葡萄糖-1-磷酸中的辐射诱导自由基。II. 结构及可能形成机制的密度泛函理论分析

Radiation-induced radicals in glucose-1-phosphate. II. DFT analysis of structures and possible formation mechanisms.

作者信息

Pauwels Ewald, De Cooman Hendrik, Vanhaelewyn Gauthier, Sagstuen Einar, Callens Freddy, Waroquier Michel

机构信息

Center for Molecular Modeling, Ghent University, Gent, Belgium.

出版信息

J Phys Chem B. 2008 Nov 27;112(47):15054-63. doi: 10.1021/jp804287c.

DOI:10.1021/jp804287c

PMID:18973365

Abstract

Four radiation-induced carbon-centered radicals in dipotassium glucose-1-phosphate dihydrate single crystals are examined with DFT methods, consistently relying on a periodic computational scheme. Starting from a set of plausible radical models, EPR hyperfine coupling tensors are calculated for optimized structures and compared with data obtained from EPR/ENDOR measurements, which are described in part I of this work. In this way, an independent structural identification is made of all the radicals that were observed in the experiments (R1-R4) and tentative reaction schemes are proposed. Also, the first strong evidence for conformational freedom in sugar radicals is established: two species are found to have the same chemical composition but different conformations and consequently different hyperfine coupling tensors. Analysis of the calculated energies for all model compounds suggests that the radiation chemistry of sugars, in general, is kinetically and not necessarily thermodynamically controlled.

摘要

利用密度泛函理论（DFT）方法，在周期性计算方案的基础上，对磷酸葡萄糖钾二水合物单晶中的四种辐射诱导碳中心自由基进行了研究。从一组合理的自由基模型出发，计算了优化结构的电子顺磁共振（EPR）超精细耦合张量，并与本工作第一部分中描述的EPR/电子核双共振（ENDOR）测量数据进行了比较。通过这种方式，对实验中观察到的所有自由基（R1-R4）进行了独立的结构鉴定，并提出了初步的反应方案。此外，还首次有力证明了糖自由基具有构象自由度：发现两种物质具有相同的化学组成，但构象不同，因此超精细耦合张量也不同。对所有模型化合物计算能量的分析表明，一般来说，糖的辐射化学是由动力学控制的，不一定受热力学控制。