Samples suitable for electron diffraction studies must satisfy certain characteristics such as having a thickness in the range of 10–100 nm. We report, to our knowledge, the first successful synthesis technique of nanometer-thin sheets of single-crystalline thymine suitable for electron diffraction and spectroscopy studies. This development provides a well-defined system to explore issues related to UV photochemistry of DNA and high intrinsic stability essential to maintaining integrity of genetic information. The crystals are grown using the evaporation technique, and the nanometer-thin sheets are obtained via microtoming. The sample is characterized via x-ray diffraction and is subsequently studied using electron diffraction via a transmission electron microscope. Thymine is found to be more radiation resistant than similar molecular moieties (e.g., carbamazepine) by a factor of 5. This raises interesting questions about the role of the fast relaxation processes of electron scattering-induced excited states, extending the concept of radiation hardening beyond photoexcited states. The high stability of thymine in particular opens the door for further studies of these ultrafast relaxation processes giving rise to the high stability of DNA to UV radiation.

中文翻译：

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纳米薄单晶胸腺嘧啶合成技术及电子束损伤研究

适用于电子衍射研究的样品必须满足某些特性，例如厚度在 10–100 nm 范围内。据我们所知，我们报告了第一个成功合成适用于电子衍射和光谱研究的单晶胸腺嘧啶纳米薄片的技术。这一进展提供了一个明确的系统来探索与 DNA 紫外光化学相关的问题以及对维持遗传信息完整性至关重要的高内在稳定性。使用蒸发技术生长晶体，并通过显微切片获得纳米薄片。通过 X 射线衍射对样品进行表征，随后通过透射电子显微镜使用电子衍射进行研究。胸腺嘧啶被发现比类似的分子部分（例如卡马西平）具有 5 倍的抗辐射能力。这提出了关于电子散射引起的激发态的快速弛豫过程的作用的有趣问题，将辐射硬化的概念扩展到了其他领域光激发态。胸腺嘧啶的高稳定性尤其为进一步研究这些超快弛豫过程打开了大门，从而提高了 DNA 对紫外线辐射的高稳定性。