Guschlbauer W, Jankowski K
Nucleic Acids Res. 1980 Mar 25;8(6):1421-33. doi: 10.1093/nar/8.6.1421.
The proton and 13C NMR spectra of uridine, deoxyuridine and four 2' substituted uridines (dUn, dUz, dUcl and dUfl) are reported. A linear relationship between the electronegativity of the 2'-substituent and the carbon-13 chemical shift of C2' is observed. Taking into account the effect of electronegativity by using the correction proposed by Karplus or by Jankowski, the proton-proton coupling constants have been used to compute the conformational equilibria of the six uridines. It is shown that the contribution of the N form (3'-endo -2'-exo) increases with the electronegativity of the 2' substituent. Thus dUfl contains some 85% N form in solution. - Applying similar corrections to published data in the adenosine series, a similar correlation is observed. This observation, that the most polar substituent pulls the pucker to its side, holds also for 3'-substituted compounds, like cordycepin (3'dAdo) and 3'-deoxy-3'-amino-adenosine. It is suggested that the influence of the electronegativity could be the dominating effect of nucleoside conformations and would also hold for arabinosides and xylosides. This effect should therefore also be the principal force which determines the differences between DNA and RNA.
报道了尿苷、脱氧尿苷以及四种2'-取代尿苷（dUn、dUz、dUcl和dUfl）的质子核磁共振谱和碳-13核磁共振谱。观察到2'-取代基的电负性与C2'的碳-13化学位移之间存在线性关系。通过使用卡尔普斯或扬科夫斯基提出的校正方法来考虑电负性的影响，质子-质子耦合常数已被用于计算这六种尿苷的构象平衡。结果表明，N型构象（3'-内式-2'-外式）的贡献随着2'-取代基电负性的增加而增加。因此，dUfl在溶液中约含有85%的N型构象。 - 对腺苷系列中已发表的数据应用类似的校正方法，观察到了类似的相关性。这一观察结果，即极性最强的取代基将褶皱拉向其一侧，对于3'-取代的化合物，如虫草素（3'dAdo）和3'-脱氧-3'-氨基腺苷也成立。有人提出，电负性的影响可能是核苷构象的主导效应，并且对阿拉伯糖苷和木糖苷也适用。因此，这种效应也应该是决定DNA和RNA差异的主要力量。
