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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Primary processes underlying the photostability of isolated DNA bases: Adenine
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Primary processes underlying the photostability of isolated DNA bases: Adenine

机译：分离的DNA碱基的光稳定性的主要过程：腺嘌呤

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摘要

The UV chromophores in DNA are the nucleic bases themselves, and it is their photophysics and photochemistry that govern the intrinsic photostability of DNA. Because stability is related to the conversion of dangerous electronic to less-dangerous vibrational energy, we study ultrafast electronic relaxation processes in the DNA base adenine. We excite adenine, isolated in a molecular beam, to its pi pi* state and follow its relaxation dynamics using femtosecond time-resolved photoelectron spectroscopy. To discern which processes are important on which timescales, we compare adenine with 9-methyl adenine. Methylation blocks the site of the much-discussed pi sigma* state that had been thought, until now, minor. Time-resolved photoelectron spectroscopy reveals that, although adenine and 9-methyl adenine show almost identical timescales for the processes involved, the decay pathways are quite different. Importantly, we confirm that in adenine at 267-nm excitation, the pi sigma* state plays a major role. We discuss these results in the context of recent experimental and theoretical studies on adenine, proposing a model that accounts for all known results, and consider the relationship between these studies and electron-induced damage in DNA.
机译：DNA中的UV发色团本身就是核酸碱基，正是它们的光物理和光化学决定了DNA固有的光稳定性。由于稳定性与危险电子向低危险振动能的转换有关，因此我们研究了DNA基础腺嘌呤中的超快电子弛豫过程。我们将在分子束中隔离的腺嘌呤激发到pi pi *状态，并使用飞秒时间分辨光电子能谱跟踪其弛豫动力学。为了辨别哪个过程在哪个时间尺度上很重要，我们将腺嘌呤与9-甲基腺嘌呤进行了比较。甲基化阻止了人们一直讨论的pi sigma *状态的位置，直到现在，这种状态仍很小。时间分辨光电子能谱显示，尽管腺嘌呤和9-甲基腺嘌呤在所涉及的过程中显示出几乎相同的时间尺度，但衰变途径却截然不同。重要的是，我们确认在267 nm激发的腺嘌呤中，pi sigma *状态起着重要作用。我们在最近关于腺嘌呤的实验和理论研究的背景下讨论这些结果，提出了一个解释所有已知结果的模型，并考虑这些研究与DNA中电子诱导的损伤之间的关系。

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