Waterhouse A L, Horváth K, Liu J
Department of Viticulture and Enology, University of California, Davis 95616.
Carbohydr Res. 1992 Nov 4;235:1-13. doi: 10.1016/0008-6215(92)80073-a.
Conformational energies for models of the disaccharide beta-D-fructofuranosyl-(2-->6)-beta-D-glucopyranoside were computed by molecular mechanics using MM2(87). An initial investigation of staggered forms examined the linkage bonds characterized by the torsion angles phi, psi, and omega, and subsequently the fructose hydroxymethyl side groups, characterized by the torsion angles chi-1 and chi-6. Then, in our major search of conformational space, the torsion angles of two linkage bonds, phi and omega, were driven through 360 degrees in 20 degree increments at all staggered side group combinations. From these results, the low-energy forms were minimized without the driver restrictions to generate the global minimum structure found and herein reported. This conformer was then used to map the conformational space of phi and omega by driving only those torsion angles through 360 degrees. Both the 4(3)T (northern) conformer (Cremer-Pople puckering phase angle of phi 2 = 265 degrees) and the 3(4)T, (southern) conformer (phi 2 = 80 degrees) of the fructofuranose ring were tested for comparison, and both were shown to be significant contributors of populated forms. As these two conformers had different minima for a number of important torsion angles, experimental studies may reveal different properties than those expected solely from the preferred northern conformer.
采用MM2(87)分子力学方法计算了二糖β-D-呋喃果糖基-(2→6)-β-D-吡喃葡萄糖苷模型的构象能。对交错形式的初步研究考察了以扭转角φ、ψ和ω为特征的连接键，随后考察了以扭转角χ-1和χ-6为特征的果糖羟甲基侧基。然后，在我们对构象空间的主要搜索中，两个连接键的扭转角φ和ω在所有交错侧基组合下以20度增量旋转360度。根据这些结果，在没有驱动限制的情况下将低能量形式最小化，以生成本文报道的全局最小结构。然后通过仅驱动扭转角φ和ω旋转360度，用该构象异构体来描绘φ和ω的构象空间。对呋喃果糖环的4(3)T（北部）构象异构体（Cremer-Pople折叠相角φ2 = 265度）和3(4)T（南部）构象异构体（φ2 = 80度）进行了比较测试，结果表明两者都是占据形式的重要贡献者。由于这两种构象异构体在许多重要扭转角上具有不同的最小值，实验研究可能会揭示出与仅从优选的北部构象异构体预期的不同性质。
