While recent research in electron-transport mechanism on a double strands DNA seems to converge into a consensus, experiments in direct electrical measurements on a long DNA molecules still lead to a conflicting result. This research investigates experimentally the attachment of DNA molecular wire to high aspect ratio three-dimensional (3D) metal electrode and the effect of temperature to its AC electrical conductivity. The 3-D microelectrode was built on a silicone oxide substrate using patterned thick layers of negative tone photoresist covered by sputtered gold on the top surface. Attachment of lambda-DNA to the microelectrode was demonstrated using oligonucleotide-DNA phosphate backbone ligation and thiol-gold covalent bonding. Electrical characterizations based on I-V and AC impedance analysis of several repeatable data points of attachment with varying lambda-DNA concentration (500 ng/microL to 0.0625 ng/microL) showed measurable and significant conductivity of lambda-DNA molecular wires. Further study was carried out by measuring I-V and impedance while ramping up the temperature to reach complete denaturation (~1100C) resulting in no current transduction. Subsequent re-annealing of the DNA through incubation in TM buffer at annealing temperature (~900C) resulted in recovery of electrical conduction, providing a strong proof that DNA molecular wire is the one generate the electrical conductivity. lambda-DNA molecular wires reported to have differing impedance response at two temperature regions: impedance increases (conductivity decrease) between 40C -- 400C, and then decreases from 400C until DNA completely denatured (~1100C). The increase conductivity after 400C is an experimental support the long distance electron transport mechanism referred as "thermal hopping" mechanism. We believe that this research represents a significant departure from previous studies and makes unique contributions through (i) modification of DNA attachment methods has increase the success rate from less than 10% to be more than 75% (ii) more accurate direct conductivity measurement of DNA molecular wires facilitated by suspension of the DNA away from the substrate, and (iii) AC impedance measurement of DNA molecular wires with the effect of temperature suggests an experimental evidence of temperature gating mechanism in charge transport through DNA wire that will be very important for further studies.
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机译：尽管最近对双链DNA的电子传输机制的研究似乎已达成共识，但对长DNA分子进行直接电学测量的实验仍会产生矛盾的结果。这项研究通过实验研究了DNA分子线与高深宽比三维（3D）金属电极的连接以及温度对其交流电导率的影响。将3-D微电极建立在氧化硅基板上，使用图案化的厚层负性光刻胶，并在其顶表面上镀金。使用寡核苷酸-DNA磷酸酯主链连接和巯基-金共价键，证明了λ-DNA与微电极的连接。基于I-V和AC阻抗分析的电学表征，具有可变的lambda-DNA浓度（500 ng / microL至0.0625 ng / microL）的几个可重复的数据连接点，显示了可测量和显着的Lambda-DNA分子线的导电性。通过测量I-V和阻抗同时进行进一步研究，同时提高温度以达到完全变性（〜1100C），从而没有电流传导。随后通过在TM缓冲液中于退火温度（〜900C）下孵育而使DNA重新退火，从而恢复了导电性，从而有力地证明了DNA分子线是产生导电性的分子。据报道，lambda-DNA分子线在两个温度区域具有不同的阻抗响应：阻抗在40°C至400°C之间升高（电导率降低），然后从400°C降低直至DNA完全变性（约1100°C）。 400℃后电导率的增加是实验支持长距离电子传输机理，称为“热跳跃”机理。我们相信这项研究代表了与以往研究的重大突破，并通过（i）修饰DNA附着方法做出了独特贡献，使成功率从不到10％提高到了超过75％（ii）更精确的直接电导率测量DNA分子线通过将DNA悬浮于底物上而得以促进，并且（iii）温度影响DNA分子线的AC阻抗测量表明，温度门控机制在通过DNA线进行电荷传输方面的实验证据对于DNA分子的传输非常重要。深度学习。
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