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      Thermomechanical Stability and Mechanochemical Response of DNA: a Minimal Mesoscale Model

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          Abstract

          We show that a mesoscale model, with a minimal number of parameters, can well describe the thermomechanical and mechanochemical behavior of homogeneous DNA at thermal equilibrium under tension and torque. We predict critical temperatures for denaturation under torque and stretch, phase diagrams for stable DNA, probe/response profiles under mechanical loads, and the density of dsDNA as a function of stretch and twist. We compare our predictions with available single molecule manipulation experiments and find strong agreement. In particular we elucidate the difference between angularly constrained and unconstrained overstretching. We propose that the smoothness of the angularly constrained overstreching transition is a consequence of the molecule being in the vicinity of criticality for a broad range of values of applied tension.

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          Nucleic acid junctions and lattices.

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            Stretching DNA

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              DNA-assisted dispersion and separation of carbon nanotubes.

              Carbon nanotubes are man-made one-dimensional carbon crystals with different diameters and chiralities. Owing to their superb mechanical and electrical properties, many potential applications have been proposed for them. However, polydispersity and poor solubility in both aqueous and non-aqueous solution impose a considerable challenge for their separation and assembly, which is required for many applications. Here we report our finding of DNA-assisted dispersion and separation of carbon nanotubes. Bundled single-walled carbon nanotubes are effectively dispersed in water by their sonication in the presence of single-stranded DNA (ssDNA). Optical absorption and fluorescence spectroscopy and atomic force microscopy measurements provide evidence for individually dispersed carbon nanotubes. Molecular modelling suggests that ssDNA can bind to carbon nanotubes through pi-stacking, resulting in helical wrapping to the surface. The binding free energy of ssDNA to carbon nanotubes rivals that of two nanotubes for each other. We also demonstrate that DNA-coated carbon nanotubes can be separated into fractions with different electronic structures by ion-exchange chromatography. This finding links one of the central molecules in biology to a technologically very important nanomaterial, and opens the door to carbon-nanotube-based applications in biotechnology.
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                Author and article information

                Journal
                2014-06-21
                2014-10-18
                Article
                10.1063/1.4895724
                1406.5641

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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                The Journal of Chemical Physics 141 (11), 115101 (2014)
                18 pages, 11 figures
                q-bio.BM

                Molecular biology

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