ELECTRONIC COUPLING PROPERTIES OF POLYNUCLEOTIDES

快速光诱导电子转移过程的动态监测 能够直接研究远程电子相互作用的依赖性， 取决于周围介质的介电性质。 这种技术 因此，可以用来测量电子耦合和核 生物材料的重组能。 然而，正确理解 非共轭分子之间的电子相互作用 很大程度上取决于设计和构建分子结构的能力 其是刚性的并且其部件间的几何形状被很好地限定。 所有 迄今所研究的模型系统未能满足这一令人生畏的要求。 在这里，我们提出了一个简单的策略，使用多核苷酸，一个基本的 结构单元，以组装供体-受体（D-A）组件 组织成有组织的单位，便于研究电子传输 宿主核苷酸的性质。 我们选择专注于双重- 链状合成多核苷酸 以最小的生物结构破坏嵌入染料分子。 这种创新方法允许两个精确定位 电子伙伴在预定的分离距离，范围从 货车范德华接触超过3 nm，但保持固定的取向。 这是第一次有机会探讨 涉及非共价键的电子相互作用（通过空间） 耦合，一个难以捉摸的过程，一直很差的特点。 一 进一步的动机是，这种方法将揭示 DNA中的长程电子隧穿机制，从而提供 进一步了解DNA损伤和修复的机制 流程. 这项研究的结果应该直接 阐明急流生物ET机制的相关性 蛋白质或核苷酸作为介质的反应。

Monitoring the dynamics of rapid photoinduced electron transfer processes enables direct study of the dependence of remote electronic interactions upon the dielectric properties of the surrounding medium. This technique can be used, therefore, to measure electronic coupling and nuclear reorganization energies of biomaterials. However, a proper understanding of electronic interactions between nonconjugated molecular components depends heavily upon the ability to design and build molecular structures that are rigid and whose intercomponent geometry is well defined. All model systems studied to date fail to meet this daunting requisite. Here, we propose a simple strategy that uses polynucleotides, a basic architectural unit in nature, to assemble donor-acceptor (D-A) components into organized units that facilitate study of the electron transporting properties of the host nucleotides. We choose to focus on double- stranded synthetic polynucleotides which readily accommodate intercalating dye molecules with minimum disruption of the biostructure. This innovation approach permits the precise positioning of two electronic partners at predetermined separation distances, ranging from van der Waals contact to over 3 nm, but retaining a fixed orientation. This offers the opportunity, for the first time, to explore mechanisms of electronic interactions involving noncovalent (through space) coupling, an elusive process that has been poorly characterized. A further motivation is that this approach will shed light on the mechanisms of long range electronic tunneling in DNA and thereby provide further understanding of the mechanisms for DNA damage and repair processes. The results originating from this study should have direct relevance for elucidating the mechanisms of rapids biological ET reactions in which proteins or nucleotides function as mediators.