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Avaliação do desempenho de emendas por entalhes múltiplos para estruturas em madeira laminada colada / Evaluation of finger joints performance for glued laminated timber structuresStüpp, Ângela 29 July 2016 (has links)
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Previous issue date: 2016-07-29 / UNIEDU / FUMDES / The geometry of finger joint is one of the most important variables when determining the connection strength among timber with structural use purpose. This research aimed to evaluate three finger joint geometries and its correlation with three species of timber from reforestation and three adhesives used for structural purposes. The species were: Eucalyptus grandis, Pinus taeda and Schizolobium parahyba var. amazonicum (known as paricá), and the adhesives: resorcinol formaldehyde, melamine urea formaldehyde and reactive polyurethane. Finger profiles were produced by means of a spindle moulder, glued and pressed in manufacture plant and laboratory. Then, the specimens were flattened obtaining the dimensions as recommended by NBR 7190/1997. The finger joint geometry was measured with a digital caliper, the specimens were tested and the failure modes determined. Statistical analysis was done by evaluating the geometric means by Tukey test with 95% probability. Results showed that E. grandis produced with resorcinol adhesive from geometry B, had the highest tensile strength parallel to the fibers (67,55 MPa). Also, the higher tensile strength values were from the specimens with higher basic density. As for failure modes, 64% of the specimens failed in modes number 3 (14%) and 4 (50%). It was found that all evaluated factors interfered in the results of resistance and, regarding the determination of the best geometry, specie and adhesive, these can not be analyzed separately / A geometria da emenda por entalhes múltiplos é uma das variáveis mais importantes quando se determina a resistência da ligação entre madeiras com finalidade de uso estrutural. O objetivo da pesquisa foi avaliar três geometrias de emendas por entalhes múltiplos e sua correlação com três espécies de madeira de florestas plantadas e três adesivos utilizados para fins estruturais. As espécies foram o Eucalyptus grandis, o Pinus taeda e o Schizolobium parahyba var amazonicum (paricá), e os adesivos: resorcina formaldeído, melamina ureia formaldeído e poliuretano reativo. Os corpos de prova foram fresados, colados e prensados em parque fabril e em laboratório. Posteriormente, eles foram aplainados obtendo-se as dimensões conforme orientação da NBR 7190/1997. Foram medidas as geometrias com paquímetro digital, realizados pré-testes e determinados os modos de ruptura. A análise estatística foi feita avaliando-se as médias de geometria pelo teste de Tukey a 95% de probabilidade. Dos resultados obtidos, destaca-se a espécie E. grandis produzida com o adesivo resorcina da geometria B, que teve a maior resistência à tração paralela às fibras (67,55 MPa). Também, os maiores valores de tensão foram provenientes dos corpos de prova com maior densidade básica. Quanto aos modos de ruptura, 64% dos corpos de prova romperam pelos tipos 3 (14%) e 4 (50%). Verificou-se que todos os fatores avaliados interferiram nos resultados de resistência e, no que se refere à determinação damelhor geometria, melhor espécie e melhor adesivo, não podem ser analisados separadamente
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[en] COMPARATIVE STUDY OF WAX DEPOSITION IN DYNAMIC COLD-FINGER AND PIPE FLOW LOOP, IN THE PRESENCE OF CHEMICAL INHIBITOR / [pt] ESTUDO COMPARATIVO DA DEPOSIÇÃO DE PARAFINA EM DEDO-FRIO DINÂMICO E SEÇÃO TUBULAR, NA PRESENÇA DE INIBIDOR QUÍMICOGUILHERME DOS SANTOS VIEIRA LIMA 27 December 2017 (has links)
[pt] A deposição de parafinas em dutos traduz-se em perdas econômicas relevantes para a indústria. Dentre as formas de mitigação do fenômeno, encontram-se os inibidores de parafina, produtos químicos injetados
continuamente e em baixas concentrações, cujo objetivo é eliminar ou reduzir a deposição. Tradicionalmente, a eficiência de inibição destes produtos para uma dada amostra de petróleo é avaliada em laboratório em equipamento denominado dedo-frio. No entanto, não há uma padronização para o projeto e uso destes equipamentos e procedimentos experimentais de teste. Também, ainda não há
consenso entre fabricantes dos inibidores e operadoras de petróleo sobre a correlação entre a eficiência de inibição apresentada nos testes de dedo frio e aquela observada no campo. O presente trabalho teve como objetivo comparar resultados de deposição de parafina obtidos em dedo frio do tipo dinâmico com aqueles obtidos em duto circular em loop de teste, utilizando solução de teste com propriedades controladas, com e sem a presença de inibidor de parafina. No dedofrio do tipo dinâmico, um cilindro refrigerado imerso no óleo gira com velocidade angular constante, promovendo um escoamento do tipo Taylor-Couette,
caracterizado por padrões de escoamento complexos e diferentes daqueles encontrados em dutos de transporte de petróleo. O trabalho teve como foco o estudo da influência de parâmetros hidrodinâmicos na deposição de parafinas, representados pelo número de Reynolds e tensão cisalhante adimensional sobre a
superfície do depósito. Testes realizados com os fluidos modelo em regime laminar e turbulento mostraram boa correlação entre os resultados de inibição obtidos no dedo frio e no loop de teste, a despeito da diferença nos padrões de escoamento. Testes em regime turbulento resultaram em depósitos menores e
menos porosos, tanto no dedo-frio quanto no loop. Foi também observada a redução da porosidade dos depósitos com a adição do inibidor,independentemente do tipo de equipamento e da condição operacional.
Experimentos no dedo-frio com um segundo fluido, mais viscoso, foram conduzidos com o objetivo de avaliar a influência da viscosidade no processo de deposição, tendo como premissa a diminuição do coeficiente de difusão esperada para o fluido mais viscoso. Ao contrário do esperado, não foi observada variação sensível na deposição com a mudança da viscosidade do fluido. Efeitos positivos e negativos de inibição foram observados nos testes para o inibidor avaliado. Observou-se uma maior atuação do inibidor, seja positiva ou negativa, para experimentos em regime laminar. O presente estudo mostrou que o inibidor pode diminuir a massa total depositada aumentando, no entanto, a massa de parafina depositada. / [en] Wax deposition in pipelines is associated with relevant economic losses for the industry. Wax deposition inhibitors are among the options available to mitigate the problem, being continuously injected in the flow at low concentrations. Traditionally, the inhibition efficiency of these products for a particular oil sample is assessed in a laboratory equipment know as cold finger. However, a standard is still not available for the design and operation of cold fingers. Also, there is no consensus among operators and inhibitor suppliers as to the level of correlation between the inhibition efficiency found in the laboratory and that in the field. The objective of the present work was to compare wax deposition results obtained in a dynamic cold finger apparatus to those obtained in a pipe flow loop, employing a test solution with controlled properties, with and without inhibitor, In the dynamic cold finger, a cylinder immersed in the oil sample rotates at constant angular velocity producing a Taylor-Couette flow in the cylindrical oil container, which is characterized by complex flow patterns, that are distinct from those found in an oil pipeline. The investigation focused on the influence of the flow hydrodynamic parameters on the wax deposition, represented by the Reynolds number and the dimensionless shear stress imposed at the deposit surface. Tests conducted with model fluids in laminar and turbulent regimes displayed good correlation between the inhibition results obtained in the cold finger apparatus and in the test loop, despite the differences in flow patterns. Turbulent flow testes produced smaller and less porous deposits both, in the cold finger and in test loop. Also observed was a reduction in the deposit porosity in the presence of the inhibitor, independently of the equipment type and operational conditions. Experiments in the cold finger for a second more viscous fluid were conducted to assesses the influence of viscosity on the deposition process, and the expected decrease in the diffusion coefficient for the higher viscosity fluid. Contrary to what was expected, no significant variation was observed on the deposits with the viscosity change. Positive and negative inhibition effects were observed in the tests for the particular inhibitor tested. A more significant influence of the inhibitor, either positive or negative, was observed for tests in laminar flow conditions. The present study revealed that the inhibitor could decrease the total deposited mass while increasing the paraffin deposited mass.
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Počítadla (abakus, finger abacus aj.) ve výuce matematických operací na prvním stupni ZŠ. Návrh pracovních listů s využitím počítače. / Abacuses (Abacus, Finger abacus) in teaching mathematic operation in lower primary school classes. Suggestion of worksheets with the use of computer.BŘEČKOVÁ, Jana January 2011 (has links)
In my thesis I am concerned with compiled interactive textbook designed for first-year primary school pupils. This textbook focuses on counting with transfer over 5 and 10 with the use of interactive white board and abacuses. In the introductory part of my work I describe the knowledge pupils have when they start their first school year and I deal with Mathematics at the beginning of the first year, abacuses, interactive white boards, textbook and interactive textbook. The main part applies to interactive textbook manual in which I describe the environment, control and particular examples. I also refer to lessons that have been taught at two primary schools. The conclusion consists of a feed-back obtained from teachers in the form of a questionnaire, my self-assessment, and evaluation of taught lessons and their effect on the basis of worksheets.
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Análise teórica e experimental de vigas de madeira de seção transversal \"I\" para uso em fôrmas para concreto / Theoretical and experimental analysis of wood I-beams for formwork purposeCátia da Costa e Silva 17 May 2010 (has links)
Devido à importância da madeira na construção civil e a preocupação com o impacto ambiental, a engenharia passou a se preocupar com a racionalização de seu uso por meio da apresentação de produtos engenheirados, buscando melhorar as propriedades técnicas das construções em madeira. Novos modos de manufatura foram introduzidos, principalmente no campo da engenharia estrutural, fazendo com que se desenvolvessem elementos comprovadamente superiores em suas propriedades físico-químicas e econômicas a outros normalmente usados. Neste trabalho foram avaliadas as propriedades de resistência e elasticidade de vigas de madeira de seção transversal \"I\", utilizadas na sustentação de painéis de fôrmas para concreto armado e em obras civis estruturais, incluindo as emendas de mesas e alma-mesa utilizadas em sua fabricação, por meio de ensaios de flexão e cisalhamento na linha de cola. Essas vigas são comercialmente chamadas de H2O devido a sua altura de 20 centímetros, sendo compostas de mesa em madeira serrada, almas em compensado sarrafeado, compensado laminado ou madeira serrada, e dois tipos de adesivos o de poliuretano e o de resorcinol-formol. As análises visaram comprovar a eficiência e viabilidade técnica da fabricação e utilização destes materiais nestas vigas. A configuração de viga H2O que apresentou os melhores resultados comparativamente com o mínimo exigido nos ensaios especificados pela norma européia EN 13377:2002 foi a composta por alma de compensado, emenda dentada e colada com o adesivo de Resorcinol-Formol. / Due to the importance of wood in construction and the concern about the environmental impact, engineers have worried about the rationalization of its use through the development of engineered products, seeking the improvement of the technical properties. In this study, the I-beams built with reforestation wood were used for concrete formwork purpose. Their mechanical properties and the connections between flanges and web used in its manufacture were evaluated by means of bending tests and shear in the glue line. These beams are commercially called H2O. The flanges were made from Pinus Oocarpa, the webs were made from laminated plywood, block plywood, and Pinus Oocarpa, and two types of adhesives were used: polyurethane and resorcinol-formaldehyde. The H2O beam configuration showed the best results compared to the minimum required by European standard EN 13377:2002 was with the flange made from lumber, glued with resorcinol-formaldehyde and the web of laminated plywood.
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Estudo experimental de adesivos para fabricação de madeira laminada colada: avaliação da resistência de emendas dentadas, da durabilidade e de vigas. / Experimental study of adhesives for the manufacture of glued laminated timber: evaluation of the strenght of the finger-joints, of durability and of the beams.Maximiliano dos Anjos Azambuja 14 September 2006 (has links)
Neste trabalho propõe-se contribuir para o desenvolvimento de tecnologia nacional investigandoa aplicação de uma nova geração de adesivos para a confecção de elementos estruturais de madeira laminada colada (MLC), viabilizando um menor custo final do produto e tornando-o competitivo no mercado interno e externo. Nesse contexto, avaliou-se a resistência à tração paralela em emendas dentadas com dimensão estrutural, em condições de temperatura ambiente e umidade padrão, usando as espécies Pinus e Eucalipto e vários tipos de adesivos, dentre eles o adesivo poliuretano à base de óleo de mamona, foco principal de estudo deste trabalho. Outro aspecto abordado é o da durabilidade, em que foi avaliado o desempenho dos adesivos Cascophen e poliuretano à base de óleo de mamona por meio de ensaios de resistência ao cisalhamento na lâmina de cola e de resistência à tração de emendas dentadas, ambos em corpos-de-prova isentos de defeitos. Também foi avaliada a qualidade da colagem das lâminas, por meio de ensaios de flexão buscando-se a ruptura por cisalhamento, em vigas de MLC com dimensões estruturais, fabricadas em laboratório com os adesivos Cascophen, poliuretano à base de óleo de mamona e Purbond. Os resultados obtidos permitem concluir o bom desempenho do adesivo poliuretano à base de óleo de mamona, demonstrando a sua adequação para aplicação na produção de madeira laminada colada. / The aim of this work is the development of national technology investigating the application of a new adhesive generation to fabrication of glued laminated timber (Glulam) structural members, making possible a lesser final cost of the product and becoming it competitive in the domestic and external market. In this context, the parallel tensile to the fibers tests in joint pieces with structural dimension, in conditions of ambient temperature and standard relative humidity, was evaluated using the species Pinus and Eucalyptus and some types of adhesives, among them the polyurethane adhesive base on castor oil, that is the main focus of study of this work. Another approached aspect is the durability, in which was evaluated the performance of the Cascophen and the polyurethane adhesive base on castor oil adhesive, by means of shear strength tests in the lamina of glue and tensile strength tests of joint laminas, both made in specimens exempt of defects. Also the quality of the collage of lamina, by means of bending and shearing tests, in glulam structural beams was evaluated, which were manufactured in laboratory with the adhesives Cascophen, polyurethane adhesive base on castor oil and Purbond. The results allow concluding the well-behaved performance of polyurethane adhesive base on castor oil, demonstrating its adequacy for application in glued laminated timber fabrication.
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Mxr1p is a Global Regulator of Multiple Metabolic Pathways in the Methylotrophic Yeast Pichia PastorisSahu, Umakant January 2016 (has links) (PDF)
The present study is aimed at examining the ability of Pichia pastoris to utilize acetate and amino acids as the sole sources of carbon. We demonstrate that the zinc finger transcription factor Mxr1p, which is a positive regulator of methanol metabolism, is also required for the growth of P. pastoris in media containing acetate or amino acids as the sole source of carbon. We have identified the target genes of Mxr1p in cells cultured in media containing acetate or amino acids as the sole carbon source. We conclude that Mxr1p is a global regulator of multiple metabolic pathways in P. pastoris.
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Beyond the Surface : Bringing attention to the origin of food with the fish finger as canvasBenevides, Lara January 2017 (has links)
The many technological processes that products go through can make consumers less related to the systems behind them and their origins. The same thing happens to food. This project highlights the implications of a food system within the global scale of today’s mainstream economy and explores the possibilities for a product that originates from a more sustainable food system. Apart from re-designing a processed everyday food product, the aim of this study is to increase awareness of the pressure that the world’s fish stocks are suffering due to overfishing – an issue that is being aggravated by our current food system. For this reason fish fingers (aka fish sticks), which is a well known food product in Sweden, have been chosen as the primary focus in order to make a complex issue more tangible. By re-evaluating what a fish is, analysing current food systems and food products, making sensory explorations and collaborating with chefs, Havsbitar 1.0 and 2.0 (”Sea Bites” 1.0 and 2.0) have been developed. It is a series of fish fingers that has been designed for a desirable future scenario, where a resilient food system has been implemented. The aesthetics of Havsbitar intends to connect it to its ingredients and to the ecosystem it comes from, while maintaining the key characteristics of the fish finger as we know it today. The acceptance of the concept as a food product is an important variable to this project. The concept is placed in the field of Transition Design. Nevertheless, the design of Havsbitar 1.0 is a proposal that is intended to create possibilities for dialogue about an ideal industrialized commercial product. On the other hand, Havsbitar 2.0 follows a more discursive, critical angle towards the fact that fish fingers do not resemble fish, its main ingredient. Havsbitar 2.0 could then be placed in the field of Critical Food Design and Discursive Design.
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Relations structure-fonctions chez la protéine multi-fonctionnelle P1 du virus de la panachure jaune du riz / Structure-function analysis of the multifunsctionnal movement protein P1 from the rice yellow mottle virusPoignavent, Vianney 15 July 2015 (has links)
Le virus de la panachure jaune du riz (virus RYMV pour Rice Yellow Mottle Virus) infecte principalement le genre Oryza et provoque d'importants dégâts sur les cultures de riz en Afrique. Bien que son génome soit rudimentaire, ce virus code des protéines essentielles pour son maintien chez l’hôte en dépit des mécanismes de défense de la plante. Les travaux récents de l’équipe ont permis d’identifier la protéine P1 codée par ce virus comme une protéine qui pourrait, grâce à sa propriété de suppresseur de RNA silencing, permettre au virus de contourner un mécanisme de défense essentiel de l’hôte et permettre au virus de perpétuer son cycle viral. Peu de données concernant les mécanismes d’action de la protéine P1 sont disponibles à ce jour. Le travail entrepris au cours de ma thèse a donc consisté à compléter les connaissances sur la biochimie de cette protéine, à définir sa structure tridimensionnelle et à mettre à jour sa localisation sub cellulaire afin de révéler des propriétés qui pourraient nous permettre non seulement de mieux comprendre comment cette protéine opère ses fonctions mais également de définir des méthodes de lutte adéquates contre ce virus. Ainsi, je montre que la protéine P1 constitue une nouvelle famille de protéine à doigt de zinc possédant une structure 3D inédite composée d’un premier domaine impliqué dans la dimérisation de la protéine et dans des interactions avec des ligands dont certains pourraient provenir de la plante hôte. Mon travail permet également d’identifier un deuxième domaine senseur de l’état redox au sein de la protéine qui lui permet probablement de sonder l’état de la plante pendant l’infection virale et d’adapter ses conformations pour assurer ses fonctions. Finalement, une approche par mutagénèse sur la protéine P1 assistée par la nouvelle structure 3D démontre qu’il est désormais possible d’identifier les résidus essentiels à la protéine pour sa participation dans l’infection virale. Ce travail ouvre donc de nombreuses perspectives pour de futures études de mécanistique sur ces domaines-clé de la protéine, ainsi que pour des études sur sa diversité génétique au sein des très nombreux isolats du virus RYMV en Afrique. / The virus of rice yellow mottle virus (RYMV for Rice Yellow Mottle Virus) mainly infects the genus Oryza and causes significant damage to rice crops in Africa. Although its genome is rudimentary, this virus code essential proteins for its maintenance in the host despite the defense mechanisms of the plant. Recent work by the team has identified the P1 protein encoded by the virus as a protein that could, through its ownership of RNA silencing suppressor, allow the virus to bypass an essential defense mechanism of the host and allow the virus to perpetuate its viral cycle. Little data on the mechanisms of action of the P1 protein is available to date. The work undertaken during my thesis was therefore to supplement the knowledge of the biochemistry of this protein, to define its three-dimensional structure and update its sub cellular localization to reveal properties that could enable us not only to understand how this protein works its functions but also to define methods of adequate response against the virus. Thus, I show that the P1 protein is a new zinc finger protein family having a unique 3D structure consisting of a first domain involved in the dimerization of the protein and in interactions with ligands some of which may originate from the plant host. My work also identifies a second sensor field in the redox state of the protein that probably allows him to probe the state of the plant during viral infection and adapt its conformation to conduct their duties. Finally, a mutagenesis approach to P1 assisted by the new 3D protein structure shows that it is now possible to identify critical residues in the protein for its participation in the viral infection. This work thus opens up many possibilities for future mechanistic studies on these key areas of the protein, as well as for studies of genetic diversity within many RYMV isolates of virus in Africa
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An Analysis of Terminology Describing the Physical Aspect of Piano TechniqueWheatley-Brown, Michèle T January 2011 (has links)
Mastering the physical aspect of piano technique has long been a topic of great interest and importance to pianists. This is borne out in the numerous pedagogical approaches on the topic of piano technique. Despite the many contributions from pedagogues and scholars in developing an understanding of piano technique, many conflicting approaches often cause more confusion than clarity. After reviewing the literature on pedagogical approaches to piano technique, this study determined that problematic language might lie at the root of the confusion. Core concepts identified in the review of literature as recurring areas of misunderstanding were tension, relaxation, co-contraction, arm weight, and hand and finger shape.
The purpose of this study is to seek where issues of language exist in contemporary piano pedagogical approaches and to show how these problems may contribute to the systemic confusion in piano technique. To do this, the language that is used to describe and define the core concepts identified in the review of literature is analyzed in five modern pedagogical approaches. Five authors who have developed approaches that reflect current trends in piano technique have been selected for this study: Barbara Lister-Sink; Dorothy Taubman; Thomas Mark; Fred Karpoff; and Alan Fraser. The first step of this study entails collecting data from each of the five pedagogical approaches. The data is then analyzed for consistency and accuracy. Problems in language that contribute to the inconsistencies and inaccuracies are examined and illustrated with material from the data collection.
This study concludes by identifying the main sources of confusion in the use of language: inconsistent and inaccurate use of terms; wavering between scientific, common, and invented language; challenges in describing opposing qualities that come from tension and relaxation; and failing to discern between the individual subjective experience and the mechanics of movement. By recognizing where the problems in language exist, this study represents an important first step for the pedagogical community to reach a common understanding of the language used to describe the physical aspect of piano technique.
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Étude fonctionnelle des sous-domaines de Pcf11 : rôle du 2nd NTD dans la terminaison de transcription des snoRNAs et des motifs liant le zinc dans les activités de maturation de l’extrémité 3’ des ARN messagers. / Functional analysis of Pcf11 sub-domains : role of the 2nd NTD in transcription termination of snoRNAs and zinc finger motifs in 3’-end processing of mRNAsGuéguéniat, Julia 03 December 2015 (has links)
Chez les eucaryotes, la maturation de l’extrémité 3’ des ARNs messagers a lieu lors de la transcription et regroupe deux étapes : le clivage endonucléolytique du transcrit au niveau d’un site spécifique et l’ajout d’une queue poly(A) sur le fragment en amont du site de clivage. Chez S. cerevisiae, le complexe de polyadénylation est formé par 20 protéines, regroupées principalement en deux sous-complexes : CF IA et CPF. Nous nous intéressons plus spécifiquement à Pcf11, sous-unité du complexe CF IA. Pcf11 est formé de sept sous-domaines, mais la fonction d’une grande partie de la protéine n’est pour l’instant pas connue. Par exemple, aucune fonction n’est associée à la région située entre le domaine d’interaction avec le CTD de l’ARN polymérase II (CID) et une répétion de 20 résidus glutamines. Récemment, la structure de ce domaine, appelé 2nd NTD a été décrite. Pour essayer de comprendre la fonction du 2nd NTD et des motifs liant le zinc encadrant le domaine d’interaction avec Clp1, nous avons mis en place une stratégie systématique de mutagénèse, soit par délétions, soit par mutations ponctuelles. Le 2nd NTD est formé de trois hélices α et interagit avec l’ARN. La délétion de ce domaine conduit à un phénotype de croissance lente chez la levure et un défaut de terminaison de transcription des snoRNAs. Malgré une similarité de structure et de fonction, le 2nd NTD présenterait une fonction indépendante. La fonction des motifs liant le zinc n’est pour l’instant pas connue. Cependant, la mutation de l’un de ces deux motifs conduit à un défaut de clivage et de polyadénylation in vitro. La mutation des deux motifs est létale chez la levure. / In eukaryotes, poly (A) tails are added to nuclear pre-mRNA 3'-ends in the two steps of cleavage and polyadenylation. This co-transcriptional processing requires the activity of a large protein complex comprising at least 20 different polypeptides in yeast organized primarily into the two factors CF IA and CPF. We are interested in the functional characterization of Pcf11, a CF IA subunit. The Pcf11 protein is organized into seven different domains, but here is still a large portion of the polypeptide that has not yet been characterized. For example the region from the end of the CTD interaction domain (CID) to an uninterrupted stretch of 20 glutamine residues has no known function. Recently, the structure of this region, called the 2nd NTD have been characterized. To gain insight into the function of the 2nd NTD and the two zinc fingers motif surrounding the Clp1 interaction domain, we have employed a systematic strategy of mutagenesis, either by deletion or via point mutations. The 2nd NTD is a folded domain composed of three α-helices. The deletion of this domain induced a severe defect of growth in yeast and impaired transcription termination of snoRNAs. Despite its similarity in structure and function with the CID, the 2nd NTD seems to act like an independent RNA binding domain. We don’t know yet the real function of the two zinc fingers motif at the C-terminal region of Pcf11, but the mutation of Cystein residues into serine of one of the two motifs impaired cleavage and polyadenylation. The mutation of the first motif is less harmful than the mutation of the second motif. The simultaneous mutation is lethal in yeast.
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