Immobilization procedures are a fundamental step in the technological use of enzymes. Among the different immobilization procedures sol–gel technique is widely recognised as a valuable approach to obtain very high quality catalytic supports. In this paper different optical techniques have been used and compared to investigate structural and dynamic properties of glucose oxidase (GOD) prior and after sol–gel immobilization process. In particular, using Fourier Transform infrared micro-spectroscopy and time-resolved fluorescence the secondary structure of GOD and the flavin adenine dinucleotide (FAD) conformational changes have been respectively investigated. Infrared spectroscopy measurements have confirmed that enzymatic activity is preserved and a predominant β-sheet subcomponent is retained by immobilized GOD. By time-resolved FAD fluorescence a three-exponential decaying behaviour has been observed for both free and immobilized enzymes with three different lifetimes, each being characteristic of a peculiar conformational state of the FAD structure. The comparison between lifetime values for free and immobilized GOD has not shown significant differences, while the fractional steady-state intensities of the single exponential components have been changed by immobilization procedure. All results reported and discussed in this paper have confirmed once again the efficacy of the adopted sol–gel immobilization procedure for enzymes and proteins. In addition, the joint use of different optical spectroscopic techniques has shown to be a very valuable tool for getting a better insight into structural and dynamic properties of immobilized enzymes. 相似文献
A novel type of glucose sensor was fabricated based on a glucose oxidase (GOD)-N,N-dimethtylformamide (DMF)-[BMIm][BF4] composites modified three-dimensional ordered macroporous (3DOM) gold film electrode. The immobilized GOD exhibits a pair
of well-defined reversible peaks in 50 mM pH 7.0 phosphate buffer solutions (PBS), which could be attributed to the redox
of flavin adenine dinucleotide (FAD) in GOD. The research results show that ionic liquid ([BMIm][BF4]), DMF and 3DOM gold film are crucial for GOD to exhibit a pair of stable and reversible peaks. It is believed that the large
active area of 3DOM gold film can increase the amount of immobilized GOD. Simultaneously, the application of IL enhances the
stability of GOD and facilitates the electron transfer between GOD and the electrode. The synergetic effect of DMF can help
the GOD to maintain its bioactivity better. GOD immobilized on the electrode exhibits the favorable electrocatalytic property
to glucose, and the prepared sensor has a linear range from 10 to 125 nM with a detection limit of 3.3 nM at a signal-to-noise
ratio of 3σ. The apparent Km (Michaelis- Menten constant) for the enzymatic reaction is 0.018 mM. 相似文献
The properties of immobilized glucose oxidase (GOD) by the complexes of diethylaminoethyl cellulose(DEAEC) with different polymers, such as polymethylacrylic acid (PMAA), polyacrylic acid (PAA), polystyrene sulfonic acid (PSSA), polyvinylaleohol (PVA), polyethylene oxide (PEO) and styrene-maleic acid copolymer (PSMA) were investigated. The activity of immobilized GOD was obviously influenced by the component of the DEAEC complexes. The relative activity of the immobilized GOD reached to maximum and over 90% of the native GOD. when the DEAEC-PMAA DEAEC-PAA complexes were used as a carrier with the molar ratio of DEAEC and polyacid of about one. Michaelis constants (Km) of the immobilized enzymes of DEAEC-GOD-PMAA and DEAEC-GOD-PAA were determined to be 1.25 and 1.00, respectively. Moreover, the immobilized GOD has a good storage stability and cyclic life. 相似文献
Sulfhydryl groups of glucose oxidase (GOD) were reacted with maleimide groups of polymaleimidostyrene (PMS) which was coated onto the porous carbon sheet, and the carbon sheet immobilized by GOD was combined with an oxygen electrode to fabricate a glucose sensor. The activity of thiolated GOD immobilized to PMS is much larger than that of native GOD immobilized to PMS. The good linear relationship of glucose and oxygen current response was obtained in a concentration range from 0.1 to 2 mM and upper limit of linear range was found to be 3.0 mM. The immobilized GOD activity is highly dependent on pH at immobilization and the maximum activity was obtained at pH 5.5, probably because the SH groups of GOD that are indispensable for generation of enzyme activity is not exposed at this pH. It was found that PMS is very effective reagent to immobilize enzyme strongly via covalent bond, because high density of maleimide groups of PMS can catch not only exposed SH groups but also buried SH groups. 相似文献
Enzymes are versatile biocatalysts and find increasing applications in many areas. The major advantages of using enzymes in biocatalytic transformations are their chemo‐, regio‐, and stereospecificity, as well as the mild reaction conditions that can be used. However, even when an enzyme is identified as being useful for a given reaction, its application is often hampered by its lack of long‐term stability under process conditions, and also by difficulties in recovery and recycling. For ease of application and stabilization purposes, enzymes are often immobilized on solid supports. Among support matrices, hydrophobic biomaterials have been extensively used as supports for enzyme immobilization because the hydrophobic interactions not only can effectively increase the amount of enzyme immobilization, but also exhibit higher activity and retention of activity compared with hydrophilic supports. On the other hand, polysiloxane can evidently increase the amount of enzyme immobilization because of its hydrophobicity and strong affinity with enzyme. Therefore, this research details the first preparation and use of a hydrophobic polysiloxane support for enzyme immobilization in which the structural and functional characteristics of new supports have been investigated by using glucose oxidase (GOD) and a simple Fenton's assay method, and extremely interesting features were revealed. The results showed that the amount of GOD immobilization and the stability of GOD loaded, which are fundamental properties for enzyme separation and purification, can be significantly improved by adsorption. Moreover, the results indicated that hydrophobic polysiloxane supports can effectively increase the enzymatic affinity and durability of GOD, and decrease the rate of GOD desorbed.
This study is concerned with chitosan-polyacrylic acid complex as a carrier to immobilize glucose oxidase (GOD)and cellulase. The optimum emperature of the immobilized GOD (IG) was determined to be 60℃which is higher than that of the native GOD about 40℃. The optimum temperature of the immobilized cellulase (IC) was determined to be about 30℃higher than that of native cellulase. Both of the optimum pH of IG and IC shifted one pH unit to acid. Immobilized enzyme may be used in more wide pH range. Their storage life are much longer compared with their native states. Both of them can be reused at least 12 times. 相似文献
A homogenous assay of FAD using a binding between glucose oxidase (apo‐GOD) and FAD labeled with an electroactive compound was developed. Because daunomycin is sensitively detected with voltammetry, daunomycin was connected to FAD with a cross‐linker. The peak current decreased due to the apo‐GOD‐labeled FAD binding. Competitive reaction to the apo‐GOD between FAD and the labeled FAD produces the increase of peak current. Accordingly, FAD is detected on the basis of the reaction. The merit of this method is that the influence from FMN and riboflavin in the measurement of FAD can be suppressed by the high selective binding. 相似文献
A simple and effective glucose biosensor based on immobilization of glucose oxidase (GOD) in graphene (GR)/Nafion film was constructed. The results indicated that the immobilized GOD can maintain its native structure and bioactivity, and the GR/Nafion film provides a favorable microenvironment for GOD immobilization and promotes the direct electron transfer between the electrode substrate and the redox center of GOD. The electrode reaction of the immobilized GOD shows a reversible and surface‐controlled process with the large electron transfer rate constant (ks) of 3.42±0.08 s?1. Based on the oxygen consumption during the oxidation process of glucose catalyzed by the immobilized GOD, the as‐prepared GOD/GR/Nafion/GCE electrode exhibits a linear range from 0.5 to 14 mmol·L?1 with a detection limit of 0.03 mmol·L?1. Moreover, it displays a good reproducibility and long‐term stability. 相似文献
New polymer/silica gel hybrid supports were prepared by coating high surface area of silica gel with modified acrylonitrile copolymer. The concentrations of the modifying agent (NaOH) and the modified polymer were varied. GOD was covalently immobilized on these hybrid supports and the relative activity and the amount of bound protein were determined. The highest relative activity and sufficient amount of bound protein of the immobilized GOD were achieved in 10% NaOH and 2% solution of modified acrylonitrile copolymer. The influence of glutaraldehyde concentration and the storage time on enzyme efficiency were examined. Glutaraldehyde concentration of 0.5% is optimal for the immobilized GOD. It was shown that the covalently bound enzyme (using 0.5% glutaraldehyde) had higher relative activity than the activity of the adsorbed enzyme. Covalently immobilized GOD with 0.5% glutaraldehyde was more stable for four months in comparison with the one immobilized on pure silica gel, hybrid support with 10% glutaraldehyde and the free enzyme. The effect of the pore size on the enzyme efficiency was studied on four types of silica gel with different pore size. Silica with large pores (CPC-Silica carrier, 375 A) presented higher relative activity than those with smaller pore size (Silica gel with 4, 40 and 100 A). The amount of bound protein was also reduced with decreasing the pore size. The effect of particle size was studied and it was found out that the smaller the particle size was, the greater the activity and the amount of immobilized enzyme were. The obtained results proved that these new polymer/silica gel hybrid supports were suitable for GOD immobilization. 相似文献
The immobilization and encapsulation of glucose oxidase (GOD) onto the mesoporous and the non-porous silica spheres prepared by co-condensation of tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane (APTMS) in the water-in-oil (W/O) emulsion system were studied. The terminal amine group was used as the important functionality for GOD immobilization on the silica substrate. When only TEOS is used as a silica source, the disordered mesoporous silica microspheres are obtained. As the molar ratio of APTMS to TEOS (RAT) increases, the surface area and pore volume of the silica particles measured by nitrogen adsorption and desorption method and SEM decrease rapidly. Particularly, the largest change of the surface morphology is observed between RAT = 0.20 and RAT = 0.25. The amount and the adsorption time of immobilized enzyme were measured by UV spectroscopy. About 20 wt% of GOD was immobilized into the silica substrates above RAT = 0.60 and was completely adsorbed into the substrate of RAT = 0.80 with lapse of 4 h after addition. In the measurement of the thermal stability, GOD dissolved in buffer solution loses nearly all of its activity after 30 min at 65 °C. In contrast, GOD immobilized on the surface-modified silica particles still retains about 90% of its activity after the same treatment. At this temperature, the immobilized glucose oxidase retained half of its initial activity after 4 h. It is shown that the suitable usage of functionalizing agent like APTMS as well as the control of surface morphology is very important on the immobilization of enzyme. 相似文献
We immobilized hydroquinone through a spacer to polymer grafted on carbon black and achieved a high-surface-area biofuel cell electrode. Quinone compounds are well-known to transfer electrons in the respiratory chain and have been considered prospective mediators in biofuel cells because of their relatively negative redox potentials. Evaluation of three different spacer arms tethering hydroquinone to linear polymers revealed that only the hydrophilic and flexible di(ethylene oxide) spacer made it possible for immobilized hydroquinone to transfer electrons from glucose oxidase (GOD) to an electrode; direct immobilization and an alkyl spacer did not. The electrode comprising hydroquinone immobilized through di(ethylene oxide) spacer to polymer grafted on carbon black transferred electrons from GOD to the electrode. The potential at which an anodic current began to increase was more negative by about 0.2 V than that for a vinylferrocene-mediated electrode, while the increase in the anodic current density was of the same order. 相似文献
The direct electron transfer of glucose oxidase (GOD) was achieved based on the immobilization of GOD/colloidal gold nanoparticles on a glassy carbon electrode by a Nafion film. The immobilized GOD displayed a pair of well-defined and nearly reversible redox peaks with a formal potential (Eo ') of -0.434 V in 0.1 M pH 7.0 phosphate buffer solution and the response showed a surface-controlled electrode process. The dependence of Eo ' on solution pH indicated that the direct electron transfer reaction of GOD was a two-electron-transfer coupled with a two-proton-transfer reaction process. The experimental results also demonstrated that the immobilized GOD retained its electrocatalytic activity for the oxidation of glucose. So the resulting modified electrode can be used as a biosensor for detecting glucose. 相似文献
Glucose oxidase (GOD) was encapsulated in liposomes, and then the GOD‐containing liposomes were immobilized to a MnO2‐based multilayered nanocomposite film grown electrochemically. Oxidation of glucose took place on the encapsulated GOD in the manganese oxide film, and the generated H2O2 molecules were oxidized catalytically at high valent Mn sites (4+) in the film. Anodic currents due to reoxidation of the reduced Mn ions (3+) were in proportion to the concentration of glucose from 19.6 to 107.1 mM. Such a simple construction of biosensor is applicable to a variety of combinations of liposomal enzymes and substrates. 相似文献