Using europium(III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7-triacedic acid Eu.DO3A as a luminescent sensor for bicarbonate

Sensing of analytes in biological fluids and biotechnological production media remains a challenge. Here, the luminescent response of the europium (III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) to bicarbonate was investigated in detail. The response of Eu.DO3A to changes in bicarbonate concentration was studied in different buffers, and the influence of ionic strength, pH, and specific ions was determined. The response is found to depend on pH and ionic strength, but it is not possible to separate contributions from the sensing event from those in the bicarbonate activity. Prior to demonstrating the ability to determine the bicarbonate concentration in bioproduction media and serum, the influence of competing carboxy anions was evaluated. It is established that while competing anions bind stronger to the responsive complex, at the relevant concentration their contribution to the recorded signal is negligible. We are thus able to conclude that Eu.DO3A is a good platform for building a bicarbonate sensor.     

Pillarquinones and Pillararenequinones

Pillar[n]quinones and pillar[n-m]arene[m]quinones are oxidation products of pillar[n]arenes. Their molecular structure resembles the parent compounds. However, their map of electron density is different. Each 1,4-benzoquinone ring, which replaces a 1,4-dialkoxy-substituted benzene ring decreases the electron density in the interior cavity and increases the electron density on the upper and lower rim of the pillar. The electron donor character is stepwise transformed to an electron acceptor status. This effect alters the complexation tendencies, which are the most interesting properties of these macrocyclic host systems.     

资本的疯狂——对当前城市中心区城市综合体建设的思考

随着我国城市建设的发展,城市综合体成为了地方政府和开发商热烈追捧的对象,有些地方甚至打出了"谁拥有城市综合体,谁就拥有城市未来"的口号。在这口号式的标语背后,隐藏着的却是一场城市综合体的"疯狂"扩张,而造成这种局面的原因无疑是资本的力量。该文分析了城市综合体建设的不同区段及其所产生的效应,讨论了城市综合体背后的资本驱动,指出了由此带来的诸多不利影响,进而借鉴发达国家和地区城市综合体的建设经验,展望我国城市综合体的发展趋势。     

Rheological Characterization of MR Polishing Fluid Used for Silicon Polishing in BEMRF Process

The finishing mechanism of the ball-end magnetorheological finishing (BEMRF) process mainly depends on the stiffened hemispheroid, which is formed at the tool tip. Magnetorheological (MR) polishing fluid imparts strength to the polishing spot because of the effect of magnetic field strength. Behavior of this polishing fluid mainly depends on the size and shape of its constituents, volume concentration, particle size distribution, and applied magnetic field strength. A detailed study was undertaken on the role of carbonyl iron particle (CIP) size on the rheological behavior of the MR polishing fluid under various magnetic flux densities. Evaluation of the behavior of MR polishing fluid for silicon polishing was attempted through designing and fabrication of a parallel-plate magnetorheometer. Rheological characterization study was carried out using the Casson fluid model and the MR polishing fluid rheological properties, namely field-induced yield stress and shear viscosity were evaluated.     

养殖对虾挥发性物质的分离与鉴定

本文对养殖对虾肌肉的主要挥发性物质进行了分析研究。应用捕集法和同时蒸馏萃取法提取煮熟养殖对虾(Penaeus orientalis)肌肉的挥发性气味物质,以气相色谱和GC-MS法分析得到主要的羰基化合物是乙醛,主要的含硫化合物是噻唑化合物。以模拟体系反应产物鉴定出2,4,6-三甲基-过氢-1,3,5-二噻嗪在虾气味中存在。     

罗非鱼皮蛋白多肽-Fe2＋结合物的制备及性质分析

以罗非鱼皮为原料,采用5?种蛋白酶对其进行酶解,以罗非鱼皮酶解物多肽（tilapia skin protein peptides,TSPP）的Fe2＋结合率为指标,筛选出Fe2＋结合率最高的TSPP;探究结合时间、pH值、温度对结合率的影响以及TSPP结合Fe2＋前后其荧光、紫外、红外等光谱的变化;对TSPP的分子质量分布、氨基酸的组成及其抗氧化活性进行测定。结果表明,罗非鱼皮蛋白经胰蛋白酶水解2?h后得到的TSPP,其Fe2＋结合率最高;pH?5、温度37?℃、时间90?min为最佳结合条件;TSPP结合Fe2＋后,肽链发生折叠,其内源性荧光强度下降,紫外特征性吸收带出现红移,肽链中的氨基、羰基、羧基可能是Fe2＋的结合位点;TSPP中的Fe2＋结合活性肽,其分子质量大约在500～3?000?Da之间,且肽链富含Asp、Glu、Gly、Arg及Pro等氨基酸;各酶解物均具有一定的抗氧化能力,TSPP结合Fe2＋前后,其抗氧化能力无显著性变化;此外,虽然TSPP的抗氧化能力明显低于谷胱甘肽,但其Fe2＋结合活性明显高于谷胱甘肽。结果显示,TSPP具有良好的Fe2＋结合活性,有望发展为新型的铁元素膳食补充剂。     

Spectroscopic behavior of some a(3)b type tetrapyrrolic complexes in several organic solvents and micellar media

The paper presents spectral studies of some unsymmetrical A(3)B tetrapyrrolic, porphyrin-type complexes with Cu(II) and Zn(II) in different solvents and micellar media aimed at estimating their properties in connection with the living cell. The results indicate that the position of the absorption and emission peaks is mostly influenced by the central metal ion and less by the environmental polarity or the peripheric substituents of the porphyrinic core. The comparison between the overall absorption and emission spectra of the compounds in methanol or cyclohexane vs. direct and reverse Triton X micellar systems, respectively, suggests for all compounds the localization at the interface between the polyethylene oxide chains and the tert-octyl-phenyl etheric residue of the Triton X-100 molecules. These findings could be important when testing the compounds embedded in liposomes or other delivery systems to the targeted cell.     

Highly unsaturated binuclear butadiene iron carbonyls: quintet spin States, perpendicular structures, agostic hydrogen atoms, and iron-iron multiple bonds

The highly unsaturated binuclear butadiene iron carbonyls (C₄H₆)₂Fe₂(CO)_n (n = 2, 1) have been examined using density functional theory. For (C₄H₆)₂Fe₂(CO)_n (n = 2, 1), both coaxial and perpendicular structures are found. The global minima of (C₄H₆)₂Fe₂(CO)_n (n = 2, 1) are the perpendicular structures 2Q-1 and 1Q-1, respectively, with 17- and 15-electron configurations for the iron atoms leading to quintet spin states. The Fe=Fe distance of 2.361 Å (M06-L) in the (C₄H₆)₂Fe₂(CO)₂ structure 2Q-1 suggests a formal double bond. The Fe≡Fe bond distance in the (C₄H₆)₂Fe₂(CO) structure 1Q-1 is even shorter at 2.273 Å (M06-L), suggesting a triple bond. Higher energy (C₄H₆)₂Fe₂(CO)_n (n = 2, 1) structures include structures in which a bridging butadiene ligand is bonded to one of the iron atoms as a tetrahapto ligand and to the other iron atom through two agostic hydrogen atoms from the end CH₂ groups. Singlet (C₄H₆)₂Fe₂(CO) structures with formal Fe–Fe quadruple bonds of lengths ∼2.05 Å were also found but at very high energies (∼47 kcal/mol) relative to the global minimum.