We use video particle tracking microrheology (VPTMR) in order to investigate the viscoelasticity of salmon DNA and correlate it to its steady-flow shear-thinning viscosity. Aqueous solutions of DNA are tested in a wide concentration range from the dilute to the semidilute unentangled concentration regime. The observed mean squared displacement shows power-law scaling with lag-time which is equivalent to power-law behavior of the complex modulus as a function of frequency that is, |G* (ω)| = S ∙ ω α . The relaxation exponent α changes abruptly with concentration in the semidilute regime from about 1 to about 0.5 which is the exponent predicted by the Rouse model. The quasi-property S follows the scaling of viscosity for uncharged polymers near θ-conditions in the semidilute regime that is, η ∼ c 1 / 3 ν eff - 1 with νeff = 0.50 - 0.51. The shear-thinning exponent observed by viscometry increases gradually towards the value of 0.5 which has been predicted for Rouse chains under flow. Our findings are in agreement with recent studies of DNA solutions where DNA is treated as a model polymer and addresses the low-molar mass regime of DNA viscoelasticity. This work demonstrates that the combination of passive particle tracking with viscometry can provide a complete picture on the viscoelasticity of DNA-based biopolymer materials.

中文翻译：

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结合粒子追踪微流变学和粘度测定法研究 DNA 水溶液

我们使用视频粒子跟踪微流变学 (VPTMR) 来研究鲑鱼 DNA 的粘弹性并将其与其稳定流动的剪切稀化粘度相关联。DNA 水溶液在从稀释到半稀释的非缠结浓度范围内的广泛浓度范围内进行测试。观察到的均方位移显示具有滞后时间的幂律缩放，​​这等效于作为频率函数的复模数的幂律行为，即 |G* (ω)| = S ∙ ω α 。弛豫指数 α 随半稀释状态中的浓度从大约 1 到大约 0.5 突然变化，这是 Rouse 模型预测的指数。准性质 S 遵循半稀释状态下接近 θ 条件的不带电聚合物的粘度缩放，即 η ∼ c 1 / 3 ν eff - 1 ，其中 νeff = 0.50 - 0.51。粘度测定法观察到的剪切稀化指数逐渐增加到 0.5 的值，这是对流动下的 Rouse 链预测的值。我们的发现与最近对 DNA 溶液的研究一致，其中 DNA 被视为模型聚合物，并解决了 DNA 粘弹性的低摩尔质量体系。这项工作表明，被动粒子跟踪与粘度测定法的结合可以提供有关基于 DNA 的生物聚合物材料粘弹性的完整图片。