Shen Gang, Tercero Napoleon, Gaspar Mariafrancis A, Varughese Bindhu, Shepard Kenneth, Levicky Rastislav
Department of Chemical Engineering, Columbia University, New York, NY 10027, USA.
J Am Chem Soc. 2006 Jul 5;128(26):8427-33. doi: 10.1021/ja0571500.
DNA monolayers are widely used in fundamental and applied genomics and are versatile experimental models for elucidating the behavior of charged polymers at interfaces. The physical behavior of these systems is to a large extent governed by their internal ionic microenvironment, which is investigated here for layers of end-tethered, single-stranded DNA oligonucleotides (DNA brushes). Retention of counterions by the DNA brush manifests as lowered susceptibility of the interfacial capacitance to external salt conditions. A physical model based on concepts adapted from polymer science was used to further elucidate the connection between monolayer organization and its charging behavior. The data indicate a reorganization of the monolayer with changes in ionic strength and strand coverage that is consistent with that expected for a polyelectrolyte brush. A method for electrochemical quantification of strand coverage, based on shift of reduction potential for redox counterions associated with the DNA monolayer, is also described. These results provide guidance for development of label-free electrochemical diagnostics employing DNA monolayers and formulate a description of monolayer behavior within a polymer science framework.
DNA单分子层在基础基因组学和应用基因组学中被广泛使用，并且是用于阐明带电聚合物在界面处行为的通用实验模型。这些系统的物理行为在很大程度上受其内部离子微环境的支配，本文针对末端 tethered 的单链DNA寡核苷酸（DNA刷）层对此进行了研究。DNA刷对抗衡离子的保留表现为界面电容对外界盐条件的敏感性降低。基于从聚合物科学中借鉴的概念建立的物理模型被用于进一步阐明单分子层组织与其充电行为之间的联系。数据表明，随着离子强度和链覆盖率的变化，单分子层会发生重组，这与聚电解质刷的预期情况一致。还描述了一种基于与DNA单分子层相关的氧化还原抗衡离子还原电位的变化来电化学定量链覆盖率的方法。这些结果为采用DNA单分子层的无标记电化学诊断方法的开发提供了指导，并在聚合物科学框架内对单分子层行为进行了描述。
