田菁胶糖链结构和反应活性的量子化学研究

STUDY ON ELECTRONIC STRUCTURE AND REACTIVITY OF SESBANIA GUM WITH QUANTUM CHEMISTRY

用HyperChem7的PM3方法计算了田菁胶(SGn=1～5)的电子结构,讨论了稳定构象、侧链内旋转势能面及羟基氧和羟基氧负离子的反应活性。结果表明,甘露糖和半乳糖糖基在SG骨架中基本能保持其单体椅式稳定构象,主链二面角Ψ1旋转对增大主链柔性和主链卷缩成螺旋贡献最大,螺旋圈中链节数n≤10。受原子间相互排斥作用,SGn=5势能面上的低能构象远少于SGn=1势能面上的。SG侧链羟基氧反应活性较强而主链的较弱。

The electronic structures and reactivity of Sesbania Gum(SG_(n=1～5)) were studied by the semi-empirical quantum chemistry method, PM3 of HyperChem7 procedure. The optimized stable geometric configurations of SG_(n=1～5) were obtained. This presentation carefully calculated the potential surfaces for SG_(n=1,5), discussed the reactivity of hydroxyl-oxygen atoms and hydroxyl-oxygen anions in SG_(n=1～5). The results indicated that the residues of both mannose and galactose in the backbone of SG_(n=1～5) could maintaine essentially the same stable chair-conformations as the original monomer. The torsion of dihedral angle Ψ_1 was important in increasing the flexibleness of the main-chain as well as crimpling SG. The number of structure units in one helix should be estimated to be n≤10. Because of atoms repulsing each other, most of lower energy conformations on the surface of SG_(n=1) did not exist on the surface of SG_(n=5). In respect of the SG reactivity, the hydroxyl-oxygen atoms in side-chain was higher than that in mian-chain.