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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.
151

Critérios de seleção para características de importância econômica em ovinos da raça Santa Inês / Selection criteria for economically important traits in Santa Inês sheep

Oliveira, Elisa Junqueira 11 April 2016 (has links)
Os objetivos deste estudo foram: estimar parâmetros genéticos para: coloração da conjuntiva ocular (CCO), contagem de ovos por grama de fezes (OPG), volume globular (VG), proteína plasmática total (PPT), escore da condição corporal (ECC) e peso corporal (PC) e, ainda, explorar o perfil genético da população, utilizando análises de agrupamento com base nos valores genéticos. E estimar parâmetros genéticos para peso corporal (PC) e características de conformação (perímetro torácico (PT), altura da garupa (AG), altura da cernelha (AC), largura da garupa (LG), comprimento corporal (CC) e escore de condição corporal (ECC)) com intuito de definir critérios de seleção. Foram analisadas um total de 2.525 informações de 771 animais nascidos entre 2002 e 2013, filhos de 68 carneiros e 352 ovelhas, pertencentes a sete rebanhos localizados no estado de São Paulo. Os animais foram avaliados mensalmente durante junho de 2013 a outubro de 2014. Os componentes de covariância foram estimados por modelo animal em análises multicaracterísticas, por meio de abordagem Bayesiana. As estimativas de herdabilidade para CCO, PC, VG, PPT, OPG e ECC foram 0,21 (0,04); 0,18 (0,05); 0,30 (0,06); 0,17 (0,05); 0,19 (0,03) e 0,31 (0,07), respectivamente, indicando que a seleção pode ser realizada com base no valor genético dos indivíduos para estas características. As correlações genéticas entre a CCO e PC, VG, PPT, OPG e ECC foram -0,40 (0,17); -0,63 (0,09); -0,23 (0,15); 0,77 (0,09); -0,59 (0,11), respectivamente, e entre PC e ECC a correlação genética foi de 0,84 (0,15). Assim como as outras medidas de resistência a verminose, a CCO pode ser incluída como critério na seleção; esta apresenta estimativa de herdabilidade mediana correlação genética favorável com as outras medidas de resistência a verminose e com PC e ECC, além de ser de fácil obtenção e baixo custo. Foi possível obter grupos de indivíduos com perfil genético de resistência/resiliência a verminose a partir das análises de agrupamento. As estimativas de herdabilidade para PC, PT, AG, AC, LG e ECC foram: 0,25 (0,08); 0,22 (0,07); 0,24 (0,07); 0,25 (0,07); 0,19 (0,05) e 0,32 (0,07), respectivamente e as correlações genéticas entre o peso e as medidas corporais foram de alta magnitude, variando entre 0,66 (0,11) a 0,98 (0,016), indicando que as medidas corporais, principalmente o perímetro torácico, pode ser incluído como um critério de seleção complementar ao peso corporal. / The objective of this study was to estimate genetic parameters for conjunctival staining score (CSS), fecal eggs count (FEC), packed cell volume (PCV), total plasma protein (TPP), body condition score (BCS) and body weight (BW), and also explore the genetic profile of the population, using cluster analysis based on genetic values. And to estimate genetic parameters for body weight (BW) and conformation traits (heart girth (HG), hip height (HH), wither height (WH), rump width (RW), body length (BL) and body condition score (BCS)) to define selection criteria. A total of 2,525 records from 771 animals born between 2002 and 2013 to 68 rams and 352 ewes, belonging to five herds located in the São Paulo state were used. The animals were evaluated monthly during June 2013 to October 2014. The covariance components were estimated by animal model multi-trait using Bayesian analysis. The estimates of heritability for CSS, BW, PCV, FEC, BCS and PPT were 0.21 (0.04); 0.18 (0.05); 0.30 (0.06); 0.19 (0.03), 0.31 (0.07) and 0.17 (0.07), respectively, indicating that you can select animals based on the genetic value of individuals. The genetic correlations between CSS and BW, CSS and PCV, CSS and PPT, CCS and FEC, CSS and BCS and between the BW and BCS -0.40 (0.17); -0.63 (0.09); -0.23 (0.15); 0.77 (0.09); 0.84 (0.15), respectively. As other resistance traits the worms, the CCO can be included as a criterion in the selection. For this trait has estimated median heritability (0.21±0.04) and positive genetic correlation with other resistance measures to worms and BW and BCS, as well as being easy to obtain and low cost. It was possible to obtain groups of individuals with genetic profile of resistance / resilience to worms from the cluster analysis. The estimates of heritability for BW, HG, HH, WH, RW, BL and BCS were 0.25 (0.08); 0.22 (0.07); 0.24 (0.07); 0.25 (0.07); 0.19 (0.05) and 0.32 (0.07), respectively and genetic correlations between weight and body measures were highest magnitude, ranging from 0.66 (0.11) to 0.98 (0,016) indicating that body measurements, mainly heart girth, can be included as a criterion in the selection in addition to body weight.
152

The effect of charge and temperature on gas phase protein conformational landscapes : an ion mobility mass spectrometry investigation

Jhingree, Jacquelyn January 2018 (has links)
The amino acid sequence of a protein determines its 3D fold, the ease with which its native structure is formed, its function, the conformational preferences sampled and the tendency to interact with itself (aggregation) and binding partners. In addition, certain conformational preferences can lead to dysfunction resulting in different diseased states in organisms. All of these conformations can be described by a protein's energy landscape; a native (functional) state being localised at the energy minimum. As protein dynamics is crucial to function it is important to monitor the sampling of different conformations. Thus the work in this thesis reports on two methods for monitoring protein conformation and conformational change in the gas phase using ion mobility mass spectrometry (IM-MS). The measurement from IM-MS methods allow the determination of a collision cross section (CCS) which is an indicator of a molecule's 3D shape. First, the effect of charge on protein structure is investigated by manipulation of protein charge, post electrospray ionisation (ESI), by exposure to radical anions of the electron transfer reagent, 1,3-dicyanaobenzene; the charge reduced products formed are the result of electron transfer to the charged protein without any dissociation (ETnoD). IM-MS is used to monitor the conformational preferences of the altered and unaltered precursor and its products. Secondly, intermediate (transient) conformers are formed by activating the charged protein in the source region of an instrument post ESI. Activation of the protein precursor allows the sampling of different conformational preferences after energetic barriers have been overcome; IM-MS following activation allows for the monitoring of protein conformational change before and after. Further, variable temperature (VT) IM-MS allows for the deduction of intermediate structures with a focus on measurements at cryogenic temperatures whereby intermediate structures can be 'frozen out' post activation; intermediate structures which would otherwise anneal out at room temperature. With both methods a range of conformer populations are mapped for different protein molecules sampled upon different energetic inputs (via activation) and the disruption of intramolecular neutralising contacts/salt bridges (via charge reduction) one of the main interactions responsible for maintaining the structural integrity (3D fold) of proteins.
153

A conformação vulvar e a espessura placentária são indicativos de placentite ascendente na égua? / The vulvar conformation and the combined thickness of the uterus and placenta (CTUP) are indicatives of ascending placentitis?

Löf, Henrique Kurtz January 2010 (has links)
O presente trabalho objetivou verificar se a conformação vulvar e a espessura da união útero placentária (EUUP) são indicativos de placentite ascendente em éguas Puro Sangue de Corrida no final da gestação. Foram utilizadas 333 éguas Puro Sangue de Corrida, com idades que variaram de 3 a 28 anos. As éguas foram examinadas nos últimos 30 dias que antecederam a previsão de parto, para avaliação da condição corporal, análise da conformação vulvar, medida da espessura da união útero placentária (EUUP). Os parâmetros de conformação vulvar foram avaliados pelo comprimento vulvar efetivo e total (CE e CT), maior ângulo de inclinação (MA) da vulva, ângulo de inclinação até a comissura dorsal (A). O resultado CE x A forneceu o Índice Caslick (IC). Após o parto uma amostra da região da estrela cervical foi retirada para exame histopatológico do cório alantóide para diagnóstico de placentite.A condição corporal média das reprodutoras foi 4,1 (±0,6); o maior ângulo de inclinação (A) médio foi de 11,5º (±8,8); o ângulo até a comissura dorsal médio foi de 10,5º (±8,3), o comprimento vulvar efetivo (CE) médio foi de 2,3 cm (±1,6) e o comprimento vulvar total (CT) médio foi de 7,2 cm (±1,9); o Índice Caslick (IC) médio foi de 24,9 (±29,6). O modelo de equação logística utilizou como variável resposta o resultado do exame histopatológico da placenta, e como variáveis explicativas o comprimento efetivo e a espessura média da união útero placentária (EUUP) e suas interações, por terem P inferiores a 0,3. Não se observaram diferenças significativas entre os termos do modelo. Conclui-se que a conformação vulvar e a espessura da união útero placentária (EUUP) não são indicativos de placentite ascendente na égua Puro Sangue de Corrida no final da gestação. / The present study aims to verify if the combined thickness of the uterus and placenta (CTUP) and vulvar conformation are indicative of ascending placentitis on thoroughbred broodmares in the end of gestation. 333 thoroughbred broodmares, with ages between 3 and 28 years old were used. The broodmares were examined 30 days prior to the expected birth date for evaluation of body condition, vulvar conformation, CTUP. The parameters of vulvar conformation were evaluated by its total length and effective length (TL and EL), vulva greater declination angle, declination angle until dorsal commmisure (A). A Caslick Index (IC) was obtained upon A x CE measurements factor (IC). A sample of the cervical star region was taken after the birth for histopathological exam of the allantochorion for placentitis diagnosis. The average body condition of the broodmares was 4,1 (±0,6); average (A) was 11,5º (±8,8); average angle until dorsal commmisure was 10,5º (±8,3), the average effective length (CE) was 2,3 cm (±1,6) and the vulvar average total length (CT) was 7,2 cm (±1,9); the average Caslick Index (IC) was 24,9 (±29,6). The model of logistic equation used as explanation variable the result of the placenta histopathological exam, and as answer variables the effective length and CTUP, and its interactions, by having P lower than 0,3. No significant differences were observed between the terms of the model. It was concluded that vulvar conformation and thickness of the uterus and placenta (CTUP) are not indicatives of ascending placentitis on the thoroughbred broodmares in the end of gestation.
154

Aspectos estruturais de proteínas do veneno crotálico modificadas por radiação ionizante / Structural aspects of crotalic venom proteins modified by ionizing radiation

Karina Corleto de Oliveira 29 January 2010 (has links)
Os acidentes ofídicos representam um sério problema de Saúde Pública, principalmente em países subtropicais. No Brasil, segundo o Ministério da Saúde, foram notificados cerca de 26 000 acidentes em 2008. O gênero Crotalus (cascavéis) é responsável por aproximadamente 7% do total, porém apresenta um alto índice de letalidade, sendo que 72% dos casos de acidentados sem o tratamento adequado com soro específico (soro anticrotálico) chegam ao óbito. A produção de soro no Brasil, único tratamento eficaz nos casos de acidentes ofídicos, utiliza equinos que, apesar do grande porte, apresentam diminuição da longevidade quando comparado com os cavalos não imunizados. A radiação ionizante tem se mostrado como excelente ferramenta na diminuição da toxicidade de venenos e toxinas isoladas e tem resultado na obtenção de melhores imunógenos para a produção de soro, além de contribuir para o bem estar dos animais soro-produtores. Visto que a ação da radiação gama em toxinas ainda não está totalmente esclarecida do ponto de vista estrutural, foi proposto neste trabalho, a caracterização de duas proteínas da espécie Crotalus durissus terrificus: a crotoxina e a crotamina. Após o isolamento das toxinas de interesse por técnicas cromatográficas, estas foram submetidas às análises estruturais com a aplicação das seguintes metodologias: Fluorescência, Dicroísmo Circular, Calorimetria Diferencial e Espectroscopia Infravermelho. Estas análises mostraram que tanto a crotamina como a crotoxina, quando submetidas à radiação gama, apresentaram alterações na conformação estrutural em comparação com as amostras no estado nativo. Tais alterações possivelmente ocorrem na estrutura terciária e secundária das proteínas e podem explicar as modificações quanto à atividade biológica destas toxinas. / Snake bites are a serious public health problem, especially in subtropical countries. In Brazil, the Ministry of Health notified around 26 000 accidents in 2008. The genus Crotalus (rattlesnakes) accounts for approximately 7% of the total, with a high mortality rate of 72% when untreated with the specific serum, the only effective treatment in case of snake bites. In Brazil, the serum is produced in horses which, despite the large size, have a reduced lifespan due to the high toxicity of the antigen. Ionizing radiation has proven to be an excellent tool for reducing the toxicity of venoms and isolated toxins, resulting in better immunogens for serum production, and contributing to the welfare of serumproducing animals. Since the action of gamma radiation on venoms and toxins has not been yet fully clarified from the structural point of view, we proposed in this paper, to characterize two toxins of the species Crotalus durissus terrificus: crotoxin and crotamine. After isolation of the toxins of interest by chromatographic techniques, they were subjected to structural analysis with the application of the following methods: Fluorescence, Circular Dichroism, Differential Calorimetry and Infrared Spectroscopy. These tests showed that both crotamine as crotoxin when subjected to gamma radiation, showed changes in their structural conformation compared with the samples in the native state. Such changes probably occur in the secondary and tertiary structure and may explain the changes on the biological activity of these toxins.
155

Desempenho reprodutivo da égua crioula / Reproductive performance of the Crioulo mare

Möller, Gabriella January 2014 (has links)
O objetivo deste trabalho foi avaliar alguns aspectos reprodutivos de éguas Crioulas a fim de verificar a influência destes nos índices de prenhez: idade das éguas, status reprodutivo, uso do cio do potro, presença de líquido intra-uterino (LIU), eficiência dos tratamentos pós-cobertura, presença de cistos endometriais, realização de vulvoplastia, incidência de ovulações duplas e gestações gemelares. Foram utilizados 517 ciclos de 406 éguas Crioulas de um rebanho comercial, com idades entre dois e vinte e dois anos. O índice de prenhez por ciclo foi de 80,5% aos 12 dias, 76,5% aos 42 dias e a mortalidade embrionária foi de 3,9%. O índice de prenhez foi influenciado pela idade das éguas (P < 0,01). O índice de prenhez no cio do potro foi de 85,4%, melhor que o índice obtido pelas éguas em que não se utilizou este cio e que foram cobertas no subseqüente (P = 0,07). O método de cobertura influenciou a prenhez, sendo a inseminação superior à monta natural (P = 0,01). A idade influenciou a presença de LIU sendo a incidência em éguas com mais de 12 anos maior que nas mais jovens (P < 0,01). A presença de cistos endometriais influenciou negativamente a taxa de prenhez aos 12 e aos 42 dias (P = 0,00). A correção cirúrgica da região perineal melhorou os índices de prenhez aos 12 e aos 42 dias (P < 0,05). A taxa de ovulações duplas foi de 4,84% e não influenciou os índices de prenhez aos 12 e aos 42 dias (P > 0,5). Em 6 ciclos (1,16%) de 5 éguas solteiras foram observadas gestações gemelares. Concluímos que a fertilidade das éguas Crioulas é influenciada pela idade das éguas, pela conformação vulvar, pela presença de cistos endometriais e pelo status reprodutivo. O acúmulo de LIU é um fator importante na reprodução da égua Crioula e deve ser observado e devidamente tratado para a obtenção de melhores índices de prenhez. / The aim of this study was to evaluate the reproductive aspects of Crioulo mares to verify the influence of the following aspects on the pregnancy rates: mare’s age, reproductive status, use of foal heat, presence of intrauterine fluid (IUF), efficiency of post-breeding treatments, presence of endometrial cysts, incidence of double ovulations and twin pregnancies. There were used 517 cycles of 406 Crioulo mares of a commercial herd, with ages varying from 2 to 22 years old. Pregnancy rate per cycle was 80.5% at 12 days, 76.5% at 42 days and embryo mortality was 3.9%. The pregnancy rate was influenced by the age of the mares (P < 0.01). Pregnancy rate on foal heat was 85.4%, better than the rate obtained by the mares which foal heat was not used and the subsequent cycle was (P = 0.07). The breeding method influenced pregnancy, being artificial insemination superior to natural breeding (P = 0.01). Age influenced the presence of IUF, once the incidence was higher in mares with more than 12 years old than in younger mares (P < 0.01). The presence of endometrial cysts negatively influenced the pregnancy rate at 12 and 42 days (P = 0.00). Surgical repair of perineal region improved the pregnancy rates at 12 and 42 days (P < 0.05). The rate of double ovulations was of 4.84% and did not influence the pregnancy rates either at 12 and 42 days (P > 0.5). In 6 cycles (1.16%) of 5 single mares there were observed twin pregnancies. We concluded that the fertility of Crioulo mares is influenced by the age of the mares, vulvar conformation, presence of endometrial cysts and reproductive status. The accumulation of IUF is an important factor on the reproduction of Crioulo mares and must be observed and correctly treated in order to obtain better pregnancy rates.
156

Mécanismes moléculaires de l'agrégation de l'insuline induite par la surface des matériaux / Molecular mechanism of material-induced insulin aggregation.

Nault, Laurent 24 October 2012 (has links)
L'agrégation protéique induite par la surface des matériaux est un phénomène important dans la stabilité des protéines thérapeutiques. En utilisant l'insuline humaine, nous avons étudié les phénomènes agrégation en présence de surfaces neutres hydrophobes ou hydrophiles et avons montré que la nucléation a lieu sur les surfaces hydrophobes que l'on soit à pH 2.5 ou 7.3. Nous avons montré que l'énergie d'activation de la nucléation est abaissée sur surface hydrophobe. De plus, il apparait que l'agitation de la solution a des effets antagonistes. En particulier, les forces hydrodynamiques de cisaillement détachent de la surface les fibres. Par Résonance Plasmonique de Surface, spectroscopie infrarouge et microscopie à fluorescence, nous avons pu définir les étapes moléculaires ayant lieu à l'interface matériaux hydrophobe/solution. L'insuline s'adsorbe tout d'abord rapidement sur la surface, puis s'accumule lentement parallèlement à une transition de la structure α initiale vers une structure β, aboutissant à la formation de fibres amyloïdes. Par la suite, nous avons étudié le mécanisme d'action d'un peptide connu pour accélérer l'agrégation de l'insuline (LVEALYL). Ce peptide s'adsorbe de façon stable sur la surface hydrophobe en structure β et facilite l'accumulation d'insuline. De plus, il apparait que la séquence du peptide n'est pas essentielle à son action car différents peptides adoptant une structure β sur la surface sont également capables d'induire l'agrégation de l'insuline. La présence de prolines aboli cette action. Ces résultats apportent d'importantes informations sur les mécanismes moléculaires d'auto-association de l'insuline. L'hydrophobicité du matériau facilite le dépliement de l'insuline adsorbée, aboutissant à l'exposition du segment LVEALYL. Cette séquence facilite la propagation du changement de conformation vers les molécules nouvellement adsorbées. Agir contre ce phénomène pourrait permettre de stabiliser les solutions protéiques. / Material surface-induced protein aggregation is important for the stability of therapeutic proteins. Using human insulin, we first study its amyloidal aggregation on neutral hydrophobic or hydrophilic surfaces and show that nucleation takes place on the hydrophobic surfaces at both pH 2.5 and 7.3. We show that the activation energy for nucleation is lower on hydrophobic surfaces than in solution. We observed that agitating the solution has several antagonistic effects. In particular, the hydrodynamic shear stress detaches surface-borne fibrils. Using Surface Plasmon Resonance imaging, infrared spectroscopy and fluorescence microscopy we then define the sequence of molecular events that happen at the interface between hydrophobic materials and fluid phase. Insulin first adsorbs rapidly on the surface and then continues to accumulate, in parallel with an alpha-to beta-structural transition leading to amyloid fibril formation. Hereafter, we study the mechanism of action of a small peptide known to accelerate insulin aggregation (LVEALYL). This peptide stably adsorbs in β-conformation on the surface and helps accumulating insulin on the surface. Moreover, it appears that its sequence is not essential for its effectiveness, since several peptides, having a β-sheet structure on the surface, induce insulin aggregation. The presence of prolines abolishes its pro-aggregative activity. These results shed light on the molecular details of insulin self-association. The hydrophobic nature of material surfaces facilitates the unfolding of adsorbed insulin, resulting in the exposure of the LVEALYL peptide segment. This peptide promotes the propagation of conformational changes among incoming proteins. Counteracting this propagation could help stabilizing protein solutions.
157

The mechanisms of serpin misfolding and its inhibition

Devlin, Glyn L. January 2003 (has links)
Abstract not available
158

On the effects of external stresses on protein conformation.

Budi, Bunarta Hendra (Akin), akin.budi@rmit.edu.au January 2006 (has links)
The use of electromagnetic devices such as microwave ovens and mobile phones has certainly brought convenience to our lives. At the same time, the proliferation of said devices has increased public awareness of the potential health hazards. It is generally assumed that there is little or no risk associated with the use of electromagnetic devices, based on the small amount of power associated with those devices. However, case studies on animals indicate that the risk cannot be entirely ruled out. It has long been known that proteins are sensitive to stress, arising from various sources such as temperature, chemical, pressure, and changes in pH condition. In all of these cases, the protein exhibits clear signs of damage and distress, which range from slight unfolding to complete loss of structure. Frequently, the damage to the protein is alleviated by refolding, either by itself or by the aid of molecular chaperones. However, if the damage to the protein is too great, the protein will generally undergo proteolysis. Opinion has been divided over the implication of prolonged use of electromagnetic devices to human health. Studies conducted on animals so far have given conflicting results. The studies on the separate components, electric and magnetic fields, also give inconclusive results. This indicates that our understanding on how electric and magnetic fields interact with biological matter is incomplete. In this project, we use molecular dynamics to explore the behaviour of two forms of insulin chain-B, isolated and monomeric (in the presence of chain-A with all disulfide bonds intact), at ambient conditions and under the influence of various stress. Specifically, we focus our attention to thermal stress and electric field stress. The electric field stress considered in this study takes several forms: static and oscillating with three different frequencies. These fields have strength ranging from 1806 V/m to 109 V/m. By performing molecular dynamics simulations totalling over 500 ns, we have gained valuable insights into the effects of elevated temperature and electric field on insulin chain-B. We observed differences in the damage mechanisms by the application of static electric field and oscillating field. The application of static fields restricts the conformational freedom of a protein, whereas the application of oscillating fields increases the mobility and flexibility of the protein, similar to the effect of thermal stress. Both of these interfere with the normal behaviour of a protein. We have also observed frequency-dependent effects, with low frequency fields having static field-like characteristics in damage mechanism.
159

Synthèse et étude physico-chimique de ligands macrocycliques, macrobicycliques et macrotricycliques dérivés du 5,12-dioxocyclame

F., Laurent 08 November 2002 (has links) (PDF)
Le travail présenté dans le mémoire apporte une contribution dans le domaine de la synthèse et de la caractérisation structurale, spectroscopique et thermodynamique de ligands macropolycycliques dérivés du 5,12-dioxocyclame (L1). <br />La première partie est consacrée à l'étude du ligand L1, de son dérivé N-méthylé L2 et d'un récepteur ditopique constitué de deux unités dioxocyclamiques maintenues face-à-face par des ponts m-xylyle (L3). Des titrages potentiométriques ont mis en évidence la protonation coopérative des deux diamides monocycliques et un phénomène d'allostérie induit par le proton dans le cas du macrotricycle L3. Les complexes de nickel(II) et de cuivre(II) de géométrie plan-carrée ont été isolés et caractérisés par diffraction des rayons X, spectroscopies IR, UV-vis et RPE. La formation de liaisons hydrogène intermoléculaires entre les atomes d'oxygène amidiques et les molécules d'eau cocristallisées affectent l'énergie des orbitales d du cuivre. <br />La seconde partie relate la synthèse et les études physico-chimiques à l'état solide et en solution de macrobicycles possédant une anse o-xylyle (L4), m-xylyle (L5 et L7) ou pyridyle (L6). Leurs propriétés structurales et acido-basiques sont gouvernées par la formation de liaisons hydrogène intramoléculaires qui impliquent les amines tertiaires dont la protonation est lente à l'échelle de temps de la spectroscopie RMN. Les complexes de cuivre(II) correspondants ont été étudiés par diffraction des rayons X et par spectroscopies IR, UV-vis et RPE. Les ligands L4, L5 et L7 coordinent l'ion Cu2+ selon une géométrie plan-carrée déformée tandis que le ligand pentadentate L6 conduit selon le pH à la formation réversible d'un complexe tétra- ou pentacoordiné. La structure cristallographique du composé [Cu(L7)](ClO4)2 a montré que les contraintes stériques imposées par la cage moléculaire rigide induisent une déformation du noyau benzénique de l'anse et une interaction entre le métal et le cycle aromatique.
160

Structural Studies of O-antigen polysaccharides, Synthesis of 13C-labelled Oligosaccharides and Conformational Analysis thereof, using NMR Spectroscopy

Olsson, Ulrika January 2008 (has links)
<p>In order to understand biological processes, to treat and diagnose diseases, find appropriate vaccines and to prevent the outbreak of epidemics, it is essential to obtain more knowledge about carbohydrate structures. This thesis deals with structure and conformation of carbohydrates, analysed by NMR spectroscopy and MD simulations.In the first two papers, the structures of O-antigen polysaccharides (PS) from two different <i>E. coli</i> bacteria were determined using NMR spectroscopy. The O-antigenic PS from <i>E. coli</i> O152 (paper I) consists of branched pentasaccharide repeating units, built up of three different carbohydrate residues and a phosphodiester, whilst the repeating unit of the O-antigen from <i>E. coli</i> O176 (paper II) is built up of a linear tetrasaccharide consisting of two different monosaccharides.</p><p>In papers III and IV, the conformational analysis of different disaccharides is described. Conformational analysis was performed using NMR spectroscopy and MD simulations (paper IV). In paper III four different glucobiosides were studied using coupling constants and Karplus-type relationships. By use of specific <sup>13</sup>C isotopically labelled derivatives, additional coupling constants were obtained and the number of possible torsion angles was reduced by half. In paper IV, we examine the conformations of two disaccharides that are part of an epitope of malignant cells. From NOE and T-ROE experiments, short proton-proton distances around the glycosidic linkage were estimated. Furthermore, interpretation of the extracted coupling constants using Kaplus relationships gave the values of the torsion angles. As in paper III, isotopically labelled compounds were synthesised in order to enhance the sensitivity of the analysis. Finally, MD simulations were performed and the results were compared with results from NMR data.</p>

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