Using density functional theory and ZINDO methods, the structures, molecular orbitals and electronic spectra of a series of spirobifluorenes were investigated, in which two identical push-pull type chromophores are connected via an insulating carbon. Based on the correct electronic spectra, according to the sum-over-states formula, the calculation program was devised and nonlinear third-order optical susceptibilities were calculated. The results show a good agreement between the calculation and experiment. The calculated nonlinear third-order susceptibility γ of the spirobifluorenes are about six times as large as those of the corresponding mono-fluorenes without an increase of λmax. Since electronic coupling between monomer units in the spirobifluorenes is negligible owing to symmetry, we attribute the large enhancement to the spiroconjugation. Thus, we conclude that derived spirobifluorenes will be a hopeful type of third-order nonlinear optical material from the standpoint of the high transparency and relatively large γ value.

The equilibrium geometries, electronic structures and UV-vis spectra of a series of spiroannelated quinone-type methanofullerenes have been determined by using Zerner’s intermediate neglect of differential overlap method. The results show that between fullerene and the addend there exists a special interaction, “periconjugation”, which results in through-space orbital interactions. The calculated UV-vis spectra are in good agreement with experiments. On the basis of the electronic spectra, the β values are calculated. The results show that spiroannelated quinone-type methanofullerenes have quite large β values. We attribute the large β values to both the charge transfer from C60 to benzoquinone and on the C60 three-dimensional conjugated sphere.

(–)–Stepholidine (SPD), an active ingredient of the Chinese herb Stephania, is the first compound found to have dual function as a dopamine receptor D1 agonist and D2 antagonist. Insights into dynamical behaviors of D1 and D2 receptors and their interaction modes with SPD are crucial in understanding the structural and functional characteristics of dopamine receptors. In this study a computational approach, integrating protein structure prediction, automated molecular docking, and molecular dynamics simulations were employed to investigate the dual action mechanism of SPD on the D1 and D2 receptors, with the eventual aim to develop new drugs for treating diseases affecting the central nervous system such as schizophrenia. The dynamics simulations revealed the surface features of the electrostatic potentials and the conformational “open-closed” process of the binding entrances of two dopamine receptors. Potential binding conformations of D1 and D2 receptors were obtained, and the D1-SPD and D2-SPD complexes were generated, which are in good agreement with most of experimental data. The D1-SPD structure shows that the K-167_EL-2-E-302_EL-3 (EL-2: extracellular loop 2; EL-3: extracellular loop 3) salt bridge plays an important role for both the conformational change of the extracellular domain and the binding of SPD. Based on our modeling and simulations, we proposed a mechanism of the dual action of SPD and a subsequent signal transduction model. Further mutagenesis and biophysical experiments are needed to test and improve our proposed dual action mechanism of SPD and signal transduction model.

Toxins have been important tools to characterize the structures and functions of K+ channels in recent years due to their unique blockage of the K+ current and other physiological functions to the K+ channels, especially the voltage-gated K+ channels. Knowledge of the interacting surfaces between the toxins and the channels has been accumulated both from biological explorations and theoretical simulations. It has been found that the electrostatic potentials act as the driving force for the recognition of the toxins with the channels, and the orientation of the toxins over the channels follows the direction of the dipole moment. The binding site is composed most of the conservative residues of the negatively charged rings of Asp/Glu and residues around the edge of the central pore. The selectivity mainly comes from the type and distribution of the positive charged residues, and the whole topologies of the toxins. Based on the molecular determinants of the complex formation, and taking advantage of the structure-based methodologies of molecular design, it is hopefully to develop new generation of lead compounds specifically binding with subtypes of K+ channels.

在AM1和ZINDO方法基础上，按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数βijk和βμ的程序，研究了一系列新推拉型多环共轭分子的结构、光谱和二阶非线性光学系数β（-2ω，ω，ω）和β(0，0，0)。考察了分子共轭链长、分子骨架和给电子取代基对βμ的影响，并设计了具有最大βμ的新型非线性光学材料分子。