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Estudo de compostos quinônicos com potencial atividade contra a doença de Chagas / Study of quinone compounds with activity against Chagas diseaseFerreira, Janaina Gomes 08 May 2008 (has links)
Este trabalho apresenta as estruturas determinadas por difração de raio X de dois compostos naftoquinônicos, 3,4-diidro-[2,2-dimetil]-2H-nafto[1,2-b]pirano-5,6-diona (β-lapachona) e dimetil-1,4-naftoquinona. A estrutura cristalina destes compostos mostrou que estes são estabilizados por ligações de hidrogênio do tipo C-H...O, formando estruturas supramoleculares. Dos compostos derivados da β-lapachona, os naftoimidazóis têm-se mostrado muito ativos contra o T. cruzi, agente causador da doença de Chagas. Partindo das estruturas modeladas de 29 compostos naftoimidazólicos, propriedades eletrônicas, geométricas e topológicas foram calculadas para análise estatística por mínimos quadrados parciais (PLS). Após a análise e redução das variáveis foram selecionados os descritores Morp17p, X4a, piPC09, RDF065v, BELp6, RDF060p, R4u, RDF035m e RCI que foram utilizados para a construção um modelo de regressão com o método de PLS. Para o modelo, o menor erro de validação foi obtido com 3 fatores e os coeficientes de correlação R= 0,71 e Q= 0,82. O estudo de docking de alguns compostos naftoquinônicos e naftoimidazólicos mostrou que, do ponto de vista energético e de complementaridade química, estes compostos possuem pouca probabilidade de se ligarem no sítio ativo da tripanotiona redutase (TR), uma enzima essencial para o metabolismo do T. cruzi, bem como no sítio ativo da enzima humana glutationa redutase (GR), homóloga a TR. Há, no entanto, uma tendência geral destes compostos se ligarem no sítio da interface, sobretudo, de se ligarem neste sítio da enzima humana. / This work presents the structure determined by X-ray analyses for two naphthoquinone compounds 3,4-dihydro-2,2-dimethyl-2H-naphtho[1,2-b]pyran-5,6- dione and dimethyl-1,4-naphthoquinone. The crystal packing of these compounds showed the existence of intermolecular hydrogen bonds of the type CH...0. These intermolecular forces are responsible for the self-assembly in three-dimensional supramolecular structure. A set of 29 naphthoimidazoles, derived from β-lapachone, that has shown activity against T. cruzi, the agent of Chagas disease, were modeled. From these structures electronic, geometric, topological, etc, properties were calculated to be used in the investigation by statistic analysis, using the partial least squares method (PLS). After reduction of the number of variables, the best PLS model found was the one obtained with the following variables: Morp17p, X4a, piPC09, RDF065v, BELp6, RDF060p, R4u, RDF035m and RCI. For the PLS model, the lower error of validation was obtained using 3 factors with the coefficients R=0.71 and Q=0.82. Two sets of compounds, naphtoquinones and naphthoimidazoles, were studied by docking method. The results showed that, for both, naphtoquinones and naphthoimidazoles and both trypanothione and glutathione reductase, the compounds have low probability to bind in the active site, and are more likely to bind in the interface site, especially in the interface site of the human protein.
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Estudo de compostos quinônicos com potencial atividade contra a doença de Chagas / Study of quinone compounds with activity against Chagas diseaseJanaina Gomes Ferreira 08 May 2008 (has links)
Este trabalho apresenta as estruturas determinadas por difração de raio X de dois compostos naftoquinônicos, 3,4-diidro-[2,2-dimetil]-2H-nafto[1,2-b]pirano-5,6-diona (β-lapachona) e dimetil-1,4-naftoquinona. A estrutura cristalina destes compostos mostrou que estes são estabilizados por ligações de hidrogênio do tipo C-H...O, formando estruturas supramoleculares. Dos compostos derivados da β-lapachona, os naftoimidazóis têm-se mostrado muito ativos contra o T. cruzi, agente causador da doença de Chagas. Partindo das estruturas modeladas de 29 compostos naftoimidazólicos, propriedades eletrônicas, geométricas e topológicas foram calculadas para análise estatística por mínimos quadrados parciais (PLS). Após a análise e redução das variáveis foram selecionados os descritores Morp17p, X4a, piPC09, RDF065v, BELp6, RDF060p, R4u, RDF035m e RCI que foram utilizados para a construção um modelo de regressão com o método de PLS. Para o modelo, o menor erro de validação foi obtido com 3 fatores e os coeficientes de correlação R= 0,71 e Q= 0,82. O estudo de docking de alguns compostos naftoquinônicos e naftoimidazólicos mostrou que, do ponto de vista energético e de complementaridade química, estes compostos possuem pouca probabilidade de se ligarem no sítio ativo da tripanotiona redutase (TR), uma enzima essencial para o metabolismo do T. cruzi, bem como no sítio ativo da enzima humana glutationa redutase (GR), homóloga a TR. Há, no entanto, uma tendência geral destes compostos se ligarem no sítio da interface, sobretudo, de se ligarem neste sítio da enzima humana. / This work presents the structure determined by X-ray analyses for two naphthoquinone compounds 3,4-dihydro-2,2-dimethyl-2H-naphtho[1,2-b]pyran-5,6- dione and dimethyl-1,4-naphthoquinone. The crystal packing of these compounds showed the existence of intermolecular hydrogen bonds of the type CH...0. These intermolecular forces are responsible for the self-assembly in three-dimensional supramolecular structure. A set of 29 naphthoimidazoles, derived from β-lapachone, that has shown activity against T. cruzi, the agent of Chagas disease, were modeled. From these structures electronic, geometric, topological, etc, properties were calculated to be used in the investigation by statistic analysis, using the partial least squares method (PLS). After reduction of the number of variables, the best PLS model found was the one obtained with the following variables: Morp17p, X4a, piPC09, RDF065v, BELp6, RDF060p, R4u, RDF035m and RCI. For the PLS model, the lower error of validation was obtained using 3 factors with the coefficients R=0.71 and Q=0.82. Two sets of compounds, naphtoquinones and naphthoimidazoles, were studied by docking method. The results showed that, for both, naphtoquinones and naphthoimidazoles and both trypanothione and glutathione reductase, the compounds have low probability to bind in the active site, and are more likely to bind in the interface site, especially in the interface site of the human protein.
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Determinação simultanea e não-destrutiva de solidos totais e soluveis, licopeno e beta-caroteno em produtos de tomate por espectroscopia no infravermelho proximo utilizando calibração multivariadaPedro, Andre Messias Krell 09 March 2004 (has links)
Orientador: Marcia Miguel Castro Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T07:55:59Z (GMT). No. of bitstreams: 1
Pedro_AndreMessiasKrell_M.pdf: 1430817 bytes, checksum: eb44b479e05288a5ad7fbdb82c18e309 (MD5)
Previous issue date: 2004 / Mestrado / Físico-Química / Mestre em Química
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Estudo da relação estrutura-atividade de compostos biologicamente ativos derivados do aripiprazol / Study of structure-activity relationships of biological active compounds derivatives of aripiprazoleSilva, Aldineia Pereira da 27 February 2014 (has links)
A esquizofrenia é uma doença que, de acordo com a Organização Mundial de Saúde, acomete cerca de 1% da população mundial. Tendo em vista a sua alta incidência e, portanto, sua relevância, o presente trabalho objetivou estudar uma classe de compostos derivados do aripiprazol, substância ativa que estimula os receptores dopaminérgicos e serotoninérgicos, receptores esses de suma importância para o entendimento da fisiopatologia da esquizofrenia. Para isso, o estudo de QSAR foi realizado através dos métodos PLS e ANN, gerando dois modelos para tentar entender a relação entre a estrutura química e a atividade biológica. Os dois modelos gerados, PLS e ANN, foram satisfatórios, explicando 82,52% e 72,90% respectivamente, da variabilidade da atividade biológica. No entanto, como o modelo obtido através do método PLS foi considerado melhor, conclui-se que as variáveis selecionadas possuem comportamento linear frente à atividade biológica. / The Schizophrenia is a disease that affects about 1% of world population, according to the World Health Organization. Looking into its high incidence and therefore its relevance, the goal of this study was to investigate a class of compounds derived from aripiprazole, the active substance that stimulates dopamine and serotonin receptors, those essential for understanding the pathophysiology of schizophrenia. For the investigation to go on, the QSAR study was performed through PLS and ANN methods, generating two models in order to understand the relationship between chemical structure and biological activity. Both model results, PLS and ANN, were considered satisfactory, explaining 82.52% and 72.90%, respectively, of the variability of the biological activity. However, since the model obtained by the PLS method showed more satisfactory results, it can be concluded that the selected variables have a linear behavior concerning the biological activity.
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Estudo teórico da toxicidade dos PAHs por meio de ferramentas teóricas e sua importância na determinação do dano ambiental / Theoretical study of the toxicity of PAHs through theoretical tools and their importance in determining the environmental damageGobi, Bruna Danielle de Oliveira 17 November 2014 (has links)
Nas questões ambientais legais, muitas vezes a referência à toxicidade de uma substância é vaga. No entanto, essa informação é essencial para a determinação da extensão do dano. Para fazer a previsão desses valores para o benzeno e hidrocarbonetos policíclicos aromáticos (PAHs), componentes do petróleo, foi feito um estudo QSAR (Quantitative Structure Activity Relationship) por meio de cálculos de mecânica quântica e quimiometria. O objetivo foi construir modelos para prever os valores de coeficiente de partição n-octanol/água, Kow (n-octanol/water partition coefficient) além do estudo das toxicidades dos PAHs. Para este estudo, as geometrias de todas as moléculas foram otimizadas utilizando os métodos semiempíricos AM1, PM3, PM6 e PM7. Desses resultados ainda foram extraídos os descritores teóricos que foram utilizados para descrever os valores de log Kow. Entre todos aqueles calculados, os descritores: energia total, energia eletrônica, área, volume e massa molar foram escolhidos como os parâmetros para o estudo PLS (Partial Least Squares). Além disso, as toxicidades dos PAHs foram calculadas por meio do programa T.E.S.T (Toxicity Estimation Software Tool) disponibilizado gratuitamente pelo EPA (Environmental Protection Agency) e estimados por meio de modelo PLS e gráficos de correlação. Observou-se com esse estudo que todos os métodos apresentaram resultados bastante satisfatórios, uma vez que valores próximos de 1 foram obtidos tanto para o coeficiente de correlação interno, Q2, quanto para o externo, R2. / In the environmental legal issues, often the reference to toxicity of a substance is vague. However, this information is essential for determining the extent of damage. To forecast these values for benzene and polycyclic aromatic hydrocarbons (PAHs), petroleum components, one study QSAR (Quantitative Structure Activity Relationship) was done by calculation of quantum mechanics and chemometrics. The goal was to build models to predict the values of the partition coefficient n-octanol / water, Kow (n-octanol / water partition coefficient) beyond the study of the toxicity of PAHs. For this study, the geometries of all molecules were optimized using the semi-empirical methods AM1, PM3, PM6 and PM7. These theoretical results also descriptors that were used to describe the Log Kow values were extracted. Among those calculated descriptors: total energy, electronic energy, area, volume and molar mass were chosen as the parameters for the study PLS (Partial Least Squares). Furthermore, the toxicities of PAHs were calculated using the TEST (Toxicity Estimation Software Tool) program available free of charge by the EPA (Environmental Protection Agency) and estimated by PLS model and correlation charts. It was observed in this study that all the methods have shown promising results, since values near one were obtained for the standard and cross-validated correlation coefficients R2 and Q2.
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Determinação dos parametros de qualidade de detergentes em po utilizando espectroscopia no infravermelho proximo / Determination of the parameters of quality of powder detergents using near infrared spectroscopyPovia, Giovana Soato 30 May 2007 (has links)
Orientador: Celio Pasquini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-09T09:59:17Z (GMT). No. of bitstreams: 1
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Previous issue date: 2007 / Resumo: Este trabalho visa o desenvolvimento de um método analítico para a determinação dos parâmetros de qualidade em detergentes em pó utilizando a Espectroscopia de Infravermelho Próximo (NIR) e técnicas de calibração multivariada. Foram utilizados dois conjuntos de amostras: o primeiro para as análises quantitativas e o segundo para análises qualitativas. As amostras do primeiro conjunto tiveram os parâmetros de qualidade determinados pelos respectivos métodos de referência. A técnica estatística utilizada para as calibrações foi o PLS. Foram desenvolvidos modelos de calibrações para a previsão do teor de umidade, matéria ativa e densidade. O desempenho dos modelos de calibrações foi avaliado por meio de validação externa. A determinação do teor de umidade apresentou RMSEP = 0,29% (m/m). O valor de RMSEP para a determinação da matéria ativa foi de 0,37% (m/m) e para a determinação da densidade o valor de RMSEP = 14 g L . Os modelos construídos apresentaram resultados satisfatórios e os erros encontrados são aceitáveis para a faixa de controle utilizada na indústria. O segundo conjunto é composto de 4 grupos, que apresentam características distintas. Foram avaliados dois métodos de classificação: SIMCA e PLS DA. É possível observar que ocorre a discriminação das amostras que apresentam teor de matéria ativa mais elevado, no entanto, os outros grupos não puderam ser discriminados. Os dois métodos de classificação avaliados apresentaram resultados semelhantes, com acerto de 100% na classificação de amostras externas somente em seus respectivos grupos / Abstract: This work aims the development of an analytical method for the determination of quality parameters on powder detergents using the near infrared spectroscopy (NIR) and multivariate calibration techniques. Two sets of samples were used: the first one for the quantitative analysis and the second one for qualitative analysis. The samples of the first set had the quality parameters determined by their respective methods of reference. The chemometric technique used for calibration was the PLS1. Calibrations for the prediction of de moisture content, active matter and density were developed. The performance of the calibration models was evaluated through external validation. The determination of the moisture content presented a RMSEP = 0,29% (w/w). The value of RMSEP for the determination of the active matter was 0,37% (w/w) and for the determination of moisture the value of RMSEP was 14 g L. The constructed models presented satisfactory results and the errors that were found are acceptable for the control range used in industry. The second set is composed of four groups of power detergents which present different characteristics. Two methods of classification were evaluated: SIMCA and PLS DA. It was possible to observe the discrimination of the samples which presents higher active matter content. However, the other groups could not be discriminated. Both methods of classifications evaluated presented similar results, with 100% correcte results of the classification of samples only in their respective groups / Mestrado / Quimica Analitica / Mestre em Química
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Estudo teórico da toxicidade dos PAHs por meio de ferramentas teóricas e sua importância na determinação do dano ambiental / Theoretical study of the toxicity of PAHs through theoretical tools and their importance in determining the environmental damageBruna Danielle de Oliveira Gobi 17 November 2014 (has links)
Nas questões ambientais legais, muitas vezes a referência à toxicidade de uma substância é vaga. No entanto, essa informação é essencial para a determinação da extensão do dano. Para fazer a previsão desses valores para o benzeno e hidrocarbonetos policíclicos aromáticos (PAHs), componentes do petróleo, foi feito um estudo QSAR (Quantitative Structure Activity Relationship) por meio de cálculos de mecânica quântica e quimiometria. O objetivo foi construir modelos para prever os valores de coeficiente de partição n-octanol/água, Kow (n-octanol/water partition coefficient) além do estudo das toxicidades dos PAHs. Para este estudo, as geometrias de todas as moléculas foram otimizadas utilizando os métodos semiempíricos AM1, PM3, PM6 e PM7. Desses resultados ainda foram extraídos os descritores teóricos que foram utilizados para descrever os valores de log Kow. Entre todos aqueles calculados, os descritores: energia total, energia eletrônica, área, volume e massa molar foram escolhidos como os parâmetros para o estudo PLS (Partial Least Squares). Além disso, as toxicidades dos PAHs foram calculadas por meio do programa T.E.S.T (Toxicity Estimation Software Tool) disponibilizado gratuitamente pelo EPA (Environmental Protection Agency) e estimados por meio de modelo PLS e gráficos de correlação. Observou-se com esse estudo que todos os métodos apresentaram resultados bastante satisfatórios, uma vez que valores próximos de 1 foram obtidos tanto para o coeficiente de correlação interno, Q2, quanto para o externo, R2. / In the environmental legal issues, often the reference to toxicity of a substance is vague. However, this information is essential for determining the extent of damage. To forecast these values for benzene and polycyclic aromatic hydrocarbons (PAHs), petroleum components, one study QSAR (Quantitative Structure Activity Relationship) was done by calculation of quantum mechanics and chemometrics. The goal was to build models to predict the values of the partition coefficient n-octanol / water, Kow (n-octanol / water partition coefficient) beyond the study of the toxicity of PAHs. For this study, the geometries of all molecules were optimized using the semi-empirical methods AM1, PM3, PM6 and PM7. These theoretical results also descriptors that were used to describe the Log Kow values were extracted. Among those calculated descriptors: total energy, electronic energy, area, volume and molar mass were chosen as the parameters for the study PLS (Partial Least Squares). Furthermore, the toxicities of PAHs were calculated using the TEST (Toxicity Estimation Software Tool) program available free of charge by the EPA (Environmental Protection Agency) and estimated by PLS model and correlation charts. It was observed in this study that all the methods have shown promising results, since values near one were obtained for the standard and cross-validated correlation coefficients R2 and Q2.
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Estudo da relação estrutura-atividade de compostos biologicamente ativos derivados do aripiprazol / Study of structure-activity relationships of biological active compounds derivatives of aripiprazoleAldineia Pereira da Silva 27 February 2014 (has links)
A esquizofrenia é uma doença que, de acordo com a Organização Mundial de Saúde, acomete cerca de 1% da população mundial. Tendo em vista a sua alta incidência e, portanto, sua relevância, o presente trabalho objetivou estudar uma classe de compostos derivados do aripiprazol, substância ativa que estimula os receptores dopaminérgicos e serotoninérgicos, receptores esses de suma importância para o entendimento da fisiopatologia da esquizofrenia. Para isso, o estudo de QSAR foi realizado através dos métodos PLS e ANN, gerando dois modelos para tentar entender a relação entre a estrutura química e a atividade biológica. Os dois modelos gerados, PLS e ANN, foram satisfatórios, explicando 82,52% e 72,90% respectivamente, da variabilidade da atividade biológica. No entanto, como o modelo obtido através do método PLS foi considerado melhor, conclui-se que as variáveis selecionadas possuem comportamento linear frente à atividade biológica. / The Schizophrenia is a disease that affects about 1% of world population, according to the World Health Organization. Looking into its high incidence and therefore its relevance, the goal of this study was to investigate a class of compounds derived from aripiprazole, the active substance that stimulates dopamine and serotonin receptors, those essential for understanding the pathophysiology of schizophrenia. For the investigation to go on, the QSAR study was performed through PLS and ANN methods, generating two models in order to understand the relationship between chemical structure and biological activity. Both model results, PLS and ANN, were considered satisfactory, explaining 82.52% and 72.90%, respectively, of the variability of the biological activity. However, since the model obtained by the PLS method showed more satisfactory results, it can be concluded that the selected variables have a linear behavior concerning the biological activity.
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Approche multidisciplinaire pour la détection de métaux lourds en environnements aquatiques / Multidisciplinary approach to heavy metal ion sensing in aquatic environmentsBrackx, Gwennhaël 23 January 2017 (has links)
La gestion de l’eau douce est un problème majeur partout dans le monde. Les activités anthropiques liées à l’industrie, à l’agriculture et à l’implantation humaine sont les principales sources de pollutions de l’eau. Afin mettre en place des politique de prévention de la pollution, de réhabilitation des environnements aquatiques ou de recyclage des eaux usées, il est nécessaire d’acquérir des données massives sur la qualité de l’eau. Or, les méthodes actuelles de suivi des contaminants présentent des coûts élevés et de faibles débits de mesure du fait de leur incompatibilité avec un déploiement sur le terrain. Ces deux freins majeurs ne permettent pas de suivre les concentrations en polluant et notamment en métaux lourds dans les milieux aquatiques à des échelles spatiales et temporelles pertinentes. Plusieurs organisations internationales, dont l’ONU, ont de ce fait recommandé le développement de nouvelles méthodes analytiques plus performantes. Nous proposons ici une technique de mesure des contaminants métalliques lourds basée sur la diffusion Raman exaltée de surface (SERS). Le SERS présente de nombreux avantages pour l’analyse environnementale dont la sensibilité, la spécificité,la rapidité de mesure, l’adaptabilité aux matrices complexes ainsi que le coût modéré d’un instrument portable. Nous détaillerons donc la construction de la sonde SERS dédiée à la quantification de l’ion métallique lourd cible Zn2+, ainsi que les traitements de données nécessaire à l’établissement d’une quantification. Puis, nous examinerons la robustesse de la méthode de quantification vis-à-vis des sources de variabilités qui seront inévitablement rencontrées dans les eaux naturelles. / Freshwater management is a major problem all over the world. Anthropogenic activities related to industry, agriculture and human settlements are the main sources of water pollution. In order to makes policies for pollution prevention, rehabilitation of aquatic environments or waste water recycling, it is necessary to acquire massive data on water quality. Current contaminant monitoring methods have high costs and low frequency of measurement due to the incompatibility with field deployment. These two major brakes do not make it possible to monitor pollutant and especially heavy metal concentrations in aquatic environments at relevant spatial and temporal scales. Several international organizations, including the United Nations, have therefore recommended the development of new and better analytical methods.We propose here a technique for measuring heavy metal contaminants based on Surface Enhanced Raman Spectroscopy (SERS), which would allow a large scale deployment in the field.SERS has many advantages for environmental analysis including sensitivity, specificity, speed of measurement, adaptability to complex matrix and the moderate cost of portable instrument. We will therefore detail the construction of the SERS probe dedicated to the quantification of the target heavy metal ion Zn2+, which is a geochemical marker of anthropogenic contamination, as well as the data processing necessary for the establishment of quantification. Then, we will examine the robustness of the method of quantification with respect to the sources of variability that will inevitably be encountered in natural waters, when used directly in the field
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Modèles de prédiction pour l'évaluation génomique des bovins laitiers français : application aux races Holstein et Montbéliarde / Prediction models for the genomic evaluation of French dairy cattle : application to the Holstein and Montbéliarde breedsColombani, Carine 16 October 2012 (has links)
L'évolution rapide des techniques de séquençage et de génotypage soulèvent de nouveaux défis dans le développement des méthodes de sélection pour les animaux d’élevage. Par comparaison de séquences, il est à présent possible d'identifier des sites polymorphes dans chaque espèce afin de baliser le génome par des marqueurs moléculaires appelés SNP (Single Nucleotide Polymorphism). Les méthodes de sélection des animaux à partir de cette information moléculaire nécessitent une représentation complète des effets génétiques. Meuwissen et al. (2001) ont introduit le concept de sélection génomique en proposant de prédire simultanément tous les effets des régions marquées puis de construire un index "génomique" en sommant les effets de chaque région. Le challenge dans l’évaluation génomique est de disposer de la meilleure méthode de prédiction afin d’obtenir des valeurs génétiques précises pour une sélection efficace des animaux candidats. L’objectif général de cette thèse est d'explorer et d’évaluer de nouvelles approches génomiques capables de prédire des dizaines de milliers d'effets génétiques, sur la base des phénotypes de centaines d'individus. Elle s’inscrit dans le cadre du projet ANR AMASGEN dont le but est d’étendre la sélection assistée par marqueurs, utilisée jusqu’à lors chez les bovins laitiers français, et de développer une méthode de prédiction performante. Pour cela, un panel varié de méthodes est exploré en estimant leurs capacités prédictives. Les méthodes de régression PLS (Partial Least Squares) et sparse PLS, ainsi que des approches bayésiennes (LASSO bayésien et BayesCπ) sont comparées à deux méthodes usuelles en amélioration génétique : le BLUP basé sur l’information pedigree et le BLUP génomique basé sur l’information des SNP. Ces méthodologies fournissent des modèles de prédiction efficaces même lorsque le nombre d’observations est très inférieur au nombre de variables. Elles reposent sur la théorie des modèles linéaires mixtes gaussiens ou les méthodes de sélection de variables, en résumant l’information massive des SNP par la construction de nouvelles variables. Les données étudiées dans le cadre de ce travail proviennent de deux races de bovins laitiers français (1 172 taureaux de race Montbéliarde et 3 940 taureaux de race Holstein) génotypés sur environ 40 000 marqueurs SNP polymorphes. Toutes les méthodes génomiques testées ici produisent des évaluations plus précises que la méthode basée sur la seule information pedigree. On observe un léger avantage prédictif des méthodes bayésiennes sur certains caractères mais elles sont cependant trop exigeantes en temps de calcul pour être appliquées en routine dans un schéma de sélection génomique. L’avantage des méthodes de sélection de variables est de pouvoir faire face au nombre toujours plus important de données SNP. De plus, elles sont capables de mettre en évidence des ensembles réduits de marqueurs, identifiés sur la base de leurs effets estimés, c’est-à-dire ayant un impact important sur les caractères étudiés. Il serait donc possible de développer une méthode de prédiction des valeurs génomiques sur la base de QTL détectés par ces approches. / The rapid evolution in sequencing and genotyping raises new challenges in the development of methods of selection for livestock. By sequence comparison, it is now possible to identify polymorphic regions in each species to mark the genome with molecular markers called SNPs (Single Nucleotide Polymorphism). Methods of selection of animals from genomic information require the representation of the molecular genetic effects. Meuwissen et al. (2001) introduced the concept of genomic selection by predicting simultaneously all the effects of the markers. Then a genomic index is built summing the effects of each region. The challenge in genomic evaluation is to find the best prediction method to obtain accurate genetic values of candidates. The overall objective of this thesis is to explore and evaluate new genomic approaches to predict tens of thousands of genetic effects, based on the phenotypes of hundreds of individuals. It is part of the ANR project AMASGEN whose aim is to extend the marker-assisted selection, used in French dairy cattle, and to develop an accurate method of prediction. A panel of methods is explored by estimating their predictive abilities. The PLS (Partial Least Squares) and sparse PLS regressions and Bayesian approaches (Bayesian LASSO and BayesCπ) are compared with two current methods in genetic improvement: the BLUP based on pedigree information and the genomic BLUP based on SNP markers. These methodologies are effective even when the number of observations is smaller than the number of variables. They are based on the theory of Gaussian linear mixed models or methods of variable selection, summarizing the massive information of SNP by new variables. The datasets come from two French dairy cattle breeds (1172 Montbéliarde bulls and 3940 Holstein bulls) genotyped with 40 000 polymorphic SNPs. All genomic methods give more accurate estimates than the method based on pedigree information only. There is a slight predictive advantage of Bayesian methods on some traits but they are still too demanding in computation time to be applied routinely in a genomic selection scheme. The advantage of variable selection methods is to cope with the increasing number of SNP data. In addition, they are able to extract reduced sets of markers based of their estimated effects, that is to say, with a significant impact on the trait studied. It would be possible to develop a method to predict genomic values on the basis of QTL detected by these approaches.
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