Patel D J, Kozlowski S A, Bhatt R
Proc Natl Acad Sci U S A. 1983 Jul;80(13):3908-12. doi: 10.1073/pnas.80.13.3908.
Single-crystal x-ray studies of d(C-G-C-G-A-A-T-T-C-G-C-G) exhibit base-pair propeller twisting [Dickerson, R. E. & Drew, H. R. (1981) J. Mol. Biol. 149, 761-786] that results in close contacts between adjacent purines in the minor groove in pyrimidine (3'-5')-purine steps and in the major groove in purine (3'-5')-pyrimidine steps [Calladine, C. R. (1982) J. Mol. Biol. 161, 343-362]. These observations require an approximately 3.4 A separation between the minor groove edges of adenosines on adjacent base pairs for the dA-dA step but predict a smaller separation for the dT-dA step and a larger separation for the dA-dT step in a D(A-T-T-A).d(T-A-A-T) fragment. We have confirmed these predictions from steady-state nuclear Overhauser effect measurements between assigned minor groove adenosine H-2 protons on adjacent base pairs in the proton NMR spectrum of the d(C1-G2-A3-T4-T5-A6-T6-A5-A4-T3-C2-G1) self-complementary dodecanucleotide duplex (henceforth called the Pribnow 12-mer) in solution. The measured cross-relaxation rates (product of steady-state nuclear Overhauser effect and selective spin- lattice relaxation rates) translate to interproton separations between adjacent adenosine H-2 protons of 4.22 A in the (dA3-dT4).(dA4-dT3) step, of 3.56 A in the (dT4-dT5).dA5-dA4) step, and of 3.17 A in the (dT5-dA6).(dT6-dA5) step for the Pribnow 12-mer duplex with an isotropic rotational correlation time of 9 ns at 5 degrees C. These proton NMR results show that the sequence-dependent base-pair stacking resulting from base-pair propeller twisting of defined handedness for right-handed DNA in the solid state is maintained in aqueous solution.
对d（C-G-C-G-A-A-T-T-C-G-C-G）进行的单晶X射线研究显示出碱基对的螺旋扭转[迪克森，R.E.和德鲁，H.R.（1981年）《分子生物学杂志》149卷，761 - 786页]，这导致在嘧啶（3'-5'）-嘌呤步的小沟中相邻嘌呤之间以及嘌呤（3'-5'）-嘧啶步的大沟中相邻嘌呤之间形成紧密接触[卡拉丁，C.R.（1982年）《分子生物学杂志》161卷，343 - 362页]。这些观察结果表明，对于dA - dA步，相邻碱基对中腺苷的小沟边缘之间的间距约为3.4 Å，但预测在D（A - T - T - A）.d（T - A - A - T）片段中，dT - dA步的间距较小，dA - dT步的间距较大。我们通过对d（C1 - G2 - A3 - T4 - T5 - A6 - T6 - A5 - A4 - T3 - C2 - G1）自互补十二聚体双链体（以下简称普里布诺12聚体）在溶液中的质子核磁共振谱中相邻碱基对中已指定的小沟腺苷H - 2质子之间的稳态核Overhauser效应测量，证实了这些预测。对于在5℃下具有9 ns各向同性旋转相关时间的普里布诺12聚体双链体，测量得到的交叉弛豫率（稳态核Overhauser效应与选择性自旋 - 晶格弛豫率的乘积）转化为相邻腺苷H - 2质子之间的质子间距离，在（dA3 - dT4）.（dA4 - dT3）步中为4.22 Å，在（dT4 - dT5）.（dA5 - dA4）步中为3.56 Å，在（dT5 - dA6）.（dT6 - dA5）步中为3.17 Å。这些质子核磁共振结果表明，固态中右手性DNA由具有特定手性的碱基对螺旋扭转导致的序列依赖性碱基对堆积在水溶液中得以维持。
