直接氧化法合成维生素E中间体2,3,5-三甲基氢醌

利用新的氧化剂体系醋酸—过氧化氢—盐酸，通过直接氧化法合成得到纯度大于９８％的２，３，５ 三甲基氢醌。在氧化反应中，以石油醚为溶剂，反应物料醋酸、过氧化氢、盐酸与２，３，６ 三甲基苯酚摩尔比为６５∶６５∶２５∶１，在回流状态下反应１～１５ｈ，２，３，５ 三甲基氢醌的产率为５４６％。     

交联菲罗啉负载铜催化剂用于合成三甲基苯醌

烷基取代的苯醌可用作多种生物活性化合物的功能结构单元。提出了一种在温和条件下，用氧气氧化2,3,6-三甲基苯酚（TMP）得到2,3,5-三甲基-1,4-苯醌（TMQ，维生素E前体）的方法。利用Friedel-Crafts烷基化反应，成功制备了一种基于1,10-菲罗啉的交联多孔聚合物负载铜催化剂Cu/PPhen。采用氮气吸附脱附、SEM、FTIR和XPS对催化剂Cu/PPhen-4进行了一系列的表征，获得了催化剂的基本结构特征。并考察了催化剂的加入量、溶剂、氧气压力、反应温度以及反应时间等因素对Cu/PPhen-4催化氧化制备2,3,5-三甲基-1,4-苯醌的影响，得到最佳的工艺条件。当2,3,6-三甲基苯酚的加入量为136 mg时，催化剂量为150 mg，乙腈量为2 ml，0.5 MPa的氧气，40℃下反应4 h，2,3,5-三甲基-1,4-苯醌的收率可以达到99%。催化剂Cu/PPhen-4具有较好的稳定性，可以回收至少五次，活性几乎没有下降。     

Removal of Persistent Sulfamethoxazole and Carbamazepine from Water by Horseradish Peroxidase Encapsulated into Poly(Vinyl Chloride) Electrospun Fibers

Enzymatic conversion of pharmaceutically active ingredients (API), using immobilized enzymes should be considered as a promising industrial tool due to improved reusability and stability of the biocatalysts at harsh process conditions. Therefore, in this study horseradish peroxidase was immobilized into sodium alginate capsules and then trapped into poly(vinyl chloride) electrospun fibers to provide additional enzyme stabilization and protection against the negative effect of harsh process conditions. Due to encapsulation immobilization, 100% of immobilization yield was achieved leading to loading of 25 μg of enzyme in 1 mg of the support. Immobilized in such a way, enzyme showed over 80% activity retention. Further, only slight changes in kinetic parameters of free (K_m = 1.54 mM) and immobilized horseradish peroxidase (K_m = 1.83 mM) were noticed, indicating retention of high catalytic properties and high substrate affinity by encapsulated biocatalyst. Encapsulated horseradish peroxidase was tested in biodegradation of two frequently occurring in wastewater API, sulfamethoxazole (antibiotic) and carbamazepine (anticonvulsant). Over 80% of both pharmaceutics was removed by immobilized enzyme after 24 h of the process from the solution at a concentration of 1 mg/L, under optimal conditions, which were found to be pH 7, temperature 25 °C and 2 mM of H₂O₂. However, even from 10 mg/L solutions, it was possible to remove over 40% of both pharmaceuticals. Finally, the reusability and storage stability study of immobilized horseradish peroxidase showed retention of over 60% of initial activity after 20 days of storage at 4 °C and after 10 repeated catalytic cycles, indicating great practical application potential. By contrast, the free enzyme showed less than 20% of its initial activity after 20 days of storage and exhibited no recycling potential.     

Immobilization of horseradish peroxidase on chitosan for use in nonaqueous media

Chitosan, a natural polysaccharide, was used for the covalent immobilization of horseradish peroxidase, an enzyme of high synthetic utility, with the carbodiimide method. Of the enzyme, 62% was immobilized on chitosan when 1‐ethyl‐3‐(3‐dimethylaminopropyl carbodiimide) was used as the peptide coupling agent. The influence of different parameters, such as the enzyme concentration, carbodiimide concentration, and incubation period, on the activity retention of the immobilized enzyme was investigated. Kinetic studies using horseradish peroxidase immobilized on chitosan revealed the effects of several parameters, such as the substrate hydrophilicity and hydrophobicity, the solubility of substrates in the medium, the solvent hydrophobicity, and the support aquaphilicity, on the catalytic activity of the immobilized enzyme in nonaqueous media. General rules for the optimization of solvents for nonaqueous enzymology based on the partitioning of the solvent were not applicable for the immobilized horseradish peroxidase. The catalytic efficiency was greatest when o‐phenylene diamine was used as the substrate and least when guaiacol was used. The aquaphilicity of the support played an important role in the kinetics of the immobilized horseradish peroxidase in water‐miscible solvents. The results were promising for the future development of chitosan‐immobilized enzymes for use in organic media. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1456–1464, 2003     

Peroxidation of free and esterified fatty acids by horseradish peroxidase

Linoleic and arachidonic acids and unsaturated esterified fatty acids of soybean lecithin liposomes were oxidized by horseradish peroxidase in the presence of hydrogen peroxide. The major products formed in the presence of oxygen were fatty acid hydroperoxides. In the absence of oxygen, other unidentified products were formed. Diene conjugation was about 5 times faster in oxygen than in nitrogen. Malondialdehyde was formed only in the presence of oxygen. Superoxide, singlet oxygen and hydroxyl radical may have been involved in the free fatty acid oxidation system but not in the liposome system. Replacement of hydrogen peroxide with the hydrogen peroxide (and superoxide) generators xanthine oxidase or galactose oxidase caused a more efficient oxidation in the presence of peroxidase than in its absence, suggesting that the in vivo toxicity of hydrogen peroxide and superoxide may be greatly increased in the presence of peroxidase.     

离子液体催化氧化2,3,6-三甲基苯酚合成2,3,5-三甲基苯醌

研究了离子液体作为助催化剂催化氧化2,3,6-三甲基苯酚合成2,3,5-三甲基苯醌的反应。催化剂CuCl₂和MnCl₂的用量分别为2,3,6-三甲基苯酚物质的量的10%,助催化剂离子液体1-丁基-3-甲基咪唑四氟硼酸盐用量为2,3,6-三甲基苯酚物质的量的20%,空气中的氧气为氧化剂, 80 ℃反应4 h,转化率100%,选择性92.60%。在后处理过程中,离子液体易于分离和回收利用,为工业合成2,3,5-三甲基苯醌提供了一种较好的选择。     

A new environmentally friendly method for the production of 2,3,5-trimethyl-p-benzoquinone

A new environmentally friendly method for the production of 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, Vitamin E precursor) based on the oxidation of 2,3,6-trimethylphenol (TMP) with aqueous H₂O₂ over various Ti-containing mesoporous silicate materials is reported. Both well-organized Ti-containing mesoporous mesophase silicate (Ti-MMM), having hexagonal arrangement of uniform mesopores, and amorphous TiO₂–SiO₂ mixed oxides (aerogels and xerogels) produced TMBQ with good to high yield. All the materials studied have been proved to operate as truly heterogeneous catalysts. No titanium leaching occurred from the solid matrixes during the oxidation process. Titanium dispersion and its accessibility were found to be crucial factors determining the catalytic properties. For samples with similar titanium loading, both the catalytic activity and TMBQ yield appeared to fall in the order TiO₂–SiO₂ aerogel>Ti-MMM>TiO₂–SiO₂ xerogel and correlate with average mesopore diameter and mesopore volume. The best results (96–98% selectivity to TMBQ at 99–100% TMP conversion) were obtained with TiO₂–SiO₂ aerogels, containing 1.7–6.5 wt.% Ti.     

酶偶联分光光度法测定胞内黄嘌呤氧化酶活性

建立了新的酶反应体系显色分光光度法检测节杆菌胞内黄嘌吟氧化酶的活性。考察了温度、pH值和底物浓度对检测体系的影响,确定了黄嘌呤氧化酶活性检测的最优条件,获得了良好的检测线性关系。此检测方法操作简便,结果准确可靠,可作为普通实验室和临床上测定黄嘌呤氧化酶活性的有效生化手段。     

Horseradish peroxidase‐catalysed oxidation of aqueous natural and synthetic oestrogens

The horseradish peroxidase (HRP)‐catalysed oxidation of selected potent oestrogens, including the natural oestrogens 17β‐oestradiol and oestriol and the synthetic oestrogen ethinyloestradiol, was studied and compared with that of phenol. HRP catalysed the oxidation of these oestrogens and phenol over a wide range of pH values, with optimal performance around neutral pH, which is in the range of typical urban wastewaters. In comparison with that of phenol, the oxidation of oestrogens consistently required less hydrogen peroxide. In addition, the rate of oxidation of oestradiol was equivalent, twofold faster and fivefold faster compared with that of ethinyloestradiol, oestriol and phenol respectively. For all substrates studied, similar kinetics of removal were observed provided that sufficient enzyme was added to reactions to compensate for differences in substrate affinity. In contrast with earlier studies with phenols in which HRP was observed to be susceptible to significant inactivation due to interactions with hydrogen peroxide and reaction products, minimal inactivation of HRP was observed during the present study, probably owing to the very low concentration of target substrates used here (i.e. 10 µmol dm^?3) relative to earlier studies with other phenolic substrates. These observations suggest that this enzymatic approach has strong potential to be used to target the treatment of oestrogenic compounds. Copyright © 2007 Society of Chemical Industry     

间苯二酚和3,5-二羟基苯甲酸共聚物的酶促合成与表征

在辣根过氧化物酶(HRP)/H2O2的催化体系下,间苯二酚(RSC)和3,5-二羟基苯甲酸(DBA)进行自由基聚合反应,制备了合成鞣剂。研究了单体配比以及反应各因素对共聚物性能的影响。结果表明,在间苯二酚和3,5-二羟基苯甲酸的摩尔配比为2∶1、反应温度为35℃、pH值为7.0、H2O2的滴加时间为90 min时,合成反应具有较高的产率。用红外光谱(FTIR)、核磁共振光谱(NMR)和凝胶渗透色谱(GPC)对聚合产物的结构和性能进行了表征。提出了RSC和DBA的自由基聚合反应机理。应用结果表明,聚合产物具有较好复鞣和助染性能。     

2,3,6-三甲基苯酚一步氧化制备2,3,5-三甲基-1,4-苯醌研究进展

2,3,6-三甲基苯酚一步氧化制备2,3,5-三甲基-1,4-苯醌相对于传统的磺化-氧化法具有产品收率高、过程简单、条件温和以及环境友好等特点。本文针对2,3,6-三甲基苯酚一步氧化制备2,3,5-三甲基-1,4-苯醌的均相催化氧化和非均相催化氧化工艺进行了综述,对两种工艺的发展过程及研究现状进行了评价及总结。详细讨论了不同方法和路线在催化活性、选择性以及产品分离和催化剂回收等方面的优缺点,简要分析并总结了2,3,6-三甲基苯酚一步氧化研究的发展规律和最新动态,展望了以非均相催化反应机制为重点的微观机理研究和以提高催化剂循环稳定性、降低制备成本为重点的工业化探索两个潜在的发展方向。     

Toxicity of soluble products from the peroxidase‐catalysed polymerization of substituted phenolic compounds

The residual toxicities of aqueous solutions of phenol and substituted phenols were investigated following polymerization under the catalytic action of soybean peroxidase (SBP) and horseradish peroxidase (HRP) enzymes. The treated mixtures obtained from the enzymatic polymerization of these phenols were usually significantly more toxic than expected, and in several cases, the residual toxicity exceeded the initial toxicity of the solution of untreated parent compound. However, this residual toxicity tended to be lower when combinations of these phenols were co‐polymerized. The decrease in toxicity was attributed to the different polymeric products which form as a result of a cross‐coupling between products of the enzyme‐catalysed oxidation of parent phenols. The residual toxicities obtained using either SBP or HRP were not significantly different in most cases. © 2000 Society of Chemical Industry     

Understanding the formation of CuS concave superstructures with peroxidase-like activity

Copper sulfide (CuS) concave polyhedral superstructures (CPSs) have been successfully prepared in an ethanolic solution by a simple solvothermal reaction without the use of surfactants or templates. Two typical well defined, high symmetry CuS concave polyhedrons, forming a concave truncated cuboctahedron and icosahedron were prepared. The effect of the reaction time, temperature and different Cu ion and sulfur sources on the formation of CuS CPSs were investigated and a possible formation mechanism was proposed and discussed based on gas chromatography-mass spectrometry. More importantly, we found, for the first time, that the CuS CPSs exhibit intrinsic peroxidase-like activity, as they can quickly catalyze the oxidation of typical horseradish peroxidase (HRP) substrates, 3,3',5,5'-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD), in the presence of hydrogen peroxide. In addition to the recent discoveries regarding peroxidase mimetics on Fe(3)O(4) NPs and carbon nanostructures, our findings suggest a new kind of candidate for peroxidase mimics. This may open up a new application field of CuS micro-nano structures in biodetection, biocatalysis and environmental monitoring.     

Synthesis and characterization of poly(catechol) catalyzed by porphyrin and enzyme

Catalytic polymerization of catechol was performed employing the cationic porphyrin and horseradish peroxidase (HRP) as catalysts. The obtained results demonstrate that the cationic metalloporphyrin is a more-efficient catalyst than the HRP in the catechol polymerization. The oxidative polymerization was carried out in the presence of polystyrene sulfonate (PSS) as a template. According to TGA data, poly(catechol) that is synthesized by porphyrin catalyst exhibits more thermal stability than the enzymatic catalyzed product. The GPC indicate higher molecular weight of polymer synthesized by porphyrin as a catalyst. Cyclic voltammetry measurements show that the synthesized polymers have convenient electroactivity. The poly(catechol) and its methyl and methoxy derivatives that are synthesized by porphyrin catalyst show low electrical conductivity.     

表面等离子体共振技术对过氧化氢的检测

表面等离子体激元共振技术是一种通过观察芯片金属薄膜表面厚度变化产生信号的光学技术,具有实时、灵敏度高、免标记等优点,本文通过辣根过氧化物酶的酶催化作用对过氧化氢进行实时快速检测。信号强度与过氧化氢浓度呈线性关系,辣根过氧化物酶共价结合至金膜表面保持了酶的活性。和其它方法相比较,该方法为过氧化氢的检测提供了一种选择。     

How to reach 100% selectivity in H2O2-based oxidation of 2,3,6-trimethylphenol to trimethyl-p-benzoquinone over Ti,Si-catalysts

A comprehensive study of structure/activity/selectivity relationships and mechanistic aspects of the oxidation of 2,3,6-trimethylphenol (TMP) with aqueous H₂O₂ over a wide variety of titanium-silicate catalysts allowed us to infer requirements to an optimal catalyst and optimal reaction conditions for this reaction and to produce 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, Vitamin E precursor) with nearly 100% selectivity at 100% substrate conversion. The main by-products in the TMP oxidation are C–C and C–O dimers, formed by coupling of intermediate phenoxyl radicals. The formation of TMBQ is favoured by (1) a poor coordinating solvent (MeCN), (2) elevated temperature (80 °C), (3) low TMP concentration (not higher than 0.1 M), (4) high H₂O₂/TMP molar ratio (ca. 3.5), and (5) low TMP/Ti ratio (<10–20). The crucial factors which determine the selectivity of Ti,Si-catalysts in TMP oxidation to TMBQ are mesoporosity and an optimal surface concentration (ca. 0.7–1.0 Ti atoms/nm²) of accessible highly dispersed, probably, dimeric Ti(IV) species. The catalysts prepared by a simple, affordable and cheap synthesis methodology via grafting titanium(IV) precursors onto the surface of commercial mesoporous silica completely fulfil these requirements and thus can be viewed as promising catalysts for environmentally benign TMBQ production.     

Ni-Cr-Co氧化物纳米催化剂对甲醇阳极氧化的电催化性能研究

采用了热分解法合成Ni-Cr-Co氧化物纳米粒子,并用作直接甲醇燃料电池(DMFC)的阳极电催化剂。通过X射线衍射(XRD)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)对催化剂进行表征,制得的纳米催化剂均匀分散,且粒径为25~50 nm。利用循环伏安法(CV)对不同金属摩尔比和焙烧温度下的催化剂在甲醇氧化反应中的活性进行了研究。结果表明,Ni-Cr-Co(摩尔比为1∶1∶1.5)的纳米氧化物对甲醇氧化反应的起始电位、峰值氧化电流密度和If/Ib分别为0.38 V,19.3 mA/cm2和1.72,表现了很好的电催化性能。     

Enzyme immobilization on polyglycidylmethacrylate graft-copolymer of different polysaccharides

Comparative results obtained in preparing and characterizing samples of enzymes immobilized by reaction with polyglycidylmethacrylate (PGMA) copolymers with different polysaccharide matrices are reported. Sepharose copolymers having between 25 and 50% synthetic polymer were used to find the best immobilization conditions of horseradish peroxidase (HRP) and glucose-oxidase (GOD) (pH, time, temperature, enzyme cncentration). Activity, enzyme loading and coupling efficiency of immobilized HRP and GOD are greatly dependent on the type of matrix while the polymer content is less important. Coupling efficiencies between 0.8 and 1.5% have been obtained for HRP samples, whereas for GOD samples coupling efficiencies three times greater were obtained. HRP and GOD immobilized samples show K_m′ values greater than those of corresponding free enzymes and this indicates diffusion limitation phenomena. Storage, thermal and operational stability were also studied. In general the storage stability could be considered satisfactory (50% residual activity after 360 days). Sepharose and starch HRP-copolymers had an improved thermal stability compared with that of free enzyme. Residual activity found in continuous operation tests carried out on HRP-immobilized samples turned out to be dependent on support. HRP-PGMA-Cellulose sample gave the best results (50% residual activity after 16 days). PGMA-graft-copolymers have also been used to immobilize other enzymes such as α-amylase, α-chymotrypsin and cellulase.     

Polyallylamine-conjugated thermo-responsive polymers for the rapid removal of phenolic compounds from water

Polyallylamine-conjugated thermo-responsive polymer (PNIPAAm-PAA) was readily prepared by the condensation of polyallylamine and poly(N-isopropylacrylamide-co-acrylic acid) with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The synthesized polymer was water-soluble below the lower critical solution temperature (LCST, ca. 34 °C) but deposited to form a condensed coagulate by heating the solution above the LCST. In the presence of phenol oxidation enzymes, phenolic compounds was oxidized and spontaneously bound to the amino group of PNIPAAm-PAA. Almost complete removal of 300 mg l⁻¹ phenol was achieved by the use of 1 g l⁻¹ PNIPAAm-PAA. However, long time was required for the oxidation of phenol by using mushroom tyrosinase. On the other hand, combined use of horseradish peroxidase and hydrogen peroxidase allowed rapid phenol removal. Furthermore, the proposed method was applicable to the removal of a wide range of phenolic compounds including estrogenic hormones. The applicability to wastewater treatment was successfully demonstrated using spiked effluents.     

A sensitive biosensor for cyanide detection using modified glassy carbon electrode with reduced graphene oxide and immobilization of horseradish peroxidase

Cyanide is a highly poisonous and hazardous substance which may release into the environment from natural sources or industrial effluent; therefore, cyanide detection is a fundamental step to prevent environmental pollution and secure health and safety. In this study, we prepared a sensitive amperometric inhibition biosensor for cyanide detection by immobilization of horseradish peroxidase (HRP) enzyme and reduced graphene oxide (rGO) on the surface of glassy carbon electrode (GCE). To do so, we performed the amperometric measurement by modified GCE to test its efficiency in detecting cyanide. The optimum conditions of pH equal to 7.5, −100 mV applied potential, 0.7 μM mediator concentration, and 0.5 mM substrate concentration were found. Then, experiments were performed at different boundary conditions in a range of 0.1 to 10 μM cyanide concentration at optimal conditions and a low detection limit of 0.01 μM was obtained. Also, the possible mechanism of inhibition was analyzed based on the Michalis–Menten equation and non-competitive inhibition was observed. Due to high sensitivity, low detection limit, and low cost, this biosensor is proposed as a useful method for cyanide determination in real samples.