Molecular weight-viscosity relationship for amylopectin,a highly branched polymer

Summary Rate of acid hydrolysis of amylopectin is discussed from molecular weight variation; a two step mechanism is found. The highly branched amylopectin fractions obtained by partial acid hydrolysis allow experimental determination of Mark-Houwink's law exponents. Theoretical and experimental a values are compared.Laboratoire Propre du C.N.R.S., associé à l'Université Scientifique et Médicale de Grenoble     

Porous polydimethylsiloxane membranes for enzyme immobilization

Porous polydimethylsiloxane (PDMS) membranes with α-amylase or glucose oxidase activity were prepared by catalytic hydrosilylation cure of PDMS in the presence of the enzymewater solution. The pores in the membrane are the result of hydrogen foams, which are generated during the curing reaction. The enzyme reactions were examined in batch and permeation experiments by using glucose and starch solutions as substrates. For the permeation set-up, the reaction yields of the immobilized α -amylase increased as the permeation rate of the starch solution decreased. The Michaelis-Menten type of reaction kinetics for the immobilized enzyme indicated that the permeation system is effective for the diffusion through the solute of the matrix, as compared with the batch system. © 1996 John Wiley & Sons, Inc.     

Properties of branched polymer chains adsorbed on a patterned surface

The aim of this study was to investigate the properties of polymer chains strongly adsorbed on a planar surface. Model macromolecules were constructed of identical segments, the positions of which were restricted to nodes of a simple cubic lattice. The chains were in good solvent conditions, thus, the excluded volume was the only interaction between the polymer segments. The polymer model chain interacted via a simple contact potential with an impenetrable flat surface with two kinds of points: attractive and repulsive (the latter being arranged into narrow strips). The properties of the macromolecular system were determined by means of Monte Carlo simulations with a sampling algorithm based on the local conformational changes of the chain. The structure of adsorbed chains was found to be strongly dependent on the distance between the repulsive strips, whenever this distance was very short. The mobility of the chains was also studied and it was found that diffusion across repulsive strips was suppressed for large distances between the strips.     

Preparation of porous polymeric structures for enzyme immobilization

Porous polymethacrylic acid‐co‐triethylene glycol dimethacrylate (MAA‐co‐3G) and polyacrylic acid‐co‐triethylene glycol dimethacrylate (AA‐co‐3G) were prepared by four different polymerization techniques, namely, suspension, dispersion, seed, and microemulsion polymerization using an inert diluent (n‐hexane and polystyrene). The morphology and porosity of the obtained polymers were examined by means of a scanning electron microscope. The surface areas of the obtained polymers were determined colorimetrically. The copolymers were modified by hydroximation and chlorination using hydroxyl amine and thionyl chloride, respectively. The effect of polymerization type, surface area, modification, and pH on the protease enzyme immobilization over poly(MAA‐co‐3G) and poly(AA‐co‐3G) was examined. The enzyme activity was measured by means of a spectrophotometer. The reactivity ratios of the two monomers MAA and 3G were determined by means of the elemental analysis method. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 594–601, 2000     

A processable prepolymer for the preparation of a stable conductive polymer

We recently reported¹ the synthesis and polymerization of a completely conjugated acetylene terminated prepolymer into an intrinsically conducting organic polymer. Although this polymer exhibited high thermal and environmental stability, its processing window, i.e., the temperature at which it melted vs. the temperature of the highly exothermic cure, was narrow. We now report the synthesis and polymerization of an isomer of this acetylene terminated material. This change in structure resulted in a 63°C decrease in the melting point (87 vs. 150°C) that provides a more than adequate liquid range between melting and the on-set of curing. Along with the greatly improved processing, this isomer results in an intrinsically conducting, thermally and oxidatively stable polymer equivalent to the original material.     

壳聚糖固定化酶和细胞研究新进展

分析评价了壳聚糖作为固定化酶和细胞载体的特性,概述了壳聚糖凝胶固定化酶和细胞的形态及制备方法,着重介绍了近年来壳聚糖固定化酶和细胞的改进方法,并指出今后壳聚糖固定化酶和细胞的发展方向。     

UV-curable methacrylated/fumaric acid modified epoxy as a potential support for enzyme immobilization

The immobilization procedure of UV-curing coating is simple and causes less loss of enzymatic activity. UV-curable methacrylated/fumaric acid modified cycloaliphatic epoxide is here proposed as a rigid support material for covalent immobilization of α-amylase. The immobilized enzyme is analyzed in terms of bioactivity retention as a function of repeated use ability, pH, storage, as well as stability under various experimental conditions, taking starch as a substrate. The properties of immobilized enzyme were also compared with those of the free enzyme. The highest activity of free enzyme was obtained at pH 7.0 while this value was shifted to pH 7.5 for immobilized system. Optimum catalytic activity was observed at 30 °C, for both free and immobilized enzyme; however, the immobilized enzyme had a higher activity than the free one. The immobilized enzyme that was used 35 times in 8 h in repeated batch experiments demonstrated that about 73% of the enzyme activity was retained. The free enzyme lost all its activity with in 15 days. The retained activity of immobilized enzyme was found to be around 80%. The amount of bound α-amylase was found 94 mg per gram polymeric support material.     

Preparation of branched polyethene using a soluble zirconocene catalyst

[Me₂C(Cp) (Ind)]ZrCl₂ metallocene catalyst has been prepared and employed in a study of ethene polymerization in the presence of the cocatalyst methylaluminoxane. C₁ and C₂ signals are detected in the ¹³C NMR spectra of the resultant polymers; this reveals that the resultant polymer is a branched polyethene (polyethylene). The influence of polymerization temperature, catalyst concentration and [Al]/[Zr] ratio on catalytic activities and polymerization kinetics is investigated. A plausible mechanism for forming branched polyethene is suggested. © 2000 Society of Chemical Industry     

Bisacryloylpiperazine as vinylating agent for enzyme immobilization by graft-copolymerization onto polysaccharides

A method of enzyme immobilization by graft-copolymerization onto polysaccharides is reported. Bisacryloylpiperazine has been used as a vinylating reagent and the reaction product with several enzymes (HRP, GOD, Am, ChT, Cel) was copolymerized onto different matrices (cellulose, Sepharose, Sephadex, starch). Immobilization parameters which influence the copolymer activity have been studied for the insolubilization of horseradish peroxidase onto cellulose. These parameters are pH, time, and temperature of bisacryloylpiperazine enzyme activation reaction. Under the best immobilization conditions copolymer activity linearly depends on enzyme concentration. Enzyme coupling efficiency depends on the type of enzyme and it ranges from 7 to 20%. The most important characteristics of these immobilized enzyme systems were tested and compared with those of similar systems obtained by glycidylmethacrylate enzyme activation (stability in continuous washing, kinetic characteristics, and storage, thermal, and operational stability). Immobilized enzyme graft copolymers have kinetic behaviour very close to that of the free enzymes. Diffusion is not seriously limited because immobilization reaction does not alter the enzymatic activity. By means of bisacryloylpiperazine it was possible to immobilize chymotrypsin with better results than those previously obtained, particularly coupling efficiency and long term continuous working.     

静电纺PU纳米纤维膜及其固定化酶的研究

采用静电纺丝技术制备聚氨酯纳米纤维膜,用壳聚糖进行亲水改性后固定柚苷酶,测定不同浓度的壳聚糖对纤维膜亲水改性下的载酶量和酶活力以及固定化柚苷酶在不同酶解温度、时间和pH条件下的酶活力。结果表明,当聚氨酯纺丝液质量分数为12%,接收距离为22 cm,纺丝电压为22 kV,注射的速率为0.5 mL/h,接收器滚轮转速为300 r/h的条件下,能够得到纤维样貌良好的纳米纤维膜;通过亲水改性,聚氨酯膜由疏水性变为亲水性,膜上接枝了作为亲水基团的羟基;壳聚糖浓度为0.5%时,聚氨酯膜上有最大的载酶量,为83.2 mg/g;同时固定化柚苷酶具有最高的相对酶活性,且固定化酶相较于游离酶在一定的温度、反应时间和pH下表现出更高的酶活性。     

介孔纳米孔道中单维交联酶策略固定青霉素酰化酶

为解决酶固定化过程中稳定性较差的问题,将单维交联酶策略引入青霉素酰化酶的固定化中,通过在介孔泡沫硅载体(MCFs)表面初步吸附作用将酶固定,再用对本醌对酶分子进行交联,从而制得单维交联酶聚体。实验结果显示:单维交联酶聚体(CLEA)的稳定性有明显提高,最适温度从游离酶的45℃上升到55℃,催化温度的适用范围更宽,在50℃下热处理25 h仍保持74.4%活力,在测试操作稳定性方面,连续操作15次,其酶活保持在61.9%。     

Diffusion and adsorption phenomena in an immobilized enzyme reactor using adsorbed polymer for attachment of the enzyme in porous alumina particles

Experiments were performed to study the effects of an immobilized enzyme on the adsorption capacity and on the diffusion in a porous solid. The enzyme invertase was immobilized by covalently binding it to a polymer matrix adsorbed in the pores of alumina. The enzyme was found to hydrolyse sucrose to glucose plus fructose with an initial activity of 60 μmol/min-g alumina. Data on the long-term stability showed a 14% decrease in initial activity in 22 days. The adsorption of glucose, fructose, or sucrose alone on porous alumina and on porous alumina containing polymer and immobilized invertase was investigated. The presence of immobilized invertase and polymer matrices decreased the adsorption capacity by about 75%. The presence of immobilized invertase on the adsorbed polymer matrices also raised the experimental tortuosity factor for diffusion in the pores from 2.0 for plain alumina to 2.75 for invertase immobilized on alumina. The decrease of particle void fraction, the enzyme blockage effect, and an increase in pore restriction effect were used to explain the increase of the tortuosity factor.     

Solubility criteria for a thermally stable polymer determined by gas–solid chromatography

The Gibbs energy of adsorption, the Flory-Huggins interaction parameter χ, and a specific interaction parameter A, based on hydrogen-bonding and charge-transfer complexing properties of solvents, are obtained by gas—solid chromatography for a type of polyquinoxaline denoted as PQF. Interactions between 40 organic solvents and PQF have been determined at 176.35° and 200.85°C. PQF is an aromatic, heterocyclic polymer which is at least partially soluble in several organic solvents. The parameters χ and Λ and the solubility parameters of solvents are proposed to be the determining factors for miscibility of a PQF—solvent pair.     

Enzyme immobilization in a photosensitive conducting polymer bearing azobenzene in the main chain

A new photosensitive and thermosensitive monomer, namely bis(4-(3-thienyl ethylene)-oxycarbonyl)diazobenzene (TDAZO), was synthesized. The photochemical and thermal cis–trans isomerization of the monomer has been investigated. The rate constants of the photoisomerization of TDAZO in ACN and DCM were 0.195 and 0.308 min^?1, respectively. For spectroelectrochemical investigation and enzyme immobilization application, TDAZO copolymerized with thiophene and pyrrole. Electrochemical and spectroelectrochemical properties of P(TDAZO-co-Th) were investigated and invertase was immobilized in P(TDAZO-co-Py) copolymer. Immobilization of enzymes was carried out by the entrapment of the enzyme in conducting polymer matrices during electrochemical polymerization of pyrrole through thiophene moieties of the TDAZO. Optimum conditions for this electrode, such as pH, temperature, kinetic parameters (K _m and V _max) and operational stability were investigated. Kinetic parameters invertase-immobilized in copolymer were smaller than free enzyme. The optimum operational temperature was 10 °C higher for immobilized enzyme than that of the free enzyme. Due to strong interaction between enzyme and diazo group in the polymer main chain, thermal, pH and operational stability of enzyme has been enhanced.     

Structured reactors for enzyme immobilization: advantages of tuning the wall morphology

A new high-porosity mullite advanced ceramic material (ACM) having an open pore structure on the micron length scale was evaluated as a monolithic support for enzyme catalyzed reactions. The hydrodynamic properties of ACM monoliths were investigated using residence time distribution (RTD) in gas–liquid Taylor flow and compared with classical cordierite monoliths. The hydrodynamic results show that the liquid phase accesses the entire open volume of the wall and exchanges rapidly with the bulk liquid in the channels. The ACM monoliths were functionalized with polyethylenimine (PEI) and with carbon prepared by different methods in order to provide adsorption sites for lactase from Aspergillus oryzae and lipase from Candida rugosa. These monolithic biocatalysts were tested for activity and stability and compared to similarly prepared biocatalysts employing classical cordierite ceramic monoliths. The use of high-porosity ACM monoliths leads to more stable and more active structured bioreactors. The highly open microstructure of ACM affords good access to catalysts deposited within the walls of a monolith and enables high enzyme loadings.     

Preparation of D-phenylalanine imprinted microbeads by the modified suspension polymerization using a magnetic impeller

Molecularly imprinted polymeric microbeads (MIPMs) were prepared by using a magnetic impeller by the modified suspension polymerization method with D-phenylalanine (Phe) as the water-soluble template without derivatization, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, toluene as the porogen, polyvinyl alcohol as the stabilizer, and sodium dodecyl sulfate as the surfactant. The mean diameter of MIPMs decreased from 12.45 μm to 8.86 μm by using a simple magnetic impeller instead of a conventional simple straight-blade turbine impeller during suspension polymerization. The adsorption selectivity of MIPMs prepared with a magnetic impeller was much improved as compared to the adsorption selectivity of MIPMs prepared with a conventional simple straight-blade turbine impeller. The adsorption selectivity of MIPMs changed from reversed adsorption (less than 1) to positive (higher than 1) as the washing time increased after suspension polymerization.     

Synthesis of magnetic polymer microspheres and application for immobilization of proteinase of balillus sublitis

Core–shell composite magnetic polymer microspheres, containing a magnetic core and a polymer shell, were synthesized by dispersion copolymerization of styrene (St) and 2-hydroxyethyl methacrylate (HEMA) in the presence of magnetic oxide (Fe₃O₄) powder. The Fe₃O₄ powder was ultrasonically disperesed in poly(ethylene glycol) (PEG) and the affinity between the obtained superfine powder and the monomer and initator was improved. It shows that the dispersion medium and stabilizer system have a great effect on the diameter and dispersion parameter of microspheres. In the condition of controlling polymerization, the magnetic polymer microspheres containing surface ? OH groups, having 50–500 μm diameter and with better magnetic induction, were synthesized. The proteinase of Balillus sublitis was immobilized on magnetic polymer microspheres with an average diameter of 50–60 μm by covalent coupling. The magnetic immobilized proteinase shows an enzyme activity of 1000 U/g, the enzyme yields are usually 20–30 mg/g of carriers, and the activity retention is about 40%. The stability of the immobilized enzyme was obviously improved. © 1995 John Wiley & Sons, Inc.     

1,3,5-Triazine-based polymer: synthesis,characterization and application for immobilization of silver nanoparticles

Six s-triazine-based polymers were prepared through the nucleophilic reaction of 2,4-dichloro-6-substituted s-triazine derivatives with 1,4-diaminobutane employing conventional heating and microwave irradiation. The prepared polymers were characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The microwave irradiation provides the target polymers in less reaction time with higher yields and purities; the results from the TGA revealed that microwave technique enhanced the thermal behavior of the prepared polymers. The effect of substituent on the thermal stability of polymers has the main factor, where incorporation of the aromatic ring on the triazine core in the prepared polymers increased their thermal stability. As a model for immobilization of silver nanoparticles (AgNPs), p-methoxy-s-triazine- 1,4-butadiamine (BDPMA) copolymer was used as an example in the presence and absence of hydrazine-hydrate. AgNPs were characterized by zeta potential, scanning electron microscope (SEM), X-ray powder diffraction analysis (XRD) and transmission electron microscope (TEM). Best results in term of particle size was obtained by using BDPMA in the absence of hydrazine hydrate, where the particle size of AgNPs was less than 20 nm as observed from TEM.

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Graphical Abstract

     

Evaluation of a robust, diimide-based, porous organic polymer (POP) as a high-capacity sorbent for representative chemical threats

A previously described porous organic polymer (NU-POP-1) was evaluated against four representative chemical threats: ammonia, cyanogen chloride, sulfur dioxide, and octane. Ammonia, cyanogen chloride, and sulfur dioxide are examples of toxic industrial chemicals (TICs) spanning the range from highly basic to strong-acid forming substances, while octane is used to assess physical adsorption capacity. Experiments were carried out using a microbreakthrough test apparatus, which measures the adsorption capacity at saturation and gives an indication of the strength of adsorption. The NU-POP-1 material exhibited substantial removal capabilities against the majority of the toxic chemicals, with capacities as high as or better than an activated, impregnated carbon. The ability to remove the highly volatile toxic chemicals ammonia and cyanogen chloride was intriguing, as these chemicals typically require reactive moieities for removal. The present work presents a benchmark for toxic chemical removal, and future work will focus on incorporating functional groups targeting the toxic chemicals of interest.