Conformations of End-Tethered DNA Molecules on Gold Surfaces: Influences of Applied Electric Potential, Electrolyte Screening, and Temperature
Conformations of End-Tethered DNA Molecules on Gold Surfaces: Influences of Applied Electric Potential, Electrolyte Screening, and Temperature
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DOI：
10.1021/ja908727d
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发表时间：
2010-06-16
影响因子：
15
通讯作者：
Rant, Ulrich
中科院分区：
文献类型：
--
作者：
Kaiser, Wolfgang;Rant, Ulrich
我们描述了在外加电场的影响下末端拴在金表面上的72聚氨基寡核苷酸的行为。DNA延伸是通过荧光能量转移作为DNA杂交状态（单链和双链）、溶液中单价盐浓度（100 μ M至1 M NaCl）、外加电极电位（-0.6至+0.1 V vs Pt）和温度（1至50℃）的函数来测量的。在高离子强度下，DNA构象非常稳定，不受施加电极电位和温度变化的影响。在中等离子强度的溶液中，通过对Au电极施加偏置电位可以有效地操纵DNA构象。分子在负电位下相互排斥，在正电位下相互吸引。当电极偏压仅在过渡电位上扫过0.1 V时，构象转变就会突然发生，当盐度降低时，构象转变为负值。这种行为可以通过静电筛选论证来理解，在单链DNA的情况下，当二级结构被考虑在内时。在低离子强度下，实验揭示了单链DNA的一种有趣的温度依赖性硬化，这可以通过将反离子凝聚理论与Odjik-Skolnick-Fixman对静电持续长度和高温下碱基解堆的描述相结合来合理化。
We describe the behavior of 72mer oligonucleotides that are end-tethered to gold surfaces under the influence of applied electric fields. The DNA extension is measured by fluorescence energy transfer as a function of the DNA hybridization state (single- and double-stranded), the concentration of monovalent salt in solution (100 mu M to 1 M NaCl), the applied electrode potential (-0.6 to +0.1 V vs Pt), and the temperature (1 to 50 C). At high ionic strength, the DNA conformations are very robust and independent of the applied electrode potential and temperature variations. In solutions of medium ionic strength, the DNA conformation can be manipulated efficiently by applying bias potentials to the Au electrodes. The molecules are repelled at negative potentials and attracted to the surface at positive potentials. The conformation transition occurs abruptly when the electrode bias is swept by merely 0.1 V across the transition potential, which shifts negatively when the salinity is decreased. The behavior can be understood by electrostatic screening arguments and, in the case of single-stranded DNA, when secondary structures are taken into account. At low ionic strength, the experiments reveal an intriguing temperature-dependent stiffening of single-stranded DNA, which can be rationalized by combining counterion condensation theory with the Odjik-Skolnick-Fixman description of the electrostatic persistence length and the unstacking of bases at elevated temperatures.