Radicals in Sucrose Single Crystals Induced by X-rays at Different Temperatures: a Combined EPR and DFT Study
Radicals in Sucrose Single Crystals Induced by X-rays at Different Temperatures: a Combined EPR and DFT Study
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不同温度下 X 射线诱导的蔗糖单晶中的自由基：EPR 和 DFT 的联合研究
DOI：
10.1051/radiopro:2008683
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
F. Callens
中科院分区：
文献类型：
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作者：
H. Cooman;E. Pauwels;H. Vrielinck;E. Sagstuen;M. Waroquier;F. Callens
了解糖化合物中辐射引起的缺陷的性质对于剂量测定目的以及DNA的辐射化学具有重要意义。蔗糖（食用糖）由于其广泛使用、其辐射敏感性、诱导自由基的稳定性以及其高达104戈伊的线性剂量响应而在核应急剂量测定中特别令人感兴趣。最近的剂量测定研究表明，糖是EPR（电子顺磁共振）和/或紫外线剂量测定在0.44-160 kGy的区域的最好的，通用的材料。在糖和糖衍生物中，X射线最初会产生各种类型的缺陷，然后通过通常复杂的多步骤过程转化为最终稳定的自由基产物。最终，对这些材料中辐射诱导过程的深入了解可以帮助建立剂量测定方案，并对糖基在DNA辐射化学中的确切作用提供更多的了解。电子磁共振（EMR）实验上的糖单晶允许通过超精细的相互作用的未成对电子自旋与晶格1H核自旋的自由基的详细的方式进行表征。在过去的几年里，高精度的密度泛函理论（DFT）计算扩展的有机固态系统已成为可能，由于在计算能力和密度泛函的进步，以及新的代码的开发，用于计算EMR参数。结合这些实验和理论分析工具，已经证明是研究糖的辐射化学的一种非常强大的方法[1-3]。我们目前的结果进行蔗糖单晶在不同的温度下，从10 K到室温，在这些温度下原位照射后，和随后的退火实验的EMR实验。通过比较实验和计算的DFT结果，最突出的自由基被确定，并获得其形成机制的信息。除其他外，我们的研究揭示了在室温下稳定的三个主要自由基的结构，这是最相关的剂量测定的背景下。1.用电子磁共振参数的密度泛函理论计算鉴定和构象研究蔗糖单晶中稳定的辐射诱导缺陷Pauwels，E.; Vrielinck，H.; Sagstuen，E.; Callens，F.; Waroquier，M.，物理化学杂志B，接受。2. Pauwels，E.; Declerck，R.;货车斯佩布鲁克; Waroquier，M. Radiat. Res. 2008，169，8. 3. Tarpan，M.; Sagstuen，E.; Pauwels，E.; Vrielinck，H.; Waroquier，M.和Callens，F. J. Phys. Chem. A，出版中，doi：10.1021/jp 7119284。
Understanding the nature of radiation-induced defects in sugar compounds is of importance for dosimetry purposes as well as in the radiation chemistry of DNA. Sucrose (table sugar) is of particular interest for nuclear emergency dosimetry because of its widespread use, its radiation sensitivity, the stability of the induced radicals, and its linear dose response up to 104 Gy. Recent dosimetric studies suggest sugar to be the best, universal material for EPR- (Electron Paramagnetic Resonance) and/or UV-dosimetry in the region 0.44-160 kGy. In sugars and sugar derivatives, X-rays initially create various types of defects which then transform into the final, stable radical products through a generally complex multi-step process. Ultimately, an advanced understanding of the radiation-induced processes in these materials could aid in establishing dosimetry protocols and provide more insight into the exact role of sugar radicals in the radiation chemistry of DNA. Electron Magnetic Resonance (EMR) experiments on sugar single crystals allow for characterisation of the radicals in a detailed way via hyperfine interactions of the unpaired electron spin with the lattice 1H nuclear spins. The last couple of years, highly accurate Density Functional Theory (DFT) calculations on extended organic solid state systems have become feasible due to advances in computing power and density functionals as well as to the development of new codes for the calculation of EMR parameters. Combining these experimental and theoretical tools has already proven to be a very powerful approach to study the radiation chemistry of sugars [1-3]. We present the results of EMR experiments performed on sucrose single crystals at different temperatures, from 10 K up to room temperature, after in situ irradiation at these temperatures, and of subsequent annealing experiments. Through comparison of experimental and computational DFT results, the most prominent radicals are identified and information is obtained on their formation mechanism. Among others, our study reveals the structure of the three predominant radicals stable at room temperature, that are most relevant in the context of dosimetry. 1. Identification and Conformational Study of Stable Radiation-Induced Defects in Sucrose Single Crystals using Density Functional Theory Calculations of Electron Magnetic Resonance Parameters, De Cooman, H.; Pauwels, E.; Vrielinck, H.; Sagstuen, E.; Callens, F.; Waroquier, M., J. Phys. Chem. B, accepted. 2. Pauwels, E.;Declerck, R.; Van Speybroeck, V.; Waroquier, M. Radiat. Res. 2008, 169, 8. 3. Tarpan, M.; Sagstuen, E.; Pauwels, E.; Vrielinck, H.; Waroquier, M. and Callens, F. J. Phys. Chem. A, in press, doi:10.1021/jp7119284.