Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, USA.
Biomicrofluidics. 2012 Oct 24;6(4):44103. doi: 10.1063/1.4762852. eCollection 2012.
Visualizing single DNA dynamics in flow provides a wealth of physical insights in biophysics and complex flow study. However, large signal fluctuations, generated from diversified conformations, deformation history dependent dynamics and flow induced stochastic tumbling, often frustrate its wide adoption in single molecule and polymer flow study. We use a hybrid field microfluidic (HFM) approach, in which an electric field is imposed at desired locations and appropriate moments to balance the flow stress on charged molecules, to effectively regulate the initial conformations and the deformation dynamics of macromolecules in flow. With λ-DNA and a steady laminar shear flow as the model system, we herein studied the performance of HFM on regulating DNA trapping, relaxation, coil-stretch transition, and accumulation. DNA molecules were found to get captured in the focused planes when motions caused by flow, and the electric field were balanced. The trapped macromolecules relaxed in two different routes while eventually became more uniform in size and globule conformations. When removing the electric field, the sudden stretching dynamics of DNA molecules exhibited a more pronounced extension overshoot in their transient response under a true step function of flow stress while similar behaviors to what other pioneering work in steady shear flow. Such regulation strategies could be useful to control the conformations of other important macromolecules (e.g., proteins) and help better reveal their molecular dynamics.
在流动中可视化单个 DNA 的动力学为生物物理学和复杂流动研究提供了丰富的物理见解。然而，由于多样化的构象、变形历史相关的动力学和流动诱导的随机翻滚产生的大信号波动，常常阻碍了其在单分子和聚合物流动研究中的广泛应用。我们使用混合场微流（HFM）方法，在该方法中在所需位置和适当时刻施加电场以平衡带电分子上的流动应力，从而有效地调节大分子在流动中的初始构象和变形动力学。使用 λ-DNA 和稳态层流剪切流作为模型系统，我们在此研究了 HFM 在调节 DNA 捕获、松弛、线圈拉伸转变和积累方面的性能。当流动和电场引起的运动达到平衡时，DNA 分子会在聚焦平面上被捕获。被捕获的大分子通过两种不同的途径松弛，最终在大小和球型构象上变得更加均匀。当去除电场时，DNA 分子的突然拉伸动力学在流动应力的真实阶跃函数下的瞬态响应中表现出更为明显的延伸过冲，而在稳态剪切流中的类似行为。这种调节策略可用于控制其他重要大分子（例如蛋白质）的构象，并有助于更好地揭示它们的分子动力学。
