Chary K V, Modi S, Hosur R V, Govil G, Chen C Q, Miles H T
Chemical Physics Group, Tata Institute of Fundamental Research, Bombay, India.
Biochemistry. 1989 Jun 13;28(12):5240-9. doi: 10.1021/bi00438a048.
Resonance assignments of nonexchangeable base and sugar protons have been obtained in double-helical d-ACATCGATGT by using two-dimensional correlated spectroscopy (COSY) and nuclear Overhauser enhancement spectroscopy (NOESY). The exchangeable imino protons have been assigned on the basis of their chemical shifts. The characteristic phase-sensitive multiplet patterns of the intrasugar cross-peaks in the omega 1-scaled COSY spectrum have been used to estimate several scalar coupling constants (J). The information on the J values combined with the intranucleotide COSY cross-peak intensities has been used to identify sugar puckers of individual nucleotide units. In most cases, the deoxyribofuranose rings are found to adopt a conformation close to O4'-endo. Spin diffusion has been monitored from the buildup of the normalized volumes of NOE cross-peaks in NOESY spectra as a function of mixing time. A set of 52 intranucleotide and internucleotide proton-proton distances have been estimated by using low mixing time NOESY spectra (tau m = 40 and 80 ms). The estimated intrasugar proton-proton distances rule out possibilities of existence of a fast equilibrium between C2'-endo and C3'-endo conformations. Intranucleotide proton-proton distances combined with the knowledge of sugar puckers have been used to fix the glycosidic bond torsion angle (chi). For this purpose, simulated distance contours depicting the dependence of intranucleotide proton-proton distances on pseudorotational phase angle (P) and glycosidic bond torsion angle (chi) have been used. Further, the proton homonuclear (J, delta) spectrum has been used to monitor the 31P-1H heteronuclear couplings, which are preserved in the omega 2 projection.(ABSTRACT TRUNCATED AT 250 WORDS)
通过使用二维相关光谱（COSY）和核Overhauser增强光谱（NOESY），已在双螺旋d-ACATCGATGT中获得了非交换性碱基和糖质子的共振归属。可交换的亚氨基质子已根据其化学位移进行了归属。ω1标度的COSY谱中糖内交叉峰的特征性相敏多重峰模式已用于估算几个标量耦合常数（J）。结合J值信息和核苷酸内COSY交叉峰强度，已用于确定各个核苷酸单元的糖折叠。在大多数情况下，发现脱氧呋喃核糖环采取接近O4'-内型的构象。通过监测NOESY谱中NOE交叉峰归一化体积随混合时间的增加来监测自旋扩散。通过使用低混合时间的NOESY谱（τm = 40和80毫秒），已估算出一组52个核苷酸内和核苷酸间的质子-质子距离。估算出的糖内质子-质子距离排除了C2'-内型和C3'-内型构象之间存在快速平衡的可能性。核苷酸内质子-质子距离与糖折叠知识相结合，已用于确定糖苷键扭转角（χ）。为此，已使用模拟距离等高线来描述核苷酸内质子-质子距离对伪旋转相角（P）和糖苷键扭转角（χ）的依赖性。此外，质子同核（J，δ）谱已用于监测31P-1H异核耦合，这些耦合在ω2投影中得以保留。(摘要截断于250字)
