Insight into the chemomechanical coupling mechanism of kinesin molecular motors

Kinesin is a two-headed biological molecular motor that can walk processively on microtubule via consumption of ATP molecules. The central issue for the molecular motor is how the chemical energy released from ATP hydrolysis is converted to the kinetic energy of the mechanical motion, namely the mechanism of chemomechanical coupling. To address the issue, diverse experimental methods have been employed and a lot of models have been proposed. This review focuses on the proposed models as well as the qualitative and quantitative comparisons between the results derived from the models and those from the structural, biochemical and single-molecule experimental studies.     

金属和非金属原子间协同效应调控气体小分子的吸附特性研究

采用基于密度泛函理论方法系统地研究了单个NO和CO小分子在非金属(B和N)与金属Ni原子共掺杂石墨烯(Bx-Ny-gra-Ni,x+y=0,1,2,3)表面的吸附特性,分析了吸附气体小分子的几何结构,吸附能,电荷转移量以及引起体系磁性变化等情况.研究结果表明：NO和CO倾向于吸附在Ni原子的顶位,B和N掺杂原子的数量和比例能够有效地调制小分子的吸附强度;与吸附的CO分子相比,Bx-Ny-gra-Ni表面吸附的NO分子能获得较多的电荷,进而表现出高的稳定性.此外,利用吸附的气体小分子与衬底间相互作用强度和灵敏性的差异、以及引起反应衬底的磁性变化将为设计石墨烯基气敏、催化和电子器件提供重要参考.     

绿色环保化学机械抛光液的研究进展

原子级加工制造是实现半导体晶圆原子尺度超光滑表面的有效途径.作为大尺寸高精密功能材料的原子级表面制造的重要加工手段之一,化学机械抛光(chemical mechanical polishing,CMP)凭借化学腐蚀和机械磨削的耦合协同作用,成为实现先进材料或器件超光滑无损伤表面平坦化加工的关键技术,在航空、航天、微电子等众多领域得到了广泛应用.然而,为了实现原子层级超滑表面的制备,CMP工艺中常采用的化学腐蚀和机械磨削方法需要使用具有强烈腐蚀性和高毒性的危险化学品,对生态系统产生了不可逆转的危害.因此,本文以绿色环保高性能抛光液作为对象,对加工原子量级表面所采用的化学添加剂进行分类总结,详尽分析在CMP过程中化学添加剂对材料表面性质调制的作用机理,为在原子级尺度下改善表面性质提供可参考的依据.最后,提出了CMP抛光液在原子级加工研究中面临的挑战,并对未来抛光液发展方向作出了展望,这对原子尺度表面精度的进一步提升具有深远的现实意义.     

Efficient photocatalytic degradation of methyl violet with two metall–organic frameworks

Two metal–organic frameworks, [Co₂(L)(H₂O)₂(4,4′-bipy)]·3CH₃CN (1) and [Mn₂(L)(1,10-phen)(H₂O)]·H₂O (2) (H₄L = 5-[bis(4-carboxybenzyl)-amino]isophthalic acid; 4,4′-bipy = 4,4′-bipyridine, 1,10-phen = 1,10-phenanthroline), with two different N-donor ligands have been synthesized. The structures of both MOFs were determined using single-crystal X-ray diffraction technique. MOF 1 shows 3D uncommon (4,6,6)-c net with (4.5³.6²)₂(5⁷.6⁶.8²)(4².5⁴.6⁶.7².8) topology while in the case of 2, only L^4? ligands link Mn(II) ions into a 2D layer structure with chelating 1,10-phen ligand. The results demonstrate that variation in the N-donor ligands plays a pivotal role in deciding the framework of the two MOFs. Both MOFs have been exploited as photocatalyst materials for the degradation of MV. The photocatalysis results indicate that the two MOFs are stable and are prospective candidates for degradation of methyl violet under UV light irradiation. Additionally, 2 displayed superior photocatalytic activity in comparison to 1. The probable photocatalytic activity mechanism for both 1 and 2 against MV has been proposed using density of states (DOS) calculations.     

Accurate Determination of Tributyltin in Tannery Wastewater by a New Procedure Using ID-HPLC–ICP-MS Combined with Low Temperature Extraction

Isotope dilution mass spectrometry is recognized as a primary method to obtain traceable values in the measurement of substances including trace elements and their organometallic compounds. This paper reports a novel method where isotope dilution high performance liquid chromatography inductively coupled plasma mass spectrometry (ID-HPLC–ICP-MS) was combined with low temperature extraction for the determination of tributyltin (TBT) in tannery wastewater from the leather industry. It has been found that the liquid–liquid extraction at very low temperature is in the favor of extraction of organotin, as the enrichment factor for low temperature (?80 °C) extraction was about 1.3 times higher than for extraction at room temperature (20 °C). The method detection limit of TBT, obtained from the proposed ID-HPLC–ICP-MS procedure after extraction with a sample volume of 7.5 by 2.5 mL of organic phase, was found to be 0.13 ng g^?1. When TBT was determined in a range of 10–1000 ng g^?1 in tannery wastewater samples, the analyte recoveries were in the range 90.1–107.2% with relative standard deviations of between 2.0 and 7.2%. Finally, the new method of ID-HPLC–ICP-MS combined with low temperature extraction was applied to the determination of TBT in actual tannery wastewater. The TBT contents from three different tanning procedures (chrome tanning, vegetable tanning and aldehyde tanning), expressed as the mean ± the expanded uncertainty (k = 2) were 378.65 ± 20.38, 110.04 ± 5.96 and 690.17 ± 35.31 ng g^?1, respectively.     

Determination of Enantiomeric Purity of GSK962040 Based on Liquid Chromatography Using Chiral Stationary Phase Combined with a Pre-column Derivatization Procedure

A sensitive and accurate LC method was developed and further validated for the determination of enantiomeric purity of GSK962040. Before separation, a pre-column derivatization procedure was performed. Baseline separation with a resolution higher than 1.9 was accomplished within 15 min using a Chiralpak AD-H (250 × 4.6 mm; particle size 5 μm) column, with n-hexane: 2-propanol (85:15 v/v) as mobile phase at a flow rate of 1 mL min^?1. The eluted analytes were subsequently detected with a UV detector at 260 nm. The effects of mobile phase components and temperature on enantiomeric selectivity as well as resolution of enantiomers were thoroughly investigated. The calibration curves were plotted within the concentration range between 4 and 200 μg mL^?1 (n = 8), and recoveries between 98.15 and 101.48% were obtained, with relative standard deviation (RSD) lower than 1.42%. The LOD and LOQ for the Boc-GSK962040 were 1.23 and 4.15 μg mL^?1 and for its enantiomer were 1.38 and 4.76 μg mL^?1, respectively. The developed method was also evaluated and validated by analyzing bulk samples with different enantiomeric ratios of GSK962040. It was demonstrated that the method was accurate, robust and sensitive, and also had practical utilities for real analysis.     

Core-shell magnetic molecularly imprinted polymer nanoparticles for the extraction of triazophos residues from vegetables

The authors report on a surface molecular imprinting strategy for synthesizing magnetic and molecularly imprinted core-shell polymer nanoparticles (MMIPs) with a typical size of 320 nm. The triazophos-imprinted polymer shell on 180-nm magnetite particles (modified with 3-methacryloxypropyl trimethoxysilane) was obtained by radical polymerization of ethylene glycol dimethacrylate in the presence of triazophos, this followed by extractive removal of triazophos. The resulting MMIPs possess large binding capacity, high recognition selectivity, and fast binding kinetics for triazophos. They can be easily separated from a solution by using a magnet. These features result in a convenient and selective solid-phase extraction procedure for triazophos prior to its determination by UV spectrometry or by GC analysis. The method was successfully applied to the extraction and clean-up of triazophos residues in spiked homogenates of vegetables with recoveries in the range of 89.2 ~ 99.0%. The detection limits for triazophos by the UV assay and GC assay are 0.93 nM and 0.32 nM, respectively.

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Graphical abstract The core-shell magnetic molecularly imprinted polymer nanoparticles (MMIPs) with a nanoscale triazophos-imprinted polymer shell were prepared by surface imprinting onto the surfaces of 3-methacryloxypropyl trimethoxysilane (MATS) modified Fe₃O₄ magnetic nanoparticles. They were successfully applied for the extraction and clean-up of ultra trace triazophos residues in spiked homogenates of vegetable samples. MMIPs exhibit the larger binding capacity, faster binding kinetics, higher recognition selectivity, good reusability and stability, and excellent magnetic responses.

     

A Re2O7 catalyzed cycloetherification of monoallylic diols

A Re₂O₇ catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture.     

Progress in fluorene-based wide-bandgap steric semiconductors

Molecular bulks are favorable for the thermal and morphological stability in organic wide-bandgap semiconducting polymers with potential applications in both information and energy electronics. In this review, we present our progress in the design of fluorene-based bulky semiconductors with a fractal four-element pattern. Firstly, we established one-pot methods to spirofluorenes, especially spiro[fluorene-9,9′-xanthene](SFX) serving as the next-generation spiro-based semiconductors. Secondly, we observed the supramolecular forces at the bulky groups and discovered the supramolecular steric hindrance(SSH) effect on polymorphisms, nanocrystals as well as device performance. Thus, a synergistically molecular attractor-repulsor theory(SMART) was proposed for the control of nanocrystal morphology, thin film phase and morphology. Thirdly, the third possible type of defects has been identified to generate green band(g-band) emission in widebandgap semiconductors by the introduction of molecular strain design of cyclofluorene. Finally, the first bulky polydiarylfluorene with highly crystalline and β conformation was achieved by an attractor-repulsor design of tadpole-shape monomer, which offered an effective platform to fabricate stable wide-bandgap semiconducting devices. All the discoveries offer the solid basis to break through bottlenecks of organic/polymer wide-bandgap semiconductors by the improvements of overall performances.