Cu(II) immobilized on mesoporous organosilica as an efficient and reusable nanocatalyst for one‐pot Biginelli reaction under solvent‐free conditions

Cu(II) immobilized on mesoporous organosilica nanoparticles (Cu²⁺@MSNs‐(CO₂^?)₂) has been synthesized, as a inorganic–organic nanohybrid catalyst, through a post‐grafting approach. Its characterization is carried out by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy dispersive X‐ray (EDX), Thermogravimetric/differential thermal analyses (TGA‐DTA), and Nitrogen adsorption–desorption analysis. Cu²⁺@MSNs‐(CO₂^?)₂ exhibits high catalytic activity in the Biginelli reaction for the synthesis of a diverse range of 3, 4‐dihydropyrimidin‐2(1H)‐ones, under mild conditions. The anchored Cu(II) could not leach out from the surface of the mesoporous catalyst during the reaction and it has been reused several times without appreciable loss in its catalytic activity.     

Effective one-pot synthesis of tetrahydrobenzo[b]pyran derivatives using nickel Schiff-base complex immobilized on iron oxide nanoparticles

Nickel Schiff-base complex immobilized on silica-coated Fe₃O₄ as a heterogeneous catalyst was designed and characterized by different techniques, such as Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP) and vibrating sample magnetometry (VSM) thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET). The synthesized nanocatalyst has been explored as a new and efficient recyclable heterogeneous catalyst for the one-pot three-component synthesis of tetrahydrobenzo[b]pyran derivatives. The reaction proceeds smoothly to supply the respective products in excellent yields and low reaction times. The catalyst can be easily recovered by a magnetic field and reused for eight consecutive reaction cycles without significant loss of activity.     

Lipophilicity and bio‐mimetic properties determination of phytoestrogens using ultra‐high‐performance liquid chromatography

This paper presents lipophilicity and bio‐mimetic property determination of 15 phytoestrogens, namely biochanin A, daidzein, formononetin, genistein, genistein‐4,7‐dimethylether, prunetin, 3,4,7‐trihydroxyisoflavon, 4,6,7‐trihydroxyisoflavon, 4,6,7‐trimethoxyisoflavon, daidzin, genistin, ononin, sissotrin, coumestrol and coumestrol dimethylether. High‐performance liquid chromatography with fast gradient elution and Caco‐2 cell line were used to determine the physicochemical properties of selected phytoestrogens. Lipophilicity was determined on octadecyl‐sylane stationary phase using pH 2.0 and pH 7.4 buffers. Immobilized artificial membrane chromatography was used for prediction of interaction with biological membranes. Protein binding was measured on human serum albumin and α‐1‐acid‐glycoprotein (AGP) stationary phases. Caco‐2 assay was used as a gold standard for assessing in vitro permeability. The obtained results differentiate phytoestrogens according to their structure where aglycones show significantly higher lipophilicity, immobilized artificial membrane partitioning, AGP binding and Caco‐2 permeability compared with glucosides. However, human serum albumin binding was very high for all investigated compounds. Furthermore, a good correlation between experimentally obtained chromatographic parameters and in silico prediction was obtained for lipophilicity and human serum albumin binding, while the somewhat greater difference was obtained for AGP binding and Caco‐2 permeability.     

固定化过氧化物酶在过氧化物测定中的应用

采用聚丙烯酰胺凝胶迭氮法固定了辣根过氧化物酶，其作为催化剂用于荧光法测定过氧化物，并探讨了固定酶测定过氧化物的最佳条件，如溶液pH值、温度、反应时间、荧光剂用量等。结果表明：酶固定化后，反应pH值范围变宽，为pH5.0-7.0和7.5-9.0，最佳pH为7.8左右；酶的热稳定性与储存稳定性也都得到提高，在室温下便可用固定酶进行长时间测定，且可较长时间保存。采用固定酶制成的酶柱用于HPLC测定过氧化物，固定酶可反复使用，简化了测定操作，并降低了成本。     

有机相中脂肪酶催化合成乳酸乙酯

 考察了在双底物抑制下脂肪酶催化合成乳酸乙酯,最佳溶剂为叔丁醇,在所选的几种脂肪酶中,固定化于大孔丙烯酸树脂的南极假丝酵母脂肪酶B (Novozym 435)的催化活性最好. 对反应条件进行了优化,当酸醇摩尔比为1∶8, 反应温度60 ℃, 酸浓度0.3 mol/L, 酶浓度45 g/mol, 摇床转速200 r/min时产率达到77%, 脂肪酶Novozym 435重复使用6次后产率仍然可达到60%.     

无溶剂及微乳液体系中脂肪酶催化红花油水解的动力学

 在无溶剂及二(2-乙基己基)丁二酸酯磺酸钠(AOT)/异辛烷/磷酸盐缓冲液微乳液体系中,研究了黑曲霉脂肪酶催化红花油水解反应的动力学. 结果表明,无溶剂及微乳液体系中反应的活化能分别为32.205和7.391 kJ/mol. 酶在无溶剂体系中的热稳定性高于微乳液中. 无溶剂及微乳液体系中的表观米氏常数分别为0.135和0.101 mol/L. 在两种体系中,乙醇对水解反应的抑制作用均为竞争性可逆抑制,且均在底物浓度大于0.819 mol/L时出现底物抑制现象. 结合胶团催化理论和酯键水解机理对两种体系中酶水解性能的差异进行了解释.     

十二烷基苯磺酸/异辛烷微乳液中脂肪酶催化合成异丁酸异戊酯

在十二烷基苯磺酸(DBSA)/异辛烷微乳液中进行了脂肪酶催化合成异丁酸异戊酯的反应, 考察了微乳体系的含水量w₀、溶解酶缓冲溶液的pH值、反应温度等因素对酯合成反应转化率的影响; 与前期研究的CTAB微乳体系进行比较发现, DBSA微乳体系中的酯合成反应速率明显增加, 短时间内的转化率显著提高, 在温和条件下反应9 h后, 转化率达90%以上; 通过DBSA体系中有酶与无酶条件下反应进程的比较得知, DBSA作为一种质子酸对酯合成反应具有一定的催化能力; 提出了该体系中微乳催化、酶催化和质子酸催化的三重催化机理.     

Preparation of Immobilized Metal Affinity Chromatographic Packings Based on Monodisperse Hydrophilic Non‐porous Beads and Their Application

Three hydrophilic immobilized metal affinity chromatographic packings for HPLC have been synthesized by chemical modification of 3.0 µm monodisperse non‐porous poly(glycidyl methacrylate‐co‐ethylenedimethacrylate) (P_GMA/EDMA) beads. The retention behavior of proteins on the metal ion chelated columns loaded with copper(II), nickel(II) and zin(II) ion was studied. The effect of pH on the protein retention was investigated on both the naked and metal ion chelated columns in the range from 4.0 to 9.0. Four proteins were quickly separated in 3.0 min with linear gradient elution at a flow rate of 3.0 mL/min by using the synthesized Ni²⁺‐IDA (iminodiacetic acid) packings. The separation time was shorter than other immobilized metal affinity chromatography reported in the literature. Purification of lysozyme from egg white and trypsin on the commercially available trypsin was performed on the naked‐IDA and Cu²⁺‐IDA columns, respectively. The purities of the purified trypsin and lysozyme were more than 92% and 95%, respectively.     

铈基介孔金属有机骨架固定化酶的构建及催化性能

金属有机骨架(MOF)材料由于其孔隙率高、比表面积大以及具有发达的内联通孔道结构等优点,可以作为优良的生物分子固定化载体。通过表面活性自组装策略制备了铈基介孔MOF(Ce-MOF-F),表征结果表明,该材料有大的比表面积和呈辐射状的介孔孔道结构。以其为载体、南极假丝酵母脂肪酶B(CALB)为模型酶,通过物理吸附法制备了生物催化剂CALB@Ce-MOF-F,对该固定化酶的酶载量和催化性能进行了研究。在优化条件下,CALB的负载量为162.0mg/g载体,水解活性为899.1U/g蛋白。与游离CALB相比,CALB@Ce-MOF-F表现出对高温、酸碱和有机溶剂等有更强的耐受性;将Ce-MOF-F用于多种酶的固定化,研究其作为载体的普适性,结果表明,介孔Ce-MOF-F对洋葱伯克氏菌脂肪酶(BCL)和漆酶有良好的固定效果,可以作为良好载体,并能对酶起到较好的保护作用。