Research Lab for Advanced Separation Processes, Department of Chemical Engineering, Iran University of Science and Technology, 16846-13114, Narmak, Tehran, Iran.
Eur Biophys J. 2021 Sep;50(6):905-914. doi: 10.1007/s00249-021-01552-2. Epub 2021 Jun 13.
Controlling the translocation velocity of DNA is the main challenge in the process of sequencing by means of nanopores. One of the main methods to overcome this challenge is covering the inner walls of the nanopore with a layer of polyelectrolytes, i.e., using soft nanopores. In this paper the translocation of DNA through soft nanopores, whose inner polyelectrolyte layer (PEL) charge is pH-dependent, is theoretically studied. We considered the polyelectrolyte to be made up of either acidic or basic functional groups. It was observed that the electroosmotic flow (EOF) induced by the PEL charge is in the opposite/same direction of DNA electrophoresis (EPH) when the PEL is made up of acidic/basic groups. It was found that, not only the DNA charge and consequently the EPH, but also the EOF are influenced by the electrolyte acidity. The synergy between the changes in the retardation, EOF and EPH, determines how the intensity and direction of DNA translocation alter with pH. In fact, for both cases, at mild values of pH (as long as [Formula: see text] for the case that PEL is of acidic nature), the more the pH, the less the translocation velocity. However, for PELs of acidic nature, higher values of pH increase the intensity of the EOF so much that DNA may experience a change in the translocation direction. Ultimately, conducting the process at a particular range of pH values, and at higher pH values, in the cases of using PELs of acidic nature, and basic nature, respectively, was recommended.
控制 DNA 的易位速度是通过纳米孔测序过程中的主要挑战之一。克服这一挑战的主要方法之一是在内壁覆盖一层聚电解质，即使用软纳米孔。本文从理论上研究了带正电荷的聚电解质层（PEL）的 DNA 通过软纳米孔的易位。我们考虑聚电解质由酸性或碱性官能团组成。结果表明，当 PEL 由酸性/碱性基团组成时，PEL 电荷诱导的电渗流（EOF）与 DNA 电泳（EPH）相反/相同。结果发现，不仅 DNA 电荷和随之而来的 EPH，而且 EOF 都受到电解质酸度的影响。滞后、EOF 和 EPH 变化的协同作用决定了 DNA 易位的强度和方向如何随 pH 值而变化。实际上，对于这两种情况，在 pH 值较低的情况下（只要 PEL 具有酸性时[公式：见文本]），pH 值越高，迁移速度越慢。然而，对于具有酸性 PEL 的情况，较高的 pH 值会增加 EOF 的强度，以至于 DNA 可能会改变易位方向。最终，建议在特定的 pH 值范围内进行该过程，并在较高的 pH 值下，对于使用酸性和碱性 PEL 的情况，分别进行。
