冠醚富集原子吸收光谱法测定水样中痕量镉

报道了用装有涂布了聚苯并15－冠－5（A型）的分子筛的玻璃分离柱可用于水中痕量镉的预富集,此分离方法是基于CdI4^2-络阴离子与冠醚的络合反应,取水样750ml调其酸度至pH3左右,加入KI 15g,溶解后,以2－3ml.min^-1的流速通过交换柱,用0．5mol.L^-1 HCl作为洗脱剂,以0．3－0．5ml.min^-1的流速将Cd^2 从络合物中解脱淋洗下,淋也液定容为25ml后用FAAS法测定其含镉量。     

锆氢化反应热力学函数的计算

用B3LYP/SDD密度泛函方法计算了ZrH的微观性质,气态ZrH(D,T)的能量(E),熵(S)以及 Zr与氢同位素气体反应的热力学函数.在ZrH(s)、ZrD(s)和ZrT(s)的E和S的计算中,近似以分 子总能量中的振动能Ev代替固态能量,以电子和振动熵SEv代替固态熵.在这种近似下,计算了 不同温度下Zr与H2、D2、T2反应的ΔH、ΔG、ΔS及氢化反应平衡压力,导出了与温度 的依赖关系.计算结果表明,ZrH(s)的生成热为161.34 kJ穖ol-1,与实验值(173.5 kJ穖ol -1)接近,表明这种近似处理方法是合理的,可以用于研究贮氢材料氢化反应的热力学.     

Cloning and expression of L-asparaginase gene in Escherichia coli

The L-asparaginase (ASN) from Escherichia coli AS1.357 was cloned as a DNA fragment generated using polymerase chain reaction technology and primers derived from conserved regions of published ASN gene sequences. Recombinant plasmid pASN containing ASN gene and expression vector pBV220 was transformed in different E. coli host strains. The activity and expression level of ASN in the engineering strains could reach 228 IU/mL of culture fluid and about 50% of the total soluble cell protein respectively, more than 40-fold the enzyme activity of the wild strain. The recombinant plasmid in E. coli AS1.357 remained stable after 72h of cultivation and 5h of heat induction without selective pressure. The ASN gene of E. coli AS1.357 was sequenced and had high homology compared to the reported data.     

Metal Ion Recognition. Interaction of New Oxygen-Nitrogen Donor Macrocycles with Selected Transition and Post-Transition Metal Ions

As part of an ongoing investigation of the factors influencing metal ionrecognition, we have investigated structure/function relationships involvingthe metal-ion binding by three new N-benzyl-substituted, 15- and 16-membered,macrocyclic ligands incorporating N₂O ₃- and N ₃O ₃-donor sets (withthe N ₃O ₃-system consisting of a N ₂O ₃-macrocyclic ring with an attachedCH ₂CH ₂NCH ₂C ₆H ₅ pendant arm). Selected solid complexes of thelatter ligand were isolated and the X-ray structures of individual Ni(II) and Ag(I) complexeswere obtained.Where solubility permitted, potentiometric titration studies in 95% methanolwere employed to investigate the binding affinities of all three ligand derivativestowards Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Ag(I) and Pb(II). The 15-memberedN ₂O ₃-ring was found to be selective for Ag(I) over the other six metalsinvestigated, including Cu(II). However, the presence of a further nitrogen donorin the form of the pendant benzylamine functionality in the N ₃O ₃-donorsystem results in an increase in its binding affinity for Ag(I) but an even greaterincrease occurs for Cu(II). As a consequence, the latter ion is now more stronglybound than Ag(I). The factors influencing these respective selectivities are discussed.     

Production of oxychemicals from precipitated hardwood lignin

Lignin is a major byproduct in the biomass-to-ethanol process. The lignin produced from acid treatment of biomass has characteristics suitable for further conversion to organic chemicals. It is free of contaminants and has a relatively low molecular weight. In this study, catalytic oxidative conversion of the acid-soluble lignin precipitated from acid hydrolysates of hardwood was investigated. The process is based on aqueous alkaline oxidation of lignin with dissolved O₂ in the presence of Fe³⁺ and Cu²⁺ catalysts at moderate reaction temperatures (160–180°C). Aromatic aldehydes, ketones, and organic acids are found to be the primary products identifiable on extraction with ether. The combined weight yield of the total ether extractable products is about 20–25% of the initial lignin. The yield of the aldehydes (vanillin + syringaldehyde) is in the vicinity of 15% with an additional 3 to 4% of aromatic ketones. The yields of aldehydes plus ketones observed in this work far exceeded those obtainable from the conventional alkaline air oxidation of spent sulfite liquors. This article also provides comprehensive batch reaction data on conversion and product distribution.     

全硅FER沸石上有机吸附物脱附行为的研究

运用热分析技术,研究吸附在体相和表面结构完美的单晶状疏水全硅FER沸石孔道中的有机化合物的脱附行为,测定亲和性指数AT值和负载量。所研究的吸附质为直链烷烃、直链烷基醇、直链烷基胺等,结果显示醇有较低的AT值,而直链烷烃有较高的AT值,胺类有最高的AT值。证明全硅FER沸石骨架对烷基、胺基呈现出强的"亲和性",而对羟基呈现出“憎性”。同时还发现吸附质的链长对脱附性质、AT值也有较大影响。     

用加速量热仪研究KClO3/CuO/S/Mg-Al/C6Cl6的热分解

The thermal decompositions of two systems(NO.1,KClO₃(52.2%)/CuO(26.0%)/S(9.6%)/Mg-Al(3.5%)/C₆Cl₆(4.35%)) and NO.2,(KClO₃(52.2%)/CuO(26.0%)/S(9.6%)/Mg-Al(3.5%)/C₆Cl₆(4.35%)) are studied using Accelerating Rate Caorimeter (ARC).Temperature vs time curve and pressure vs time curve of reactions are shown in Fig.1 and Fig.2 respectively.The basic data including reaction time(1.3 and 7.3 min respectively),initial temperature (159 and 150℃ respectively),temperature at the maximum rate(272 and 272℃ respectively),the maximum pressure (420 and 190kPa respectively) and the activation energies(175.6 and 135.2 kJ mol-1 respectively) of the thermal decomposition are given to evaluate the safety of the two systems.Results indicate that system NO.2 is safer than NO.1.Compared with the traditional methods,ARC technique can be used to measure temperature and pressure of exothermic reaction concurrently,to find the tiny exothermicity and to determine the initial temperature of exothermic reaction.     

Photooxidation of a Twisted Isoquinolinone

Understanding the oxidation mechanism and positions of twistacenes and twistheteroacenes under ambient conditions is very important because such knowledge can guide us to design and synthesize novel, larger stable analogues. Herein, we demonstrated for the first time that a twisted isoquinolinone can decompose under oxygen and light at room temperature. The as‐decomposed product 1 was fully characterized through conventional methods as well as single‐crystal structure analysis. Moreover, the physical properties of the as‐obtained product were carefully investigated and the possible formation mechanism was proposed.     

Hierarchical MoS2@TiO2 Heterojunctions for Enhanced Photocatalytic Performance and Electrocatalytic Hydrogen Evolution

Hierarchical MoS₂@TiO₂ heterojunctions were synthesized through a one‐step hydrothermal method by using protonic titanate nanosheets as the precursor. The TiO₂ nanosheets prevent the aggregation of MoS₂ and promote the carrier transfer efficiency, and thus enhance the photocatalytic and electrocatalytic activity of the nanostructured MoS₂. The obtained MoS₂@TiO₂ has significantly enhanced photocatalytic activity in the degradation of rhodamine B (over 5.2 times compared with pure MoS₂) and acetone (over 2.8 times compared with pure MoS₂). MoS₂@TiO₂ is also beneficial for electrocatalytic hydrogen evolution (26 times compared with pure MoS₂, based on the cathodic current density). This work offers a promising way to prevent the self‐aggregation of MoS₂ and provides a new insight for the design of heterojunctions for materials with lattice mismatches.     

Analysis of Protein Moiety of Polysaccharide Conjugates Water-extracted from Low Grade Green Tea

Tea polysaccharide conjugates(TPCs) were water-extracted and purified from low-grade green tea. Although TPC contains 1.97% covalent binding proteins, Coomassie brilliant blue G250 and R250 could not detect this protein. The "should-shape" absorption peak observed at 250-280 nm in the UV-Vis spectrum was caused by quinone compounds derived from polyphenol oxidation during TPC extraction. The UV-Vis spectrum could be used to detect the decolorizing degree of TPC. TPC aqueous solution merely presented the negative charge properties of its polysaccharides instead of the acid-base property of its protein section, and exhibited higher stability at pH greater than 5.0. No precipitation or haze occurred in three TPC/epigallocatechin gallate(EGCG) aqueous mixtures during 12 h storage. TPC had emulsifying activity, which indicated that its protein moiety formed hydrophobic groups. It is proposed that some of the physicochemical properties of the TPC protein moiety are shielded by its polysaccharide chain.