Untenability of the heteronomous DNA model for poly(dA).poly(dT) in solution. This DNA adopts a right-handed B-DNA duplex in which the two strands are conformationally equivalent. A 500 MHz NMR study using one dimensional NOE.
Untenability of the heteronomous DNA model for poly(dA).poly(dT) in solution. This DNA adopts a right-handed B-DNA duplex in which the two strands are conformationally equivalent. A 500 MHz NMR study using one dimensional NOE.
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溶液中 Poly(dA).poly(dT) 的异律 DNA 模型不成立。
DOI：
10.1080/07391102.1985.10507624
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发表时间：
1985
影响因子：
4.4
通讯作者：
Sarma,RH
中科院分区：
文献类型：
--
作者：
Sarma,MH;Gupta,G;Sarma,RH
采用500 MHz的ID NOE 1 H NMR光谱来检查溶液中的聚(dA)·聚(dT)的结构。 NOE 实验根据预饱和脉冲长度（50、30、20 和 10 毫秒）和功率（19 和 20 db）进行，以区分主要 NOE 和自旋扩散。 10 毫秒 NOE 实验耗时 49 小时，每种情况进行超过 55,000 次扫描，差异光谱几乎没有扩散。自旋扩散 NOE 差异光谱以及 TNH3 预饱和的 90% H2O + 10% D2O 中的差异 NOE 光谱能够对碱质子和糖质子进行完整分配。结果表明，随着温度的升高，聚(dA)·聚(dT)以形成单链气泡的方式熔化。当AH8和TH6预饱和时，在H2'/H2''处观察到极强的初级NOE。在 AH2' 和 AH2" 处观察到的 NOE 非常相似，在 TH2' 和 TH2" 处观察到的 NOE 也非常相似。当 AH8 预饱和时，在 AH2' 和 AH2" 处观察到的 NOE 与当 TH6 预饱和时在 TH2' 和 TH2" 处观察到的 NOE 非常相似。此外，A 和 T 残基的 H1' 预饱和导致 AH2'/H2" 和 TH2'/H2" 区域类似的 NOE，并且 H2' 和 H2" 处的这些 NOE 明显不对称，如 C2'-内糖褶皱中预期的那样。当 AH3' 和 TH3' 预饱和时，AH8 和 TH6 处没有 NOE 痕迹，表明 C3'-endo, × = 30–40° 构象对此 DNA 无效。根据这些 NOE 数据、化学位移屏蔽计算和基于立体化学的计算机建模，我们得出结论，溶液中的聚（dA）·聚（dT）采用右手 B-DNA 双链体，其中 dA 和 dT 链在构象上与 C2'-内糖皱褶和糖基扭转，×，≃73°，其余主链扭转角为 φ′ = 221°，ω′ = 212°，ω = 310°，φ = 149°，ψ = 42°，ψ′ = 139°。实验数据与Arnott等人的异律DNA模型完全不一致。等人。建议为纤维状态。 （Arnott, S.、Chandrasekaran, R.、Hall, I.H. 和 Puigjaner, L.C.，Nucl. Acid Res. 11, 4141, 1983）。
ID NOE1H NMR spectroscopy at 500 MHz was employed to examine the structure of poly(dA)·poly(dT) in solution. NOE experiments were conducted as a function of presaturation pulse length (50, 30, 20 and 10 msec) and.power (19 and 20 db) to distinguish the primary NOEs from spin diffusion. The 10 msec NOE experiments took 49 hrs and over 55,000 scans for each case and the difference spectra were almost free from diffusion.The spin diffused NOE difference spectra as well as difference NOE spectra in 90% H2O + 10% D2O in which TNH3 was presaturated enabled to make a complete assignment of the base and sugar protons. It is shown that poly(dA) ·poly(dT) melts in a fashion in which single stranded bubbles are formed with increasing temperature.Extremely strong primary NOEs were observed at H2′/H2″ when AH8 and TH6 were presaturated. The observed NOEs at AH2′ and that AH2″ were very similar as were the NOEs at TH2′ and TH2″. The observed NOEs at AH2′ and AH2″when AH8 was presaturated were very similar to those observed at TH2′ and TH2″ when TH6 was presaturated. In addition, presaturation of H1′ of A and T residues resulted in similar NOEs at AH2′/H2″ and TH2′/H2″ region and these NOEs at H2′ and H2″ were distinctly asymmetric as expected in a C2′-endosugar pucker. There was not a trace of NOE at AH8 and TH6 when AH3′ and TH3′ were presaturated indicating that C3′-endo, × = 30–40° conformation is not valid for this DNA. From these NOE data, chemical shift shielding calculations and stereochemistry based computer modellings, we conclude that poly(dA)·poly(dT) in solution adopts a right- handed B-DNA duplex in which both dA and dT strands are conformationally equivalent with C2′-endosugar pucker and a glycosyl torsion, ×, of ≃73°, the remaining backbone torsion angles being φ′ = 221°, ω′ = 212°, ω = 310°, φ = 149°, ψ = 42°, ψ′ = 139°. The experimental data are in total disagreement with the heteronomous DNA model of Arnott et. al. proposed for the fibrous state. (Arnott, S., Chandrasekaran, R., Hall, I.H., and Puigjaner, L.C.,Nucl. Acid Res. 11, 4141, 1983).