Department of Physics, University of Arkansas, Fayetteville, AR 72701, USA.
Electrophoresis. 2012 Dec;33(23):3448-57. doi: 10.1002/elps.201200165. Epub 2012 Nov 12.
In this work, we report on how salt concentration and cation species affect DNA translocation in voltage-biased silicon nitride nanopores. The translocation of dsDNA in linear, circular, and supercoiled forms was measured in salt solutions containing KCl, NaCl, and MgCl(2) . As the KCl concentrations were decreased from 1 to 0.1 M, the time taken by a DNA molecule to pass through a nanopore was shorter and the frequency of the translocation in a folded configuration was reduced, suggesting an increase in DNA electrophoretic mobility and DNA persistence length. When the salt concentration was kept at 1 M, but replacing K(+) with Na(+) , longer DNA translocation times (t(d) ) were observed. The addition of low concentrations of MgCl(2) with 1.6 M KCl resulted in longer t(d) and an increased frequency of supercoiled DNA molecules in a branched form. These observations were consistent with the greater counterion charge screening ability of Na(+) and Mg(2+) as compared to K(+) . In addition, we demonstrated that dsDNA molecules indeed translocated through a ∼10 nm nanopore by PCR amplification and gel electrophoresis. We also compared the dependence of DNA mobility and conformation on KCl concentration and cation species measured at single molecule level by silicon nitride nanopores with existing bulk-based experimental results and theoretical predictions.
在这项工作中，我们报告了盐浓度和阳离子种类如何影响带电压的氮化硅纳米孔中的 DNA 迁移。在含有 KCl、NaCl 和 MgCl2 的盐溶液中测量了线性、圆形和超螺旋 DNA 的迁移。当 KCl 浓度从 1 M 降低到 0.1 M 时，DNA 分子通过纳米孔的时间变短，折叠构象的迁移频率降低，表明 DNA 电泳迁移率和 DNA 持久长度增加。当盐浓度保持在 1 M 时，用 Na+代替 K+，观察到更长的 DNA 迁移时间 (t(d))。在 1.6 M KCl 中添加低浓度的 MgCl2 导致更长的 t(d) 和更多的超螺旋 DNA 分子以分支形式存在。这些观察结果与 Na+和 Mg2+相比 K+具有更大的抗衡离子电荷屏蔽能力一致。此外，我们通过 PCR 扩增和凝胶电泳证明了 dsDNA 分子确实通过了约 10nm 的纳米孔。我们还比较了硅氮化物纳米孔在单分子水平上测量的 DNA 迁移率和构象对 KCl 浓度和阳离子种类的依赖性，以及现有的基于体相的实验结果和理论预测。
