DNA-MEDIATED ELECTRON TRANSFER REACTIONS

这项提案的总体目标是，利用金属核酸 化学，是探索DNA作为聚合物在介导 电子转移反应 将构建寡核苷酸，其 含有与双螺旋共价连接的金属络合物， 开展光诱导电子转移的研究， DNA双链体上的受体对作为DNA长度、序列和 结构 DNA螺旋，作为一种合成上的顺从性和结构上的 良好表征的聚合物，可用于（i）基本上， 描绘了通过π-π 堆栈，（ii）生物学上，了解如何激进的反应， 可能会损害DNA，和（iii）实际上，在生物传感器的发展。 将构建含有金属嵌入剂的寡核苷酸， 连接到5 '-末端的供体或受体;二吡啶并吩嗪（dppz） 钌（II）的络合物将作为供体， (phi)铑（III）的络合物将充当电子受体。 将建立复合物在螺旋内的嵌入 通过对经修饰的寡核苷酸的发光研究， 与未修饰的互补物碱基配对。 夹层位置 因此将建立聚合物上的金属-金属距离 通过使用铑改性聚合物的光裂解实验， 与未标记的补体结合。 之间的光电子转移速率 双链上的金属位点通过退火铑改性的 聚合物与经季铵盐改性的聚合物的比率将通过以下测定： 时间分辨发光和瞬态吸收光谱。 初步结果表明，快速光电子转移超过41 通过DNA双链体。 插入金属之间的长度不同的寡核苷酸 供体和受体将准备建立距离依赖性 在电子转移速率，和序列将被合成， 优先采用A-或Z-构象来确定 基极堆积对电子转移过程的贡献。 到 比较穿透键与π-堆叠机制，电子转移速率 将在形式（5 '-Ru-1）的双螺旋之间进行比较。 利多卡因肽-Rh-3 '）。（3 '互补物-5'）和（5 'Ru-寡核苷酸- 3 '）。（3 '-补体'Rh-5 '）。 位点特异性地结合至 插入双链体，如顺铂、限制性内切酶或 替代的，位点特异性结合的铑络合物，将用于 研究远程电子转移过程中的扰动。 一 潜在的DNA-“二极管”也将被构建，以检查是否 在螺旋上引入给电子或接受电子的基团可以 赋予电子转移“序列依赖性”方向性 过程

The overall objective of this proposal, using metal-nucleic acid chemistry, is to explore the role of DNA as a polymer in mediating electron transfer reactions. Oligonucleotides will be constructed which contain metal complexes covalently linked to the double helix so as to carry out studies of photoinduced electron transfer between the donor- acceptor pairs on a DNA duplex as a function of DNA length, sequence, and structure. The DNA helix, as a synthetically amenable and structurally well characterized polymer, may be useful (i) fundamentally, in delineating aspects of long range electron transfer processes through pi- stacks, (ii) biologically, towards understanding how radical reactions may damage DNA, and (iii) practically, in the development of biosensors. Oligonucleotides will be constructed which contain a metallointercalating donor or acceptor tethered to the 5'-terminus; dipyridophenazine (dppz) complexes of ruthenium(II) will serve as donors and phenanthrenequinone (phi) complexes of rhodium(III) will serve as electron acceptors. Intercalation of the complexes within the helix will be established through luminescence studies of the ruthenium-modified oligonucleotide base-paired with unmodified complement. The position of intercalation and hence the metal-metal distance on the polymer will be established through photocleavage experiments using the rhodium-modified polymer bound to unlabeled complement. Photoelectron transfer rates between the metal sites on a double strand formed by annealing the rhodium-modified polymer to the ruthenium-modified polymer will be determined through time-resolved luminescence and transient absorption spectroscopy. Preliminary results indicate fast photoelectron transfer over 41 angstrome through the DNA duplex. Oligonucleotides which differ in length intervening between the metal donor and acceptor will be prepared to establish the distance-dependence in electron transfer rate, and sequences will be synthesized which can adopt preferentially the A- or Z-conformations to determine the contribution of base stacking to the electron transfer process. To compare through-bond versus a pi-stack mechanism, electron transfer rates will be compared between double helices of the form (5'-Ru- oligonucleotide-Rh-3'). (3'complement-5') and (5'Ru-oligonucleotide- 3').(3'-complement'Rh-5'). Agents which bind site-specifically to the intervening duplex, such as cis-platin, a restriction enzyme, or an alternate, site-specifically bound rhodium complex, will be employed to examine perturbations in the long-range electron transfer process. A potential DNA-"diode" will also be constructed to examine whether the incorporation of electron-donating or accepting groups on the helix can impart a "sequence-dependent" directionality to the electron transfer process.