双[4-(2,4-二特戊基苯氧基)邻苯二腈铜]LB膜材料的合成

近年来,随着LB膜研究的进展,成膜材料的种类逐渐增多、其中有关酞菁衍生物LB膜材料的报道较多。本文合成了下述新型结构的化合物:     

负载型贵金属催化剂的硫中毒机理——载体的酸碱性与催化剂抗硫性能的关系

以H_2S为毒物,H_2-O_2反应为催化模型反应,制备并考察了一系列不同酸碱性的负载型钯催化剂。以NH_3和吡啶为探针分子,用程序升温脱附(TPD)或红外光谱法测定了催化剂的酸碱性。用交替脉冲微反色谱技术评价了催化剂的活性和耐硫中毒性,并对催化剂的耐硫性能和载体酸碱性进行关联和解释。在以上研究基础上,指出了提高催化剂抗硫性能的途径。     

黄芪中微量元素的形态分析

按照传统煎煮法对中药黄芪中铜、锌、铁、镁、钙和铬6种元素进行提取;用微孔滤膜分离提取液中的可溶态与悬浮态;利用大孔吸附树脂柱对可溶态中的有机态与无机态进行分离;采用火焰原子吸收光谱法对各种形态中的6种元素进行测定。结果显示:黄芪中6种元素的总提取率在44.0%~74.4%,浸留比在79·4%~293.8%,悬浮态颗粒吸附率在10%左右,可溶态中铬的有机态与无机态的比例为114.6%,铜、锌、铁、镁、钙的有机态与无机态的比例在3.7%~43.5%。该法对各元素的加标回收率在96.8%~103.1%;相对标准偏差小于1.5%。     

Acetylcholinesterase complexed with bivalent ligands related to huperzine a: experimental evidence for species-dependent protein-ligand complementarity

Acetylcholinesterase (AChE) inhibitors improve the cognitive abilities of Alzheimer patients. (-)-Huperzine A [(-)-HupA], an alkaloid isolated from the club moss, Huperzia serrata, is one such inhibitor, but the search for more potent and selective drugs continues. Recently, alkylene-linked dimers of 5-amino-5,6,7,8-tetrahydroquinolinone (hupyridone, 1a), a fragment of HupA, were shown to serve as more potent inhibitors of AChE than (-)-HupA and monomeric 1a. We soaked two such dimers, (S,S)-(-)-bis(10)-hupyridone [(S,S)-(-)-2a] and (S,S)-(-)-bis(12)-hupyridone [(S,S)-(-)-2b] containing, respectively, 10 and 12 methylenes in the spacer, into trigonal TcAChE crystals, and solved the X-ray structures of the resulting complexes using the difference Fourier technique, both to 2.15 A resolution. The structures revealed one HupA-like 1a unit bound to the "anionic" subsite of the active-site, near the bottom of the active-site gorge, adjacent to Trp84, as seen for the TcAChE/(-)-HupA complex, and the second 1a unit near Trp279 in the "peripheral" anionic site at the top of the gorge, both bivalent molecules thus spanning the active-site gorge. The results confirm that the increased affinity of the dimeric HupA analogues for AChE is conferred by binding to the two "anionic" sites of the enzyme. Inhibition data show that (-)-2a binds to TcAChE approximately 6-7- and > 170-fold more tightly than (-)-2b and (-)-HupA, respectively. In contrast, previous data for rat AChE show that (-)-2b binds approximately 3- and approximately 2-fold more tightly than (-)-2a and (-)-HupA, respectively. Structural comparison of TcAChE with rat AChE, as represented by the closely related mouse AChE structure (1maa.pdb), reveals a narrower gorge for rat AChE, a perpendicular alignment of the Tyr337 ring to the gorge axis, and its conformational rigidity, as a result of hydrogen bonding between its hydroxyl group and that of Tyr341, relative to TcAChE Phe330. These structural differences in the active-site gorge explain the switch in inhibitory potency of (-)-2a and 2b and the larger dimer/(-)-HupA potency ratios observed for TcAChE relative to rat AChE. The results offer new insights into factors affecting protein-ligand complementarity within the gorge and should assist the further development of improved AChE inhibitors.     

Two noncentrosymmetric complexes: [W(CO)4(bipy)] and [W(CO)4(phen)](bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline) obtained through solvothermal synthesis and their optical properties

Solvothermal treatments of W(CO)₆ with 2,2′-bipyridine and 1,10-phenanthroline give [W(CO)₄(bipy)] (1) and [W(CO)₄(phen)] (2), respectively, which both crystallize in noncentrosymmetric space groups, suggesting that they meet the requirement of second harmonic generation (SHG) investigations. The preliminary experiment indicates that they are SHG active, and approximately estimated to be that of urea.     

DNA-modified electrodes; part 4: optimization of covalent immobilization of DNA on self-assembled monolayers

The covalent immobilization of DNA onto self-assembled monolayer (SAM) modified gold electrodes (SAM/Au) was studied by X-ray photoelectron spectrometry and electrochemical method so as to optimize its covalent immobilization on SAMs. Three types of SAMs with hydroxyl, amino, and carboxyl terminal groups, respectively, were examined. Results obtained by both X-ray photoelectron spectrometry and cyclic voltammetry show that the largest covalent immobilization amount of dsDNA could be gained on hydroxyl-terminated SAM/Au. The ratio of amount of dsDNA immobilized on hydroxyl-terminated SAMs to that on carboxyl-terminated SAMs and to that on amino-terminated SAMs is (3-3.5): (1-1.5): 1. The dsDNA immobilized covalently on hydroxyl-terminated SAMs accounts for 82.8-87.6% of its total surface amount (including small amount of dsDNA adsorbed). So the hydroxyl-terminated SAM is a good substrate for the covalent immobilization of dsDNA on gold surfaces.     

PBA@POM Hybrids as Efficient Electrocatalysts for the Oxygen Evolution Reaction

To realize the effective conversion of renewable energy through water decomposition, efficient electrocatalysts for the oxygen evolution reaction (OER) are essential. In this article, PBA@POM was successfully prepared with a Prussian blue analogue (PBA) as the initial structure. A facile hydrothermal process is reported for obtaining PBA@POM by etching the cubic PBA with a strong Brønsted acid, H₃PMo₁₂O₄₀ (HPMo). The hollow cube structure not only exposes more active sites but also promotes electron transport, which results in excellent electrocatalytic activity for the OER. Compared with the PBA, which initially simply adhered to POM, the optimum PBA@POM hybrids display remarkably enhanced OER catalytic activity, with an almost constant overpotential of 440 mV at a current density of 10 mA cm^?2 and a small Tafel slope (23.45 mV dec^?1). The facilely prepared PBA@POM with good electrochemical activity and stability promises great potential for the OER.     

Electrocatalysis of Metalloporphyrins(Ⅷ)——Electrocatalytic Reduction of Molecular Oxygen with Water-Soluble Cobalt (Ⅱ) Tetrakis(4-Trimethyl Ammonium Phenyl) Porphyrin Catalyst

Reported here is the electrocatalytic reduction of molecular oxygen in the presence of water-soluble cobalt(Ⅱ) tetrakis(4-trimethyl ammonium phenyl) porphyrin (Co(Ⅱ)TTAPP) as catalyst in solutions of various pH values. The overpotential of molecular oxygen reduction is reduced by ca. 200-400 mV in acidic and neutral solutions compared with several decades of millivolts in alkaline solutions, indicating that Co(Ⅱ)TTAPP possesses much higher catalytic activity in acidic and neutral solutions than in alkaline. H2TTAPP in solutions of various pH exhibits no significant catalytic activity for oxygen reduction. The significant difference in the electrocatalytic activity of Co(Ⅱ)TTAPP from that of H2TTAPP for oxygen reduction indicates that the electrocatalytic activity of Co(Ⅱ)TTAPP should be attributed to the central cobalt atom (Co(Ⅱ)) coordinated by N4 internal ring in Co(Ⅱ)TTAPP. The total number of electrons involved in oxygen reduction electrocatalyzed by Co (Ⅱ)TTAPP is 2, and the product of suc     

高硅沸石骨架结构及其稳定性的模拟计算(I)*

The lattice energy of a series of high-silica zeolites was determined using the lattice energy minimization method. The results were compared to the lattice energy of dense polymorphs of SiO2. All high-silica zeolites frameworks are only 30～67kJ•mol-1 less stable than α-quartz This may imply that there is little energy barrier to the formation of high-silica zeolites frame-works and explain the structural diversity observed for high-silica zeolites. The relationships of calculated lattice energies and framework Structures was disscussed. The results revealed a good linear relationship between framework density of these molecular sieves and all-silica framework lattice energies.     

Recovery of palladium from basic reprocessing waste of spent nuclear fuel

The methods including collection method, extraction-collection method, and special extraction-collection method have been investigated for high speed and efficient recovery of palladium from high pH reprocessing waste of spent nuclear fuel. The equilibrium of the reactions can be obtained is less than 1 minute. The maximum percent recovery of Pd is about 89%, 96% and 97% for collection, extraction-collection, and special extraction-collection methods, respectively. Nearly 100% of back extraction of Pd in the organic phase can be attained by using 7.4M ammonia solution, with a phase ratio of 1:1. The purity of the Pd product is high. The percent recovery of Pd is constant, up to 5·10³ Gy of irradiation dose.