Benevides J M, Thomas G J
Division of Cell Biology and Biophysics, School of Basic Life Sciences, University of Missouri, Kansas City 64110.
Biochemistry. 1988 May 17;27(10):3868-73. doi: 10.1021/bi00410a051.
Equilibrium Raman spectra show that A- and B-form phosphodiester backbone geometries are both present in the solution structure of the RNA.DNA hybrid poly(rA).poly(dT) and that these arise from C3'-endo-rA and C2'-endo-dT nucleosides, respectively. Raman dynamic measurement of deuterium exchange of adenine 8CH groups reveals (i) a single kinetic class of rA conformers and (ii) extraordinary retardation of 8CH exchange in this class--more than 100-fold slower than in canonical DNA structures. The equilibrium and kinetic results, in conjunction with model building, indicate an unusual intrastrand hydrogen bond involving adenosine donor (8C-H) and acceptor (5'O) groups and a double-helical conformation in solution similar to that proposed for fibers at high relative humidity [Zimmerman, S. B., & Pheiffer, B. H. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 78-82]. In fibers of poly(rA).poly(dT) at low relative humidity, the Raman spectra indicate a conventional A-helix structure.
平衡拉曼光谱表明，A 型和 B 型磷酸二酯主链几何结构都存在于 RNA·DNA 杂交体聚（rA）·聚（dT）的溶液结构中，且这些结构分别源自 C3'-内型 -rA 和 C2'-内型 -dT 核苷。腺嘌呤 8CH 基团氘交换的拉曼动力学测量结果显示：（i）rA 构象体存在单一动力学类别；（ii）该类别中 8CH 交换显著迟缓——比典型 DNA 结构慢 100 多倍。平衡和动力学结果，结合模型构建，表明存在一种不寻常的链内氢键，涉及腺苷供体（8C-H）和受体（5'O）基团，以及溶液中的双螺旋构象，类似于在高相对湿度下纤维所提出的构象[齐默尔曼，S. B.，& 菲弗，B. H.（1981 年）美国国家科学院院刊 78，78 - 82]。在低相对湿度下的聚（rA）·聚（dT）纤维中，拉曼光谱表明存在传统的 A 螺旋结构。
