Pauwels Ewald, Van Speybroeck Veronique, Waroquier Michel
Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium.
Spectrochim Acta A Mol Biomol Spectrosc. 2006 Mar 13;63(4):795-801. doi: 10.1016/j.saa.2005.10.027. Epub 2006 Feb 20.
Using density functional theory (DFT) calculations, an enhanced theoretical examination was made of the radiation-induced radicals in alpha-d-glucose. For the carbon-centred radicals in this sugar, the effect of the model space on the radical geometry as well as on the calculated radical hyperfine coupling tensors was examined. The findings were compared with previously published tensors, as determined by electron paramagnetic resonance (EPR) experiments and single molecule DFT calculations. A cluster approach was adopted, in which intermolecular interactions (predominantly hydrogen bonds) between the radical species and its environment were explicitly incorporated. This substantially improved the correspondence with experimental findings in comparison with single molecule calculations of an earlier examination. In a direct comparison between both computational methods for the glucose radicals, it was shown that the extent of the model space plays an important part in the determination of the radical geometry. Furthermore, the model space also has an impact on the calculated hyperfine coupling tensors. Full cluster EPR calculations, in which the paramagnetic properties are calculated for the entire model space of the cluster, give an excellent agreement with the experimental EPR measurements.
利用密度泛函理论（DFT）计算方法，对α-D-葡萄糖中辐射诱导自由基进行了深入的理论研究。对于该糖类中以碳为中心的自由基，研究了模型空间对自由基几何结构以及对计算得到的自由基超精细耦合张量的影响。将研究结果与先前发表的张量进行了比较，这些张量是通过电子顺磁共振（EPR）实验和单分子DFT计算确定的。采用了一种簇方法，其中明确纳入了自由基物种与其环境之间的分子间相互作用（主要是氢键）。与早期研究中的单分子计算相比，这大大提高了与实验结果的一致性。在对葡萄糖自由基的两种计算方法的直接比较中，结果表明模型空间的范围在确定自由基几何结构中起着重要作用。此外，模型空间对计算得到的超精细耦合张量也有影响。全簇EPR计算，即对簇的整个模型空间计算顺磁性质，与实验EPR测量结果非常吻合。
