CONFORMATIONAL-ANALYSIS OF SUGAR RING IN NUCLEOSIDES AND NUCLEOTIDES - IMPROVED METHOD FOR INTERPRETATION OF PROTON MAGNETIC-RESONANCE COUPLING-CONSTANTS
CONFORMATIONAL-ANALYSIS OF SUGAR RING IN NUCLEOSIDES AND NUCLEOTIDES - IMPROVED METHOD FOR INTERPRETATION OF PROTON MAGNETIC-RESONANCE COUPLING-CONSTANTS
复制标题
DOI：
10.1021/ja00788a038
复制
发表时间：
1973-01-01
影响因子：
15
通讯作者：
SUNDARALINGAM, M
中科院分区：
文献类型：
--
作者：
ALTONA, C;SUNDARALINGAM, M
本文用五元环的假旋转模型，从60个核苷和磷酸核苷的X射线数据导出了糖CH键间的扭转角H_h。两种赝旋转范围被认为是N型[C（2 '）-exo，C（3'）-endo]和S型[C（2 '）-endo，C（3'）-exo]构象，每种构象的特征是赝旋转相位角P的范围很窄。Hh沿着环键的不同值以及相应的耦合常数必须服从一定的相互关系。结果表明，耦合-3-以及和-2-+ Jw实际上应该与N<=<$S构象平衡的位置无关;然后使用文献中的值提取一组对所讨论的构象有效的Karplus参数。探讨了赝转动（在两个P范围内）对耦合常数的影响。出于所有实际目的，常见核苷和核苷磷酸盐的水溶液中S型构象异构体的百分比可以通过取10/vs·来计算。嘌呤核苷显示出对S型构象的较小构象偏好（AGav=-0.12 kcal mol-1），而嘧啶衍生物略微偏好N型核糖构象（阿加，，=+0.16 kcal mol-1）。发表
Torsion angles<#> Hh between the sugar CH bonds were deduced from X-ray data on 60 nucleosides and nucleoside phosphates with the aid of the pseudorotation model for five-membered rings. Two pseudo-rotation ranges were considered classified as type N [C (2')-exo, C (3')-endo] and type S [C (2')-endo, C (3')-exo] con-formers, each characterized by a narrow range of the phase angle of pseudorotation P. The various values of Hh along the ring bonds, andhence the corresponding coupling constants, must obey certain interrelationships. It was shown that the coupling-3-as well as the sum-2-+ Jw should be practically independent of the position of the N<= í S conformational equilibrium; values taken from the literature were then used to extract a set ofKarplus parameters valid for thesystem in question. Theeffect of pseudorotation (within each of the two ranges of P) on the coupling constants is explored. For all practical purposes, the percentage of S-type conformer in aqueous solution of the common nucleosides and nucleoside phosphates can be calculated by taking lO/vs·. The purine ribosides show a small conformational preference for the S type conformer (AGav=—0.12 kcal mol-1), whereas the pyrimidine derivatives slightly favor the N-type ribose conformer (AGa,,=+ 0.16 kcal mol-1). Published