Covalent Immobilization (covalent + immobilization)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


COVALENT IMMOBILIZATION OF INVERTASE ON CHEMICALLY ACTIVATED POLY (STYRENE-2-HYDROXYETHYL METHACRYLATE) MICROBEADS

JOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2008
HAYDAR ALTINOK
ABSTRACT A carrier for invertase enzyme was synthesized from styrene (S) and 2- hydroxyethyl methacrylate (HEMA) in the form of microbeads. These poly (styrene-2-hydroxyethyl methacrylate), P(S-HEMA) microbeads were activated by epichlorohydrin (ECH) treatment for covalent immobilization. The free and immobilized invertase were assayed in the hydrolysis of sucrose to glucose, and the obtained results were compared. The optimum pH was 4.5 for free and 5.5 for immobilized invertase. The optimum temperature of invertase shifted from 45C to 55C upon immobilization. For free and immobilized enzymes, kinetic parameters were calculated as 4.1 10,3 mol L,1and 9.2 10,3 mol L,1for Km, and 6.6 10,2 mol L,1 min,1and 4.1 10,1 mol L,1 min,1for Vmax, respectively. After 1 month of storage at 4C, free enzyme retained 36% of its initial activity, while for the ECH-activated P(S-HEMA) immobilized enzyme, P(S-HEMA)-E, this value was observed as 67%. In repeated batch use, i.e., 20 times in 3 days, 78% retention of the initial activity was observed for P(S-HEMA)-E system. PRACTICAL APPLICATIONS Immobilization of enzymes are very important for many industrial applications, e.g., food, medicine, pharmacology, etc. Invertase converts sucrose to glucose and fructose, which have wide applications in food industry especially as sweeteners. Glucose,fructose mixture has much lower crystallinity compared to sucrose and therefore used in the production of noncrystallizing jams and creams. They are also used as liquid sweeteners. Immobilization enables repeated use, provides significant reduction in the operation costs, facilitates easy separation and speeds up recovery of enzyme and extends the stability of enzyme by protecting the active material from deactivation. Industrial application of immobilized invertase may decrease the production cost of glucose,fructose mixture because it could be used repeatedly for long periods. Although invertase is not a very expensive enzyme, the technique can also be applied to expensive ones for biotechnological productions. [source]


A Flexible and Versatile Strategy for the Covalent Immobilization of Chiral Catalysts Based on Pyridinebis(oxazoline) Ligands.

CHEMINFORM, Issue 49 2005
Alfonso Cornejo
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Covalent immobilization of ,-galactosidase on carrageenan coated with chitosan

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009
Magdy M.M. Elnashar
Abstract ,-Galactosidase was covalently immobilized to carrageenan coated with chitosan for the hydrolysis of lactose. The chitosan-carrageenan polyelectrolyte interaction was found to be dependent on the chitosan pH. At pH 4, the chitosan reached its maximum binding of 28.5% (w/w) where the chitosan surface density was 4.8 mg chitosan/cm2 g of carrageenan gel disks, using Muzzarelli method. Glutaraldehyde was used as a mediator to incorporate new functionality, aldehydic carbonyl group, to the bio-polymers for covalent attachment of ,-galactosidase. The enzyme was covalently immobilized to the biopolymer at a concentration of 2.73 mg protein per g of wet gel. FTIR proved the incorporation of the aldehydic carbonyl group to the carrageenan coated with chitosan at 1720 cm,1. The optimum time for enzyme immobilization was found to be 16 h, after which a plateau was reached. The enzyme loading increased from 2.65 U/g (control gel) to 10.92 U/g gel using the covalent technique. The gel's modification has shown to improve the carrageenan gel thermal stability as well as the immobilized enzyme. For example, the carrageenan gel treated with chitosan showed an outstanding thermal stability at 95C compared with 35C for the untreated carrageenan gel. Similarly, the immobilization process shifted the enzyme's optimum temperature from 50C for the free enzyme towards a wider temperature range 45,55 C indicating that the enzyme structure is strengthened by immobilization. In brief, the newly developed immobilization method is simple; the carrier is cheap, yet effective and can be used for the immobilization of other enzymes. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]


Electrocatalytic Reduction of Nitrite Ion on a Toluidine Blue Sol-Gel Thin Film Electrode Derived from 3-Aminopropyl Trimethoxy Silane

ELECTROANALYSIS, Issue 22 2007
K. Thenmozhi
Abstract An organically modified sol-gel electrode using 3-aminopropyltrimethoxy silane for covalent immobilization of a redox mediator namely toluidine blue has been reported. Cyclic voltammetric characterization of the modified electrode in the potential range of 0.2,V to ,0.6,V exhibited stable voltammetric behavior in aqueous supporting electrolyte with a formal potential of ,0.265,V vs. SCE, corresponding to immobilized toluidine blue. The electrocatalytic activity of the modified electrode when tested towards nitrite ion exhibited a favorable response with the electrocatalytic reduction of nitrite occurring at a reduced potential of ,0.34,V. A good linear working range from 2.9410,6,M to 2.1110,3,M with a detection limit of 1.7610,6,M and quantification limit of 5.8710,6,M was obtained for nitrite determination. The stable and quick response (4,s) of the modified electrode towards nitrite under hydrodynamic conditions shows the feasibility of using the present sensor in flow systems. Significant improvements in the operational stability by overcoming the leachability problem and repeatability with a relative standard deviation of 1.8% of the TB thin film sensor have been obtained by the strategy of immobilization of the mediator in the sol-gel matrix. [source]


Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide

ELECTROANALYSIS, Issue 6 2007
Aminur Rahman
Abstract A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly-5, 2,: 5,, 2,-terthiophine-3-carboxylic acid), poly-TTCA through the formation of amide bond between carboxylic acid groups of poly-TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly-TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X-ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly-TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73,s,1. The biosensor efficiently detected xanthine through oxidation at +0.35,V and reduction at ,0.25,V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.010,6,1.010,4 M and 5.010,7 to 1.010,4,M, respectively. The detection limits were determined to be of 1.010,6,M and 9.010,8,M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. [source]


Chitosan-Glutamate Oxidase Gels: Synthesis, Characterization, and Glutamate Determination

ELECTROANALYSIS, Issue 23 2005
Maogen Zhang
Abstract The biopolymer chitosan (CHIT) was chemically modified with glutaric dialdehyde (GDI) and used for the covalent immobilization of enzyme glutamate oxidase (GmOx). The relationships between the loaded, retained, and active units of GmOx in the CHIT-GDI-GmOx gels were determined by electrochemical assays. The latter indicated that on average ca. 95% of the GmOx was retained in the CHIT-GDI matrix that was loaded with 0.10,3.0 units of the enzyme. The maximum activity of the GmOx immobilized in the gels corresponded to ca. 5% of the activity of the free enzyme. Platinum electrodes coated with CHIT-GDI-GmOx gels (films) were used as amperometric biosensors for glutamate. Such biosensors displayed good operational and long-term stability (at least 11,h and 100 days, respectively) in conjunction with low detection limit of 0.10,,M glutamate (S/N=3), linear range up to 0.5,mM (R2=0.991), sensitivity of 100 mA M,1 cm,2, and short response time (t90%=2,s). This demonstrated an efficient signal transduction in the Pt/CHIT-GDI-GmOx+glutamate system. The CHIT-GDI-GmOx gels constitute a new biosensing element for the development of glutamate biosensors. [source]


Simple Preparation of Dimeric Cinchona Alkaloid Derivatives on Polystyrene Supports and a Highly Enantioselective Catalytic Heterogeneous Dimerization of Ketenes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010
Ravindra
Abstract A convenient route for the covalent immobilization of quinidine and hydroquinidine pyridazine ethers on insoluble polystyrene supports is described, which avoids the need of chromatographic purifications at any stage. The use of the heterogeneized alkaloid derivatives in the asymmetric organocatalytic dimerization of ketenes afforded high enantioselectivity values (90,97% ee) in the course of 20 reaction cycles. [source]


Novel thermally and mechanically stable hydrogel for enzyme immobilization of penicillin G acylase via covalent technique

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Magdy M. M. Elnashar
Abstract ,-Carrageenan hydrogel crosslinked with protonated polyethyleneimine (PEI+) and glutaraldehyde (GA) was prepared and evaluated as a novel biocatalytic support for covalent immobilization of penicillin G acylase (PGA). The method of modification of the carrageenan biopolymer is clearly illustrated using a schematic diagram and was verified by FTIR, elemental analysis, DSC, and INSTRON using the compression mode. Results showed that the gels' mechanical strength was greatly enhanced from 3.9 kg/cm2 to 16.8 kg/cm2 with an outstanding improvement in the gels thermal stability. It was proven that, the control gels were completely dissolved at 35C, whereas the modified gels remained intact at 90C. The DSC thermogram revealed a shift in the endothermic band of water from 62 to 93C showing more gel-crosslinking. FTIR revealed the presence of the new functionality, aldehydic carbonyl group, at 1710 cm,1 for covalent PGA immobilization. PGA was successfully immobilized as a model industrial enzyme retaining 71% of its activity. The enzyme loading increased from 2.2 U/g (control gel) to 10 U/g using the covalent technique. The operational stability showed no loss of activity after 20 cycles. The present support could be a good candidate for the immobilization of industrial enzymes rich in amino groups, especially the thermophilic ones. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Stabilization of penicillin V acylase from Streptomyces lavendulae by covalent immobilization

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2001
Jess Torres-Bacete
Abstract Penicillin,V acylase from the actinomycete Streptomyces lavendulae ATCC 13664 has been immobilized to epoxy-activated acrylic beads (Eupergit C) by covalent binding. Further linkage of bovine serum albumin after enzyme immobilization was carried out in order to remove the remaining oxirane groups of the support. The obtained immobilized biocatalyst displayed double exponential deactivation kinetics at temperatures below 55,C, while the native enzyme followed single exponential decay at the same temperatures. We concluded that soluble penicillin acylase was deactivated in one step, whereas the immobilized enzyme showed an enzymatic intermediate state which is highly thermostable. As a consequence of the immobilization process, the enzyme displayed a 10-fold increase in its half-life at 40,C. At this temperature, the enzymatic intermediate state was progressively destabilized as the pH of the medium was increased. Thus, the optimum pH range for the immobilized enzyme preparation was established as being from 7.0 to 8.0. Higher pH values led to quicker enzyme deactivation. 2001 Society of Chemical Industry [source]


COVALENT IMMOBILIZATION OF INVERTASE ON CHEMICALLY ACTIVATED POLY (STYRENE-2-HYDROXYETHYL METHACRYLATE) MICROBEADS

JOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2008
HAYDAR ALTINOK
ABSTRACT A carrier for invertase enzyme was synthesized from styrene (S) and 2- hydroxyethyl methacrylate (HEMA) in the form of microbeads. These poly (styrene-2-hydroxyethyl methacrylate), P(S-HEMA) microbeads were activated by epichlorohydrin (ECH) treatment for covalent immobilization. The free and immobilized invertase were assayed in the hydrolysis of sucrose to glucose, and the obtained results were compared. The optimum pH was 4.5 for free and 5.5 for immobilized invertase. The optimum temperature of invertase shifted from 45C to 55C upon immobilization. For free and immobilized enzymes, kinetic parameters were calculated as 4.1 10,3 mol L,1and 9.2 10,3 mol L,1for Km, and 6.6 10,2 mol L,1 min,1and 4.1 10,1 mol L,1 min,1for Vmax, respectively. After 1 month of storage at 4C, free enzyme retained 36% of its initial activity, while for the ECH-activated P(S-HEMA) immobilized enzyme, P(S-HEMA)-E, this value was observed as 67%. In repeated batch use, i.e., 20 times in 3 days, 78% retention of the initial activity was observed for P(S-HEMA)-E system. PRACTICAL APPLICATIONS Immobilization of enzymes are very important for many industrial applications, e.g., food, medicine, pharmacology, etc. Invertase converts sucrose to glucose and fructose, which have wide applications in food industry especially as sweeteners. Glucose,fructose mixture has much lower crystallinity compared to sucrose and therefore used in the production of noncrystallizing jams and creams. They are also used as liquid sweeteners. Immobilization enables repeated use, provides significant reduction in the operation costs, facilitates easy separation and speeds up recovery of enzyme and extends the stability of enzyme by protecting the active material from deactivation. Industrial application of immobilized invertase may decrease the production cost of glucose,fructose mixture because it could be used repeatedly for long periods. Although invertase is not a very expensive enzyme, the technique can also be applied to expensive ones for biotechnological productions. [source]


Principle of a New Immunoassay Based on Electrophoretic Mobility of Poly(styrene/, - tert -butoxy- , -vinylbenzyl-polyglycidol) Microspheres: Application for the Determination of Helicobacter pylori IgG in Blood Serum

MACROMOLECULAR BIOSCIENCE, Issue 1 2005
Teresa Basinska
Abstract Summary: The principle of a novel latex diagnostic test for the determination of antibodies against Helicobacter pylori in blood sera is described. The test is based on the measurement of the electrophoretic mobility of the microspheres with immobilized H. pylori antigens. The electrophoretic mobility of these microspheres depends on the concentration of the antibodies against H. pylori in suspending medium. Particles with hydrophilic polyglycidol in the surface layer were used for the test. The microspheres were obtained by an emulsifier-free emulsion copolymerization of styrene and , - tert -butoxy- , -vinylbenzyl-polyglycidol macromonomer (,=,220 nm, diameter polydispersity factor ,=,1.02). Activation of polyglycidol hydroxyl groups with cyanuric chloride allowed for covalent immobilization of H. pylori antigens. The fraction of H. pylori not specifically adsorbed onto the microspheres was negligible. Changes of the electrophoretic mobility of the microspheres with the surface concentration of the covalently immobilized H. pylori antigens ,,=,(1.6,,0.3),,10,3 g m,2 were suitable for the detection of the antibodies in the sera of patients with titer in the range (determined by the indirect ELISA test) from 1:500 to 1:32,000. [source]


Effect of immobilization of polysaccharides on the biocompatibility of poly(butyleneadipate- co -terephthalate) films

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2010
Win-Chun Jao
Abstract Aiming to improve the hydrophilicity, antibacterial activity, cytocompatibility, and hemocompatibility of poly(butyleneadipate- co -terephthalate) (PBAT) films, PBAT films were treated with ozone, grafted with chitosan (CS), and followed by covalent immobilization of either heparin (HEP) or hyaluronic acid (HA). The surface graft density of modified PBAT films was detected by X-ray photoelectron spectroscopy (XPS) and dyeing. The surface roughness of PBAT films was measured using an atomic force microscope (AFM). After immobilizing CS, PBAT films acquired antibacterial activity against Staphylococcus aureus and Escherichia coli. The adsorption of human serum albumin (HSA) and human plasma fibrinogen (HPF) on PBAT,CS,HEP and PBAT,CS,HA films was lower compared to that of native PBAT. Moreover, HEP immobilization could effectively reduce platelet adhesion and prolong the blood coagulation time, thereby improving the blood compatibility of PBAT. In addition, the growth of L929 fibroblasts was improved for HEP or HA immobilized PBAT, suggesting this surface modification was non-cytotoxic. Furthermore, PBAT,CS,HEP and PBAT,CS,HA exhibited higher cell proliferation than native PBAT. Copyright 2009 John Wiley & Sons, Ltd. [source]


High-level production and covalent immobilization of Providencia rettgeri penicillin G acylase (PAC) from recombinant Pichia pastoris for the development of a novel and stable biocatalyst of industrial applicability

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2006
Lidija Senerovic
Abstract A complete, integrated process for the production of an innovative formulation of penicillin G acylase from Providencia rettgeri(rPACP.rett)of industrial applicability is reported. In order to improve the yield of rPAC, the clone LN5.5, carrying four copies of pac gene integrated into the genome of Pichia pastoris, was constructed. The proteinase activity of the recombinant strain was reduced by knockout of the PEP4 gene encoding for proteinase A, resulting in an increased rPACP.rett activity of approximately 40% (3.8 U/mL vs. 2.7U/mL produced by LN5.5 in flask). A high cell density fermentation process was established with a 5-day methanol induction phase and a final PAC activity of up to 27 U/mL. A single step rPACP.rett purification was also developed with an enzyme activity yield of approximately 95%. The novel features of the rPACP.rett expressed in P.pastoris were fully exploited and emphasized through the covalent immobilization of rPACP.rett. The enzyme wasimmobilized on a series of structurally correlated methacrylic polymers, specifically designed and produced for optimizing rPACP.rett performances in both hydrolytic and synthetic processes. Polymers presenting aminic functionalities were the most efficient, leading to formulations with higher activity and stability (half time stability >3 years and specific activity ranging from 237 to 477 U/g dry based on benzylpenicillin hydrolysis). The efficiency of the immobilized rPACP.rett was finally evaluated by studying the kinetically controlled synthesis of ,-lactam antibiotics (cephalexin) and estimating the synthesis/hydrolysis ratio (S/H), which is a crucial parameter for the feasibility of the process. 2005 Wiley Periodicals, Inc. [source]


Synthesis and Characterization of Oriented Glyco-Capturing Macroligand

CHEMBIOCHEM, Issue 14 2010
Srinivas Chalagalla
Abstract An oriented glyco-capturing macroligand was synthesized by site-specific immobilization of an O -cyanate chain-end-functionalized boronic acid containing polymer (boropolymer) onto an amine surface. The O -cyanate chain-end-functionalized boropolymer was synthesized by arylamine-initiated cyanoxyl-mediated free-radical polymerization in a one-pot fashion. The chain-end O -cyanate was confirmed by 13C NMR spectroscopy. The specific carbohydrate-binding capacity of the boropolymer was evaluated by an alizarin red S assay. Oriented and covalent immobilization of the O -cyanate chain-end-functionalized boropolymer onto the amine-modified solid surfaces and its specific glyco-capturing capacity were confirmed by the quartz crystal microbalance (QCM) and atomic force microscopy (AFM) techniques. The oriented multivalent glyco-capturing ligand can be used for efficient carbohydrate and glycoconjugate purification and identification, and thus is expected to constitute a core strategy of glycomics and glycoproteomics and carbohydrate-sensing applications. [source]


Catalysis of a Peptidic Micellar Assembly Covalently Immobilized within Mesoporous Silica Channels: Importance of Amphiphilic Spatial Design

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2007
Wataru Otani
Abstract A mesostructured silica/organic composite 1-MS, constructed from a rodlike micelle of amino acid amphiphile 1 that has a condensable head group and that can be used as a template, was found to be able to catalyze the acetalization of cyclohexanone, in ethanol at 25,C (50,% in 12,h), whereas no reaction took place with unfunctionalized mesoporous silica. In sharp contrast, hydrolytic removal of the C16 alkyl tail of immobilized 1 resulted in the complete disappearance of the catalytic activity, which suggests the importance of a hydrophobic inner domain for the admission of cyclohexanone. Unsupported peptide amphiphile 2, under identical conditions to those above, was inefficient for acetalization regardless of the absence (2,% in 24,h) or presence of mesoporous silica (7,% in 24,h). Reference composite 2-MS, which is a noncovalently immobilized peptidic micelle, was virtually inactive (1,% in 24,h). These observations indicate the importance of covalent immobilization of the peptidic rod micelle for catalysis. Mesostructured silicate 3-MS hybridized with a nonpeptidic, ammonium ion amphiphile (3) showed a certain catalytic activity, but the yield (12,% in 24,h) of the acetal was much lower than that achieved by using 1-MS as the catalyst. Amorphous silica with immobilized 1 on its surface was much less active than 1-MS for acetalization (5,% in 24,h). [source]


Nucleic Acid Biosensor for Detection of Human Immunodeficiency Virus Using Aquabis(1,10-phenanthroline)copper(II) Perchlorate as Electrochemical Indicator

CHINESE JOURNAL OF CHEMISTRY, Issue 1 2008
Shu-Yan NIU
Abstract The electrochemical behavior of aquabis(1,10-phenanthroline)copper(II) perchlorate [Cu(H2O)(phen)2]2ClO4, where phen=1,10-phenanthroline, on binding to DNA at a glassy carbon electrode (GCE) and in solution, was described. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that [Cu(H2O)(phen)2]2+ had excellent electrochemical activity on the GCE with a couple of quasi-reversible redox peaks. The interaction mode between [Cu(H2O)(phen)2]2+ and double-strand DNA (dsDNA) was identified to be intercalative binding. An electrochemical DNA biosensor was developed with covalent immobilization of human immunodeficiency virus (HIV) probe for single-strand DNA (ssDNA) on the modified GCE. Numerous factors affecting the probe immobilization, target hybridization, and indicator binding reactions were optimized to maximize the sensitivity and speed of the assay. With this approach, a sequence of the HIV could be quantified over the range from 7.810,9 to 3.110,7 molL,1 with a linear correlation of ,=0.9987 and a detection limit of 1.310,9 molL,1. [source]