DNA MEDIATED ELECTRON TRANSFER REACTIONS

拟议研究的总体目标是勾勒出 DNA碱基对堆叠可能介导长程电荷传输。这个 通过DNA的长距离自由基迁移的后果是重要的 从理解癌症发生的角度来考虑 开发新的化疗策略。远程电子 将使用定义明确的双链来探索DNA中的转移化学 捐赠者和接受者堆积得很好的集会。在美国的研究 目前以嵌入剂为探针的授权期表明，DNA- 介导性电子转移可以以一种肤浅的依赖 距离，但对碱基对堆叠的敏感性很高。程序集将 其中施主/受主对是(I)两者 嵌入剂，(Ii)一个嵌入剂，一个改性碱，或(Iii)两个 修改过的碱基。被拴住的插层剂包括菲醌 Rh的二亚胺，Ru和Om的二吡啶并吩嗪配合物， 和乙锭。修饰的碱基包括2-氨基嘌呤、去氮鸟嘌呤、 和恶鸟嘌呤。荧光和瞬时吸收实验将 来确定电子转移速率作为以下参数的函数 距离、顺序和驱动力。RU(II)/OS(II)已修改 组件将准备检查三重态能量转移，以及 RU(II)/Os(III)组件将用于测试价间电荷 调职。含有系链Ru(III)嵌入剂和 将构建系链的Lys-Trp-Lys作为模型进行探索 蛋白质-DNA电子转移。通过考虑双螺旋DNA不 在过去的资助期间，我们不仅作为桥梁，而且作为反应物，我们 利用DNA碱基对堆栈进行远距离化学， 在那里，氧化从一个偏远的位置被促进，以破坏或修复DNA。 因此，我们建议将光谱分析和生化分析结合起来使用 定义DNA组件以检查DNA氧化损伤是如何发生在 一段距离。使用远程站点启动的DNA氧化损伤 插层氧化剂的特性将通过变化在 干扰DNA序列、结构和构象。的影响 蛋白质诱导的碱基对堆叠的变化，特别是碱基翻转， 还将检查远程氧化损伤，以努力 开发蛋白质促进的螺旋扭曲的溶液分析方法。 此外，DNA的氧化损伤将在DNA片段上进行比较 并在核小体内确定DNA包装如何影响远程 充电式运输。我们的长期目标是确定收费是否 从长远来看，通过DNA的运输在生理上是重要的 化学信息的传递。

The overall objective of the proposed research is to delineate how the DNA base pair stack may mediate long range charge transport. The consequences of long range radical migration through DNA are important to consider with respect to understanding carcinogenesis and to developing new chemotherapeutic strategies. Long range electron transfer chemistry in DNA will be probed using well-defined duplex assemblies with well stacked donors and acceptors. Studies in the current grant period with intercalators as probes have shown that DNA- mediated electron transfer can proceed with a shallow dependence on distance but a high sensitivity to base pair stacking. Assemblies will be constructed in which the donor/acceptor pair are (i) both intercalators, (ii) one intercalator, one modified base, or (iii) two modified bases. The tethered intercalators include phenanthrene quinone diimine of rhodium, dipyridophenazine complexes of ruthenium and osmium, and ethidium. The modified bases include 2-aminopurine, deazaguanine, and oxoguanine. Fluorescence and transient absorption experiments will be conducted to determine rates of electron transfer as a function of distance, sequence, and driving force. Ru(II)/Os(II) modified assemblies will be prepared to examine triplet energy transfer, and Ru(II)/Os(III) assemblies will be used to test for intervalence charge transfer. DNA assemblies containing a tethered Ru(III) intercalator and a tethered Lys-Trp-Lys will be constructed as a model to explore protein-DNA electron transfer. By considering double helical DNA not only as a bridge but also as a reactant, in the past grant period, we exploited the DNA base pair stack to carry out chemistry at a distance, where oxidation is promoted from a remote site to damage or repair DNA. Thus we propose to couple spectroscopic and biochemical assays using defined DNA assemblies to examine how oxidative damage to DNA occurs at a distance. Oxidative DNA damage initiated from a remote site using an intercalating oxidant will be characterized through variations in intervening DNA sequence, structure, and conformation. The effects of protein-induced changes in the base pair stack, notably base flipping, on long range oxidative damage will also be examined in an effort to develop solution assays for protein-promoted helix distortions. Additionally, oxidative damage to DNA will be compared on DNA fragments and within nucleosomes to determine how DNA packaging affects long range charge transport. Our long term objective is to establish whether charge transport through DNA is physiologically important in the long range transmission of chemical information.