Experimental evidence for ultrafast intermolecular relaxation processes in hydrated biomolecules
Experimental evidence for ultrafast intermolecular relaxation processes in hydrated biomolecules
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DOI：
10.1038/s41567-018-0214-9
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发表时间：
2018-07
期刊：
影响因子：
19.6
通讯作者：
X. Ren;Enliang Wang;A. D. Skitnevskaya;A. Trofimov;K. Gokhberg;A. Dorn
中科院分区：
文献类型：
--
作者：
X. Ren;Enliang Wang;A. D. Skitnevskaya;A. Trofimov;K. Gokhberg;A. Dorn
电离辐射引起的细胞和基因损伤已被研究多年。人们普遍认为，DNA 损伤（例如单链和双链断裂）是由二次物质（例如自由基、离子和初级辐射产生的丰富的低能二次电子）引起的。特别有害的是生物分子系统典型体积内多个电离过程的密集电离簇。在这里，我们报告了对称为分子间库仑衰变（ICD）的非局部自电离过程形式的损伤机制的观察。它直接涉及水环境中的 DNA 成分或其他有机分子。这些产物是两个高能离子和三个反应性二次电子，可能在其附近造成进一步的损害。由一个四氢呋喃 (THF) 分子（DNA 主链中脱氧核糖的替代物）和一个水分子组成的氢键复合物被用作模型系统。内价电子层中的水分子发生电子碰撞电离后，空位被外价电子填充。释放的能量通过氢桥转移，导致邻近的 THF 分子电离。这种从水到 THF 的能量转移比其他情况下发生的分子间质子转移更快。 ICD 反应的特征通过离子和终态电子之一的三重符合测量来识别。这些结果可以提高对生物组织辐射损伤的理解。
Cell and gene damage caused by ionizing radiation has been studied for many years. It is accepted that DNA lesions (single- and double-strand breaks, for example) are induced by secondary species such as radicals, ions and the abundant low-energy secondary electrons generated by the primary radiation. Particularly harmful are dense ionization clusters of several ionization processes within a volume typical for the biomolecular system. Here we report the observation of a damage mechanism in the form of a non-local autoionizing process called intermolecular Coulombic decay (ICD). It directly involves DNA constituents or other organic molecules in an aqueous environment. The products are two energetic ions and three reactive secondary electrons that can cause further damage in their vicinity. Hydrogen-bonded complexes that consist of one tetrahydrofuran (THF) molecule—a surrogate of deoxyribose in the DNA backbone—and one water molecule are used as a model system. After electron impact ionization of the water molecule in the inner-valence shell the vacancy is filled by an outer-valence electron. The released energy is transferred across the hydrogen bridge and leads to ionization of the neighbouring THF molecule. This energy transfer from water to THF is faster than the otherwise occurring intermolecular proton transfer. The signature of the ICD reaction is identified in triple-coincidence measurements of both ions and one of the final state electrons. These results could improve the understanding of radiation damage in biological tissue.