最大重迭分子轨道和核自旋偶合常数的计算

利用前文中建立的AM1级别上最大重迭对称性分子轨道计算方案,并结合最大键级杂化轨道方法,在对分子几何优化的基础上,计算系列化合物分子中各原子的电荷分布和杂化轨道组成系数,拟合出计算C-H及C-C偶合常数的简单关系式,计算各种分子中不同C-H键和C-C键偶合常数,所得计算值和实验数据较为吻合,两者相关系数和标准偏差:.1JCH为0.982 0和6.020 5,1JCC为0.988 8和7.346 2,为计算1JCH和1JCC提供简便而直观的方法.建立的公式可预测新化合物中的C-H及C-C偶合常数,对新化合物的性质和结构及成键情况也能起到辅助推断作用,且在大分子体系的研究中极易推广.计算结果进一步表明所建AM1级别上最大重迭对称性分子轨道计算方法是可行的.     

分子轨道对称性和反应机理的计算机模拟

以3DMAX和Visual Basic为主开发工具,制作了既有交互功能又有自播放功能的分子轨道对称性及其反应机理模拟的多媒体软件。介绍了软件的基本内容、设计思想、制作方法、关键技术、特点和功效。该软件充分应用计算机多媒体,特别是三维动画技术,反映分子轨道对称性和化学反应机理,有利于学习者对这些概念和理论更加直观、深入地认识。     

C60-S-TTF及其衍生物的结构与电子性质的AM1研究

利用半经验AM1法研究了硫桥联的四硫富瓦烯衍生物的优势构型、电子结构及前线分子轨道。计算结果表明,目标分子的前线分子轨道主要由C60决定,C60母体与加成基团之间存在着较强的分子内电荷转移,C60m部分是电子受体,TTF部分为电子给体。并且预测了四硫富瓦烯硫桥稠环合C60衍生物可能在基态下产生长寿命的电荷分离态。     

Ab initio molecular orbital calculations on specific interactions between urokinase-type plasminogen activator and its receptor

Cancer invasions and metastases are controlled by various proteases. In particular, the binding of urokinase-type plasminogen activator (uPA) to the uPA receptor (uPAR) existing on the surface of cancer cell is considered to be a trigger for cancer invasions. In the present study, we determined the structure of uPA and uPAR complex in water and investigated the specific interactions between uPA and uPAR by ab initio molecular orbital (MO) calculations based on fragment MO method. The result indicates that the 20–26 amino acid residues of uPA are important for the binding between uPA and uPAR, and that the electrostatic interactions between the charged amino acid residues existing in both uPA and uPAR have large contribution to the binding. The influence of crystal water molecules existing between uPA and uPAR was also investigated to be significant on the specific interactions between uPA and uPAR. These results are expected to be informative for developing new medicines blocking the binding of uPA and uPAR.     

Hydration of ligands of influenza virus neuraminidase studied by the fragment molecular orbital method

The fragment molecular orbital (FMO) method was applied to quantum chemical calculations of neuramic acid, the natural substrate of the influenza virus neuraminidase, and two of its competitive inhibitors, Oseltamivir (Tamiful^®) and Zanamivir (Relenza^®), to investigate their hydrated structures and energetics. Each of the three ligands was immersed in an explicit water solvent, geometry-optimized by classical MM and QM/MM methods, and subjected to FMO calculations with 2-, 3-, and 4-body corrections under several fragmentation options. The important findings were that QM/MM optimization was preferable to obtain reliable hydrated structures of the ligands, that the 3-body correction was important for quantitative evaluation of the solvation energy, and that the dehydration effect was most remarkable near the hydrophobic sections of the ligands. In addition, the hydration energy calculated by the explicit solvent was compared with the hydration free energy calculated by the implicit solvent via the Poisson-Boltzmann equation, and the two showed a fairly good correlation. These findings will serve as useful information for rapid drug design.