Modification of DNA towards high conductance and transport measurements with controllable electrodes

我们研究了通过机械可控断链技术(MCB)与金电极相连的人工合成DNA分子的电子输运。这一方面允许使用短序列(10到30个碱基)，这有利于具有可测量的电流，另一方面允许改变同一分子的电极距离。后者对于研究分子结构对同一分子的输运性质的影响是很重要的。有了特殊的连接臂，部分构象变化可以被抑制(所谓的LNA：锁定的DNA)。对LNA的测量将作为解锁的DNA的参考。DNA运输中的一个重要问题是序列的作用。相互竞争的理论模型预测了不同的序列，这些序列应该是有利的。预测了高电子转移率的纯CG(胞嘧啶-鸟嘌呤)DNA。然而，该序列在通常的构象中并不稳定。实验证明，纯腺嘌呤胸腺嘧啶脱氧核糖核酸(AT)DNA没有明显的构象变化，而对电荷传输的预测是矛盾的。我们将系统地研究不同的序列。根据现有的实验，天然DNA的电阻似乎太大，不能作为分子电子学的导体。然而，制造具有任意序列的合成DNA的方法是非常先进的。因此，如果接触和构象的影响最终被揭示，基于DNA的杂化材料将被开发出来，从而产生高电导值。总结：该项目的目标有三个。首先，我们想要弄清楚DNA分子的运输机制。实现这一目标的先决条件是找到一种合适的、可重复使用的联系方法(目标2)。第三个也是最后一个目标是开发DNA的修饰，从而产生高电导。

We investigate the electronic transport through synthetic DNA molecules contacted by the mechanically controllable breakjunction technique (MCB) with thiol bonds to gold electrodes. This allows on the one hand to use short sequences (10 to 30 basepairs) which is favorable to have a measurable current and on the other hand to vary the distance of the electrodes for the same molecule. The latter is important to investigate the influence of the structure of the molecules on the transport properties at the very same molecule. With special linking arms, part of the conformational changes can be suppressed (so-called LNA: locked DNA). Measurements on LNA will serve as reference for the unlocked DNA.An important issue in the transport through DNA is the role of the sequence. Competing theoretical models predict different sequences that should be favorable. A high electron transfer rate is predicted for pure CG (cytosine-guanine) DNA. However, this sequence is not stable in the usual conformation. Pure AT (adenine-thymine) DNA has been shown experimentally to have no significant conformational change while the predictions for charge transport are contradictory. We will investigate systematically different sequences. In the light of existing experiments natural DNA appears to be too resistive to serve as conductors in molecular electronics. However, the methods to create synthetic DNA with arbitrary sequence are very elevated. Consequently, if finally the influence of the contacts and conformation is revealed, DNA-based hybrid materials will be developed that give rise to high conductance values.In summary: the goal of the project is threefold. At first we want to clarify the transport mechanism of the DNA molecule. A prerequisite for this aim is to find a suitable, reproducible contacting method (goal 2). The third and final goal would then be to develop modifications of DNA that result in high conductance.