Nitrogen-hydrogen bond lengths in DNA
Nitrogen-hydrogen bond lengths in DNA
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DNA 中的氮氢键长度
DOI：
10.1002/chin.198227043
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
S. Opella
中科院分区：
文献类型：
--
作者：
J. DiVerdi;S. Opella
由于其在生物学中的核心作用，DNA的结构引起了人们的极大兴趣，并成为许多研究的主题。取向聚合物纤维1·2和寡核苷酸晶体3的X射线衍射研究已经根据C、N、O和P原子的位置相当详细地描述了DNA的构象。尽管链间氢键对DNA的结构和生物学作用很重要，但由于X射线衍射的限制，人们对碱基对之间的氢的位置知之甚少。X射线4和中子5衍射都被用来测量氢键供体的NH键长；然而，结果是来自参与Hoogsteen的甲基化碱基的晶体，而不是Watson-Crick碱基对。核磁共振波谱非常适合于结构测定，特别是通过核间偶极-偶极耦合的空间相关性来确定质子的位置。6在复杂的化学体系中，大量的偶极相互作用导致位置和偶合之间严重的光谱重叠。分离的局域光谱学使用化学位移位置来区分各个位置，并使用选择性平均技术来测量这些位置上的异核偶极耦合。用这种方法在单晶、取向纤维、粉末样品中研究了碳与质子之间的偶极相互作用。10‘11统一标记的15N标记的DNA给出了几乎所有氮位置的具有分辨共振的固体核磁共振谱；12特别是，腺嘌呤-胸腺嘧啶(AT)和鸟嘌呤-胞嘧啶(GC)碱基对的氢键供体和受体氮都可以区分开来。通过测定15N-‘H的大小
Because of its central role in biology, the structure of DNA is of substantial interest and has been the subject of numerous investigations. X-ray diffraction studies of oriented polymer fibers1· 2 and crystals of oligonucleotides3 have described the conformations of DNA in considerable detail based on the positions of theC, N, O, and P atoms. In spite of the importance of interstrand hydrogen bonds to the structure and biological roles of DNA, little is known about the locations of the hydrogens between the base pairs because of the limitations of X-ray diffraction. Both X-ray4 and neutron5 diffraction have been used to measure NH bond lengths of hydrogen-bond donors; however, the results are from crystals of methylated bases participating in Hoogsteen rather than Watson-Crick base pairs. NMR spectroscopy is well suited for structure determinations, especially in locating the positions of protons, through the spatial dependence of internuclear dipole-dipole couplings. 6 The large number of dipolar interactions in complex chemical systems result in severe spectral overlap among sites and couplings. Separated local field spectroscopy uses chemical shift positions to distinguish among individual sites and selective averaging techniques to measure the heteronuclear dipolar couplings at those sites. 7 The dipolar interactions between carbons and protons have been characterized with this approach in single crystals, 8 oriented fibers, 9 and powder samples. 10’11Uniformly 15N labeled DNA gives solid-state NMR spectra with resolved resonances for nearly all nitrogen sites; 12 in particular, both the hydrogen-bond donor and acceptor nitrogens of the adenine-thymine (AT) and guanine-cytosine (GC) base pairs can be distinguished. By determination of the size of the 15N-'H