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arXiv 1807.01415cond-mat.softcond-mat.stat-mechphysics.chem-ph
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DNA包被胶体的相对动力学模型

Modeling the relative dynamics of DNA-coated colloids

James P. Lee-Thorp, Miranda Holmes-Cerfon

摘要:

我们构建了一个理论模型的动力学的微尺度胶体颗粒,建模为一个间隔,水平移动的DNA涂层的表面上,建模为一条线涂有弹簧,可以坚持的间隔。对快速的DNA动力学求平均,得到孤立粒子的演化方程,其中包含摩擦和扩散。DNA诱导的摩擦系数取决于DNA的物理性质,并且用弱相互作用DNA密集涂覆的1 $μ$ m胶体的典型参数值替代,得到比相应的流体动力学摩擦系数大约100倍的系数。我们使用平均场扩展的模型,以更高的维度来估计摩擦张量的光盘旋转和平移水平沿一条线。当DNA链非常硬和短时,圆盘滚动的摩擦系数接近于零,而圆盘滑动的摩擦仍然很大。总之,这些结果可能对DNA包被的胶体或其他配体-受体系统的动力学具有重要意义,这意味着DNA诱导的胶体之间的摩擦可能比流体动力学摩擦更强,应该纳入模拟,并且它非常依赖于相对运动的类型,可能导致颗粒聚集成由具有最小摩擦的路径控制的非平衡亚稳态。

英文摘要:

We construct a theoretical model for the dynamics of a microscale colloidal particle, modeled as an interval, moving horizontally on a DNA-coated surface, modelled as a line coated with springs that can stick to the interval. Averaging over the fast DNA dynamics leads to an evolution equation for the particle in isolation, which contains both friction and diffusion. The DNA-induced friction coefficient depends on the physical properties of the DNA, and substituting parameter values typical of a 1$μ$m colloid coated densely with weakly interacting DNA gives a coefficient about 100 times larger than the corresponding coefficient of hydrodynamic friction. We use a mean-field extension of the model to higher dimensions to estimate the friction tensor for a disc rotating and translating horizontally along a line. When the DNA strands are very stiff and short, the friction coefficient for the disc rolling approaches zero while the friction for the disc sliding remains large. Together, these results could have significant implications for the dynamics of DNA-coated colloids or other ligand-receptor systems, implying that DNA-induced friction between colloids can be stronger than hydrodynamic friction and should be incorporated into simulations, and that it depends nontrivially on the type of relative motion, possibly causing the particles to assemble into out-of-equilibrium metastable states governed by the pathways with the least friction.

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