Hricovíni M, Scholtzová E, Bízik F
Institute of Chemistry, Slovak Academy of Sciences, 845 38 Bratislava, Slovakia.
Carbohydr Res. 2007 Jul 23;342(10):1350-6. doi: 10.1016/j.carres.2007.03.020. Epub 2007 Mar 24.
Structures of heparin disaccharide have been analyzed by DFT using the B3LYP/6-311++G( * *) method. The optimized geometries of two forms of this disaccharide, differing in the conformation ((1)C(4) and (2)S(0)) of the IdoA2S residue, confirmed considerable influences of the sulfate and the carboxylate groups upon the pyranose ring geometries. The computed energies showed that disaccharide having the (1)C(4) form of the IdoA2S residue is more stable than that with the (2)S(0) form. Interatomic distances, bond and torsion angles showed that interconversion of the IdoA2S residue results in geometry changes in the GlcN,6S residue as well. Three-bond proton-proton and proton-carbon spin-spin coupling constants computed for both forms agree with the experimental data and indicate that only two chair forms contribute to the conformational equilibrium in disaccharide. Influences of the charged groups upon the magnitudes of spin-spin coupling constants are also discussed.
已使用B3LYP/6-311++G(**)方法通过密度泛函理论（DFT）分析了肝素二糖的结构。这种二糖的两种形式，其艾杜糖醛酸2-硫酸酯（IdoA2S）残基的构象（(1)C(4)和(2)S(0)）不同，其优化几何结构证实了硫酸酯和羧基对吡喃糖环几何结构有相当大的影响。计算得到的能量表明，具有IdoA2S残基(1)C(4)形式的二糖比具有(2)S(0)形式的二糖更稳定。原子间距离、键角和扭转角表明，IdoA2S残基的相互转化也会导致葡糖胺6-硫酸酯（GlcN,6S）残基的几何结构发生变化。为两种形式计算的三键质子-质子和质子-碳自旋-自旋耦合常数与实验数据相符，表明只有两种椅式构象对二糖的构象平衡有贡献。还讨论了带电基团对自旋-自旋耦合常数大小的影响。
