Concomitant polymorphism of an antiferromagnetically coupled dicopper(II,II) complex with single strand helical assembly: Synthesis,structure, DSC,magnetic and heterogeneous catalytic studies

Two concomitant polymorphic coordination complexes (dark blue – I and black – II) with the formula (Cu₂C₄₄H₆₀N₄O₄) have been synthesized and characterized crystallographically. Magnetic measurements show the presence of a strong antiferromagnetic interaction and the 2J value corresponds extremely well to the theoretically calculated one, indicating the fact that it follows nicely the magneto-structural relationship. Immobilization of the copper(II) complex 1 on a 2D-hexagonal mesoporous silica showed good catalytic efficiency in the liquid phase partial oxidation of olefins in the presence of TBHP as an oxidant.     

蛋黄-壳结构Fe3O4@SiO2@PMO磁性微球的制备及对漆酶的固定化

以蛋黄-壳结构的Fe₃O₄@SiO₂@PMO磁性微球作为载体, 采用交联法对漆酶进行固定, 考察了戊二醛浓度等对固定效果的影响, 并对固定后漆酶的活性进行了研究. 结果表明, 蛋黄-壳结构的磁性微球负载漆酶仅需6 h, 磁性微球对漆酶的固载量高达475 mg/g. 固定后漆酶的稳定性显著提高, 在pH=2.5~4.5的强酸性条件下, 固定后漆酶酶活仍可保持70%以上, 即使温度升高至60 ℃, 固定后漆酶的相对酶活仍保持65%以上. 这说明漆酶经所合成的材料固定后, 其耐酸和耐热能力都明显优于游离漆酶. 包覆的Fe₃O₄粒子使得材料很容易经磁铁分离法回收, 固定后漆酶经磁分离循环使用10次后仍然能保留85%的酶活, 具有良好的可操作性和稳定性, 有效降低了漆酶的使用成本.     

Wang Resin-supported Enantioselective Catalysts for the Asymmetric Michael Additions ofAcetone to β-Nitroolefins

Two Wang resin-supported (1R,2R)-(+)-1,2-DPEN(DPEN=diphenylethylenediamine) catalysts were synthesized from cyanuric chloride and trimesoyl chloride, respectively. These two catalysts were characterized by FTIR, TGA and elemental analysis. The results demonstrated that (1R,2R)-(+)-1,2-DPEN was successfully bonded to the surface of Wang resin through the amido linkage. Subsequently, the asymmetric Michael addition of acetone to β-nitrostyrene was employed to evaluate their catalytic performance. It was found that the catalyst generated from trimesoyl chloride exhibited much better catalytic behavior than our previously reported catalyst, likely attributed to the multiple hydrogen-bond interaction between β-nitrostyrene and amide group, which made the catalytic transition intermediates more stable. Under the optimal conditions, 76.1% β-nitrostyrene conversion and 93.8% enantioselectivity were obtained. Finally, the generality of this catalyst was examined with Michael additions of acetone to β-nitroolefins and excellent enantioselectivities(91.9% to 99.9%) were achieved.     

环氧基修饰周期性介孔有机氧化硅对漆酶的固定化作用

以三嵌段共聚物P123为模板剂, 在酸性条件下通过1,2-三乙氧基硅基乙烷(BTESE)和3-含氧缩水甘油基-丙基-三甲氧基硅烷(GPTMS)共水解缩聚合成环氧基修饰的周期性介孔氧化硅(PMOs), 以修饰后的PMOs为载体对漆酶进行固定化, 研究了环氧基修饰对固定化酶稳定性的影响. 通过XRD、TEM、固态NMR和N₂吸附等手段表征材料的修饰效果、孔结构以及漆酶的固定化. 结果表明, 修饰后的材料保持良好的孔结构, 环氧基的修饰有利于提高固定化酶的活力, 基于环氧基修饰PMOs的固定化酶具有较高稳定性.     

Synthesis and solid state NMR characterization of novel peptide/silica hybrid materials

The successful synthesis and solid state NMR characterization of silica-based organic–inorganic hybrid materials is presented. For this, collagen-like peptides are immobilized on carboxylate functionalized mesoporous silica (COOH/SiO_x) materials. A pre-activation of the silica material with TSTU (O-(N-Succinimidyl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate) is performed to enable a covalent binding of the peptides to the linker. The success of the covalent immobilization is indicated by the decrease of the ¹³C CP-MAS NMR signal of the TSTU moiety. A qualitative distinction between covalently bound and adsorbed peptide is feasible by ¹⁵N CP-MAS Dynamic Nuclear Polarization (DNP). The low-field shift of the ¹⁵N signal of the peptide's N-terminus clearly identifies it as the binding site. The DNP enhancement allows the probing of natural abundance ¹⁵N nuclei, rendering expensive labeling of peptides unnecessary.     

Resolution of Ibuprofen Catalyzed with Free and Immobilized Lipases

Enzymatic hydrolyses of ibuprofen esters produced 99% optically pure S-(+)-ibuprofen. The ee values of two enantiomers of ibuprofen were determined on a HPLC equipped with a chiral column.     

Separation and determination of molybdenum by inductively coupled plasma optical emission spectrometry using quercetin immobilization on silica gel

A new method is described for the separation of molybdenum based on its chelation in a column packed with quercetin, immobilized on silica gel in a slightly acidic medium (pH 5.0). Recovery ranged from 95% (NIST 1515 apple leaves) to 99% (deionized, distilled water; DDW) with an absolute blank of 27.5±1.6 pg obtained for the analysis of DDW. Detection limits, absolute and relative, based on a 5.0-ml sample volume were 4.8 pg and 1 ng l⁻¹, respectively. Results are presented for molybdenum determination in two standard reference materials, NIST 1515 and NIST 1547 peach leaves, using simple calibration curves for quantification. α-Benzoinoxime was used as the eluent.     

Reactive oxygen species, cell growth, and taxol production of Taxus cuspidata cells immobilized on polyurethane foam

Dynamic changes in reactive oxygen species (ROS) of Taxus cuspidata cells immobilized on polyurethane foam were investigated and the relation between ROS content and taxol production was discussed. Immobilization shortened the lag period of cell growth and moderately increased H₂O₂ and O₂ ^−• contents inside the microenvironment within the first 15 d. After 20 d, excessive production of H₂O₂ and O₂ ^−• was observed accompanied by marked increases in membrane lipid peroxidation and cell membrane permeability. The taxol content of immobilized cells was fourfold that of suspended cells at d 35. The addition of exogenous H₂O₂ barely affected malondialdehyde content and cell membrane permeability but led to an obvious accumulation of taxol. It is inferred that the intracellular and extracellular H₂O₂ inside the microenvironment might be one factor promoting taxol biosynthesis under the immobilization stress.     

Preparation and characteristics of two new GC stationary phases-dihydroxy crown ether containing polysiloxane

Summary Two new kinds of crown ethers: 3,5-dibutyl-unsymmetrydibenzo-14-crown-4-dihydroxy (cis-, and trans-) with the OH-terminal silicone oil in different proportion were coated on glass capillary columns, and immobilized by condensation using a coupling agent of alkyltrimethoxysilane. Chromatographic characteristics, including column efficiency, polarity, selectivity, phase transition temperature and thermal stability were studied. The columns were compared with PEG-20M in terms of polarity and selectivity. The immobilization and retention mechanisms are also discussed.     

聚苯胺葡萄糖氧化酶电极的催化过程

用电化学方法固定在直径为0.5mm铂丝上的聚苯胺(PANI)葡萄糖(GOD)电极对葡萄糖有催化氧化作用.在0～-0.6V(vs.SCE)的电极范围内,在电极的循环伏安曲线上观察到与葡萄糖浓度有关的氧的还原峰和GOD还原态的氧化峰,用此GOD还原态的氧化峰电流可定量检测葡萄糖的浓度。本文提出在PANI电极上存在着酶反应氧化还原电荷直接传递的可能性。