基于虚拟现实的分子对接教学软件*

由于其强大的沉浸性和交互性等特征,虚拟现实技术在教育教学方面有着独特的优势。基于分子建模工具和虚拟现实技术构建了一种关于分子对接的教学软件,该软件将语音讲解、动画演示、分子可视化、交互操作等内容有机整合在虚拟现实环境中,从理论知识讲解和VR实验操作2个方面展开,深入浅出地讲解了分子对接的知识点,达到辅助教学的目的。     

Solvent extraction and self-assembly of nanosized aggregates of p-tert-butyl thiacalix[4]arenes tetrasubstituted at the lower rim by tertiary amide groups and monocharged metal cations in the organic phase

New p-tert-butyl thiacalix[4]arenes functionalized with morpholide and pyrrolidide groups at the lower rim in cone, partial cone, and 1,3-alternate conformations were synthesized, and their receptor properties for monocharged cations (alkali metal and silver ions) were studied using the picrate extraction method and dynamic light scattering (DLS). To evaluate the ability of the p-tert-butyl thiacalix[4]arene derivatives to recognize metal ions, liquid-liquid extraction of their picrate salts has been carried out in a mutually saturated water-dichloromethane system. The degrees of extraction and the extraction constants for monocharged metal cations (Li⁺, Na⁺, K⁺, Cs⁺) have been determined. The ability of the systems, consisting of host and guest molecules, to self-assembly was proved by DLS using a Zetasizer Nano ZS particle size analyzer. It was shown that all the investigated thiacalix[4]arenes are able to form nanoscale particles with silver cations under the experimental conditions. The pyrrolidide derivative in the cone conformation showed both self-association and aggregation processes with lithium cations. The degree of extraction for all the investigated systems that formed nanoscale aggregates in the organic phase was more than 67% and the extraction constants, log K_ex determined by the picrate extraction method, more than 6.     

Characterization of poly(lactic acid)s with reduced molecular weight fabricated through an autoclave process

Poly(lactic acids) (PLAs) with different molecular weights (MWs) were prepared by autoclaving a commercial PLA for different time periods. The harvested PLAs were characterized by different techniques. Gel permeation chromatography results showed that the MW of PLA decreased with increasing autoclaving time. The Mark–Houwink parameters for PLA in dichloromethane at 25 °C were determined for the first time. The melting endotherms, revealed by differential scanning calorimetry, were observed for the 60 and 120 min-autoclaved PLAs (cf. PLA60 and PLA120) but hardly detected for the original and 30 min-autoclaved PLA (PLA30). The PLA120 exhibited higher crystallinity than that of PLA60. Thermogravimetric analysis showed that the activation energy for thermal degradation decreased from 186 kJ mol⁻¹ to 140 kJ mol⁻¹ for original PLA and PLA120. The hydrophilicity of the PLA increased, indicating higher number of COOH groups, with increasing autoclaving time, as revealed by the contact angle measurement. Rheological data showed that the complex viscosity and storage modulus of PLA decreased with increasing autoclaving time due to the decreasing MW. Unlike original PLA and PLA30, PLA60 and PLA120 exhibited Newtonian fluid behavior at all test frequencies.     

Selectivity features of molecularly imprinted polymers recognising the carbamate group

The molecular recognition properties of molecular imprinted polymers which bind the carbamate function were studied. Functional monomers potentially able to form non-covalent interactions with the model molecule N,O-dibenzylcarbamate were selected on the basis of a computational approach describing possible interactions between the template and a small library of vinylic monomers. These results were in accordance with N,O-dibenzylcarbamate batch-rebinding measurements performed on several miniMIPs prepared with the same library. From these preliminary results, four polymers were prepared by thermoinduced radical polymerization, using ethylene dimethacrylate as a cross-linker, chloroform (MIP1, MIP3) or acetonitrile (MIP2, MIP4) as porogens and methacrylic acid (MIP1, MIP2) or acrylamide (MIP3, MIP4) as functional monomers. Molecular recognition features of these materials were studied by high-performance liquid chromatography. In this manner selectivity was evaluated by considering the column retention of a library of sixteen structural analogues of dibenzylcarbamate, characterized by the transformation of the carbamate into a related function, or by the alteration of the molecular structure.The experimental results show that methacrylic acid is more efficient than acrylamide as a functional monomer (imprinting factors: MIP1 = 24.1, MIP2 = 25.6, MIP3 = 13.3, MIP4 = 2.44), and that chloroform enhances polymer selectivity. As regards structural motifs which conditionate the selectivity, the carbamate function strictly controls the presence/absence of molecular recognition, while shape and dimension of the substituents modulate the recognition itself. In particular, a marked recognition for analogs which were slightly bigger than the template was observed (N-benzyl-O-phenethylcarbamate: MIP1 α = 1.13, MIP2 α = 1.41, MIP3 α = 0.97; N-phenethyl-N-benzylcarbamate: MIP1 α = 1.61, MIP2 α = 1.17, MIP3 α = 0.81; N,O-diphenethylcarbamate: MIP1 α = 0.89, MIP2 α = 1.20, MIP3 α = 0.55).     

新型磷酸硅铝分子筛SAPO-56的合成与表征

以N,N,N',N'-四甲基-1,6-己二胺(TMHD)为模板剂,采用水热法在Al₂O₃-P₂O₅-SiO₂体系中合成了SAPO-56分子筛.固定模板剂和水,得到Al-Si-P三元体系相图.当原料物质的量比为0.52)/n(M)<0.7(M=SiO²⁺Al₂O³⁺P₂O₅),0.152O₃)/n(M)<0.4及0.12O₅)/n(M)<0.3时,出现SAPO-56合成的纯相区.固定合成凝胶中硅、铝、磷和水的量,模板剂的用量改变对合成影响较大.n(TMHD)/n(P₂O₅)≥2时,产物是纯SAPO-56.用XRD,SEM,IR,DTA-TG和吸附等方法研究了产物的物化性能.结果表明,SAPO-56分子筛具有较好的热稳定性(骨架坍塌温度为1150℃)和较大的水吸附量(41%).SAPO-56分子筛催化剂对甲醇转化制烯烃反应表现出了良好的催化活性和较高的C₂和C₃烯烃选择性.     

聚苯胺在一些有机溶剂中溶解性

本文通过改变反应条件用化学方法制得了不同分子量的聚苯胺，考察了它们在有机溶剂中的溶解性．实验结果表明：分子量的大小是影响它们在有机溶剂中溶解度的主要因素，能在有机溶剂中溶解的只是聚苯胺中分子量较小的级分．我们还用聚苯胺（［η］＝０．４９ｄｌ／ｇ）与－ＣＯＣＩ封端的果对苯二甲酰对苯二胺（ＰＰＴＡ）进行嵌段共聚，经过产物的元素分析与计算结果比较，确定出特性黏数为０．４９ｄｌ／ｇ的聚苯胺平均分子量．     

C-methyl flavonoid from the leaves of Cleistocalyx conspersipunctatus: α-glucosidase inhibitory,molecular docking simulation and biosynthetic pathway

We extracted one new C-methyl flavonoid, farrerol 7-O-β-d-(6-O-galloyl)glucopyranoside (1), along with 11 known flavonoids, from the Cleistocalyx (C.) conspersipunctatus leaves. Elucidation of these flavonoid structures was accomplished through spectroscopic investigation and electronic circular dichroism (ECD) computation. Compared to corosolic acid (IC₅₀: 15.5 ± 0.9 μM), an established inhibitor, the compound 1 (IC₅₀: 6.9 ± 1.2 μM) was found more active in suppressing α-glucosidase. These findings imply the potential of compound 1 as a valid α-glucosidase inhibitor, which also offer evidence for future animal experiments and clinical trials. Besides, molecular docking was employed to explore the probable mechanism for α-glucosidase–compound 1 interaction. The biosynthetic pathway of these flavonoids in C. conspersipunctatus were proposed.     

Partition coefficients of organic molecules in squalane and water/ethanol mixtures by molecular dynamics simulations

Accurate partition coefficient data of migrants between a polymer and a solvent are of paramount importance for estimating the migration of the migrant over time, including the concentration of the migrant at infinite time in the two solvents. In this article it is shown how this partition coefficient can be estimated for both a small hydrophilic and a hydrophobic organic molecules between squalane (used here to mimic low density poly ethylene) and water/ethanol solutes using thermodynamic integration to calculate the free energy of solvation. Molecular dynamics simulations are performed, using the GROMACS software, by slowly decoupling of firstly the electrostatic and then the Lennard-Jones interactions between molecules in the simulation box. These calculations depend very much on the choice of force field. Two force fields have been tested in this work, the TraPPE-UA (united-atom) and the OPLS-AA (all-atom). The computational cheaper TraPPE-UA force field showed to be more accurate over the whole range of systems compared to the OPLS-AA force field. Moreover, some of the calculations were done with five different water models to investigate the influence of the specific water model on the calculations. It was found that the combination of the TraPPE-UA force field and the TIP4p water model gave the best results. Based on the methodology proposed in this article, it is possible to obtain good partition coefficients only knowing the chemical structure of the molecules in the system.     

F and C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

Fluorine, hydrogen, and ¹³C NMR spectral data have been obtained for vinyl alkyl ethers containing fluorines. Some of the molecules are perfluorinated and others include hydrogen, bromine, and chlorine substituents. New generalizations regarding FF spin-spin coupling are developed and used, along with previously recognized correlations, in the confirmation of structures and the assignments of resonances. ¹³C spectroscopy, especially the analysis of ¹³C¹⁹F coupling, is critical in several of the structure determinations. Chlorine isotope effects on fluorine chemical shifts are observed when the chlorine and fluorine are attached to the same carbon, and are also used in the structure analyses. Long-range couplings between fluorines in the vinyl group and fluorines in the alkyl group are interpreted in terms of molecular geometry which allows certain of the alkyl fluorines to “touch” the fluorines cis and gem to the ether oxygen but not the fluorine trans to the oxygen. Two bond ¹³C¹⁹F coupling across the vinyl double bond is found to vary dramatically with the electronegativity of the vinyl substituents in the ethers, in accordance with previous observations for olefins.