Munzarová Markéta L, Sklenár Vladimír
National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlárská 2, CZ-611 37 Brno, Czech Republic.
J Am Chem Soc. 2002 Sep 11;124(36):10666-7. doi: 10.1021/ja026502p.
(3)J(C2/4-H1') and (3)J(C6/8-H1') scalar spin-spin coupling constants have been calculated for deoxyadenosine, deoxyguanosine, deoxycytidine, and deoxythymidine as functions of the glycosidic torsion angle chi by means of density functional theory. Except for deoxythymidine, (3)J(C2/4-H1') depends little on the base type. On the contrary, (3)J(C6/8-H1') follows the usual trans to cis ratio ((3)J(C-H(cis)) < (3)J(C-H(trans))) for purine nucleosides, but reveals the opposite relation ((3)J(C-H(cis)) > (3)J(C-H(trans))) for pyrimidine nucleosides. Our results compare well with the experiment for deoxyguanosine and predict a novel trend in the case of pyrimidine bases for which no NMR results are available in the syn region. A breakdown of the key Fermi contact part of (3)J(C6/8-H1') into MO contributions rationalizes this trend in terms of an unusual coupling mechanism in the syn orientation that is very effective for pyrimidine nucleosides and considerably weaker for purine nucleosides.
通过密度泛函理论，计算了脱氧腺苷、脱氧鸟苷、脱氧胞苷和脱氧胸苷中(3)J(C2/4-H1')和(3)J(C6/8-H1')标量自旋-自旋耦合常数与糖苷扭转角χ的函数关系。除脱氧胸苷外，(3)J(C2/4-H1')对碱基类型的依赖性很小。相反，对于嘌呤核苷，(3)J(C6/8-H1')遵循通常的反式到顺式比例((3)J(C-H(顺式)) < (3)J(C-H(反式)))，但对于嘧啶核苷则呈现相反的关系((3)J(C-H(顺式)) > (3)J(C-H(反式)))。我们的结果与脱氧鸟苷的实验结果吻合良好，并预测了在嘧啶碱基的情况下一种新的趋势，即在顺式区域尚无核磁共振结果。将(3)J(C6/8-H1')的关键费米接触部分分解为分子轨道贡献，从顺式取向中一种不寻常的耦合机制方面解释了这种趋势，这种机制对嘧啶核苷非常有效，而对嘌呤核苷则相当弱。
