Nanoscale Multifunctional Molecules using DNA as scaffold

在过去的25年里，纳米尺度的功能实体的设计已经发展成为一个令人着迷的，跨学科的领域。与传统的物理组件缩小规模相比，从化学构建模块生产功能组件的向上工程最有希望满足未来技术的需求。超分子化学是目前在纳米尺度上获得功能分子的研究热点之一。直到最近，DNA才成为一种有吸引力的超分子支架来生产纳米级实体。然而，双链DNA（dsDNA）到目前为止仅被使用，因为其通过碱基配对识别的高选择性，以特异性地连接纳米颗粒，用于DNA芯片技术和纳米光刻，在表面组装阵列，创建纳米机械设备或构建蛋白质阵列和纳米线。只有少数报告存在的核碱基本身已被取代，以创建一个功能性的DNA.Porphyrins提供了多功能的建筑块在超分子化学由于其中心金属结合位点，其相对容易的功能化，以及其特有的物理和电化学性质。后者可以使用适当的取代基、中心金属和配体来调节，这是不同卟啉单元之间的最佳相互作用（即能量或电子转移）所需的。因此，多卟啉阵列提供了有用的结构应用于几乎所有领域的science.This项目的目的是实现一个模块化的积木系统，其中结构不同的卟啉，并在不同的metabolites状态，组装到一个结构预定的骨干，并在一个序列特异性的方式，独立于卟啉结构。这个想法是使用DNA作为一个作用模板来组装多卟啉系统。通过改变卟啉的结构和位态，可以在纳米尺度上取代核苷酸，从而形成多功能分子。其中我们已经建立了一种通用的合成路线来获得二苯基和四苯基卟啉取代的dU。将卟啉上的侧链从羧酸酯改变为相应的羧酸酯改变了卟啉的溶解度。从可溶于有机溶剂到可溶于水溶液。二核苷酸-双卟啉体系的合成表明，单元之间存在电子相互作用。然而，溶液相合成不适合于生产更大的组件。因此，我们已经评估了使用标准的固相化学，使用DNA合成仪，以获得同源和杂卟啉四核苷酸双卟啉系统。在这里，吸收和发射光谱测量揭示了两种不同的卟啉之间的电子相互作用时，纳入四核苷酸，从而表明可能性微调的物理性质，使用我们的积木system.We进一步能够纳入多达11个卟啉到21聚体寡脱氧核苷酸链。第一个分析数据表明，当卟啉在有机溶剂中作为散装材料测量时，发色团之间不会发生电子相互作用。也可以检测到结构向细长螺旋结构的变化，以及单链卟啉-DNA缀合物的结构稳定性。第一个数据证明了这一概念，并且使用我们的策略可以在纳米尺度上创建功能分子。下一阶段是详细了解结构的物理特性。有了这些知识，就有可能设计出电子线路，从而产生适用于光电子学或计算的全新系统。

The design of functional entities of nanoscale dimensions has developed over the past 25 years into a fascinating, interdisciplinary field of ever growing interest. In contrast to the classical downscaling of physical components, upwards engineering to produce functional assemblies from chemical building blocks is most promising to meet the needs of future technologies. Supramolecular chemistry is one of the strategies which are currently under intense investigation to obtain functional molecules on the nanometre scale. Only very recently, DNA has become attractive as a supramolecular scaffold to produce nanoscaled entities. However, the double stranded DNA (dsDNA) has so far only been used because of its high selectivity in recognition through base-pairing to specifically connect nano particles, in DNA chip technology and nanolithography, to assemble arrays at surfaces, to create nanomechanical devices or to construct protein arrays and nanowires. Only few reports exist where the nucleobases themselves have been substituted to create a functional DNA.Porphyrins provide versatile building blocks in supramolecular chemistry due to their central metal binding site, their relative ease of functionalisation, and their characteristic photophysical and electrochemical properties. The latter can be tuned using appropriate substituents, central metals and ligands, which is required for an optimal interplay between different porphyrin units (i.e. energy or electron transfer). Thus, multiporphyrin arrays offer useful constructs for applications in almost all areas of science.This project aims to realise a modular building block system, in which structurally different porphyrins, and in different metallation states, are assembled onto a structurally predetermined backbone, and in a sequence specific manner, independent on the porphyrin structure. The idea is to use DNA as an acting template to assemble multiporphyrin systems. Nucleotides are substituted with porphyrins varying both in structure and metallation state to create a multifunctional molecule on the nanometre scale.We have now focused on the modification of deoxyuridine (dU), where we have established a general synthetic route to access both diphenyl and tetraphenyl porphyrin substituted dU. Changing the side chain on the porphyrin from a carboxylic ester to the corresponding carboxylates alters the solubility of the conjugate from being soluble in organic solvents to being soluble in aqueous solutions. The synthesis of dinucleotide-diporphyrin systems has shown that electronic interactions between the units occur. The solution phase synthesis, however, is not suitable to produce larger assemblies. We have therefore evaluated the use of standard solid phase chemistry using a DNA synthesiser to obtain homo- and hetero-porphyrinic tetranucleotide diporphyrin systems. Here, the absorption and emission spectroscopy measurements revealed electronic interactions between two different porphyrins when incorporated into the tetranucleotide, thus indicating the possibility to fine-tune the physical properties using our building block system.We have further been able to incorporate up to eleven porphyrins into a 21mer olgio-deoxynucleotide strand. First analytical data indicate an electronic interaction between the chromophores which does not occur when the porphyrins are measured as bulk material in organic solvents. A change in the structure towards an elongated helical structure can also be detected, together with a structure stabilisation in the single stranded porphyrin-DNA conjugate.The first data proof the concept, and the creation of a functional molecule on the nano-metre scale is possible using our strategy. The next stage is to get a detailed understanding of the physical properties of the construct. With this knowledge it will be possible to design the electronic wires that may lead to fundamentally new systems applicable in photovoltaics or computing.