Wackerbarth Hainer, Grubb Mikala, Zhang Jingdong, Hansen Allan G, Ulstrup Jens
Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Langmuir. 2004 Mar 2;20(5):1647-55. doi: 10.1021/la035547g.
Oligonucleotides modified by a hexamethylene linker group adsorb on gold electrodes via Au-S bond formation. We have obtained novel data for adsorption of thiol-modified (HS) single-strand HS-10A and double-stranded HS-10AT oligonucleotides and for analogous thiol-free 10A (A = adenine) and 10T (T = thymine) nonspecifically adsorbed as reference molecules. Mercaptohexanol has served as a second reference molecule. The data are based on cyclic and differential pulse voltammetry, interfacial capacitance data, and in situ scanning tunneling microscopy (STM) directly in an aqueous buffer solution, with electrochemical potential control of both the sample electrode and the tip. All the data are based on single-crystal, atomically planar Au(111)-electrode surfaces. The high sensitivity of such surfaces provides accurate HS-10A and HS-10AT electrode coverages on the basis of the reductive desorption of the Au-S bond. The coverage is high and in keeping with dense monolayers of adsorbed HS-10A and HS-10AT in an upright or tilted orientation, with the oligonucleotide backbone repelled from the strongly negatively charged electrode surface. Adsorbed thiol-free 10A only gives a Au(111)-reconstruction peak, while 10T shows a subtle pattern involving pronounced voltammetric adsorption peaks indicative of both nonspecific adsorption via single thymine units and potential-dependent structural reorganization in the surface layer. In situ STM supports these findings at the molecular level. In situ STM of HS-10A discloses large, highly ordered domains at strongly negative sample potentials. Reversible domain formation and disordering could, moreover, be controlled by an electrochemical potential variation in the negative and positive directions, respectively. 10A and 10T did not form ordered adsorbate domains, substantiating that domain formation rests on adsorption of thiol-modified oligonucleotide adsorption in an upright or tilted orientation. The comprehensive, high-resolution information reported may hold prospects for single-molecule electronic conduction and molecular-scale mapping of oligonucleotide hybridization.
由六亚甲基连接基团修饰的寡核苷酸通过形成Au-S键吸附在金电极上。我们已经获得了硫醇修饰的（HS）单链HS-10A和双链HS-10AT寡核苷酸吸附以及类似的无硫醇10A（A =腺嘌呤）和10T（T =胸腺嘧啶）作为参考分子非特异性吸附的新数据。巯基己醇用作第二个参考分子。这些数据基于循环伏安法和差分脉冲伏安法、界面电容数据以及直接在水性缓冲溶液中的原位扫描隧道显微镜（STM），同时对样品电极和探针进行电化学势控制。所有数据均基于单晶、原子平面的Au(111)电极表面。这种表面的高灵敏度基于Au-S键的还原解吸提供了准确的HS-10A和HS-10AT电极覆盖率。覆盖率很高，与直立或倾斜取向的吸附HS-10A和HS-10AT的致密单层一致，寡核苷酸主链被带强负电荷的电极表面排斥。吸附的无硫醇10A仅给出Au(111)重构峰，而10T显示出一种微妙的模式，涉及明显的伏安吸附峰，表明通过单个胸腺嘧啶单元的非特异性吸附以及表面层中电位依赖性结构重组。原位STM在分子水平上支持了这些发现。HS-10A的原位STM在强负样品电位下揭示了大的、高度有序的区域。此外，可逆的区域形成和无序可以分别通过负向和正向的电化学势变化来控制。10A和10T没有形成有序的吸附质区域，证实区域形成依赖于硫醇修饰的寡核苷酸以直立或倾斜取向的吸附。所报道的全面、高分辨率信息可能为寡核苷酸杂交的单分子电子传导和分子尺度映射带来前景。
