DNA-mediated electron transfer from a modified base to ethidium:: π-stacking as a modulator of reactivity
DNA-mediated electron transfer from a modified base to ethidium:: π-stacking as a modulator of reactivity
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DOI：
10.1016/s1074-5521(98)90158-2
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发表时间：
1998-08-01
影响因子：
--
通讯作者：
Barton, JK
中科院分区：
文献类型：
--
作者：
Kelley, SO;Barton, JK
背景：DNA双螺旋由一系列芳香杂环碱基对组成，作为分子π堆栈，代表了一种用于研究长程电子转移的新颖系统。由于许多碱基损伤和修复过程都是由电子转移反应引起的，因此 DNA 介导电荷传输的能力具有重要的生物学意义。从许多不同的研究中，我们得出了关于 DNA 中电子转移的看似矛盾的结论。这些研究必须协调一致，以便从根本上和生物系统的背景下理解这种现象。 结果：已检查修饰碱基 7-脱氮鸟嘌呤的光诱导氧化与乙锭共价修饰的 DNA 双链体中距离、序列和碱基堆积的函数关系。在 6-27 埃的乙锭/脱氮鸟嘌呤分离范围内，光氧化反应在亚纳秒时间尺度上进行，并且猝灭产率表现出浅距离依赖性。反应效率对碱组成的微小变化高度敏感。此外，尽管光激发的乙锭作为受体具有恒定性，但反应的整体距离依赖性对序列很敏感。结论：嵌入乙锭在长距离内进行脱氮鸟嘌呤光氧化的显着效率为通过DNA的快速电子转移途径提供了新的证据。通过改变序列以及反应物分离，这项工作首次通过实验证明了反应物堆积在调节长距离DNA介导的电子转移中的重要性。
Background: The DNA double helix is composed of an array of aromatic heterocyclic base pairs and, as a molecular pi-stack, represents a novel system for studying long-range electron transfer. Because many base damage and repair processes result from electron-transfer reactions, the ability of DNA to mediate charge transport holds important biological implications. Seemingly contradictory conclusions have been drawn about electron transfer in DNA from the many different studies that have been carried out. These studies must be reconciled so that this phenomenon can be understood both at a fundamental level and in the context of biological systems.Results: The photoinduced oxidation of a modified base, 7-deazaguanine, has been examined as a function of distance, sequence, and base stacking in DNA duplexes covalently modified with ethidium. Over ethidium/deazaguanine separations of 6-27 Angstrom, the photooxidation reaction proceeded on a subnanosecond time scale, and the quenching yield exhibited a shallow distance dependence. The efficiency of the reaction was highly sensitive to small changes in base composition. Moreover, the overall distance-dependence of the reaction is sensitive to sequence, despite the constancy of photoexcited ethidium as acceptor.Conclusions: The remarkable efficiency of deazaguanine photooxidation by intercalated ethidium over long distances provides new evidence for fast electron-transfer pathways through DNA, By varying sequence as well as reactant separation, this work provides the first experimental demonstration of the importance of reactant stacking in the modulation of long-range DNA-mediated electron transfer.