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Structure and dynamics of DNA confined in-between non-cationic lipid membranes

Abstract : An experimental study on the structural and dynamical properties of a hydrated DNA-zwitterionic complex is presented. By varying the water amount, it is possible to control the confinement imposed by this host matrix over the organization of the nucleotides inserted within the water layers. The supramolecular assembly is investigated by X-rays diffraction and techniques involving both optical and electron microscopy. A rich polymorphism of mesophases is observed in function of confinement. In the more hydrated regime, the fragments are distributed according to nematic orientation in-between lamellae. As the water amount decreases, the confinement of bilayers over the particles increases and transmembrane correlations appear, giving raise to highly-ordered phases, with 2D- rectangular and -hexagonal symmetries of DNA embodied in the lamellar phase. The full incorporation of nucleotides by the lamellar phase is observed only in the presence of large amounts of DNA. This finding points to major importance of excluded volume interactions. An analysis of the Caillé parameter shows that the insertion of DNA reduces the fluctuations of membranes. From these observations, it is suggested that changes in the interactions between bilayers, together with the appearance of interfacial effects between DNA and membranes, are a mechanism relevant for the phase behavior of these systems. The dynamical properties of nucleotides are investigated through the fluorescence recovery after photobleach (FRAP). A model recently developed for analyses of anisotropic diffusion is successfully tested, demonstrating a close relationship between structure and dynamics.
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Emerson Rodrigo Teixeira da Silva. Structure and dynamics of DNA confined in-between non-cationic lipid membranes. Biological Physics [physics.bio-ph]. Université Sciences et Technologies - Bordeaux I, 2011. English. ⟨tel-00755050⟩

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