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. 2003 Mar 26;125(12):3649-58. doi: 10.1021/ja028931t.
The relationship between the glycosidic torsion angle chi, the three-bond couplings (3)J(C2/4-H1') and (3)J(C6/8-H1'), and the one-bond coupling (1)J(C1'-H1') in deoxyribonucleosides and a number of uracil cyclo-nucleosides has been analyzed using density functional theory. The influence of the sugar pucker and the hydroxymethyl conformation has also been considered. The parameters of the Karplus relationships between the three-bond couplings and chi depend strongly on the aromatic base. (3)J(C2/4-H1') reveals different behavior for deoxyadenosine, deoxyguanosine, and deoxycytidine as compared to deoxythymidine and deoxyuridine. In the case of (3)J(C6/8-H1'), an opposite trans to cis ratio of couplings is obtained for pyrimidine nucleosides in contrast to purine nucleosides. The extremes of the Karplus curves are shifted by ca. 10 degrees with respect to syn and anti-periplanar orientations of the coupled nuclei. The change in the sugar pucker from S to N decreases (3)J(C2/4-H1') and (3)J(C6/8-H1'), while increasing (1)J(C1'-H1') for the syn rotamers, whereas all of the trends are reversed for the anti rotamers. The influence of the sugar pucker on (1)J(C1'-H1') is interpreted in terms of interactions between the n(O4'), sigma*(C1'-H1') orbitals. The (1)J(C1'-H1') are related to chi through a generalized Karplus relationship, which combines cos(chi) and cos(2)(chi) functions with mutually different phase shifts that implicitly accounts for a significant portion of the related sugar pucker effects. Most of theoretical (3)J(C2/4-H1') and (3)J(C6/8-H1') for uracil cyclo-nucleosides compare well with available experimental data. (3)J(C6/8-H1') couplings for all C2-bridged nucleosides are up to 3 Hz smaller than in the genuine nucleosides with the corresponding chi, revealing a nonlocal aspect of the spin-spin interactions across the glycosidic bond. Theoretical (1)J(C1'-H1') are underestimated with respect to the experiment by ca. 10% but reproduce the trends in (1)J(C1'-H1') vs chi.
利用密度泛函理论分析了脱氧核糖核苷以及一些尿嘧啶环核苷中糖苷扭转角χ、三键耦合(3)J(C2/4-H1')和(3)J(C6/8-H1')与一键耦合(1)J(C1'-H1')之间的关系。同时也考虑了糖环构象和羟甲基构象的影响。三键耦合与χ之间的Karplus关系参数强烈依赖于芳香碱基。与脱氧胸苷和脱氧尿苷相比，(3)J(C2/4-H1')在脱氧腺苷、脱氧鸟苷和脱氧胞苷中表现出不同的行为。对于(3)J(C6/8-H1')，嘧啶核苷的耦合反式与顺式比例与嘌呤核苷相反。Karplus曲线的极值相对于耦合原子核的顺式和反式平面取向偏移了约10度。对于顺式旋转异构体，糖环构象从S变为N会降低(3)J(C2/4-H1')和(3)J(C6/8-H1')，同时增加(1)J(C1'-H1')，而对于反式旋转异构体，所有趋势均相反。糖环构象对(1)J(C1'-H1')的影响是根据n(O4')、σ*(C1'-H1')轨道之间的相互作用来解释的。(1)J(C1'-H1')通过广义Karplus关系与χ相关，该关系将cos(χ)和cos²(χ)函数与相互不同的相移相结合，隐含地考虑了相关糖环构象效应的很大一部分。尿嘧啶环核苷的大多数理论(3)J(C2/4-H1')和(3)J(C6/8-H1')与现有实验数据比较吻合。所有C2-桥连核苷的(3)J(C6/8-H1')耦合比具有相应χ的天然核苷小3 Hz以上，揭示了糖苷键自旋-自旋相互作用的非局部性。理论(1)J(C1'-H1')相对于实验低估了约10%，但重现了(1)J(C1'-H1')与χ的趋势。
