不同调节剂制备MOF-Fe的性质及对Se(Ⅳ)的吸附性能

以HF、HCl、H_2O和Na Ac溶液为调节剂合成了4种MOF-Fe样品,用X射线衍射(XRD)、透射电镜(TEM)、N_2等温吸附-脱附、综合热分析(TG/DTG和DTA)和质子电位滴定研究了4种样品的结构与表面性质,以及对亚硒酸根(Se(Ⅳ))等温吸附特性。MOF-Fe(HF)、MOF-Fe(HCl)、MOF-Fe(H_2O)和MOF-Fe(Na Ac)四种样品均具有八面体MIL-100(Fe)的晶体结构,但它们的结晶度和晶面取向略有差异。4种样品的比表面积分别为1 683、1 517、1 641和1 734 m~2·g~(-1),其总孔体积依次降低,微孔孔径分别为1.27、1.22、1.22和1.17 nm。MOF-Fe(HF)样品的脱羧基失重峰温度最高(415℃),苯环碳化失重峰温度最低(462℃);MOF-Fe(HCl)、MOF-Fe(H_2O)和MOF-Fe(Na Ac)样品出现了因氧化铁被碳还原所致的失重平台(566~716℃)。样品悬浮液从p H=6.0降到3.0时,消耗H~+的量表现为MOF-Fe(H_2O)MOF-Fe(HCl)MOF-Fe(HF)=MOF-Fe(Na Ac),它们的电荷零点(p H_(ZPC))依次为3.1、3.5、3.6和3.5。MOF-Fe(Na Ac)、MOF-Fe(HCl)、MOF-Fe(H_2O)和MOF-Fe(HF)对Se(Ⅳ)的吸附亲和力依次减小,它们对Se(Ⅳ)的吸附容量(Q_m)分别为77.69、107.07、117.40和87.15 mg·g~(-1)。显著性分析显示,MOF-Fe的羟基密度与样品吸附Se(Ⅳ)的Q_m显著正相关。研究结果表明,MOF-Fe样品的结构热稳定性和羟基/配位水分子等活性位点密度受合成样品时加入的调节剂影响,用HF作为调节剂合成MOF-Fe样品有利于提高样品中羧基与苯环之间的C-C键合强度和热分解产物的稳定性,降低苯环碳化温度;HCl和H_2O作为调节剂有利于提高样品的活性位点密度,可提高MOF-Fe样品对Se(Ⅳ)吸附容量。     

Structure-activity relationship study of leucinostatin A,a modulator of tumor−stroma interaction

Structure-activity relationship study of leucinostatin A, a natural nonapeptide, was performed to gain insight into the structural requirements for leucinostatin A to exhibit antiproliferative activity against DU-145 prostate cancer cells under cocultured conditions with the corresponding stromal cells. Twenty truncated peptide analogs of leucinostatin A revealed that the nonapeptide structure as a whole is essential for the biological activity. Alanine scanning demonstrated the importance of some of the amino acid components, including hydroxyleucine and the second leucine from the N-terminus. Two of the three aminoisobutyric acids could be substituted with one of the enantiomers of alanine, clearly demonstrating that each methyl group in these portions has a distinct influence on the growth-inhibitory activity.     

Total syntheses and endoplasmic reticulum stress suppressive activities of hericenes A−C and their derivatives

We report the syntheses and neuroprotective activities of hericenes and their derivatives against endoplasmic reticulum (ER) stress-dependent cell death. Four natural products, including hericenes A?C and hericenol A, and five synthetic derivatives were synthesized and their protective activities were evaluated. In designing the synthetic derivatives, we focused on the binding position of the fatty chain. Hericenes B and C showed moderate protective activity against thapsigargin-induced ER stress-dependent cell death. In contrast, their regioisomers (with respect to the position of the fatty chain) exhibited higher protective activity against tunicamycin-induced ER stress. This study clearly shows that the number and the binding position of the fatty chain are critical for protective activity against ER stress-dependent cell death.     

毒气之王和糜烂性毒剂

糜烂性毒剂是一种以皮肤糜烂为主兼有全身中毒为特点的毒剂。文章介绍了芥子气、氮芥和路易氏气等糜烂性毒剂的发现历史、理化性质、中毒机理、救治方法;同时探讨了无害化转化的方法,包括利用芥子气和路易氏气转化成为太阳能电池的重要物质和利用糜烂性毒剂的中毒机理来研究治癌的化疗药物。     

Preparation of nanocrystalline titania films with different porosity by water-based chemical solution deposition

This study describes the synthesis of nanocrystalline titania layers on silicon and glass substrates by chemical solution deposition, using a water-based citratoperoxo-Ti(IV) precursor solution. The same aqueous solution–gel precursor is used for deposition of, both, thin dense layers by spin-coating and thicker porous layers by tape-casting. In the latter, the precursor solution is modified by the addition of polyvinyl alcohol (PVA), which acts as a thickener and pore-forming agent. Phase composition, film morphology, and the hydrophilic character of the films are studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–VIS transmission measurements, variable angle spectroscopic ellipsometry (VASE), and by contact angle measurements. The thin 180 nm titania film, deposited from the unmodified precursor solution, shows a density of about 96%. Upon ultraviolet illumination, it acquires a highly hydrophilic surface. One hour of illumination is sufficient to obtain a water contact angle of almost 0°. Furthermore, the hydrophilisation process shows to be reversible. Tape-casting and thermal treatment of the modified precursor solution gives rise to the formation of a 500 nm thick, porous, pure anatase film. The nanocrystalline thick film is composed of 20–40 nm particles, and contains clearly defined pores of 20 nm, homogeneously distributed along the surface.     

Surface modification of superfine tourmaline powder with titanate coupling agent

The effects of surface modification of the superfine tourmaline powder with a titanate coupling agent were discussed by investigating its hydrophobicity and distribution in poly (ethylene terephthalate) (PET). The modified tourmaline powder became hydrophobic, which resulted in better distribution in the PET matrix. The mechanism of the surface modification was analyzed.     

Synthesis, characterization and structural investigation of the first vanadocene(IV) carboxylic acid complexes prepared from the vanadocene dichloride

Two types of vanadocene complexes with carboxylic acids have been synthesized from the aqueous solution, Cp₂V(OOCR)₂ (R=H, CCl₃ and CF₃) and Cp₂V(OOC-A-COO) (A= - and CH₂), and characterized by EPR, IR, and Raman spectroscopy and X-ray diffraction analysis. Monocarboxylic and dicarboxylic acids form monodentate and chelate complexes, respectively. Both bonding types were evidenced by X-ray diffraction analysis. Structures and EPR HFC tensors were also calculated at the DFT level. Correlation between the complex structure and HFC tensor was established. HFC tensors are characteristic for the type of bond of carboxylic acid on vanadocene fragment. It is shown that the structure of complexes can be determined by the combination of theoretical method with experimental EPR spectra.     

Quantum mechanics and mixed quantum mechanics/molecular mechanics simulations of model nerve agents with acetylcholinesterase

 The accurate modeling of biological processes presents major computational difficulties owing to the inherent complexity of the macromolecular systems of interest. Simulations of biochemical reactivity tend to require highly computationally intensive quantum mechanical methods, but localized chemical effects tend to depend significantly on properties of the extended biological environment – a regime far more readily examined with lower-level classical empirical models. Mixed quantum/classical techniques are gaining in popularity as a means of bridging these competing requirements. Here we present results comparing two quantum mechanics/molecular mechanics implementations (the SIMOMM technique of Gordon et al. as implemented in GAMESS, and the ONIOM technique of Morokuma et al. found in Gaussian 98) as performed on the enzyme acetylcholinesterase and model nerve agents. This work represents part of the initial phase of a DoD HPCMP Challenge project in which we are attempting to reliably characterize the biochemical processes responsible for nerve agent activity and inhibition, thereby allowing predictions on compounds unrelated to those already studied. Received: 10 October 2001 / Accepted: 13 November 2002 / Published online: 1 April 2003 Contribution to the Proceedings of the Symposium on Combined QM/MM Methods at the 222nd National Meeting of the American Chemical Society, 2001 Correspondence to: M. M. Hurley e-mail: hurley@arl.army.mil     

Effects of simulation conditions on antibacterial performance of polypropylene and polystyrene doped with HPQM antibacterial agent

2-Hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM) antibacterial agent in two different forms, solid form (HPQM-supported Neusilin absorbance; HPQM-neu) and liquid form (HPQM dissolved in deionized water; HPQM-water), were added to polypropylene (PP) and polystyrene (PS). The antibacterial performance against Escherichia coli and mechanical properties of the specimens were investigated. The effects of simulated conditions, including immersion in water (at room temperature and 80 °C), immersion in surfactant solution (at room temperature and 80 °C) and exposure to UV aging, on the antibacterial performance of specimens were also studied. The results showed that the optimal HPQM concentration for PP/HPQM-neu and PP/HPQM-water were 500 and 750 ppm, respectively, in order to reach 99.9% E. coli bacteria reduction, but those for PS/HPQM-neu and PS/HPQM-water were 1250 ppm. Addition of HPQM in both forms to PP and PS did not change the mechanical performance. HPQM-water was more appropriate and effective for antibacterial peformance for PP and PS than HPQM-neu. Immersion of all specimens in water and detergent solution (at room temperature and 80 °C) and UV aging decreased the antibacterial performance at different rates, the effect being very pronounced for the specimens with HPQM-neu.     

High performance long chain polyamide/calcium silicate whisker nanocomposites and the effective reinforcement mechanism

PA1012/calcium silicate whisker nanocomposites with contents of whisker ranging from 10 wt% to 40 wt%, are prepared by twin screw extruder without any additions of coupling agent. The effect of whisker on the matrix is analyzed by the studies of morphology, the mechanical properties, water absorption and thermal stabilities. SEM micrographs obviously demonstrate, even under the high filler content of 40 wt% and without surface treatment, calcium silicate whisker can be homogeneously dispersed in polyamide, directly leading to the enhanced mechanical properties. The mechanism of higher efficiency of reinforcement is needle-like shape whisker, having access to be intercalated, and mutual affinity caused by hydrogen bonding interaction between carbonyl group in polyamide chain and hydroxyl group in whisker surface. Both aspects attach matrix with excellent stress-transfer properties. In addition, with the assistance of whisker, the nanocomposite favors an improved water absorption as well as thermal stability, which is intimately associated with physical performance.