Analysis of Sugar Puckers and Glycosidic Torsion Angles in a DNA G-Tetrad Structure by Heteronuclear Three-Bond J Couplings
Analysis of Sugar Puckers and Glycosidic Torsion Angles in a DNA G-Tetrad Structure by Heteronuclear Three-Bond J Couplings
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通过异核三键 J 耦合分析 DNA G-四分体结构中的糖皱褶和糖苷扭转角
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发表时间：
1994
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通讯作者：
A. Bax
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作者：
G. Zhu;D. Live;A. Bax
用异核三键J偶联分析DNA g -四元体结构中的糖粒和糖苷扭转角大卫•生活*。细胞生物化学和生物物理项目纪念Sloan-Kettering癌症中心，纽约，纽约10021化学物理实验室NIDDK/NIH， Bethesda，马里兰州20892 1994年5月23日由于没有可用于定义糖苷扭转角的同核三键1H偶联，寡核苷酸结构中这一重要变量的确定完全依赖于对NOE数据的解释。即使除了NOES之外，可以获得同核IH-IH J偶联s2 1.2中包含的重要信息，准确测定寡核苷酸中的糖构象仍然是困难的。在这里，我们证明了糖质子与糖或碱碳之间的异核三键lH-W偶联可以很容易地测量，为确定核酸结构提供了重要的补充信息在本工作中使用的方法是基于定量J相关的概念。10并且即使在异核J耦合的大小明显小于相关共振的线宽时也适用。鉴于目前13C标记DNA的局限性，下面描述的实验的可行性，适用于自然丰度，是非常吸引人的。该策略可以扩展到测量一系列其他分子中的异核偶联，包括RNA，其中1H光谱色散的减少和C3'端糖折叠经常使测量1H- lh偶联变得更加困难。当然，同位素富集RNA的能力和DNA标记技术的不断发展可以大大提高远程JCH偶联测量的灵敏度。下面我们报道了未标记DNA低聚物d（GGTCGG）的3j ~ ~偶联的测量。在所研究的条件下，该片段采用g -四聚体结构。11-12据推测，这种结构存在于染色体的末端，其长度随年龄的变化控制着染色体的稳定性和细胞的寿命。假设了与四个G残基在一个平面上的氢键相一致的各种可能的分子构象，例如，链与糖平行或反平行，碱基与糖同步或反。在本文研究的模型系统中，G1和G5先前被发现是同步的，G2和G6是抗。11j2的
Analysis of Sugar Puckers and Glycosidic Torsion Angles in a DNA G-Tetrad Structure by Heteronuclear Three-Bond J Couplings Guang Zhu,? David Live,*.$ and Ad Baxs Department of Electrical Engineering University of Maryland, College Park, Maryland 20874 Cellular Biochemistry and Biophysics Program Memorial Sloan-Kettering Cancer Center New York, New York 10021 Laboratory of Chemical Physics NIDDK/NIH, Bethesda, Maryland 20892 Received May 23, 1994 As no homonuclear three-bond 1H couplings are available to define the glycosidic torsion angle, determination of this important variable in oligonucleotide structure has relied entirely on interpretation of NOE data. Accurate determination of sugar conformation in oligonucleotides remains difficult even when in addition to NOES the important information contained in homonuclear IH-IH J couplings1.2 can be obtained. Here we demonstrate that heteronuclear three-bond lH-W Jcouplings between sugar protons and either sugar or base carbons can readily be measured, providing important supplemental information for determining nucleic acid structure.24 The approach used in the present work is based on the concept of quantitative J correlationg.10 and is applicable even when the size of the heteronuclear J coupling is significantly smaller than the line widths of the pertinent resonances. In view of the current limitations with 13C labeling DNA, the viability of an experiment such as described below, which is applicable at natural abundance, is very appealing. This strategy can be extended to measuring heteronuclear couplings in a range of other molecules, including RNA, where the reduced 1H spectral dispersion and C3' endo sugar pucker frequently make measurement of 1H-lH couplings more difficult. Of course, the ability to isotopically enrich RNA and the ongoing development of techniques for labeling DNA can greatly increase the sensitivity of the long range JCH coupling measurement. Below we report the measurement of 3 J ~ ~ couplings for the unlabeled DNA oligomer, d(GGTCGG). Under the conditions studied, this fragment adopts a G-tetrad structure.11-12 It has been postulated that such structures are found at the ends of chromosomes, and variation in their length with age controls stability of the chromosome and longevity of the cell. A variety of possible molecular conformations consistent with four G residues hydrogen bonded in a plane have been postulated, e.g., chains parallel or antiparallel and bases syn or anti relative to the sugar."-21 In the model system studied here, the G1 and G5 previously were found to be syn and G2 and G6 anti.11J2