Anisotropic Brownian motion in ordered phases of DNA fragments |
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Authors: | J Dobrindt E Rodrigo Teixeira da Silva C Alves C L P Oliveira F Nallet E Andreoli de Oliveira L Navailles |
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Institution: | Université de Bordeaux, Centre de recherche Paul-Pascal - CNRS, 115 avenue du Docteur-Schweitzer, F-33600, Pessac, France. |
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Abstract: | Using Fluorescence Recovery After Photobleaching, we investigate the Brownian motion of DNA rod-like fragments in two distinct
anisotropic phases with a local nematic symmetry. The height of the measurement volume ensures the averaging of the anisotropy
of the in-plane diffusive motion parallel or perpendicular to the local nematic director in aligned domains. Still, as shown
in using a model specifically designed to handle such a situation and predicting a non-Gaussian shape for the bleached spot
as fluorescence recovery proceeds, the two distinct diffusion coefficients of the DNA particles can be retrieved from data
analysis. In the first system investigated (a ternary DNA-lipid lamellar complex), the magnitude and anisotropy of the diffusion
coefficient of the DNA fragments confined by the lipid bilayers are obtained for the first time. In the second, binary DNA-solvent
system, the magnitude of the diffusion coefficient is found to decrease markedly as DNA concentration is increased from isotropic
to cholesteric phase. In addition, the diffusion coefficient anisotropy measured within cholesteric domains in the phase coexistence
region increases with concentration, and eventually reaches a high value in the cholesteric phase. |
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