Immobilization of microbial cells by radiation-induced polymerization of glass-forming monomers and immobilization ofStreptomyces phaeochromogenes cells by polymerization of various hydrophobic monomers

The immobilization ofStreptomyces phaeochromogenes cells was studied by the radiation-induced polymerization of various hydrophobic glass-forming monomers at low temperatures. The glucose isomerase activity of cells immobilized in hydrophobic polymers showed no decrease in activity with repeated use (batch enzyme reaction). Activity increased with increasing monomer concentration in contrast to results with the immobilized enzyme. The hydrophobic polymer composite was microspheric in form. The particle diameter of the composite increased with the increasing monomer concentration.K _m values of the immobilized cells were close to that of intact cells. It was deduced that the cells were trapped on the surface part of the hydrophobic polymer ready to react with the substrate, and not within the matrix where diffusion would play an important role in reaction rates.     

Mechanism of Immobilization of Enzymes by Radiation-Induced Polymerization of Glass-Forming Monomers

Immobilization of enzymes by radiation-induced polymerization has been studied at low temperatures by use of various hydrophilic and hydrophobic glass-forming monomers such as hydroxy-alkyl methacrylate and poly(ethylene glycol diacrylate). Activity yield of the immobilized enzyme depends on the monomer concentration in polymerization. In the immobilized enzymes with strongly hydrophobic matrices, the activity shows a maximum at an optimum monomer concentrations in a certain stage of repeated usage for the enzyme reaction. The decrease of activity with repeated use is very little in strongly hydrophobic systems, particularly in diethylene glycol diacrylate polymer matrices. The hydrophobic polymer-enzyme composite has the microsphere form. In the present method, a model scheme for immobilization mechanism is proposed, which is compared with that formed in the polymerization of a nonglass-forming monomer system and also by the solution polymerization at higher temperatures.     

Entrapment of plant invertase within novel composite of agarose-guar gum biopolymer membrane

Invertase or β-d-Fructofuranosidase (E.C.3.2.1.26) was extracted from Cucumis melo. L. fruit (Family-Cucurbitaceae). Soluble, plant invertase enzyme was immobilized in novel composite of agarose-guar gum biopolymer matrix in the form of hydrophilic, porous membranes. The immobilized invertase was characterized for sucrose hydrolytic activity and leakage from the matrix support. The efficiency of immobilization was found to be 91% with negligible leaching. The kinetic parameters K_m and V_max for free and immobilized invertase were also determined. Immobilized invertase was optimally active in the wide pH range of 4.5-6.5. The immobilization process also enhanced the thermal stability of enzyme up to 65 °C. Immobilized invertase membranes showed excellent storage stability with shelf life of 110 days. Entrapped invertase showed better operational stability and reusability up to 12 cycles. The fluorescence spectra of the composite membranes were studied and compared with that of soluble enzyme. All these characteristics of the immobilized invertase membranes make them suitable for the fabrication of biosensors.     

Preparation method of porous polymer materials by radiation technique and its application

The radiation polymerization of hydrophilic hydroxyethyl methacrylate monomer solution at temperatures below 0 °C leads to the formation of a porous structure in the polymers. The melting peak of the eutectic water–monomer composition at the eutectic point (above ?24 °C) could be distingushed and a glass transition temperature was observed at ?96 °C. The porous structure was developed after melting small ice pieces in the polymers after polymerization. The porous structure formed above 0 °C contained discontinuous pores and that formed below 0 °C had continuous pores leading to reticular structure. In a mixture of water –dioxane –monomer, the pore diameter decreased with increasing monomer concentration. Replacing dioxane with decane led to a maximum pore diameter at 70% monomer concentration. The pore diameter in 70% monomer concentration using water and dioxane was 1～4 µm, maximum activity in immobilized enzyme tablets was observed at this diameter. The porous structure was also varied by controlling the polymerization temperature. The durability of the immobilized enzyme tablets was demonstrated by the retention of high enzyme activities after repeated batch enzyme reactions. Copyright © 2001 John Wiley & Sons, Ltd.     

壳聚糖–精氨酸树脂固定化胰凝乳蛋白酶及其性质

以自制的多孔、具柔性亲水手臂的壳聚糖–精氨酸树脂为载体,戊二醛为交联剂固定胰凝乳蛋白酶,确定了酶与载体的最佳比例为20 mg酶/g湿树脂,交联剂的最佳用量为10 mL 1.0%戊二醛/1.5 g湿树脂,交联时间为60 min,所得固定化酶的活力回收率达68.95%。固定化胰凝乳蛋白酶的Km为8.36 mg/mL,比游离酶增大1.52倍,其酶促反应10 min达到最大速率,具有接近游离酶的催化时间进程曲线;其最适温度为70 ℃,比游离酶升高10 ℃;其最适pH值为5.92,比游离酶酸性偏移2个pH值。此外,固定化胰凝乳蛋白酶具有良好的热稳定性和贮存稳定性,75 ℃时的半衰期为8 h,4 ℃时的半衰期为46天。     

亲水纳米二氧化硅修饰丝网印刷碳糊电极的改进性能研究

研究了以铁氰化钾为电子传递剂,亲水纳米二氧化硅为固定化酶的载体与高分子成膜材料掺杂制作的生物敏感膜修饰丝网印刷碳糊电极葡萄糖生物传感器的改进特性,并从机理上分析了形成这种优化的原因。实验采用柠檬酸作为缓冲液,在高分子成膜材料、铁氰化钾、稳定剂、葡萄糖氧化酶中掺杂均相处理后的纳米二氧化硅制备生物敏感膜,并制成腔体,将其与未经过纳米二氧化硅掺杂制备的生物传感器进行对比实验。实验证明:用掺杂纳米二氧化硅制作的生物敏感膜修饰的丝网印刷碳糊电极与未修饰电极相比,灵敏度提高了2.6倍,线性检测范围为1.1~33.3 mmol/L,对测试范围内不同浓度的葡萄糖样本,相对标准偏差<5%,重现性和稳定性良好,具有较高的研究价值和应用前景。     

Immobilization of Enzymes by Radiation-Induced Copolymerization of 2-Hydroxyethyl Methacrylate and Other Hydrophilic or Hydrophobic Comonomers

Immobilization of enzymes by radiation-induced copolymerization was studied at low temperatures by use of various comonomer systems consisting of 2-hydroxyethyl methacrylate and other more hydrophilic or hydrophobic comonomers. The matrices obtained by copolymerization with more hydrophilic and more hydrophobic comonomers decreased the porosity in the matrix equally. However, the activity yield of the immobilized enzyme showed different changes with repeated use in the more hydrophilic and more hydrophobic matrices. That is, the initial activity decreased rapidly with repeated use owing to the enzyme leakage from the matrix, in the increased hydrophilic matrices. On the other hand, in the more hydrophobic matrices enzyme leakage was completely retarded and activity did not change with repeated use. Moreover, the activity yield showed a maximum at a certain monomer composition in the copolymerization with hydrophobic comonomer. Finally, it was found that the maximum activity yield of the hydrophobic matrices was larger in general than that of the hydrophilic copolymer matrices.     

含氨基和环氧基双功能基的聚合物刷磁性微球的制备及对青霉素G酰化酶的固定化

在内部分散超顺磁性Fe3O4纳米粒子的二乙烯苯交联聚丙烯酸微球表面引入原子转移自由基聚合(ATRP)引发剂,引发聚合向微球表面分别引入P(GMMA-r-DMAEMA-r-GMA)、P(GMMA-r-DMAEMA)和P(GMMA-r-GMA)无规共聚物刷(GMMA为甲基丙烯酸甘油单酯,DMAEMA为甲基丙烯酸-N,N-二甲氨基乙酯,GMA为甲基丙烯酸缩水甘油酯),聚合物刷中GMMA链节的作用是使聚合物刷具有亲水性,DMAEMA引入氨基,GMA引入环氧基.研究了青霉素G酰化酶在这些载体上的固定化和其酶活性.结果表明,同时引入环氧基和氨基的P(GMMA-r-DMAEMA-r-GMA)刷磁性微球固定化青霉素G酰化酶的活性和活性收率都最高,其固定化动力学比只含环氧基P(GMMA-r-GMA)刷磁性微球的好.固定化酶比自由酶更耐热,固定化酶的最佳pH值比自由酶的略高,固定化酶重复使用10次后其活性保留70%.     

Thermal analysis of PMMA/gel silica glass composites

Thermal analysis of poly-methylmethacrylate (PMMA) impregnated porous gel silica glasses confirms that the PMMA chains form hydrogen bonds with the pore surface silanol groups. The adopted conditions for the insitu polymerisation result in about 4% of residual monomers trapped in the polymer, most of them in the amorphous structure. The polymer and monomer mixture takes up the whole of the free pore volume. Most of the residual monomer polymerises during the DSC scans above the glass transition temperature providing an excellent probe for the weak glass transition. Polymerisation in the gel silica glass medium affects the glass transition temperature, the length of polymer chains, and the degree of polymerisation.     

Construction by molecular dynamics modeling and simulations of the porous structures formed by dextran polymer chains attached on the surface of the pores of a base matrix: characterization of porous structures

Significant increases in the separation of bioactive molecules by using ion-exchange chromatography are realized by utilizing porous adsorbent particles in which the affinity group/ligand is linked to the base matrix of the porous particle via a polymeric extender. To study and understand the behavior of such systems, the M3B model is modified and used in molecular dynamics (MD) simulation studies to construct porous dextran layers on the surface of a base matrix, where the dextran polymer chains and the surface are covered by water. Two different porous polymer layers having 25 and 40 monomers per main polymer chain of dextran, respectively, are constructed, and their three-dimensional (3D) porous structures are characterized with respect to porosity, pore size distribution, and number of conducting pathways along the direction of net transport. It is found that the more desirable practical implications with respect to structural properties exhibited by the porous polymer layer having 40 monomers per main polymer chain, are mainly due to the higher flexibility of the polymer chains of this system, especially in the upper region of the porous structure. The characterization and analysis of the porous structures have suggested a useful definition for the physical meaning and implications of the pore connectivity of a real porous medium that is significantly different than the artificial physical meaning associated with the pore connectivity parameter employed in pore network models and whose physical limitations are discussed; furthermore, the methodology developed for the characterization of the three-dimensional structures of real porous media could be used to analyze the experimental data obtained from high-resolution noninvasive three-dimensional methods like high-resolution optical microscopy. The MD modeling and simulations methodology presented here could be used, considering that the type and size of affinity group/ligand as well as the size of the biomolecule to be adsorbed onto the affinity group/ligand are known, to construct different porous dextran layers by varying the length of the polymeric chain of dextran, the number of attachment points to the base matrix, the degree of side branching, and the number of main polymeric chains immobilized per unit surface area of base matrix. After the characterization of the porous structures of the different porous dextran layers is performed, then only a few promising structures would be selected for studying the immobilization of adsorption sites on the pore surfaces and the subsequent adsorption of the bioactive molecules onto the immobilized affinity groups/ligands.     

Synthesis and properties of transparent luminescent nanocomposites with surface functionalized semiconductor nanocrystals

5-Amino-1,10-phenanthroline (Aphen) was used as an organic ligand to functionalize CdS nanocrystals (NCs) by a ligand-exchange process. The functional Aphen-CdS NCs have strong luminescent emission at 552 nm and good dispersibility in the polar organic monomers. The Aphen-CdS NCs were dispersed in polymeric monomers to prepare a series of transparent luminescent nanocomposites with excellent thermal stability via in-situ bulk polymerization. The fluorescent properties of the Aphen-CdS NCs were well retained in the polymer matrix. It was found that when the methacrylic acid (MAA) and glycidyl methacrylate (GMA) as the comonomers were introduced into the polymer matrix, the emission peaks of the resultant nanocomposites had a blue shift and the fluorescent intensities also increased due to the interaction between NCs and the polymer matrices. The transparent NCs/polymer nanocomposites with tunable fluorescent emission can be potentially used for the fabrication of optoelectronic devices.     

Step‐Growth Copolymerization Between an Immobilized Monomer and a Mobile Monomer in Metal–Organic Frameworks

The A–A/B–B step‐growth copolymerization between a monomer immobilized in the crystalline state and a monomer mobile in the solution state is demonstrated. One of the two monomers was immobilized as organic ligands of the metal–organic framework (MOF) and polymerized with the mobile guest monomer, resulting in the formation of linear polymers. The polymerization behavior was completely different from that of the solution polymerizations. In particular, the degrees of polymerization (DP) converged to a specific value depending on the MOF structures. The inevitable termination is caused not by imperfectness of the polymerization reaction, but by the selection of the two polymerization partners among the several adjacent immobilized monomers. This is fully supported by the Monte Carlo simulation on the basis of the polymerization mechanism. Precise immobilization of monomers in the supramolecular assemblies is a promising way for the controlled A–A/B–B step‐growth polymerization.     

Effect of monomer hydrophilicity on ARGET–ATRP kinetics in aqueous mini-emulsion polymerization

Activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP)-based aqueous miniemulsion polymerization where the polymerization takes place in the stabilized monomer droplets is described. In this work, we compared styrene, n-butyl methacrylate (nBMA) and tert-butyl methacrylate (tBMA) and investigated the influence of their hydrophobicity on dispersity, molecular weight and particle stability based their partition coefficients (logP) (2.67, 2.23, and 1.86, respectively). Tetrabutylammonium bromide (TBAB) was used as a phase transfer agent for the controlled delivery of Cu²⁺-Br/tris(2-pyridylmethyl)amine (TPMA), a hydrophilic catalyst, into monomer droplets of varying hydrophobicity. The resulting dispersity and particle stability of each polymer is a function of its logP value, with the most hydrophobic monomer (styrene) displaying the narrowest dispersity and most control (Đ < 1.3), and the most hydrophilic polymer poly(tert-butyl methacrylate) (PtBMA) having reduced emulsion stability, determined by the observation of aggregate formation. Selected polymerization parameters, including effects of total ascorbic acid feed concentration and the monomer concentration and their effects on dispersity are reported. The controlled polymerizations of hydrophilic monomers using ARGET-ATRP in miniemulsion conditions and understanding the effect of monomer hydrophilicity on the emulsion stability will broaden the use of ARGET-ATRP in emulsion polymerization for the synthesis of polymer-grafted nanoparticles with hydrophilic corona.     

Substrate effect on the formation of hydrogels with heterogeneous network structure

It was found that when an aqueous solution of vinyl monomers is polymerized on a hydrophobic substrate, obvious heterogeneity occurs in the region of the interface. This substrate effect was observed on polytetrafluroethylene (Teflon), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinylchloride (PVC), but not on hydrophilic substrates. Compared with synthesis on hydrophilic surfaces, the surfaces of hydrogels synthesized on a hydrophobic substrate exhibit a larger degree of swelling, a lower surface coefficient of friction and elastic modulus, weaker interfacial adhesion, and reduced interaction with biological cells. This substrate effect has been observed for many types of aqueous monomer solutions. It was found that the above properties are related to the loosely cross-linked architecture, containing some graft-like polymer chains, that is formed on the gel surface when the gel is prepared on a hydrophobic substrate. To understand the mechanism of the substrate effect, two novel optical methods, electric speckle pattern interferometry (ESPI) and real-time laser sheet refraction (RT-LSR), were developed. It was found that oxygen trapped in the composite interface between the monomer solution and rough hydrophobic substrates played an important role in the substrate effect.     

Immobilization of penicillin G acylase on poly[(glycidyl methacrylate)-co-(glycerol monomethacrylate)]-grafted magnetic microspheres

Poly[(glycidyl methacrylate)-co-(glycerol monomethacrylate)]-grafted magnetic microspheres were prepared by graft random copolymerization via ATRP from polymer microspheres with dispersed Fe(3)O(4) nanoparticles. Penicillin G acylase (PGA) was immobilized onto the polymer brush-grafted magnetic microspheres. The immobilized PGA prepared with initial glycidyl methacrylate/glycerol monomethacrylate ratios of 40/60 to 60/40 possessed higher catalytic activity than that prepared with higher proportions of glycidyl methacrylate in the initial monomer mixture. The immobilized PGA showed high thermal stability and enhanced tolerability to the pH variance.     

超声引发无皂乳液聚合制备纳米银/PAAEM复合材料及其表征

在不使用气体保护及乳化剂的条件下,超声辐射引发无皂乳液聚合双原位合成纳米银/聚乙酰乙酸基甲基丙烯酸乙酯(PAAEM)复合材料。并通过XRD、FTIR、TEM、HRTEM、XPS和TG等分析方法对其进行表征。结果表明:纳米银粒子具有面心立方结构和球形或近球形形貌,且较均匀地分散在聚合物基体中;纳米银粒子与基体之间的相互作用是纳米银与基体中乙酰乙酸基的羰基氧原子配位所产生的;而且纳米银粒子对基体PAAEM的热学性能有很大影响。     

Radiation target analyses of free and immobilized glucose 6-phosphate dehydrogenase

The sensitivity of the enzyme glucose 6-phosphate dehydrogenase to ionizing radiation was examined under several conditions, including the presence of several free-radical scavengers. The enzyme was also irradiated when covalently bound to polyacrylamide beads whose structure is very similar to the polypeptide backbone of proteins. All the enzyme forms were irradiated in the frozen state with high-energy electrons from a linear accelerator. Surviving enzyme activity and surviving monomers were determined; the data were analyzed by target theory.Free-radical scavengers reduced the radiation target size of both the activity and monomers of the free enzyme, but not that of the immobilized enzyme activity. The target size of the activity of the free enzyme was that of a dimer mass, but in the case of the immobilized enzyme it was equal to the smaller mass of the monomer.Free-radical scavengers reduce the target size by modifying radiation energy transfer. The target size of the polyacrylamide-bound enzyme activity was expected to be very large since the connection between polyacrylamide and protein is a peptide bond which permits transfer of radiation-deposited energy. Several explanations concerning energy transfer are suggested for this result.     

Investigation by QCM of the Specific and Nonspecific Avidin Interaction onto a Biotinylated Polypyrrole Film

We have studied by gravimetric measurements using a quartz crystal microbalance (QCM), the adsorption of avidin onto a polypyrrole film. From QCM results, it appears that both the thickness and the redox state of polypyrrole strongly influence the avidin adsorption. This nonspecific interaction is larger for a thick film than for a thin one and, also for when the polymer is in its reduced state. We have also investigated by QCM the specific and nonspecific interaction of avidin onto biotinylated polypyrrole films having either a hydrophilic or hydrophobic character. It is shown that the amount of avidin immobilized by specific recognition is almost the same whatever the nature of the polymer matrix.     

Immobilization of glucoamylase onto novel porous polymer supports of vinylene carbonate and 2-hydroxyethyl methacrylate

Glucoamylase was immobilized onto novel porous polymer supports. The properties of immobilized glucoamylase and the relationship between the activity of immobilized enzyme and the properties of porous polymer supports were investigated. Compared with the native enzyme, the temperature profile of immobilized glucoamylase was widened, and the optimum pH was also changed. The optimum substrate concentration of immobilized glucoamylase was higher than that of native enzyme. After storage for 23 d, the immobilized glucoamylase still maintained about 84% of its initial activity, whereas the native enzyme only maintained about 58% of the initial activity. Moreover, after using repeatedly seven times, the immobilized enzyme maintained about 85% of its initial activity. Furthermore, the properties of porous polymer supports had an effect on the activity of the immobilized glucoamylase.     

耐电解质高吸水性树脂

在简述高吸水性树脂吸水机理的基础上,综述了改善高吸水性树脂耐电解质性能的四种途径,结合聚合方法重点讨论了提高亲水性、引入长链疏不性单体以及合成两性聚合物三种改性途径。