Location and orientation of the N,N-diisopropylethylamine template molecule in the AlPO4-18 framework by X-ray synchrotron diffraction and molecular modelling

Phase pure AlPO4 with the AlPO4-18 (AEI) structure was synthesised using N,N-diisopropylethyla-mine as a template. Using a combination of X-ray powder diffraction and computational methods, the location and orientation of the N,N-diisopropylethylamine molecules inside the cages of the AEI structure were determined. Thermogravimetric analysis confirmed that the number of template molecules per unit cell was consistent with the diffraction study. We unequivocally show that only one template molecule is present in each cage of the crystalline AEI material. Our work demon-strates that a combined approach enables accurate structure resolution of such complex materials.     

Controlled formation of novel supramolecular microbelts or microprisms from aniline and H2PdCl4 driven by coordination and π–π interactions

In this communication, I report the formation of novel supramolecular one-dimensional (1D) structures including microbelts and microprisms by a direct mix of aniline and H₂PdCl₄ aqueous solutions at room temperature. As-formed supramolecular structures were characterised by scanning electron microscopy, X-ray photoelectron spectra and X-ray diffraction techniques. Both coordination and π–π interactions are expected to be responsible for these 1D microstructures. It suggests that the molar ratio of the reactants is crucial to the formation of such 1D structures.     

分子自组装法制备具有可控浸润性的铜表面简

通过简单浸泡的方法在铜基底上制备出了具有微纳米复合结构的氧化铜,再利用混合硫醇溶液[含HS(CH2)9CH3和 HS(CH2)11OH]对浸泡后的表面进行修饰,通过控制溶液中HS(CH2)11OH的浓度,制备出一系列具有不同浸润性的铜表面,实现表面从超疏水到超亲水的有效调控. 研究发现,表面浸润的可控性源于表面复合结构与不同化学组成的协同作用,微纳米复合结构的存在为表面浸润性的调节提供了必要的条件.     

Characterization and Three-dimensional Structural Modeling of Humic Acid via Molecular Mechanics and Molecular Dynamic Simulation

The humic acid（HA） sample obtained from the alluvial soil was characterized by elemental composition, pyrolysis gas chromatography-mass spectrometry（Py-GC-MS） and solid-state 13C nuclear magnetic resonance （13C NMR） spectroscopy. There is high fat content and a few nitrogen-containing functional groups in HA. Py-GC-MS demonstrates the characterization and structural identification of HA. One long list of identified pyrolysis products was proposed for the construction of conceptual model of HA. Solid-state 13C NMR data indicate there are higher values of alkyl-C, O-alkyl-C and aryl-C in HA. The elemental composition, structural carbon distribution and L3C NMR spectroscopy of simulated HA are consistent with those of experimental HA. HyperChem was used to simulate the three-dimensional molecular structure of the monomer, which was optimized by the molecular mechanics of the optimized potential for liquid simulations（OPLS） force field and molecular dynamics simulation to get the stable and balanced conformation. The deprotonation process study depicts that the degree of ionization of HA gets deeper, while the electronegativity of HA and the energy of van der Waals（vdW） increase. Moreover, the 3D structure of humic acid with -4 charges is the most stable. The deprotonation process is an endothermic process.     

激酶ABL与肉豆蔻酰位点小分子作用机理的分子动力学模拟及自由能计算

采用分子动力学方法研究激酶ABL 与ATP 位点小分子imatinib、P16 及变构位点小分子STJ、MS7、MS9、3YY、MYR等的结合, 并用GBSA (generalized Born surface area)方法将结合自由能分解到各残基. 自由能计算结果表明, 小分子STJ、MS7、MS9 有利于imatinib 与ABL 结合; 小分子STJ、MS7、MS9 与激酶ABL的结合自由能接近, 绝对值均大于ABL 与3YY、MYR 的结合自由能. 能量分解表明, ABL 残基ILE502、VAL506、LEU510与STJ和MYR的相互作用是αI 螺旋处于弯曲状态的重要原因. 模拟过程中ABL肉豆蔻酰口袋残基均方根偏差(RMSD)变化值表明, STJ等小分子抑制剂与ABL结合后降低了肉豆蔻酰口袋残基的柔性.     

Electrochemical Behaviors of Adenosine‐5′‐triphosphate on Molecular Wire Modified Carbon Paste Electrode and Its Sensitive Detection

A new electrochemical method was proposed for the determination of adenosine‐5′‐triphosphate (ATP) based on the electrooxidation at a molecular wire (MW) modified carbon paste electrode (CPE), which was fabricated with diphenylacetylene (DPA) as the binder. A single well‐defined irreversible oxidation peak of ATP appeared on MW‐CPE with adsorption‐controlled process and enhanced electrochemical response in a pH 3.0 Britton‐Robinson buffer solution, which was due to the presence of high conductive DPA in the electrode. The electrochemical parameters of ATP were calculated with the electron transfer coefficient (α) as 0.54, the electron transfer number (n) as 1.9, the apparent heterogeneous electron transfer rate constant (k_s) as 2.67 × 10^?5 s^?1 and the surface coverage (Γ_T) as 4.15 × 10^?10 mol cm^?2. Under the selected conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10^?7 mol L^?1 to 2.0 × 10^?3 mol L^?1 with the detection limit as 1.28 × 10^?8 mol L^?1 (3σ) by sensitive differential pulse voltammetry. The proposed method showed good selectivity without the interferences of coexisting substances and was successful applied to the ATP injection samples detection.     

吡喃并[3,2-c]吡啶-5-酮衍生物与血清白蛋白相互作用的光谱和分子对接研究

通过荧光光谱和紫外-可见吸收光谱法,在模拟生理条件下,研究了吡喃并[3,2-c]吡啶-5-酮衍生物-2-氨基-7-甲基-3-氰基-4-(4-甲苯)-吡喃并[3,2-c]吡啶-5-酮(AMP)与牛血清白蛋白(BSA)的相互作用。探讨了AMP对BSA的荧光猝灭过程的猝灭机理。不同温度下的Stern-Volmer曲线和紫外-可见吸收光谱表明:该衍生物主要以静态猝灭的方式使牛血清白蛋白的荧光猝灭。热力学参数表明两者之间的作用力类型主要为疏水作用力。用同步荧光技术考察了这一衍生物对牛血清白蛋白构象的影响。分子对接表明,该衍生物可能位于白蛋白的疏水腔IIA处。     

水在纳米管道中流动行为的分子动力学模拟

采用分子动力学方法模拟了纳米管道内水分子的流动行为. 考察了压强差、 管道直径和管道长度对通量的影响, 验证了流体在直径为2～2.8 nm管道中的流动行为符合Hagen-Poiseuille(HP)方程. 研究发现, 末端效应具有长度依赖性, 对于较短的管道其末端效应更为显著. 为了深入了解真实非均匀管道的流动行为, 使用直径不同的2种管道以不同的连接顺序组合成4种非均匀管道模型, 最终得到了不同的流量. 提出了二元管道模型, 对非均匀管道内的流动行为进行了初步探讨.     

Polymer networks by molecular dynamics simulation: Formation, thermal, structural and mechanical properties

A molecular dynamics simulation method is presented and used in the study of the formation of polymer networks. We study the formation of networks representing the methylene repeating units as united atoms. The network formation is accomplished by cross-linking polymer chains with dedicated functional end groups. The simulations reveal that during the cross-linking process, initially branched molecules are formed before the gel point; approaching the gel point, larger branched entities are formed through integration of smaller branched molecules, and at the gel point a network spanning the simulation box is obtained; beyond the gel point the network continues to grow through the addition of the remaining molecules of the sol phase onto the gel (the network); the final completion of the reaction occurs by intra-network connection of dangling ends onto unsaturated cross-linkers. The conformational properties of the strands in the undeformed network are found to be very similar with the conformational properties of the chains before cross-linking. The uniaxial deformation of the formed networks is investigated and the modulus determined from the stress-strain curves shows reciprocal scaling with the precursor chain length for networks formed from sufficiently large precursor chains (N ≥ 20).     

A temperature and pH double sensitive cholesteric polymer film from a photopolymerizable chiral hydrogen-bonded assembly

In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal (Ch-LC) monomers mixture containing a photopolymerizable chiral H-bonded assembly (PCHA). The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green/yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Additionally, the selective reflection band (SRB) of the cholesteric polymer film in solution with pH > 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH < 7 hardly changed. This pH sensitivity in solutions with pH > 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by―OH and―K + ions in the alkaline solution. In contrast, it couldn’t happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical/photonic papers, optical sensors and LCs displays, etc.