Immobilization of redox mediators on functionalized carbon nanotube: A material for chemical sensor fabrication and amperometric determination of hydrogen peroxide

Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) on graphite electrode was achieved by gently rubbing the electrode surface on carbon nanotubes supported on a glass slide. The electrochemical behaviour of the modified electrodes was investigated by cyclic voltammetry. The SWNT-modified electrodes showed excellent electrocatalytic effect for the reduction of hydrogen peroxide. A decrease in overvoltage was observed as well as an enhanced peak current compared to a bare graphite electrode for the reduction of hydrogen peroxide. The catalytic current was found to be directly proportional to the amount of hydrogen peroxide taken.     

含环氧基亲水性固定化青霉素酰化酶共聚载体的合成与性能研究

环氧基团可以在温和条件下与酶分子的氨基反应使其固定于载体表面.选用含有活性环氧基团的甲基丙烯酸缩水甘油酯(GMA)和亲水性的N-乙烯吡咯烷酮(NVP)两种单体,以N,N′-亚甲基双丙烯酰胺(MBAA)为交联剂,甲醇水溶液作致孔剂,液体石蜡为主介质,通过反相悬浮聚合技术成功地合成了亲水性大孔GMA-NVP-MBAA三元共聚物载体(GNM).通过调节交联剂的用量和单体NVP与GMA的比例,可以调节载体的孔径、比表面积及在水中的溶胀性能.将巨大芽孢杆菌青霉素酰化酶共价偶联于平均孔径为16.5nm、表面环氧基含量为0.906mmol/g的GNM共聚物载体,制成固定化酰化酶,其表观活性高达625U/g,水解青霉素G钾盐的最适宜温度为50℃,pH值为8.0.固定化酶在4℃保存40d,活性保持不变.经3次使用后,活性达到稳定值(601U/g左右),再经12次使用,活性几乎保持不变.     

硅胶及其衍生物作为基体的激光解吸离子化飞行时间质谱

制备了一种新型无机基体材料(硅胶及其衍生物)用于测定激光解吸离子化飞行时间质谱,建立了一种新的质谱分析方法,并用以解决传统MALDI-TOFMS存在的基体干扰问题.该法适合于低分子量化合物的分析.同时探讨了该新解吸离子化方法的机理.     

亲水金和憎水二氧化硅纳米颗粒对葡萄糖生物传感器响应灵敏度的增强作用

用亲水金、憎水二氧化硅纳米颗粒固定葡萄糖氧化酶(GOD),采用聚乙烯醇缩丁醛(PVB)为辅助固酶膜基质来制备葡萄糖生物传感器,并考察了亲水金、憎水二氧化硅纳米颗粒对酶电极电流响应的影响.实验表明,引入纳米粒子可显著增强电极响应灵敏度.并对两种不同性质纳米颗粒所起作用的可能机理进行讨论,从理论和实验上证明了纳米颗粒对固定酶的作用.为制备有实用价值的葡萄糖生物传感器提供了可供参考的实验和理论依据.     

STUDY ON THE IMMOBILIZATION OF PAPAIN WITH A MACROPOROUS BEAD CARRIER OF COPOLYMER CONTAINING MONOMER UNITS OF NAMINOETHYL ACRYLAMIDE AND VINYL ALCOHOL*

 A kind of macroporous bead carrier of copolymer containing monomer units of N-aminoethyl acrylamide and vinylalcohol was synthesized, i.e. the MR-AA carrier. Papain was immobilized on the carrier using glutaraldehyde as the couplingagent. The enzymatic activity of the immobilized papain was compared with free papain using casein as a substrate, and theeffects of glutaraldehyde concentration, pH, temperature, time and papain amount added on the activity recovery were alsoinvestigated. The results show that the MR-AA carrier contains reactive primary amine groups,hydrophilic amido links and hydroxyl groups,as well as macroporous structures based on its matrix (MR-AV matrix),furthermore,the activity recovery of papain in the immobilization could reach 48%～58%.In comparison with free papain,the resulting immobilized papain exhibits a remarkable thermostability and better reusability.     

Immobilization of Transition-metal Hydroxamates on Polystyrene Resins: Effective Biomimetic Heterogeneous Catalysts for Aerobic Oxidation of Ethylbenzene

Salicylhydroxamic acid(SHA) was covalently grafted onto chloromethylated crosslinked polystyrene spheres(CMCPS) by the Friedel-Crafts alkylation reaction. The amount of SHA on CPS was found to be mainly dependent on the amount of Lewis acid(SnCl₄) used and the reaction temperature. Under optimized conditions, the amount of SHA attached to CPS could reach up to 0.43 g/g CPS. Transition metal ions[Co(II), Cu(II), Fe(III) or Mn(II)] were then introduced into the resulting SHA-functionalized microspheres(SHA/CPS) through SHA-metal ion chelation. The obtained microspheres MSHA/CPS were explored as biomimetic catalysts for the aerobic oxidation of ethylbenzene(EB) to ethylbenzene hydroperoxide(EBHP). Among the four supported metal catalysts, FeSHA/CPS showed the highest catalytic activity and good reusability, indicating its great potential as an effective heterogeneous catalyst for the aerobic oxidation of hydrocarbons under mild conditions.     

Pu在Gd2Zr2O7基质中的模拟固化: (Gd1-xCex)2Zr2O7+x的热物理性能研究

采用高温固相反应,以NaF作助熔剂,在1000 ℃的温度下合成了锕系元素Pu的模拟固化体(Gd_1-xCe_x)₂Zr₂O_7+x (0 ≤ x ≤ 0.7).研究了模拟固化体的物相、热膨胀系数(TEC)、热导率(TC)随温度及组成的变化规律.粉末X射线衍射(XRD)测试结果表明: Gd₂Zr₂O₇基质本身呈弱有序烧绿石结构,而用Ce⁴⁺取代Gd³⁺的模拟固化体都呈缺陷萤石结构. (Gd_1-xCe_x)₂Zr₂O_7+x的Ce(3d) X射线光电子能谱(XPS)有六个峰,结合能分别位于881.7, 888.1, 897.8, 900.4, 907.1, 916.1 eV处,与CeO2的XPS图谱非常相似,说明Ce为四价.随着温度的升高,所有样品的热膨胀系数总体上呈增大趋势.在室温至750 ℃附近,大部分样品的热导率随温度的升高而降低,之后热导率又呈小幅上升.在相同温度下,固化体(Gd_1-xCe_x)₂Zr₂O_7+x (0 ≤ x ≤ 0.7)的热膨胀系数及热导率随组成变化呈相同趋势:在0 ≤ x ≤ 0.1范围内随x的增大而增大,随后在x = 0.1-0.7时逐渐减小.     

周期有序介孔Rh(Ⅰ)有机金属催化剂用于水介质Heck反应的研究

以1,4-双(三乙氧基硅基)苯和2-(二苯基膦)乙基三乙氧基硅烷为混合硅源, 在表面活性剂作用下共缩聚得到二苯基膦功能化的有序介孔有机硅材料[PPh₂-PMO(Ph)], 通过配位作用将Rh(Ⅰ)有机金属催化剂固载到PPh₂-PMO上得到Rh(Ⅰ)-PPh₂-PMO(Ph)非均相催化剂, 并采用FTIR, NMR, XRD, TEM和氮气吸附等手段对催化剂进行了表征. 考察了该催化剂在水介质Heck反应中的催化性能, 实验结果表明, 所制备的Rh(Ⅰ)-PPh₂-PMO(Ph)具有与均相催化剂Rh(PPh₃)₃Cl相当的催化活性, 这主要归因于催化剂的高比表面积、有序介孔结构有利于提高Rh(Ⅰ)活性位的分散度, 减少了传质阻力; 同时PMO构建形成的微环境增强了表面疏水性, 有利于反应底物的吸附和扩散. 此外, 催化剂重复使用多次后活性仍没有明显降低.     

青霉素G酰化酶在含环氧基团的顺磁性聚合物微球上的固定化（英文）

青霉素G酰化酶(PGA)是一种重要的工业生物催化剂,常用于以青霉素G为底物生产7-氨基去乙酰氧基头孢烷酸(7-ADCA)和6-氨基青霉烷酸(6-APA)等半合成β-内酰胺类抗生素.然而,PGA较差的稳定性和可重复使用性能限制了其在工业上的广泛应用.因此,将PGA固定在固体载体上是很有必要的,可以形成一种可重复使用的高性能的多相催化剂.用于生物酶固定化的良好载体应具备以下条件:(1)载体表面具有可用于与生物酶多点结合的高密度的官能团;(2)载体具有较大的比表面积以固定更多的生物酶.通常情况下,可以通过减小载体的粒径来增加其比表面积,然而,小粒径的载体很难从反应混合液中分离出来,造成固定化酶回收使用困难.为了将聚合物微球的优异固定化性能与磁性纳米粒子的独特顺磁性结合起来,我们制备了一种含环氧基团的顺磁性聚合物微球作为PGA的固定化载体.但由于Fe_3O_4纳米颗粒具有较高的表面能,在反相悬浮聚合反应过程中容易团聚成大颗粒,从而导致制备的顺磁性聚合物微球的磁体含量、表面形貌和粒径分布存在差异.此外,Fe_3O_4纳米颗粒与聚合反应单体之间的相容性不好,使得部分磁性颗粒不能很好地包埋于聚合物微球内部,影响固定化酶的活性和操作稳定性.本文以N,N′–亚甲基双丙烯酰胺为交联剂,以甲基丙烯酸缩水甘油酯和烯丙基缩水甘油醚为功能性单体,用反相悬浮聚合方法在SiO_2包覆的Fe_3O_4纳米颗粒表面成功制备出含环氧基团的顺磁性聚合物微球.用SEM,FT-IR,XRD,VSM和低温氮气吸附等手段对含环氧基团的顺磁性聚合物微球进行了表征.研究了SiO_2对Fe_3O_4纳米颗粒的包覆和Fe_3O_4/SiO_2纳米颗粒的数量对于固定化酶的初始活性和操作稳定性的影响.SiO_2在反相悬浮聚合过程中发挥重要作用,用SiO_2对Fe_3O_4纳米颗粒进行亲水性改性,有效改善了Fe_3O_4纳米颗粒与聚合反应单体的相容性,将其引入反相悬浮聚合体系中,可以制备得到球形度好、粒径分布均匀和超顺磁性的含环氧基团的顺磁性聚合物微球,其中当Fe_3O_4/SiO_2纳米颗粒的质量比为7.5%时制备的含环氧基团的顺磁性聚合物微球具有最好的PGA固定化性能.PGA通过其活性非必需侧链基团–氨基与顺磁性聚合物微球表面的环氧基团的共价结合来制备顺磁性固定化酶,该固定化PGA的初始活性为430 U/g(wet),在外加磁场的作用下容易回收使用,重复使用10次后可保留99%的初始活性,具有良好的热稳定性和酸碱稳定性,具有较好的工业应用前景.