Olson W K
Nucleic Acids Res. 1981 Mar 11;9(5):1251-62. doi: 10.1093/nar/9.5.1251.
A general procedure is described to treat the pseudorotation of the furanose ring in terms of a three-state conformational equilibrium. In addition to the principal n (C3'-endo) and s (C2'-endo) puckering domains, the unusual e (01'-endo) intermediate is included in the analysis. Each of these three conformational categories is represented by a blend of five closely related puckered forms rather than by a single rotational isomeric state. Using this model together with experimentally measured nmr coupling constants, the puckering populations of various nucleic acid analogs are estimated. The conventional two-state n/s equilibria is confirmed in ordinary ribose and deoxyribose systems. The e domain, however, is found to be of major importance in several chemically modified furanoses including certain pyrimidine deoxynucleosides damaged by radiation and various nucleosides and nucleotides forced by bulky substituents on the base into unusual syn glycosyl arrangements. The "free" pseudorotation of these modified systems is not detected by conventional two-state puckering analyses.
描述了一种根据三态构象平衡来处理呋喃糖环假旋转的通用程序。除了主要的n(C3'-内型)和s(C2'-内型)褶皱域之外,分析中还包括了不寻常的e(01'-内型)中间体。这三种构象类别中的每一种都由五种密切相关的褶皱形式的混合表示,而不是由单一的旋转异构体状态表示。使用该模型以及实验测量的核磁共振耦合常数,估计了各种核酸类似物的褶皱丰度。在普通的核糖和脱氧核糖系统中证实了传统的二态n/s平衡。然而,发现e域在几种化学修饰的呋喃糖中至关重要,包括某些受辐射损伤的嘧啶脱氧核苷以及各种核苷和核苷酸,这些核苷和核苷酸由于碱基上的庞大取代基而被迫形成不寻常的顺式糖苷排列。传统的二态褶皱分析未检测到这些修饰系统的“自由”假旋转。