利用^1H—NMR模拟谱研究二核苷酸A3^`P（CH3）5^`A的构象性质

CONFORMATIONAL ANALYSIS OF DINUCLEOTIDES A3'P(CH_3)5'A BY H-NMR SIMULATED SPECTRUM

本文根据Altona等人的方法,在利用~1H-NMR模拟谱确定18℃、40℃、70℃三种温度下有关质子化学位移及偶合常数的基础上,分析了A3′P(CH_3)5′A的两种非对映异构体a和b的构象状态。它们与A3′P(OH)5′A相比发现:(1)在18℃时两个核糖环是S型构象占主要成分,并随温度升高S型构象成分增多;(2)磷酸骨架的扭角ε′和β′分别改变±15°及±4°;(3)在优势构象情况下,两个核糖环都部分重叠,而且A3′P(CH_3)5′A(a)的重叠程度比A3P′(CH_3)5′A(b)小;(4)腺嘌呤碱基都更倾向去堆积状态,而且随温度升高A3′P(CH_3)5′A(a)比A3′P(CH_3)5′A(b)有着更强的去堆积效应。

According to Altonas' method, the chemical shifts and the coupling constants of the relevant protons for two stereoisomers a and b were determined by means of simulated spectrum of ID 1H-NMR at 18℃, 40℃ and 70℃ respectively. Their conformations were analysed by their parameters. Compared with known compound A3'P(OH)5'A, two ribose rings of a and b predominantly adopt S conformation at 18℃, and with increasing of temperature, the constituents of the S conformation increased; the torsion angles ε' and β of the phosphate backbone estimated were changed +15° and +4° respectively; two ribose rings of A3'P(CH3)5'A (a) and (b) both were partially overlapped and the degree of overlapping of the former was smaller than that of the latter; with increasing of temperature, the ade-nine moiety of A3'P(CH3)5'A (a) showed a stronger tendency to unstack than A3'P(CH3)5'A (b).