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Conformation, inetraction et organisation des particles coeur de nucleosome

Abstract : In all eucaryotic cells, DNA is associated with different proteins to form the chromatin which is condensed in cell nucleus. Its organisation is still under discussion. To adress this question, we studied in vitro the behaviour of solutions of nucleosome core particles, the structural units of chromatin. In conditions similar to those found in the cell nucleus (concentration of particles and concentration of monovalent salt), nucleosome core particles form different ordered phases which nature highly depends on the ionic conditions. Using X-ray diffraction, we showed that at low salt concentration, particles form a lamellar phase of bilayers. At high salt concentration, hexagonal or quasi-hexagonal phases, organised at two or three dimensions are observed. In order to understand the origin of the polymorphism of the dense phases, we performed small angle X-ray scattering and osmometry measurements in dilute solution. We pointed out small conformational changes in the nucleosome core particle, and more precisely an histone tails extension when the salt concentration increases from 10 to 200 mM. This increase of the salt concentration also modifes the interactions between particles. We showed that these two phenomena (tails extension and variation of interactions) are coupled. These salt-induced conformational changes and variations of interactions could explain the polymorphism of organisation in concentrated solutions. Such comparisons require to carefully analyse how the salt concentration varies when the particles concentrations is increased.
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Contributor : Stephanie Mangenot <>
Submitted on : Wednesday, December 11, 2002 - 2:35:04 PM
Last modification on : Wednesday, October 14, 2020 - 4:00:30 AM
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Stephanie Mangenot. Conformation, inetraction et organisation des particles coeur de nucleosome. Biophysique [physics.bio-ph]. Université Paris Sud - Paris XI, 2001. Français. ⟨tel-00002115⟩

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