Cornelis A G, Haasnoot J H, den Hartog J F, de Rooij M, van Boom J H, Cornelis A
Nature. 1979 Sep 20;281(5728):235-6. doi: 10.1038/281235a0.
Nuclear magnetic resonance is a technique which permits direct observation of the Waton--Click hydrogen-bonded ring imino protons (guanine N1H and thymine N3H). As the formation and disruption of hydrogen bonds of double-helical RNA and DNA structures are key events during various biological processes, NMR thus provides a useful tool for studying the fluctuational mobility of the individual base pairs. Indeed, several NMR studies of oligo- and polynucleotides have been carried out to probe the structure and dynamics of nucleic acids in solution (for a review see ref. 1). The present study constitutes the first part of our attempt to assess the influence of non-complementary base pairs on the stability of nucleic acid double helices. We report the spectral assignment and temperature-dependent NMR profiles of the hydrogen-bonded imino protons of the two DNA fragments shown in Fig. 1. The assignment is based solely on experimental grounds using the principle of chemical modification. It will be demonstrated that the introduction of a non-complementary (wobble) base pair in a DNA duplex introduces an extra melting site in addition to the sequential melting which starts with the terminal base pairs in the double helix structure.
核磁共振是一种能够直接观测沃森-克里克氢键连接环亚氨基质子（鸟嘌呤N1H和胸腺嘧啶N3H）的技术。由于双螺旋RNA和DNA结构中氢键的形成与断裂是各种生物过程中的关键事件，因此核磁共振为研究单个碱基对的波动流动性提供了一个有用的工具。实际上，已经开展了多项针对寡核苷酸和多核苷酸的核磁共振研究，以探究溶液中核酸的结构与动力学（综述见参考文献1）。本研究是我们评估非互补碱基对对核酸双螺旋稳定性影响的首次尝试的第一部分。我们报告了图1所示两个DNA片段中氢键连接亚氨基质子的光谱归属及温度依赖性核磁共振谱图。该归属完全基于使用化学修饰原理的实验依据。结果将表明，在DNA双链体中引入一个非互补（摆动）碱基对，除了从双螺旋结构末端碱基对开始的顺序解链外，还会引入一个额外的解链位点。
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