Chen Kaikai, Bell Nicholas A W, Kong Jinglin, Tian Yu, Keyser Ulrich F
Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom; State Key Laboratory of Tribology, Tsinghua University, Beijing, China.
Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
Biophys J. 2017 Feb 28;112(4):674-682. doi: 10.1016/j.bpj.2016.12.033.
Solid-state nanopores are promising tools for single-molecule detection of both DNA and proteins. In this study, we investigated the patterns of ionic current blockades as DNA translocates into or out of the geometric confinement of conically shaped pores across a wide range of salt conditions. We studied how the geometry of a nanopore affects the detected ionic current signal of a translocating DNA molecule over a wide range of salt concentration. The blockade level in the ionic current depends on the translocation direction at a high salt concentration, and at lower salt concentrations we find a nonintuitive ionic current decrease and increase within each single event for the DNA translocations exiting from confinement. We use a recently developed method for synthesizing DNA molecules with multiple position markers, which provides further experimental characterization by matching the position of the DNA in the pore with the observed ionic current signal. Finally, we employ finite element calculations to explain the shapes of the signals observed at all salt concentrations and show that the unexpected current decrease and increase are due to the competing effects of ion concentration polarization and geometric exclusion of ions. Our analysis shows that over a wide range of geometries, voltages, and salt concentrations, we are able to understand the ionic current signals of DNA in asymmetric nanopores, enabling signal optimization in molecular sensing applications.
固态纳米孔是用于DNA和蛋白质单分子检测的很有前景的工具。在本研究中，我们研究了在广泛的盐条件下，当DNA进出锥形孔的几何限制区域时离子电流阻断的模式。我们研究了纳米孔的几何形状如何在广泛的盐浓度范围内影响易位DNA分子的检测离子电流信号。在高盐浓度下，离子电流的阻断水平取决于易位方向，而在低盐浓度下，我们发现在DNA从限制区域逸出的每个单事件中，离子电流会出现非直观的下降和增加。我们使用最近开发的一种合成带有多个位置标记的DNA分子的方法，通过将孔中DNA的位置与观察到的离子电流信号相匹配，提供了进一步的实验表征。最后，我们采用有限元计算来解释在所有盐浓度下观察到的信号形状，并表明意外的电流下降和增加是由于离子浓度极化和离子几何排斥的竞争效应。我们的分析表明，在广泛的几何形状、电压和盐浓度范围内，我们能够理解不对称纳米孔中DNA的离子电流信号，从而实现分子传感应用中的信号优化。
