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Electron Transfer Chemistry between DNA and DNA-Binding Tripeptides

机译：DNA和DNA结合三肽之间的电子转移化学

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摘要

A DNA system consisting of pyrene-modified oligonucleotides and nitrobenzoate (Nb)-modified DNA-binding tripeptides has been applied to study electron-transfer processes through the DNA-peptide interface.5-(Pyren-l-yl)-2'-deoxyuridine (Py-dU) has been used as the photoinducible charge generator.Upon excitation at 350 nm,a pyrene-like excited state (Py-dU) is formed which undergoes an electron transfer yielding the charge-separated state which is the contact ion pair Py~(centre dot+)-dU~(centre dot-).The subsequent electron shift from dU~(centre dot-) into the base stack competes with charge recombination and can be probed chemically by trapping the electron at the 5-bromo-2'-deoxyuridine (Br-dU) group leading to strand cleavage which can be quantified by HPLC analysis.Several Nb-modified DNA-binding tripeptides influence these DNA-mediated electron-transfer processes as shown by fluorescence spectroscopy experiments.Fluorescence quenching can occur primarily through a reductive electron-transfer process in which the Nb group traps the electron thermodynamically from the contact ion pair Py~(centre dot+)-dU~(centre dot-).Moreover,our results indicate that,once the negative charge has been trapped on the peptide,oxidative processes from Py~(centre dot+) take place resulting in an enhanced and nonspecific strand degradation of the Py-dU-modified duplexes.The latter type of strand cleavage can be inhibited by the presence of tryptophane or tyrosine as part of the peptides.Most remarkably,DNA-binding tripeptides,which bear both the Nb and the tryptophan/tyrosine moiety,are able to trap both the negative and the positive charge from the contact ion pair Py~(centre dot+)-dU~(centre dot-).
机译：由pyr修饰的寡核苷酸和硝基苯甲酸酯（Nb）修饰的DNA结合三肽组成的DNA系统已用于研究通过DNA-肽界面进行的电子转移过程.5-（吡喃-1-基）-2'-脱氧尿苷（Py-dU）已被用作光诱导电荷产生剂。在350 nm激发时，形成-样激发态（Py-dU），它经历电子转移，产生电荷分离态，即接触离子对Py〜（中心点+）-dU〜（中心点-）。随后从dU〜（中心点-）进入基堆的电子移动与电荷重组竞争，可以通过将电子俘获在5溴原子-上进行化学探测。 2'-脱氧尿苷（Br-dU）基团导致链断裂，可通过HPLC分析定量。荧光光谱实验表明，几个Nb修饰的DNA结合三肽会影响这些DNA介导的电子转移过程，可能会发生荧光猝灭。主要通过还原电n转移过程，其中Nb基团从接触离子对Py〜（中心点+）-dU〜（中心点-）热力学上捕获电子。此外，我们的结果表明，一旦负电荷被捕获在肽上，从Py〜（中心点+）开始的氧化过程导致Py-dU修饰的双链体的增强和非特异性链降解。色氨酸或酪氨酸作为肽的一部分可以抑制后一种类型的链断裂最明显的是，DNA结合三肽同时具有Nb和色氨酸/酪氨酸部分，能够捕获来自接触离子对Py〜（中心点+）-dU〜（中心点- ）。

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