Institute of Organic Chemistry and Biochemistry, v.v.i., Academy of Sciences of the Czech Republic, Flemingovo square 2, 166 10 Prague 6, Czech Republic.
J Phys Chem A. 2010 Sep 23;114(37):10202-8. doi: 10.1021/jp102329t.
The pyramidalizations of N9/1 glycosidic nitrogens in DNA and RNA nucleosides, recently discovered and analyzed in their ultrahigh-resolution X-ray crystal structures ( Sychrovský ; et al. Nucleic Acid Res. 2009 , 37 , 7321. ), were found to have significant effects on the structural interpretation of the (3)J(C4/2-H1') and (3)J(C8/6-H1') NMR scalar couplings in purine/pyrimidine nucleosides. The calculated effects on IR and vibrational circular dichroism (VCD) spectra were only minor. The calculated structural deformations in nucleosides, depending on sugar-to-base orientation, gave rise to corrections in the phase shift of the Karplus equations for the (3)J(C8/6-H1') and (3)J(C4/2-H1') couplings ranging from -26° to +25° and from -5.7° to +2.0°, respectively. The sign alternation of this correction in syn and anti nucleosides arises from the stereoinversion of the N9/1 glycosidic nitrogen occurring upon reorientation of the glycosidic torsion. The effect was calculated consistently in the dG, dA, dC, dT, rA, and rG nucleosides. Utilization of the calculated phase-shift corrections in the design of Karplus equations for the (3)J couplings was suggested, and the effects on structural interpretation of the experimental couplings were evaluated.
最近在 DNA 和 RNA 核苷的超高分辨率 X 射线晶体结构中发现并分析了 N9/1 糖苷氮的金字塔化，（Sychrovský 等人，Nucleic Acid Res. 2009, 37, 7321.），发现其对嘌呤/嘧啶核苷中（3）J（C4/2-H1'）和（3）J（C8/6-H1'）NMR 标量耦合的结构解释有重大影响。对 IR 和振动圆二色性（VCD）光谱的计算影响仅为次要。糖基与碱基取向有关的核苷结构变形导致 Karplus 方程中（3）J（C8/6-H1'）和（3）J（C4/2-H1'）耦合的相移校正值在-26°到+25°和-5.7°到+2.0°之间变化。这种在顺式和反式核苷中校正的符号交替来自于糖苷扭转重新定向时 N9/1 糖苷氮的立体反转。在 dG、dA、dC、dT、rA 和 rG 核苷中一致地计算了这种效应。建议在设计（3）J 耦合的 Karplus 方程时利用计算出的相移校正值，并评估了它们对实验耦合结构解释的影响。
