Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA.
Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, Illinois 61801, USA.
Phys Rev Lett. 2018 Jun 29;120(26):268101. doi: 10.1103/PhysRevLett.120.268101.
Electric field-driven motion of biomolecules is a process essential to many analytics methods, in particular, to nanopore sensing, where a transient reduction of nanopore ionic current indicates the passage of a biomolecule through the nanopore. However, before any molecule can be examined by a nanopore, the molecule must first enter the nanopore from the solution. Previously, the rate of capture by a nanopore was found to increase with the strength of the applied electric field. Here, we theoretically show that, in the case of narrow pores in graphene membranes, increasing the strength of the electric field can not only decrease the rate of capture, but also repel biomolecules from the nanopore. As the strong electric field polarizes water near and within the nanopore, the high gradient of the field also produces a strong dielectrophoretic force that compresses the water. The pressure difference caused by the sharp water density gradient produces a hydrostatic force that repels DNA or proteins from the nanopore, preventing, in certain conditions, their capture. We show that such local compression of fluid can regulate the transport of biomolecules through nanoscale passages in the absence of physical gates and sort proteins according to their phosphorylated states.
电场驱动生物分子的运动是许多分析方法的基本过程，特别是在纳米孔传感中，纳米孔离子电流的瞬时减小表明生物分子通过了纳米孔。然而，在任何分子可以通过纳米孔进行检测之前，该分子必须首先从溶液中进入纳米孔。以前，研究发现，在石墨烯膜的窄孔的情况下，施加电场的强度增加不仅会降低捕获率，还会将生物分子从纳米孔中排斥出去。由于强电场使纳米孔附近和内部的水分子极化，电场的高梯度还会产生强大的介电泳力，从而压缩水。由尖锐的水密度梯度引起的压力差会产生静电力，将 DNA 或蛋白质从纳米孔中排斥出去，在某些情况下会阻止它们的捕获。我们表明，在没有物理门的情况下，这种局部压缩流体可以调节生物分子通过纳米级通道的传输，并根据其磷酸化状态对蛋白质进行分类。
