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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

POST-TORNADO SALVAGE HARVEST INCREASES BIODIVERSITY AND SUPPORTS KEY WETLAND SPECIES IN A SOUTHERN ILLINOIS BOTTOMLAND HARDWOOD FOREST

Schammel, Laura 01 May 2024 (has links) (PDF)
Catastrophic wind events can play an important role in the stand structure and composition in Bottomland Hardwood Forests. Regeneration and stand structure following these events depends on a variety of factors, including disturbance severity, past land use, and post-disturbance management. This study revisits a 2004 survey conducted at Mermet Lake State Fish and Wildlife Area in Southern Illinois following a tornado and subsequent salvage logging operation. We established 164 plots on four different disturbance types as mapped by the original survey: Undisturbed, Transition, Wind Damaged Only, and Wind Damaged Salvaged. The objective of this study was to see how recovery differed among these. Data collected included density, basal area, and Shannon’s H, as well as visual evidence of remaining soil rutting resulting from the salvage logging operation, tree height as a metric for productivity, and invasive percent cover. There were slight but significant differences in the densities, basal area, and diversity among disturbance types, although diameter distributions revealed similar age distributions and there was no impact of the salvage logging on productivity. Evidence of soil rutting was still present, adding to microsite diversity that contributed to the significantly higher species diversity of Wind Damaged Salvaged areas. The proportion of Quercus spp. in both Wind Damaged Only and Wind Damaged Salvaged areas was lower than in Undisturbed and Transition areas, while the proportion of other species, including Fraxinus pennsylvanica and key bottomland taxa Salix spp., Taxodium distichum, and Nyssa aquatica, were higher. Invasive non-native species cover was higher in Wind Damaged Salvaged and Wind Damaged Only areas than in Transition and Undisturbed but was confined to forest edges and did not differ between Wind Damaged Salvaged and Wind Damaged Only areas. The results indicate that twenty years after the disturbance, forest structure is still recovering in tornado-damaged areas and has shifted in composition away from Quercus toward domination by Acer spp., Ulmus spp., Fraxinus pennsylvanica, and Liquidambar styraciflua species in both Wind Damaged Only and Wind Damaged Salvaged areas. The salvage logging operation did not have any negative impacts on forest recovery and supported biodiversity by further diversifying overstory community composition to include key wetland species that support the conservation area’s bottomland restoration efforts. Active management should be considered in both Wind Damaged Only and Wind Damaged Salvaged areas to prevent the spread of non-native species and ensure the persistence of Quercus and other key bottomland species in support of conservation objectives.
92

Forest management in changing landscapes: Evaluating hurricane damage and salvage market dynamics

Sartorio, Ian Pereira 13 August 2024 (has links) (PDF)
This dissertation comprises three interrelated studies exploring the effects of hurricanes on forestlands and the optimization of salvage logging practices. The first study examines land cover changes and salvage logging patterns following Hurricane Michael. It utilizes predictive models to identify key drivers of these changes, exploring the relative influence of storm intensity, forest vulnerability, and economic/operational factors. The second study builds upon these findings, focusing on the agent attribution for land cover change observations leveraging advanced remote sensing tools and relevant spatial data. By distinguishing between wind damage and salvage logging activities, it advances the understanding of post-hurricane land cover dynamics. The third study introduces a novel timber supply model that utilizes robust stochastic optimization to optimize salvage operations under uncertainty. It integrates various data sources to optimize site selection, transportation logistics, and resource allocation under uncertain timber stocks, aiming to enhance salvage operations' efficiency and economic returns. Collectively, these studies provide valuable insights for improved hurricane disturbance management.
93

Prognostischer Wert der kardialen Magnetresonanztomographie bei Patienten mit ST-Hebungsinfarkt - Analyse der Parameter linksventrikuläre Ejektionsfraktion, Infarktgröße, mikrovaskuläre Obstruktion und myokardialer „Salvage“ in einer multizentrischen Studie

Sünkel, Henning 28 May 2015 (has links)
Die kardiale Magnetresonanztomographie (MRT) ermöglicht nach einem akuten Myokardinfarkt (AMI) die Visualisierung und Quantifizierung der Myokardschädigung anhand verschiedener Parameter wie Ejektionsfraktion (EF), Infarktgröße, Mikrovaskuläre Obstruktion (MO) und „Myocardial Salvage Index“ (MSI). Anhand dieser MRT-Marker kann das Risiko für kardiovaskuläre Komplikationen eingeschätzt werden, was für die Weiterversorgung des Patienten sowie für die kardiologische Forschung von großem Interesse ist. In dieser Arbeit wurde die prognostische Relevanz der MRT-Parameter erstmals in einer großen, multizentrischen Studie untersucht. Zudem sollte unter den vier genannten MRT-Markern derjenige mit der größten prognostischen Aussagekraft ermittelt werden. Dazu wurden 795 Patienten aus der AIDA STEMI Studie einer MRT unterzogen und dann zwölf Monate lang im Hinblick auf den kombinierten Endpunkt „Major Adverse Cardiac Events“ (MACE; bestehend aus Tod, Reinfarkt und Klinikaufnahme wegen Herzinsuffizienz) nachbeobachtet. Die Ergebnisse belegen, dass die genannten MRT-Parameter prognostisch relevant sind und insbesondere die MO und die Infarktgröße einen Einfluss auf die Prognose ausüben, welcher über den Wert etablierter klinischer Risikomarker hinausgeht. Herausragende Bedeutung kommt dabei der MO zu, welche nach multivariater Analyse der potenteste MRT-Prädiktor für kardiovaskuläre Ereignisse ist. Somit sollten die MRT-Parameter in kommenden kardiologischen Studien als Surrogatmarker für klinische Endpunkte berücksichtigt werden. Zudem könnten sie für den klinischen Alltag die Möglichkeit bieten, die Patientenversorgung enger an die individuelle Prognose anzupassen.
94

Unfair prices in contracts in English and French law

Kennefick, Ciara M. January 2013 (has links)
When and why can parties escape from a contract on the ground that the price is unfair? This question is considered in a comparative and historical perspective in English and French law. The general rule in both systems is that the parties are free to determine the price and they are then bound by their contract. One well known exception in French law, which derives from Roman law, is Article 1674 of the Code civil which allows a vendor to rescind a contract for the sale of land if the price agreed in the contract is less than five-twelfths of the fair price. It is generally thought that there are no analogous rules in English law. However, the law on this subject is in fact considerably more complex and more colourful than this simple contrast would suggest. Numerous rules on unfair prices in contracts were created in French law by the legislature and the courts since the promulgation of the Code civil in 1804. In English law, courts intervened in contracts on the ground of an unfair price in a few instances in the nineteenth century. However, only the rule on unfair prices in salvage contracts has survived until today. In both systems, the policies of preserving family wealth, protecting weak parties and giving special treatment to certain parties for economic, political, social or cultural reasons underpin these rules. There are two principal conclusions. First, freedom of contract is much less extensive in French law than in English law. This is evident in the numerous rules on unfair prices in contracts in French law and in the primacy of the remedy of altering the price rather than rescission. Secondly, while in theory, French courts play a much less significant role than English courts in the development of law, the creation and abolition of certain rules on unfair prices in contracts by French courts shows that judicial creativity in French law can be much less constrained in practice than in English law.
95

Investigation of Pyrimidine Salvage Pathways to Categorize Indigenous Soil Bacteria of Agricultural and Medical Importance and Analysis of the Pyrimidine Biosynthetic Pathway's Enzyme Properties for Correlating Cell Morphology to Function in All Phases of Growth

Meixner, Jeffery Andrew 05 1900 (has links)
This dissertation comprises three parts and is presented in two chapters. Chapter 1 concerns Arthrobacter, a bacterium with an intriguing growth cycle. Whereas most bacteria exist as either a rod or coccus, this bacterium shares the rod/coccus lifestyle. It therefore seemed important to examine the growth regulatory pathways from the rod and coccus. The committed step, that catalyzed by aspartate transcarbamoylase (ATCase), in the pyrimidine biosynthetic pathway was chosen. The ATCase in Arthrobacter is like the well known Pseudomonas enzyme except that it has an active dihydroorotase (DHOase) associated. Included in Chapter 1 is the description of a microorganism, Burkholderia cepacia, whose ATCase has characteristics that are at once reminiscent of bacteria, mammals, and fungi. It differs in size or aggregation based on environmental conditions. In addition, it has an active DHOase associated with the ATCase, like Arthrobacter. B. cepacia is important both medically and for bioremediation. Since B. cepacia is resistant to most antibiotics, its unique ATCase is a prime target for inhibition. Whereas the first chapter deals with the de novo pathway to making pyrimidines, which is found mainly in the lag and log phase, Chapter 2 addresses the salvage pathway, which comes more into play during the stationary phase. This section focuses on the isolation, identification, and grouping of a number of natural soil bacteria from various soil locations. These organisms are important agriculturally, medically, and industrially. Addition of these soil isolates to poor soils has been found to improve the soil. In a previous study by D.A. Beck, the salvage schemes for a number of laboratory strains of microorganisms were determined. Nine separate classes of salvage were designated by determining the salvage enzymes present. In this study emphasis has been placed on soil bacteria, which had not previously been analyzed. A number of species of soil bacteria were identified using the MIDI. The salvage enzymes were then determined for these organisms and a comparison of these isolates to the previous study was performed in order to group the new organisms into 19 salvage schemes, that is 10 more than in the previous study.
96

Modeling The Effects Of The Hemlock Woolly Adelgid On Carbon Storage In Northern New England Forests

Krebs, Jeffrey John 01 January 2014 (has links)
The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is an invasive insect that threatens to eradicate native eastern hemlock (Tsuga canadensis (L.) Carr.) across the eastern United States. In southern New England and southern Appalachian forests, HWA-induced hemlock mortality has impacted carbon (C) flux by altering stand age, litter composition, species composition, and coarse woody debris levels. However, no one has examined how total C storage and sequestration may be impacted by these changes. Further, while projections are that HWA will ultimately infest hemlock across its entire geographic range, the majority of studies have been limited to southern New England and Appalachian forests where HWA infestation has been ongoing. To address these gaps, we examined how HWA might alter C dynamics in northern New England forests using the Forest Vegetation Simulator (FVS) and Forest Inventory Analysis (FIA) data to model C storage and successional pathways under three different scenarios: preemptive harvesting of hemlock, HWA-induced hemlock mortality, and a control mimicking natural stand development absent of disturbance. Our 150 year simulation showed that, while all treatments differed significantly in C storage in the short term, there was no significant difference in total C stocks between HWA infestation and presalvage treatments by the 75th year. Compared to the control, both simulated treatments resulted in a significant decrease in total C storage, with greater impacts on stands with higher hemlock densities. However, net C losses over the 150 year simulation were significantly higher for the presalvage scenario, indicating that allowing HWA infestation to progress naturally through a stand may result in the least impact to long-term C sequestration for the region's forests.
97

Case study - municipal solid waste management in Benoni, Ekurhuleni

Molomo, Ntolo Colette January 2017 (has links)
This research report submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Environmental Science. Johannesburg, 2016 Research work and course work. Johannesburg, 2016. / The unprecedented population growth, urbanisation and accelerating living standards, significant amounts of solid waste have accumulated all over the world. These changes, therefore, left most municipalities in African countries grappling to find viable solutions to their waste management problems (Özbay 2015). Indeed, studies have shown that the estimated annual growth rate of MSW is 3.2% to 4.5% for developed countries and 2% to 3% for developing countries (Özbay 2015). Notably, continuous increase in accumulation of solid wastes poses risks to not only human health but to the ecological environment (Al-Khatib, Kontogianni, Abu Nabaa, Alshami & Al-Sari 2015; Menikpura, Gheewala & Bonnet 2012). Improper waste management stems from the poor implementations of policies and regulations, to identify the most sustainable approaches to dealing with waste as to meet environmental and socio-economic aspirations, to address waste management efficiently. The objectives of this research are as follow:  Locate, consolidate and organise secondary data that is relevant to understanding the specific waste management situation of Benoni, Ekurhuleni.  Identify the importance of Municipal Solid Waste Management (MSWM).  Analyse these data and determine how it can be utilised in the case of Benoni.  Identify and suggest the best strategy implement an effective MSWM system, and  Discuss the difficulties and challenges faced by Benoni and Ekurhuleni at large, due to ineffective and inefficient MSWM. The case study area Benoni is a mere example to highlight waste management burdens and challenges, which might be characteristic of most African towns. This research seeks to understand the solid waste collection and proper disposal in informal areas of Benoni and the environmental impacts thereof. In particular, the research assumes that there is yet to be implemented a more rigid and structured approach to waste management in the area which justifies and necessitates the need for research aimed at shedding light on how modern waste management systems can be adapted to the case of the informal settlements in this area. Proper waste management implementation will benefit both the specific community in informal parts of Benoni as well as the global practice of waste management. This study used the qualitative method to describe, explore, and discover phenomena related to MSWM in Benoni (Creswell, 2003). Qualitative research is typically interpretive, with the researcher using critical analysis for the interpretation of data collected (Shenton & Hay-Gibson, 2009). The quantitative research uses hypotheses in determining the form, quantity, and scope of data to be collected (Morse & Richards 2002). In doing so, the researcher pre-empts alternative ways through which the study questions may be addressed. On the other hand, qualitative investigations are not pre-emptive. In this study of MSWM in Benoni, the form, quantity, and scope of inquiry hinged upon the research questions, the study purpose, and goals, as well as from the data collected (Morse & Richards 2002). 3 Benoni has reached the dilemma in which adverse health and environmental impacts of ineffective waste management are felt, while the numbers of landfill sites have been decreasing with no planning in evidence for establishing new ones. Because of these, improvements to Benoni's MSWM will entail the cooperation of all tiers of Government as well as industry and the commercial sectors. The EMM will have to restructure the recycling industry with the support of waste management legislation. An option that EMM has is to contemplate upon the outsourcing of the management of sanitary landfill sites to public-private partnerships, based on study findings that these discharges are better managed in South Africa (Naidoo 2009). In the case of Benoni, albeit the EMM has sufficient resources to manage waste effectively, there were numerous gaps related to the challenges that exist within the municipality's waste management sector. For instance, household wastes are not timely collected, and no notices are given when collection dates are changed (Tembon 2012). Apart from these, Benoni has an underdeveloped recycling system perhaps largely because the EMM itself has no comprehensive municipal recycling program and recycling facilities. Somehow, this contradicts the impression being given by providers that they have access to all the necessary resources needed for them to be effective in their work. This research will discuss an approach to strengthening the capacity to solve the problems that come with MSWM, along with investigating whether modern waste management practices are be present implemented such as; waste diversion from landfills, as well as shifting from incinerators and using unlined landfill sites to more sustainable methods. Based on the combined experiences in the three cases, some recommendations may stand in Benoni Ekurhuleni. First, every member of the community should be empowered with education and skills on waste management to increase their levels of participation in waste sorting at the source of generation. Public involvement will encourage effective recycling that ultimately generates income. This will be particularly useful to Benoni's squatter communities. Benoni has to look into the possibility of providing skills to informal settlers so that they can construct well-planned houses for themselves. With assistance from the national government, the EMM can decide whether this type of housing can be subsidised. Third, it is essential that EMM involves stakeholders from the different sectors of the municipal area in the planning and implementation of waste management strategies. Group leaders from various communities as well as social groups such as church communities should be invited to participate because they are crucial links between the council and the community. / LG2017
98

Estudos das enzimas adenosina kinase isoforma 1, hipoxantina-guanina fosforibosiltransferase isoformas 1, 2 e 3, adenilsuccinato liase, adenilsuccinato sintetase de Schistosoma mansoni / Studies of adenosine kinase isoform 1, hypoxanthine-guanine phosphoribosyltransferase isoforms 1, 2 and 3, adenylosuccinate lyase, adenylosuccinate synthetase enzymes from Schistosoma mansoni

Larissa Romanello 03 June 2016 (has links)
O Schistosoma mansoni, parasita responsável pela esquistossomose (barriga dágua), doença que afeta cerca de 300 milhões de pessoas em todo mundo, não possui a via de síntese de purinas, dependendo integralmente da via de salvação de purinas para seu suprimento dessas bases. Uma vez que a terapia se resume a administração de um único fármaco, o praziquantel, diversos casos de resistência do parasita a esse medicamento foram reportadas, sendo assim esta via tem sido citada como alvo potencial para o desenvolvimento de novos fármacos contra a doença. As enzimas adenosina kinase (AK), hipoxantina-guanina fosforibosiltransferase (HGPRT), adenilsuccinato liase (ADSL) e adenilsuccinato sintetase (ADSS) são enzimas chave desta via. Este trabalho faz parte de um projeto maior que visa a obtenção de todas as estruturas das enzimas envolvidas na via de salvação de purinas de Schistosoma mansoni. O cDNA correspondente às enzimas foi amplificado e clonado no vetor de expressão pOPIN; as enzimas AK isoforma 1, HGPRT isoforma 1 e ADSL foram expressas em E. coli Lemo21(DE3) e HGPRT isoforma 3 em E. coli B834(DE3); purificadas em coluna de cobalto agarose por afinidade, concentradas e cristalizadas no kit de cristalização Morpheus (Molecular Dimensions) no Oxford Protein Production Facility (OPPF) em Harwell UK. As coletas de dados por difração de raio-X foram realizadas no Síncrotron Diamond Light Source (DLS) - UK. Foram coletadas duas estruturas de ADSL, a 2.36Å de resolução em complexo com AMP e 2.14Å na forma Apo. A análise das estruturas revelou uma estrutura tetramérica bastante conservada entre as ADSLs, sendo este estado de oligomerização requerido, uma vez que resíduos de três das quatro subunidades compõem o sítio ativo. Apesar do sítio ativo ser altamente conservado entre SmADSL e ADSL humana, a interface dimérica dessas enzimas tem se apresentado suficientemente distintas, o que pode representar um potencial alvo para o desenvolvimento de um inibidor. O ensaio de atividade enzimática de ADSL revelou uma reação endotérmica, indicando que a contribuição da entropia relacionada a grande quantidade de moléculas de água presentes no sítio ativo é importante para a reação cinética. Após diversos experimentos de otimização dos cristais de HGPRT1 e aproximadamente 200 cristais testados, foi obtida uma estrutura em complexo com IMP a 2.8Å de resolução. A análise da estrutura revelou uma estrutura tetramérica. Apesar das subunidades não compartilharem o sítio ativo, este estado de oligomerização é requerido, uma vez que resíduos que compõem o sítio ativo também estão envolvidos em interações na interface dimérica, orientando o resíduo invariável Arg206 na direção do sítio ativo. Foram identificadas quatro mutações na região do sítio ativo entre SmHGPRT e HGPRT humana: Ile149Met, Pro176Arg, Val189Ile e Arg192Lys. Desta forma, a obtenção das estruturas contribui para o entendimento bioquímico desta via essencial para o parasita e de como este pode ser seletivamente privado de recursos. / Schistosoma mansoni is the parasite responsible for schistosomiasis, disease that affects about 300 million people worldwide, and does not have the purine de novo pathway, depending entirely on the purine salvage pathway to supply its demands on purines. Currently, both direct treatment and most disease control initiatives, rely on chemotherapy using a single drug, praziquantel. Concerns over the possibility of resistance developing to praziquantel, has stimulated efforts to develop new drugs for the treatment of schistosomiasis. The purine salvage pathway has been reported as a potential target for developing new drugs against schistosomiasis. Adenosine kinase (AK), hypoxanthine-guanine phosphoribosyltransferase (HGPRT), adenylosuccinate lyase (ADSL), adenylosuccinate synthetase (ADSS) are key enzymes in this pathway. This work is part of a larger project aimed at obtaining all the structures of enzymes involved in purine salvage pathway of Schistosoma mansoni. The cDNA corresponding to the enzymes was amplified and cloned in vector pOPIN, AK isoform 1, HGPRT isoform 1 and ADSL were expressed in E. coli Lemo 21 (DE3) and HGPRT isoform 3 in E. coli B834(DE3); purified in cobalt agarose column, concentrated and crystallized in several conditions of the Morpheus (Molecular Dimensions) crystallization kit at the Oxford Protein Production Facility (OPPF) in Harwell UK. The data collection by xray diffraction were performed at Diamond Light Source UK. Two ADSL structures were obtained, ADSL in complex with AMP at 2.36Å resolution and ADSL Apo form at 2.14Å The analysis revealed a tetrameric structure highly conserved between ADSLs, and this oligomerization state is required since residues three of the four subunits comprise the active site. Despite the active site being highly conserved between human ADSL and SmADSL, the dimeric interface of these enzymes it has been shown sufficiently distinct, which may represent a potential target for the development of an inhibitor. The ADSL enzymatic activity assay showed an endothermic reaction, indicating the contribution of the entropy related to the large quantity of water molecules present in the active site is important for the reaction kinetics. After several optimization experiments of HGPRT1 crystals and about 200 crystals tested was obtained a structure in complex with IMP at 2.8Å resolution. The structure analysis revealed a tetrameric structure. Despite the subunits do not share the active site, this oligomerization state is required, since residues that make up the active site are also involved in interactions in dimeric interface, guiding the invariable residue Arg206 toward the active site. Four mutations were identified in the region of the active site between SmHGPRT and human HGPRT: Ile149Met, Pro176Arg, Val189Ile e Arg192Lys. These structures increase the important structural information available about the Schistosoma mansoni purine salvage pathway and how it can be selectively private resources.
99

Estudos das enzimas adenosina kinase isoforma 1, hipoxantina-guanina fosforibosiltransferase isoformas 1, 2 e 3, adenilsuccinato liase, adenilsuccinato sintetase de Schistosoma mansoni / Studies of adenosine kinase isoform 1, hypoxanthine-guanine phosphoribosyltransferase isoforms 1, 2 and 3, adenylosuccinate lyase, adenylosuccinate synthetase enzymes from Schistosoma mansoni

Romanello, Larissa 03 June 2016 (has links)
O Schistosoma mansoni, parasita responsável pela esquistossomose (barriga dágua), doença que afeta cerca de 300 milhões de pessoas em todo mundo, não possui a via de síntese de purinas, dependendo integralmente da via de salvação de purinas para seu suprimento dessas bases. Uma vez que a terapia se resume a administração de um único fármaco, o praziquantel, diversos casos de resistência do parasita a esse medicamento foram reportadas, sendo assim esta via tem sido citada como alvo potencial para o desenvolvimento de novos fármacos contra a doença. As enzimas adenosina kinase (AK), hipoxantina-guanina fosforibosiltransferase (HGPRT), adenilsuccinato liase (ADSL) e adenilsuccinato sintetase (ADSS) são enzimas chave desta via. Este trabalho faz parte de um projeto maior que visa a obtenção de todas as estruturas das enzimas envolvidas na via de salvação de purinas de Schistosoma mansoni. O cDNA correspondente às enzimas foi amplificado e clonado no vetor de expressão pOPIN; as enzimas AK isoforma 1, HGPRT isoforma 1 e ADSL foram expressas em E. coli Lemo21(DE3) e HGPRT isoforma 3 em E. coli B834(DE3); purificadas em coluna de cobalto agarose por afinidade, concentradas e cristalizadas no kit de cristalização Morpheus (Molecular Dimensions) no Oxford Protein Production Facility (OPPF) em Harwell UK. As coletas de dados por difração de raio-X foram realizadas no Síncrotron Diamond Light Source (DLS) - UK. Foram coletadas duas estruturas de ADSL, a 2.36Å de resolução em complexo com AMP e 2.14Å na forma Apo. A análise das estruturas revelou uma estrutura tetramérica bastante conservada entre as ADSLs, sendo este estado de oligomerização requerido, uma vez que resíduos de três das quatro subunidades compõem o sítio ativo. Apesar do sítio ativo ser altamente conservado entre SmADSL e ADSL humana, a interface dimérica dessas enzimas tem se apresentado suficientemente distintas, o que pode representar um potencial alvo para o desenvolvimento de um inibidor. O ensaio de atividade enzimática de ADSL revelou uma reação endotérmica, indicando que a contribuição da entropia relacionada a grande quantidade de moléculas de água presentes no sítio ativo é importante para a reação cinética. Após diversos experimentos de otimização dos cristais de HGPRT1 e aproximadamente 200 cristais testados, foi obtida uma estrutura em complexo com IMP a 2.8Å de resolução. A análise da estrutura revelou uma estrutura tetramérica. Apesar das subunidades não compartilharem o sítio ativo, este estado de oligomerização é requerido, uma vez que resíduos que compõem o sítio ativo também estão envolvidos em interações na interface dimérica, orientando o resíduo invariável Arg206 na direção do sítio ativo. Foram identificadas quatro mutações na região do sítio ativo entre SmHGPRT e HGPRT humana: Ile149Met, Pro176Arg, Val189Ile e Arg192Lys. Desta forma, a obtenção das estruturas contribui para o entendimento bioquímico desta via essencial para o parasita e de como este pode ser seletivamente privado de recursos. / Schistosoma mansoni is the parasite responsible for schistosomiasis, disease that affects about 300 million people worldwide, and does not have the purine de novo pathway, depending entirely on the purine salvage pathway to supply its demands on purines. Currently, both direct treatment and most disease control initiatives, rely on chemotherapy using a single drug, praziquantel. Concerns over the possibility of resistance developing to praziquantel, has stimulated efforts to develop new drugs for the treatment of schistosomiasis. The purine salvage pathway has been reported as a potential target for developing new drugs against schistosomiasis. Adenosine kinase (AK), hypoxanthine-guanine phosphoribosyltransferase (HGPRT), adenylosuccinate lyase (ADSL), adenylosuccinate synthetase (ADSS) are key enzymes in this pathway. This work is part of a larger project aimed at obtaining all the structures of enzymes involved in purine salvage pathway of Schistosoma mansoni. The cDNA corresponding to the enzymes was amplified and cloned in vector pOPIN, AK isoform 1, HGPRT isoform 1 and ADSL were expressed in E. coli Lemo 21 (DE3) and HGPRT isoform 3 in E. coli B834(DE3); purified in cobalt agarose column, concentrated and crystallized in several conditions of the Morpheus (Molecular Dimensions) crystallization kit at the Oxford Protein Production Facility (OPPF) in Harwell UK. The data collection by xray diffraction were performed at Diamond Light Source UK. Two ADSL structures were obtained, ADSL in complex with AMP at 2.36Å resolution and ADSL Apo form at 2.14Å The analysis revealed a tetrameric structure highly conserved between ADSLs, and this oligomerization state is required since residues three of the four subunits comprise the active site. Despite the active site being highly conserved between human ADSL and SmADSL, the dimeric interface of these enzymes it has been shown sufficiently distinct, which may represent a potential target for the development of an inhibitor. The ADSL enzymatic activity assay showed an endothermic reaction, indicating the contribution of the entropy related to the large quantity of water molecules present in the active site is important for the reaction kinetics. After several optimization experiments of HGPRT1 crystals and about 200 crystals tested was obtained a structure in complex with IMP at 2.8Å resolution. The structure analysis revealed a tetrameric structure. Despite the subunits do not share the active site, this oligomerization state is required, since residues that make up the active site are also involved in interactions in dimeric interface, guiding the invariable residue Arg206 toward the active site. Four mutations were identified in the region of the active site between SmHGPRT and human HGPRT: Ile149Met, Pro176Arg, Val189Ile e Arg192Lys. These structures increase the important structural information available about the Schistosoma mansoni purine salvage pathway and how it can be selectively private resources.
100

Plant community recovery after high severity wildfire and post-fire management in the Klamath Region /

Lopez Ortiz, Maria Jose. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 98-108). Also available on the World Wide Web.

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