé :
碩士國立中山大學
環境工程研究所
95
In this research, nanoscale zero-valent iron (NZVI) was synthesized using the chemical reduction method. Experimental results have revealed that nanoiron synthesized by the reagent-grade chemicals had a size range of 50-80 nm, as determined by FE SEM. BET specific surface area of thus synthesized nanoparticles was 66.34 m2/g. NZVI prepared by the industrial-grade chemicals had a broader particle size distribution (30-80 nm) and its BET specific surface area was 61.50 m2/g. Results of XRD showed that both types of NZVI were composed of iron with a poor crystallinity. Additional test results further showed that both types of NZVI had similar characteristics. NZVI prepared by the chemical reduction method tends to aggregate resulting in a significant loss in reactivity. To overcome this disadvantage, four water-soluble dispersants were used in different stages of the NZVI preparation process. Of these, Dispersant A (an anionic surfactant) has shown its superior stabilizing capability to others. An addition of 0.5 vol % Dispersant A during the nanoiron preparation process would result in a good stability of NZVI slurry (NZVIS). Degradation of trichloroethylene (TCE) by NZVIS under different atmospheres was carried out in batch experiments. Experimental results have shown that the TCE dechlorination rate increased markedly when the reaction proceeded under hydrogen gas atmosphere as compared with that of air. Methane was the primary end product with a trace amount of ethane and ethylene when the reaction was conducted under the atmosphere of H2. It was suggested that an addition of H2 to the reaction system could promote the hydrogenolysis reaction for better degradation. On the other hand, ethane was the main product when the reaction system consisted of nanoscale palladized iron and H2 atmosphere. It demonstrated that Pd-catalyzed TCE dechlorination has resulted in a direct conversion of TCE to ethane in the study. The greatest dechlorination rate was obtained when 2 g/L nanoscale palladized iron and 50 mL H2 was employed in the reaction system. Under the circumstances, the TCE (10 mg/L) removal efficiency was up to 99 % in 3 minutes. Experimental results have demonstrated that the reaction system with both nanoscale palladized iron and H2 atmosphere would promote TCE degradation rate. The culture of microorganism in soil showed minor changes to microbial community structures between the pre- and post-injection conditions. The number of microorganism colony was found to be increased after adding 1 mL NZVIS to 1 g soil. Experimental results revealed that NZVIS would not cause the inhibition or reduction of microorganism activity. Surface modification of NZVI slurry by Dispersant A could enhance its transport in saturated porous media. Sticking coefficients were determined to be 0.56 and 0.11, respectively, for bare and Dispersant A-modified NZVIS transporting in quartz sand columns. The sticking coefficient for modified NZVIS transport in soil (loamy sand) column was determined to be 0.0061. Apparently, NZVIS modified by Dispersant A would enhance the transport of NZVI in saturated porous media. The results of combining electrokinetic technology and NZVIS injection tests in horizontal soil column illustrated that the sticking coefficient was 0.00034 and the total content of iron reduced 10 wt. %. Experimental results revealed that the transport distance of NZVIS in saturated horizontal soil column would be greatly increased under electronkinetic conditions.
38
Chen, Bin. « A mechanistic study of redox pathway in iron/ZSM-5 ». 2006. http://proquest.umi.com/pqdweb?did=1051279821&sid=3&Fmt=2&clientId=39334&RQT=309&VName=PQD.
Texte intégralRésumé :
Thesis (Ph.D.)--State University of New York at Buffalo, 2006.Title from PDF title page (viewed on July. 14, 2006) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Lund, Carl R.F. Includes bibliographical references.
39
BASU, Somsuvro. « Erv1 associated mitochondrial import-export pathway and the cytosolic iron-sulfur protein assembly machinery in Trypanosoma brucei ». Doctoral thesis, 2014. http://www.nusl.cz/ntk/nusl-175336.
Texte intégralRésumé :
This thesis highlights a divergent mitochondrial intermembrane assembly pathway in the parasitic protist Trypanosoma brucei. A comparative genomic study reveals the connection of Erv1 with the cytosolic iron-sulfur protein assembly (CIA) pathway in trypanosomatids. Further, the CIA machinery of T. brucei has been described using RNAi interference and other biochemical and complementation assays. Finally, part of the divergent CIA machinery has been identified in the human intestinal pathogen Giardia intestinalis by means of complementation assays in T. brucei.
40
HAINDRICH, Alexander Christoph. « Late Steps in the cytosolic Iron-Sulfur Cluster Assembly in Trypanosoma brucei ». Master's thesis, 2015. http://www.nusl.cz/ntk/nusl-202660.
Texte intégralRésumé :
The aim of this thesis was to investigate genes involved in the late steps of the Cytosolic Iron sulfur cluster Assembly (CIA) pathway in procyclic T. brucei, to determine their cellular localization and find their possible interaction partners and substrates.
41
Sohrabi, Nader. « Pathways, Contingencies, and the Secular in Iran’s First Revolution ». 2019. https://ul.qucosa.de/id/qucosa%3A36144.
Texte intégralRésumé :
Iran’s constitutional revolution of 1906 is arguably the most significant
turn toward the secular in its modern history.1 I start this investigation by
making a conceptual distinction between secularism and secularity.2 Here,
secularism is defined as the ideologically-driven separation of religion and
state according to an agenda, a blueprint, a model, that could be indigenously,
or externally informed and is achieved with the assistance of the
modern state and explicit political motivations. Secularity, on the other
hand, is expressed in terms of a non-ideological separation that comes
about unintentionally. In some accounts, this separation may take on evolutionary
connotations in terms of the natural separation of functions as
a result of the growing complexity of a natural organism or social system.
What I have in mind here is a separation of functions that is agent-driven
but the secularity that emerges is both unintentional and unideological.
42
Song, Po-Ching, et 宋柏青. « Study on the iron-harvesting pathway of host-harbored zooxanthellae and the high temperature induces Symbiodinium iron-deficiency genes expression during Aiptasia-Symbiodinium endosymbiosis ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/98501562492808508766.
Texte intégralRésumé :
博士國立中山大學
海洋科學系研究所
104
Coral bleaching is the consequence of disruption of the mutualistic Cnidaria-dinoflagellate association. Elevated seawater temperatures have been proposed as the most likely cause of coral bleaching whose severity is enhanced by a limitation in the bioavailability of iron. Iron is required by numerous organisms including the zooxanthellae residing inside the symbiosome of cnidarian cells. However, the knowledge of how symbiotic zooxanthellae obtain iron from the host cells and how elevated water temperature affects the association is very limited. Since cellular iron acquisition is known to be mediated through transferrin receptor-mediated endocytosis, a vesicular trafficking pathway specifically regulated by Rab4 and Rab5, we set out to examine the roles of these key proteins in the iron acquisition by the symbiotic Symbiodinium. Thus, we hypothesized that the iron recruitments into symbiotic zooxanthellae-housed symbiosomes may be dependent on rab4/rab5-mediated fusion with vesicles containing iron-bound transferrins and will be retarded under elevated temperature. In this study, we cloned a novel monolobal transferrin (ApTF) gene from the tropical sea anemone Aiptasia pulchella and confirmed that the association of ApTF with A. pulchella Rab4 (ApRab4) or A. pulchella Rab5 (ApRab5) vesicles is inhibited by elevated temperature through immunofluorescence analysis. We confirmed the iron-deficient phenomenon by demonstrating the induced overexpression of iron-deficiency-responsive genes, flavodoxin and high-affinity iron permease 1, and reduced intracellular iron concentration in zooxanthellae under desferrioxamine B (iron chelator) and high temperature treatment. In conclusion, our data are consistent with algal iron deficiency being a contributing factor for the thermal stress-induced bleaching of symbiotic cnidarians.
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Tsai, Tsung-Mu, et 蔡宗穆. « Early events in the signal pathway for the activation of MAPKs in rice roots exposed to iron ». Thesis, 2006. http://ndltd.ncl.edu.tw/handle/96491228639240198494.
Texte intégralRésumé :
碩士國立成功大學
生命科學系碩博士班
94
Iron is an essential micronutrient for normal growth and development of plants. However, at high concentrations iron can become toxic to plants. Very little information is known about the molecular mechanism responsible for the regulation of plant growth by excess iron. The aim of this study was to investigate the signal transduction pathway activated by increasing concentrations (0.5, 1.0, and 2.5 mM) of iron. We showed that iron elicited a remarkable MBP kinase activity. By western blot and immunoprecipitation analysis, we suggested that iron-activated 42-kDa MBP kinase is a mitogen-activated protein kinase (MAPK). Cell death in rice roots due to iron toxicity was investigated using inhibitors of signal molecules known to regulate programmed cell death in plants. Phenylarsine oxide (PAO) and sodium orthovanadate, known inhibitors of tyrosine phosphatase, reduced iron-induced root cell death, but, cantharidin and endothall two-serine/threonine phosphatase inhibitor enhanced iron-induced root cell death. Moreover, our results revealed that H+-ATPase might participate in iron-induced cell death. These results suggested that the MAPK, reactive oxygen species (ROS), potassium channel, protein phosphatase, and H+-ATPase might function in the plant iron-triggered signalling pathway in rice roots. With analysis of the rice genome database, we identified eleven dual specificity phosphotases in rice genome. We found some dual-specificity phosphatases of gene expression pattern could be induced by vanadate. The pyronitrophenyl phosphatase (pNPP) was used as substrate and the phosphatase activity of OsDSP11 were measured in the present study.
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Tiong, Jacqueline Woang Cheing. « Metal binding properties of p97 and the trafficking of a novel iron internalization pathway by GPI-anchored p97 ». Thesis, 2001. http://hdl.handle.net/2429/13820.
Texte intégralRésumé :
Iron is an essential for cellular metabolism yet excessive iron can lead to
deleterious oxidative damages in the cells. Since humans have no physiological pathways
for iron excretion, dietary iron absorption in the intestine is tightly regulated. Although
the essential nature of iron for normal celular functions is beyond doubt, only in the two decades has its uptake and regulation been relatively wel understood.
The transferrin/ transferrin receptor-independent iron transport pathways play a
major role in iron overload diseases such as hemochromatosis. However, very little known about the molecular details of these pathways. P97, also known as
melanotransferrin, is an example of iron binding proteins that mediates such pathways.
P97 is a member of the transferrin family, which includes serum transferrin, lactoferrin
and ovotransferrin. Unlike members of the transferrin family, which are all serum
proteins, p97, in addition to being a serum protein, also exists as a
glycosylphosphatidylinositol-anchored protein. The primary iron-binding site in the Nterminal
lobe is highly conserved among the other transferrin members. However, the
iron binding site at the C-terminal lobe of p97 is not. This leads to the question whether p97 is a functional iron transport protein. In addition, the iron binding affinity p97 has never been ascertained. Therefore, an aspect of this thesis was to determine binding affinity of iron to p97 and to establish whether the C-lobe of p97 can bind The results in this thesis will demonstrate that the iron binding affinity for the N-lobe p97 is 2.2 x 10¹⁷ M⁻¹ at 25 °C. In addition, the data will show that C-lobe is able iron albeit very weakly.
Metals such as iron, copper, aluminum and zinc have been implicated in pathology of several neurological disorders. The expression of p97 in the brain capilary
endothelium and the elevated level of serum p97 associated with Alzheimer s disease
have led to the hypothesis that p97 may play an important role in disease progression the disease. Therefore, another goal of this study was to establish whether p97 can metals such as copper, aluminum and zinc. The results will show that copper, aluminum
and zinc are able to interfere with iron binding to GPI-anchored p97 and soluble able to bind to these metals as shown by urea polyacrylamide gel electrophoresis.
Though the internalization pathways of many GPI-anchored proteins have been
studied, debate still exists as to whether caveolae or clathrin-coated vesicles are involved
in their uptake. Surprisingly, very little is known about the fate of the ligands
internalized by GPI-anchored molecules. Also, there is controversy as to whether iron
bound to p97 can be donated to ferritin. Therefore, another aspect of this thesis was examine the uptake of GPI-anchored p97 and its ligand, iron. The results from confocal
immunofluorescence microscopy and sub-celular fractionation demonstrate that GPIanchored
p97 bound with iron is endocytosed into SK-MEL 28 cells via caveolae traffics to early endosomes. In addition, the data also shows that GPI-anchored p97 present in the same vesicles as Nramp2, a metal transporter thought to mediate transport across the vesicular membrane into the cytoplasm. Furthermore, it is shown
that iron taken up by p97 becomes bound by the iron storage molecule, ferritin. The establishes that iron bound to GPI-anchored p97 is internalized through caveolae and
donated to ferritin for cellular metabolism and supports an improved understanding of
both GPI anchor mediated uptake of ligand and the novel transferrin/ transferrin receptorindependent
mechanism of iron uptake.
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Sousa, Filipe Fernandes de. « Analysis of the induction of the cytoprotective Nrf2 signalling pathway in reticuloendothelial cells from iron-treated mice and HFE Haemochromatosis patients ». Master's thesis, 2012. https://repositorio-aberto.up.pt/handle/10216/74331.
Texte intégral
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Sousa, Filipe Fernandes de. « Analysis of the induction of the cytoprotective Nrf2 signalling pathway in reticuloendothelial cells from iron-treated mice and HFE Haemochromatosis patients ». Dissertação, 2012. https://repositorio-aberto.up.pt/handle/10216/74331.
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Samba, Mondonga Macha. « Study of the role of the adaptor protein MyD88 in the iron-sensing pathway and of the effect of curcumin in the development of anemia in a DSS-induced colitis mouse model ». Thèse, 2018. http://hdl.handle.net/1866/21855.
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Özyurt, Baris. « Identifikation von Genen und Mikroorganismen, die an der dissimilatorischen Fe(III)-Reduktion beteiligt sind ». Doctoral thesis, 2009. http://hdl.handle.net/11858/00-1735-0000-0006-B66A-8.
Texte intégral