Correlating the 31P NMR Chemical Shielding Tensor and the 2JP,C Spin-Spin Coupling Constants with Torsion Angles ζ and α in the Backbone of Nucleic Acids
Correlating the 31P NMR Chemical Shielding Tensor and the 2JP,C Spin-Spin Coupling Constants with Torsion Angles ζ and α in the Backbone of Nucleic Acids
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DOI：
10.1021/jp2099043
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发表时间：
2012-03-29
影响因子：
3.3
通讯作者：
Sychrovsky, Vladimir
中科院分区：
文献类型：
--
作者：
Benda, Ladislav;Vokacova, Zuzana Sochorova;Sychrovsky, Vladimir
用NMR光谱法测定核酸（NA）结构受到缺乏对NA磷酸构象的限制的限制。在这项工作中，P-31化学屏蔽张量，伽玛（P，C5'H5' 1）和伽玛（P，C5'H5' 2）交叉相关弛豫速率，和（2）J（P，C3 '），（2）J（P，C5'），（3）J（P，C4 '）耦合常数依赖于NA骨架扭转角zeta和alpha计算。虽然P-31化学屏蔽张量的取向几乎与NA磷酸盐构象无关，但主张量分量的变化高达40 ppm。这种变化以及磷酸盐几何形状对扭转角zeta和alpha的依赖性对计算的Gamma（P，C5'H5' 1）和Gamma（P，C5'H5' 2）交叉相关弛豫速率只有很小的影响，因此，所谓的刚性张量近似在这里得到验证。首次将（2）J（P，C）自旋-自旋耦合常数与NA磷酸盐的构象进行了关联。虽然两个J-耦合中的每一个都被扭转ζ和α显著地调制，但是（2）J（P，C3 '）1耦合可以在结构上被分配给扭转ζ，并且（2）J（P，C5'）耦合可以被分配给扭转α。我们提出了定性的规则，他们的结构解释为松散的约束扭转角ζ和α。（3）J（P，C4 '）耦合与扭转角β有关，也依赖于扭转角zeta和alpha，这意味着用标准Karplus曲线测定β的不确定度可能大到25度。计算提供了一个统一的图片适用于确定NA磷酸构象的NMR参数。
Determination of nucleic acid (NA) structure with NMR spectroscopy is limited by the lack of restraints on conformation of NA phosphate. In this work, the P-31 chemical shielding tensor, the Gamma(P,C5'H5'1) and Gamma(P,C5'H5'2) cross-correlated relaxation rates, and the (2)J(P,C3'), (2)J(P,C5'), and (3)J(P,C4') coupling constants were calculated in dependence on NA backbone torsion angles zeta and alpha. While the orientation of the P-31 chemical shielding tensor was almost independent of the NA phosphate conformation, the principal tensor components varied by up to similar to 40 ppm. This variation and the dependence of the phosphate geometry on torsion angles zeta and alpha had only a minor influence on the calculated Gamma(P,C5'H5'1) and Gamma(P,C5'H5'2) cross-correlated relaxation rates, and therefore, the so-called rigid tensor approximation was here validated. For the first time, the (2)J(P,C) spin-spin coupling constants were correlated with the conformation of NA phosphate. Although each of the two J-couplings was significantly modulated by both torsions zeta and alpha, the (2)J(P,C3'), coupling could be structurally assigned to torsion zeta and the (2)J(P,C5') coupling to torsion alpha. We propose qualitative rules for their structural interpretation as loose reStraints on torsion angles zeta and alpha. The (3)J(P,C4') coupling assigned to torsion angle beta was found dependent also on torsions zeta and alpha, implying that the uncertainty in determination of beta with standard Karplus curves could be as large as similar to 25 degrees. The calculations provided a unified picture of NMR parameters applicable for the determination of NA phosphate conformation.