Specificity of amino acid sequence and its role in secondary and supersecondary structure generation

Schematic presentation of loops (7 aa) linking two β-strands (fragments of β-sheets). The left one – helical form represents fuzzy oil drop distribution of hydrophobicity. The right one not able to generate the helical form represents the status recognized as amyloid seed in amyloids discussed in this work

Analysis of protein chameleon sequence characteristics

Conversion of local structural state of a protein from an α-helix to a β-strand is usually associated with a major change in the tertiary structure. Similar changes were observed during the self assembly of amyloidogenic proteins to form fibrils, which are implicated in severe diseases conditions, e.g., Alzheimer disease. Studies have emphasized that certain protein sequence fragments known as chameleon sequences do not have a strong preference for either helical or the extended conformations. Surprisingly, the information on the local sequence neighborhood can be used to predict their secondary at a high accuracy level. Here we report a large scale-analysis of chameleon sequences to estimate their propensities to be associated with different local structural states such as α -helices, β-strands and coils. With the help of the propensity information derived from the amino acid composition, we underline their complexity, as more than one quarter of them prefers coil state over to the regular secondary structures. About half of them show preference for both α-helix and β-sheet conformations and either of these two states is favored by the rest

Identification au collège, identification aux pairs et estime de soi : quelles relations avec l’image de l’établissement ?

Cette étude explore les processus d’identification au collège et aux pairs s’actualisant chez des élèves de troisième. Des échelles d’identification au groupe de pairs, au collège et d’estime de soi ont été proposées à 175 élèves appartenant à des collèges situés en zone d’éducation prioritaire (ZEP) versus non situés en ZEP. Les résultats obtenus par classification ascendante hiérarchique révèlent différents modèles de relations entre ces variables selon l’image perçue du collège. Ainsi, une perception positive de cette image est associée à des niveaux élevés d’identification au collège et aux pairs, indépendamment du niveau d’estime de soi. À l’inverse, percevoir son collège comme stigmatisé génère des difficultés à s’y identifier ; celles-ci semblent compensées par une identification plus marquée aux pairs, préservant ainsi le niveau d’estime de soi de l’élève.This study investigates the processes of school and peer identification among secondary school students. A sample of 175 students whose schools are located in ZEP (zone d’éducation prioritaire, priority zone of education) versus not located in ZEP was administered self-esteem, peer identification and school identification scales. A hierarchical ascending classification suggests that various models of relations are generated between these three measures as a function of the perception of the school. In fact, students with positive perception of their school have high levels of school and peer identification, independently of their level of self-esteem. On the contrary, perceiving ones school as stigmatized, generates difficulties in identifying with it; these difficulties are probably compensated by a more salient identification to the peer group, so as to protect the level of self-esteem

Diversité des pratiques d'élevage bovin à viande dans le massif du Dahra (Algérie)

Pour appréhender la diversité des pratiques d’élevage bovin à viande dans les zones rurales du massif du Dahra (nord-ouest algérien), une typologie a été réalisée à partir des résultats d’une enquête dans 56 exploitations. Les groupes définis diffèrent par les structures et sont de 5 types (A, B, C, D et E). L’analyse technico - économique de 20 exploitations réparties sur les différents types préalablement identifiés révèle 4 systèmes de pratiques différents selon l’objectif de production, le plus souvent en cohérence avec les structures disponibles. Le contrôle des performances réalisé au niveau de 9 exploitations montre que lorsqu'on exclut le système d’élevage bovin commercial sans femelles reproductrices (engraisseur), le système à logique de capitalisation apparaît alors comme le plus performant

Typology of dairy farming systems in the Mediterranean basin (case of Algeria)

Characterization of breeding dairy cattle systems from the Mediterranean basin was conducted on 16 farms in the north center region of Algeria through a survey. Results are highly variable both structurally and in techno- economic management terms. The principal component analysis and clusters analysis have identified four groups of farms that differ in feeding strategies. The first group contains four farms that promote the use of forages (61.8% of the total dry matter (DM) intake). The costs are above the general averages (cost of production: 38.4 DA / liter ≈ 0.34 € and cost of food in total production costs = 71.8%). The average annual productivity is about 4328.6 kg. Five farms of group 2 are characterized by milk yields below average (4146.5 kg). The concentrates represent only 39.3% of total DM intake. The cost of production (37.1 DA ≈ 0.33 €/ liter of milk) and food costs are the lowest (65.17% of total production costs). The third group contains 5 farms dominated by profitable farms (4833.4 kg) and the lower cost of production (35.2 DA ≈ 0.31 €). A relatively high proportion of DM is provided by forages (53.6%). Food accounts for 69.2% of the total production cost. The fourth group consists of two farms whose main characteristic is the total absence of forage production. This is associated with a significant contribution of concentrates in the global feed balance (48.8% of total DM intake). These concentrated foods were poorly converted into milk as recorded yields are the lowest (3561.2 kg). Production costs are highest (45.1 DA ≈ 0.40 €) and relation price of food/total cost of production is very high (79.3%). So there are areas for improvement via land restructuring and the adoption of healthy feeding practices in order to ensure the profitability and sustainability of farms identified in this study

Impact of Place Identity, Self-Efficacy and Anxiety State on the Relationship Between Coastal Flooding Risk Perception and the Willingness to Cope

Inhabitants of coastal areas are constantly confronted with minor or major events such as storms, erosion or flooding. This article investigates the predictors of coping willingness among citizens exposed to coastal flooding. Coping can be defined as a set of cognitive and behavioral efforts to master, reduce or tolerate a given risk and these strategies are generally regrouped into two different categories: active coping strategies oriented toward the risk to reduce or master it, and passive coping strategies focused on the reduction of internal tensions such as anxiety or fear. In this paper, we focus especially on how place identity, perceived self-efficacy, anxiety-state and coastal flooding risk perception shape both active and passive coping willingness. Data were obtained from different areas at risk of coastal flooding located in France. The sample is composed of 315 adult participants (mean age = 47; SD = 15). Two competing models were tested using path modeling. We expected a direct relation between risk perception and the willingness to cope actively and that a higher perceived self-efficacy would increase active coping willingness. Concerning passive coping strategies, we expected that a higher anxiety-state increases passive coping willingness, and that place identity would act as a mediator and increases the relation between anxiety-state and passive coping willingness. Results suggest that place identity increased when the living place is threatened and that the use of passive coping strategies also increased. Also, we demonstrated a direct relation between risk perception and active coping willingness but it appeared that self-efficacy has no effect on this relation. Model fit indices suggest the good fit of our model and Bayesian model comparison reveals a very strong evidence of the best fit of this model compared to its saturated and independent equivalents

Développement de méthodes bioinformatiques dédiées à la prédiction et l'analyse des réseaux métaboliques et des ARN non codants

L'identification des interactions survenant au niveau moléculaire joue un rôle crucial pour la compréhension du vivant. L'objectif de ce travail a consisté à développer des méthodes permettant de modéliser et de prédire ces interactions pour le métabolisme et la régulation de la transcription. Nous nous sommes basés pour cela sur la modélisation de ces systèmes sous la forme de graphes et d'automates. Nous avons dans un premier temps développé une méthode permettant de tester et de prédire la distribution du flux au sein d'un réseau métabolique en permettant la formulation d'une à plusieurs contraintes. Nous montrons que la prise en compte des données biologiques par cette méthode permet de mieux reproduire certains phénotypes observés in vivo pour notre modèle d'étude du métabolisme énergétique du parasite Trypanosoma brucei. Les résultats obtenus ont ainsi permis de fournir des éléments d'explication pour comprendre la flexibilité du flux de ce métabolisme, qui étaient cohérentes avec les données expérimentales. Dans un second temps, nous nous sommes intéressés à une catégorie particulière d'ARN non codants appelés sRNAs, qui sont impliqués dans la régulation de la réponse cellulaire aux variations environnementales. Nous avons développé une approche permettant de mieux prédire les interactions qu'ils effectuent avec d'autres ARN en nous basant sur une prédiction des interactions, une analyse par enrichissement du contexte biologique de ces cibles, et en développant un système de visualisation spécialement adapté à la manipulation de ces données. Nous avons appliqué notre méthode pour l'étude des sRNAs de la bactérie Escherichia coli. Les prédictions réalisées sont apparues être en accord avec les données expérimentales disponibles, et ont permis de proposer plusieurs nouvelles cibles candidates.The identification of the interactions occurring at the molecular level is crucial to understand the life process. The aim of this work was to develop methods to model and to predict these interactions for the metabolism and the regulation of transcription. We modeled these systems by graphs and automata.Firstly, we developed a method to test and to predict the flux distribution in a metabolic network, which consider the formulation of several constraints. We showed that this method can better mimic the in vivo phenotype of the energy metabolism of the parasite Trypanosoma brucei. The results enabled to provide a good explanation of the metabolic flux flexibility, which were consistent with the experimental data. Secondly, we have considered a particular class of non-coding RNAs called sRNAs, which are involved in the regulation of the cellular response to environmental changes. We developed an approach to better predict their interactions with other RNAs based on the interaction prediction, an enrichment analysis, and by developing a visualization system adapted to the manipulation of these data. We applied our method to the study of the sRNAs interactions within the bacteria Escherichia coli. The predictions were in agreement with the available experimental data, and helped to propose several new target candidates.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF