Lane A N, Ebel S, Brown T
Laboratory of Molecular Structure, National Institute for Medical Research, London, England.
Eur J Biochem. 1993 Jul 15;215(2):297-306. doi: 10.1111/j.1432-1033.1993.tb18035.x.
Nearly complete assignments of the 1H-NMR spectrum of the DNA.RNA hybrid d(GTGAACTT).r(AAGUUCAC) have been obtained by two-dimensional methods. Three-bond coupling constants measured from cross-sections of two-dimensional NOE spectra and double quantum-filtered correlation spectra showed that the sugars in the DNA strand are predominantly in the S domain of puckers, whereas the ribofuranoses are mainly C3'-endo. Analysis of time-dependent NOE intensities from one- and two-dimensional experiments showed that the glycosidic torsion angles in the DNA strand are near -120 degrees, whereas those in the RNA strand are in the range- 140 degrees to -160 degrees. These nucleotide conformations correspond to those typically found in B-DNA and A-RNA, respectively. The circular dichroism of the duplex is similar to that of A-form RNA, consistent with a global A-like conformation. A large number of duplex structures was generated in which the nucleotides were fixed in the experimentally determined conformations. A subset of these structures was found that satisfied the internucleotide NOE intensities, backbone constraints and had acceptable Lennard-Jones energies. The base pairs in the duplex were found to have positive inclinations, a translation (Dx) of about 0.4 nm from the helix axis, and more than 10 bp/turn on average. This implies a helical structure in the A family of conformations.
通过二维方法已几乎完成了DNA.RNA杂交体d(GTGAACTT).r(AAGUUCAC)的1H-NMR谱的归属。从二维NOE谱和双量子滤波相关谱的截面测得的三键耦合常数表明，DNA链中的糖主要处于褶皱的S区域，而呋喃核糖主要是C3'-内向型。对一维和二维实验中随时间变化的NOE强度的分析表明，DNA链中的糖苷扭转角接近-120度，而RNA链中的扭转角在-140度至-160度范围内。这些核苷酸构象分别对应于B-DNA和A-RNA中通常发现的构象。双链体的圆二色性与A-form RNA相似，这与整体的A样构象一致。生成了大量双链体结构，其中核苷酸固定在实验确定的构象中。发现这些结构的一个子集满足核苷酸间NOE强度、主链限制并且具有可接受的Lennard-Jones能量。发现双链体中的碱基对具有正倾斜度，从螺旋轴平移（Dx）约0.4 nm，平均每圈超过10个碱基对。这意味着在A家族构象中有螺旋结构。
