Search results for " Seconda"
showing 10 items of 975 documents
Localization of the N-terminal Domain in Light-harvesting Chlorophyll a/b Protein by EPR Measurements
2005
The conformational distribution of the N-terminal domain of the major light-harvesting chlorophyll a/b protein (LHCIIb) has been characterized by electron-electron double resonance yielding distances between spin labels placed in various domains of the protein. Distance distributions involving residue 3 near the N terminus turned out to be bimodal, revealing that this domain, which is involved in regulatory functions such as balancing the energy flow through photosystems (PS) I and II, exists in at least two conformational states. Models of the conformational sub-ensembles were generated on the basis of experimental distance restraints from measurements on LHCIIb monomers and then checked f…
Secondaire-supérieur
2008
Même si le lien entre le niveau de diplôme obtenu et la qualité de l'insertion professionnelle n'est pas parfait, posséder un diplôme de l'enseignement supérieur est un atout majeur à l'entrée sur le marché du travail. Cependant, alors qu'une des spécificités françaises du système d'enseignement supérieur est son caractère relativement différencié, son accès reste relativement typé socialement selon les distinctions qualitatives qu'il permet. Ces distinctions qualitatives, dans un contexte où l'accès aux différents niveaux d'enseignement s'est démocratisé, ne sont pas sans incidence sur l'insertion. Afin de comprendre les différences d'accès à l'enseignement supérieur et à ses types de curs…
Comportement des bacheliers : modèle de choix de disciplines
1979
The paper tries to take into account the choices taken by the high school graduates at the time of their immatriculation in higher education. The purpose is not a statistical description, but an attempt to test theoretical hypothesis of the individual behaviour. The analytical framework is based on the trade-off carried out by every student between the economical attractiveness of the different fields of education and professional careers which are linked on one hand, and the personal probability of success in every field on the other hand. In a first section, success models are estimated in various disciplines to get estimations of the objective chances of success for every student in ever…
S'orienter et élaborer un projet au sein d'un système hiérarchisé, une injonctoin paradoxale ? L'exemple du choix de la série et de l'enseignement de…
1997
The French "lycée" (higher secondary school), pupils are faced with successive subjects choices, and with the choice of Baccalauréat's speciality. This paper investigates from empirical data how these choices are progressively generated, along time and under which academic and social mechanisms. Those academic subjects choices prove to be influenced less by educational factors than by the concern to optimize one's schooling career. As long as the different routes are perceived as a hierarchy, and if concern for distinction and utilitarism are prevailing, the relevance of the notion of project has to be questionned.
Fluorescence and circular dichroism spectroscopy to understand the interactions between cyclodextrins and α-galactosidase from green coffee beans
2017
Abstract The potential of fluorescence measurement and circular dichroism spectroscopy (CDSP) to evaluate the interaction between cyclodextrins (CDs) (CD cavity size, concentration, pH, reaction time, and temperature as well as different side chain groups) and α-galactosidase was evaluated. A strong relationship was observed between α-galactosidase fluorescence intensity and CD cavity size, concentration, pH, reaction time, and temperature as well as different side chain groups. Therefore, it can be concluded that fluorescence intensity measurement can be a promising tool to ascertain β-CD-α-galactosidase interactions. CDSP is also an interesting tool to understand β-CD-α-galactosidase inte…
Entrapment of A Beta 1-40 peptide in unstructured aggregates
2012
Recognizing the complexity of the fibrillogenesis process provides a solid ground for the development of therapeutic strategies aimed at preventing or inhibiting protein-protein aggregation. Under this perspective, it is meaningful to identify the possible aggregation pathways and their relative products. We found that Aβ-peptide dissolved in a pH 7.4 solution at small peptide concentration and low ionic strength forms globular aggregates without typical amyloid β-conformation. ThT binding kinetics was used to monitor aggregate formation. Circular dichroism spectroscopy, AFM imaging, static and dynamic light scattering were used for structural and morphological characterization of the aggre…
Irreversible formation of intermediate BSA oligomers requires and induces conformational changes.
2004
Understanding the relation between protein conformational changes and aggregation, and the physical mechanisms leading to such processes, is of primary importance, due to its direct relation to a vast class of severe pathologies. Growing evidence also suggests that oligomeric intermediates, which may occur early in the aggregation pathway, can be themselves pathogenic. The possible cytotoxicity of oligomers of non-disease-associated proteins adds generality to such suggestion and to the interest of studies of oligomer formation. Here we study the early stages of aggregation of Bovine Serum Albumin (BSA), a non pathogenic protein which has proved to be a useful model system. Dynamic light sc…
Protein/lipid coaggregates are formed during α-synuclein-induced disruption of lipid bilayers.
2014
Amyloid formation is associated with neurodegenerative diseases such as Parkinson's disease (PD). Significant α-synuclein (αSN) deposition in lipid-rich Lewy bodies is a hallmark of PD. Nonetheless, an unraveling of the connection between neurodegeneration and amyloid fibrils, including the molecular mechanisms behind potential amyloid-mediated toxic effects, is still missing. Interaction between amyloid aggregates and the lipid cell membrane is expected to play a key role in the disease progress. Here, we present experimental data based on hybrid analysis of two-photon-microscopy, solution small-angle X-ray scattering and circular dichroism data. Data show in real time changes in liposome …
Effects of succinylation on thermal induced amyloid formation in Concanavalin A.
2007
We have recently shown that upon slight thermal destabilization the legume lectin Concanavalin A may undergo two different aggregation processes, leading, respectively, to amyloid fibrils at high pH and amorphous aggregates at low pH. Here we present an experimental study on the amyloid aggregation of Succinyl Concanavalin A, which is a dimeric active variant of Concanavalin. The results show that, as for the native protein, the fibrillation process appears to be favoured by alkaline pH, far from the isoelectric point of the protein. Moreover, it strongly depends on temperature and requires large conformational changes both at secondary and tertiary structure level. With respect to the nati…
Glucagon fibril polymorphism reflects differences in protofilament backbone structure
2010
Amyloid fibrils formed by the 29-residue peptide hormone glucagon at different concentrations have strikingly different morphologies when observed by transmission electron microscopy. Fibrils formed at low concentration (0.25 mg/mL) consist of two or more protofilaments with a regular twist, while fibrils at high concentration (8 mg/mL) consist of two straight protofilaments. Here, we explore the structural differences underlying glucagon polymorphism using proteolytic degradation, linear and circular dichroism, Fourier transform infrared spectroscopy (FTIR), and X-ray fiber diffraction. Morphological differences are perpetuated at all structural levels, indicating that the two fibril class…