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Adsorption of heavy metal ions onto ethylene diamine-derived and Cibacron Blue F3GA-incorporated microporous poly(2-hydroxyethyl methacrylate) membranes
(Elsevier Science Bv, 2000) Denizli, A; Say, R; Patir, S; Arica, MY
Microporous poly( 2-hydroxyethylmethacrylate) (PHEMA) membranes carrying ethylene diamine (EDA) and Cibacron Blue F3GA were prepared for the removal of heavy metal ions (i.e. mercury, copper, lead and cadmium) from aqueous solutions containing different amounts of these ions (5-700 mu g 1(-1)) and at different pH values (2.0-8.0). The non-specific adsorption of heavy metal ions on the underived membranes was very low (3.3 mmol/m(2) for Hg(II), 0.5 mmol/m(2) for Cu(II), 1.2 mmol/m(2) for Pb(II) and 1.1 mmol/m(2) for Cd(II)). Cibacron Blue F3GA attachment significantly increased the heavy metal adsorption (16.3 mmol/m(2) for Hg(II), 19.9 mmol/m(2) for Cu(II), 23.4 mmol/m(2) for Pb(II) and 38.4 mmol/m(2) for Cd(LI)). When the heavy metal ions competed (in the case of the adsorption from a mixture) the adsorption capacities were 7.1 mmol/m(2) for Hg(II), 17.9 mmol/m(2) for Cu(II), 6.2 mmol/m(2) for Pb(II) and 9.1 mmol/m(2) for Cd(lI). The observed order in adsorption was found to be Cd(II) > Pb(II) > Cu(II) > Hg(II) for non-competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. Desorption of heavy metal ions was achieved using 0.1 M HNO3. These membranes are suitable for repeated use for more than five cycles without considerable loss of adsorption capacity. (C) 2000 Elsevier Science B.V. All rights reserved.
Affinity interaction of hydroxypyruvate reductase from Methylophilus spp. with Cibacron blue F3GA-derived poly(HEMA EGDMA) microspheres: partial purification and characterization
(Elsevier Sci Ltd, 1999) Arica, MY; Halicigil, C; Alaeddinoglu, G; Denizli, A
A methylotrophic hydroxypyruvate reductase was partially purified and characterized from Methylophilus spp. using the biomimetic dye, Cibacron Blue F3FA attached to poly(HEMA-EGDMA) microspheres. The absorption capacities of the dye-affinity microspheres were determined by changing pH and the concentration of the proteins in the adsorption medium. Hydroxypyruvate reductase was desorbed from the dye-affinity support specifically with 2 mM NADH solution. The enzyme was purified 10.4-fold with 47% yield. The molecular mass and subunit molecular mass of the enzyme was estimated to be 75 kDa and 37 kDa on the basis of its mobility in polyacrylamide and SDS-polyacrylamide gels, respectively. This suggested a homogeneous dimer structure. The optimal pH was between 5.0 and 7.0, and the maximum enzyme activity was obtained at 50 degrees C. The K-m values of hydroxpyruvate reductase were 0.222 mM for hydroxpyruvate and 0.067 mM for NADH. (C) 1999 Elsevier Science Ltd. All rights reserved.
Affinity microspheres and their application to lysozyme adsorption: Cibacron Blue F3GA and Cu(II) with poly(HEMA-EGDMA)
(Wiley, 1999) Denizli, F; Denizli, A; Arica, MY
Lysozyme adsorption onto Cibacron Blue F3GA attached and Cu(II) incorporated poly(2-hydroxyethyl methacrylate-ethylene glycol dimethacrylate) [poly(HEMA-EGDMA)] microspheres was investigated. The microspheres were prepared by suspension polymerization. Various amounts of Cibacron Blue F3GA were attached covalently onto the microspheres by changing the initial concentration of dye in the reaction medium. The microspheres with a swelling ratio of 65%, and carrying different amounts of dye (between 1.4 and 22.5 mu mol/g(-1)) were used in the lysozyme adsorption studies. Lysozyme adsorption on these microspheres from aqueous solutions containing different amounts of lysozyme at different pH values was investigated in batch reactors. The lysozyme adsorption capacity of the dye-metal chelated microspheres (238.2 mg g(-1)) was greater than that of the dye-attached microspheres (175.1 mg g(-1)). The maximum lyzozyme adsorption capacities (q(m)) and the dissociation constant (k(d)) values were found to be 204.9 mg g(-1) and 0.0715 mg ml(-1) with dye-attached and 270.7 mg g(-1) and 0.0583 mg ml(-1) with dye-metal chelated microspheres, respectively. More than 90% of the adsorbed lysozyme were desorbed in 60 min in the desorption medium containing 0.5 M KSCN at pH 8.0 or 25 mM. EDTA at pH 4.9. (C) 1999 Society of Chemical Industry.
Biosorption of inorganic mercury and alkylmercury species on to Phanerochaete chrysosporium mycelium
(Elsevier Sci Ltd, 1999) Saglam, N; Say, R; Denizli, A; Patir, S; Arica, MY
The biosorption of inorganic mercury (HgCl2), methyl mercury (CH3HgCl) and ethyl mercury (C2H5HgCl) onto the dry biomass of Phanerochaete chryosponum was studied from aqueous media which concentrations in the range of 5-500 mg l(-1). The surface charge density varied with pH, and the concentration of mercury species adsorbed significantly increased from pH 3.0 to maximum levels at pH 8.0. The biosorption of mercury ions by Phanerochaete chrysosporium increased as the initial concentration of Hg(II) ion increased in the adsorption medium. A biosorption equilibrium were established after about 6 h, the adsorbed Hg(II) ion did not significantly change further with time. The dissociation constant (k(d)) values were 72, 63, and 61 mg l(-1) for CH3HgCl, C2H5HgCl and for Hg(II), respectively. The maximum biosorption capacity (q(m)) at pH 7.0 was 79 mg for CH3HgCI, 67 mg for C2H5HgCl and 61 mg for Hg(II) per g of dried fungal biomass. The affinity order of mercury species was CH3HgCl > C2H5HgCl > and Hg(II). (C) 1999 Elsevier Science Ltd. All rights reserved.
Catalase adsorption onto cibacron blue F3GA and Fe(III)derivatized poly(hydroxyethyl methacrylate) membranes and application to a continuous system
(Elsevier Science Bv, 1997) Arica, MY; Denizli, A; Salih, B; Piskin, E; Hasirci, V
Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) membranes were prepared by W-initiated photopolymerization of HEMA in the presence of an initiator (a-a'-azobisisobutyronitrile, AIBN). An affinity dye, i.e. Cibacron Blue F3GA (CB) was incorporated covalently and then complexed with Fe(III) ions. The polyHEMA-CB and polyHEMA-CB-Fe(III) derivatized membranes were used in the adsorption of catalase (CAT). The enzyme-loading capability of the Fe(III)-containing membrane (23.6 mu g/cm(2)) was greater than that of the poly(HEMA)-CB derivatized membrane (17.1 mu g/cm(2)). The adsorption phenomena appeared to follow a typical Langmuir isotherm. The K-m values for both immobilized catalases (poly(HEMA)-CB-CAT (22.4 mM) and poly(HEMA)-CB-Fe(III)-CAT (19.3 mM)) were higher than that of free enzyme (16.5 mM). Optimum operational temperature was 5 degrees C higher than that of the free enzyme and was significantly broader. A similar observation was made for the optimum pH. Operational, thermal and storage stabilities were found to increase with immobilization, especially in the presence of Fe(III). It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity or enzyme activity.
Cibacron Blue F3GA and Cu(II) derived poly(2-hydroxyethylmethacrylate) membranes for lysozyme adsorption
(Elsevier Science Bv, 1998) Denizli, A; Senel, S; Arica, MY
Lysozyme adsorption onto Cibacron Blue F3GA and Cu(II) derived poly(2-hydroxyethyl methacrylate) [poly(HEMA)] membranes was investigated. Microporous poly(HEMA) membranes were prepared by photopolymerization of HEMA. The triazine dye, Cibacron Blue F3GA was attached covalently as a dye-ligand. These dye-membranes with a swelling ratio of 58% (w/w), and carrying different amounts of Cibacron Blue F3GA (between 0.35 and 1.07 mu mol cm(-2)) were used in the lysozyme adsorption studies. The effect of initial concentration and pH on the adsorption efficiency of dye-derived and metal-chelated membranes were studied in a batch reactor. The effect of Cu(II) incorporation on lysozyme adsorption was also studied. The non-specific adsorption of lysozyme on the poly(HEMA) membranes was 0.9 mu g cm(-2). Cibacron Blue F3GA attachment significantly increased the lysozyme adsorption up to 133.3 mu gcm(-2) Lysozyme adsorption capacity of the Cu(II) incorporated membranes (165.1 mu g cm(-2)) was greater than that of the Cibacron Blue F3GA-attached membranes. More than 85% of the adsorbed lysozyme was desorbed in 1 h in the desorption medium containing 0.5 M potassium thiocyanate (KSCN) at pH 8.0. (C) 1998 Elsevier Science B.V. All rights reserved.
Cibacron Blue F3GA-incorporated macroporous poly(2-hydroxyethyl methacrylate) affinity membranes for heavy metal removal
(Elsevier Science Bv, 1997) Denizli, A; Salih, B; Arica, MY; Kesenci, K; Hasirci, V; Piskin, E
Macroporous poly(2-hydroxyethyl methacrylate), poly(HEMA), membranes were prepared by UV-initiated photo-polymerization of HEMA in the presence of an initiator (azobisisobutyronitrile, AIBN). An affinity dye, i.e., Cibacron Blue F3GA was then incorporated covalently. These affinity membranes with a swelling ratio of 58%, and carrying 10.67 mmol Cibacron Blue F3GA/m(2) membrane were used in the adsorption/desorption of some selected heavy metal ions [i.e., As(III), Cd(II) and Pb(II)] from aqueous media. Very high adsorption rates were observed and adsorption equilibria were reached in about 30 min. The maximum adsorptions of heavy metal ions onto the dye-incorporated affinity membranes from their single solutions were 12.6 mmol/m(2) for As(III), 61.0 mol/m(2) for Cd(II) and 79.0 mol/m(2) for Pb(II), However, when the heavy metal ions competed (in the case of the adsorption from their mixture) the amounts of adsorption for As(III), Cd(II) and Pb(II) were quite close. Desorption of heavy metal ions was carried out by using 0.1 M HNO3 (pH 1.0). Up to 95% of the adsorbed heavy metal ions were desorbed in 60 min. Repeated adsorption/desorption cycles showed the feasibility of this novel affinity membrane for heavy metal removal.
Comparison of β-galactosidase immobilization by entrapment in and adsorption on poly(2-hydroxyethylmethacrylate) membranes
(John Wiley & Sons Ltd, 1997) Baran, T; Arica, MY; Denizli, A; Hasirci, V
beta-Galactosidase was immobilized in/on poly(2-hydroxyethyl methacrylate) (pHEMA) membranes by two different methods: adsorption on Cibacron F3GA derivatized pHEMA membranes (pHEMA-CB), and entrapment in the bulk of the pHEMA membranes. The maximum beta-galactosidase adsorption on pHEMA-CB membranes was obtained as 95.6 mu g cm(-2) in 2.0 mg cm(-3) enzyme solution. The adsorption phenomena appeared to follow a typical Langmuir isotherm. In the entrapment, an increase in beta-galactosidase loading resulted in a consistent increase in membrane activity from 3.3 x 10(-2) to 17.8 x 10(-2) U cm(-2) pHEMA membranes. The K-m values for both immobilized beta-galactosidase (adsorbed 0.32 mM and entrapped 0.81 mM) were higher than that of the free enzyme (0.26 mM). The optimum reaction temperature of the adsorbed enzyme was 5 degrees C higher than that of both the free and the entrapped enzyme. The optimum reaction pH was 7.5 for free and both immobilized preparations. After 15 successive uses the retained activity of the adsorbed and the entrapped enzymes was 80% and 95%, respectively. The storage stability of the enzyme was found to increase upon immobilization.
Covalent immobilisation of invertase onto a reactive film composed of 2-hydroxyethyl methacrylate and glycidyl methacrylate: properties and application in a continuous flow system
(Elsevier Science Sa, 2003) Bayramoglu, G; Akgol, S; Bulut, A; Denizli, A; Arica, MY
Invertase was covalently immobilised on the poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) (poly(HEMA-GMA)) film. The invertase immobilisation capacity of the films was increased as the GMA ratio increased in the film structure. The immobilised invertase on the poly(HEMA-GMA-3) composition exhibited an activity of 32.7 U cm(-2) film. The optimum temperature of the immobilised invertase increased by 5 degreesC, and the optimal pH values for the free and the immobilised enzymes were determined as 5.0. The retained activity of the immobilised invertase was between 53 and 85%. Kinetic parameters were determined for immobilised invertase as well as for the free enzyme. The values of the Michael's constant K-m of invertase were significantly larger, ca. 2.7 times upon immobilisation, indicating decreased affinity by the enzyme for its substrate, whereas V-max was smaller for immobilised invertase. Activity of the immobilised invertase was quite stable with respect to free counterpart. After 168 h reaction, only 8% of immobilised invertase activity was lost. The operational inactivation rate constant (k(opi)) of the immobilised invertase at 35 degreesC with 200 mM sucrose was 8.23 x 10(-6) min(-1). (C) 2002 Elsevier Science B.V. All rights reserved.
Dithiocarbamate-incorporated monosize polystyrene microspheres for selective removal of mercury ions
(Elsevier Science Bv, 2000) Denizli, A; Kesenci, K; Arica, Y; Piskin, E
Dithiocarbamate-incorporated monosize polystyrene based microspheres (2 mu m in diameter) were used for selective removal of Hg(II) from aqueous solutions containing different amounts of Hg(II) (10-100 ppm). Adsorption rates were observed as high at the beginning of adsorption and then equilibrium was reached in about 30 min. The maximum Hg(II) adsorption capacity of the dithiocarbamate-incorporated PS microspheres was about 33.2 mg per gram of dry polymer, which was observed at pH 7.0. While non-specific Hg(II) adsorption onto the plain microspheres was 0.85 mg per gram of dry microsphere. The Hg(II) adsorption ability increased with increasing pH, in the range where the solubility of the Hg(II) was not affected by the pH. The preferential (i.e., competitive adsorption) binding of Hg(II) by the microspheres implies that this sorbent system might contain higher-affinity binding sites for Hg(ll) than Cu(II), Cd(II) and Pb(II) ions. More than 96% of the adsorbed Hg(II) was desorbed in 15 min by using 0.1 M HNO3 as an elution agent. The regeneration of the dithiocarbamate-incorporated PS microspheres was also sufficient. (C) 2000 Elsevier Science B.V. All rights reserved.
Dye affinity poly(2-hydroxyethyl methacrylate) membranes for removal of heavy metal ions
(Marcel Dekker Inc, 2000) Denizli, A; Say, R; Arica, MY
The dichlorotriazinyl dye-ligand Procion Red HE-3B-anchored poly(EGDMA-HEMA) membranes were used for removal of heavy metal ions (i.e., copper, arsenic, cadmium and mercury) from aqueous media containing different amounts of these ions (0.1-4.5 mmol/L) and at different pH values (2.0-8.0). The HE-3B-anchored membranes from their single solutions were 6.4 mmol/m(2) for Cu(II), 30.1 mmol/m(2) for As(III), 76.3 mmol/m(2) for Cd(II) and 130.3 mmol/m(2) for Hg(II). When the heavy metal ions competed tin the case of the adsorption from their mixture) the adsorption capacities were 7.8 mmol/m(2) fur Cu(II), 24.5 mmol/m(2) for As(III), 27.6 mmol/m(2) for Cd(II) and 42.3 mmol/m2 for Hg(II). The same affinity order was observed under non-competitive and competitive adsorption which was as follows: Hg(II) > Cd(II) > As(III) > Cu(IT). The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. Heavy metal ion adsorption from artificial wastewater was also studied. The adsorption capacities are 4.1 mmol/m(2) for Cu(II), 12.5 mmol/m(2) for As(III), 16.7 mmol/m(2) for Cd(II) and 21.3 mmol/m(2) for Hg(II). Desorption of heavy metal ions was achieved using 0.1 M HNO3. The Procion Red HE-3B-anchored membranes are suitable for repeated use for more than 5 cycles without noticeable loss of capacity.
Dye derived and metal incorporated affinity poly(2-hydroxyethyl methacrylate) membranes for use in enzyme immobilization
(John Wiley & Sons Ltd, 1998) Arica, MY; Denizli, A; Baran, T; Hasirci, V
Microporous poly(2-hydroxyethyl methacrylate) (PHEMA) membranes were prepared by W-initiated photopolymerization of HEMA in the presence of an initiator (alpha,alpha'-azobisisobutyronitrile, AIBN). An affinity dye Cibacron Blue F3GA (CB) was attached covalently and then Fe3+ ions incorporated. The PHEMA-CB and PHEMA-CB-Fe3+ membranes derived were used for adsorption of glucose oxidase (GOD). The adsorption capacities of these membranes were determined under conditions of different pH and with different concentrations of the adsorbate in the medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The glucose oxidase adsorption capacity of the Fe3+ incorporated membrane (87 mu g cm(-2)) was greater than that of the dye-derived membrane (66 mu g cm(-2)). Non-specific adsorption of the glucose oxidase on the PHEMA membranes was negligible. The K-m values for both immobilized glucose oxidase PHEMA-CB-GOD (8.3) and PHEMA-CB-Fe3+-GOD (7.6) were higher than that of the free enzyme (6.2 mM). Optimum reaction pH was 5.5 for the free and 6.0 for both immobilized preparations. The optimum reaction temperature of the adsorbed enzymes was 5 degrees C higher than that of the free enzyme and was significantly broader. After 15 successive uses the retained activity of the adsorbed enzyme was 87%. It was observed that enzymes could be repeatedly adsorbed and desorbed on the derived PHEMA membranes without significant loss in adsorption capacity or enzymic activity. (C) 1998 SCI.
Dye-ligand and metal chelate poly(2-hydroxyethylmethacrylate) membranes for affinity separation of proteins
(Elsevier Science Bv, 1998) Arica, MY; Testereci, HN; Denizli, A
Cibacron Blue F3GA was covalently immobilized onto poly(2-hydroxyethyl methacrylate) (pHEMA) membranes via the nucleophilic reaction between the chloride of its triazine ring and the hydroxyl group of pHEMA. Then, Fe3+ ions were complexed by chelation with the immobilized Cibacron Blue F3GA molecules. Different amounts of Fe3+ ions were loaded on the membranes by changing the concentration of Fe3+ ions and pH of the reaction medium. Membranes with or without Fe3+ were used in the adsorption of glucose oxidase, catalase and bovine serum albumin. The adsorption capacities of these membranes were determined by changing pH and the concentration of the proteins in the adsorption medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The maximum capacities (q(m)) of the Fe3+ complexed membranes for glucose oxidase, catalase and bovine serum albumin (8.70.10(-3) mu mol m(-2), 2.15.10(-3) mu mol m(-3) and 2.21.10(-3) mu mol m(-2)) were greater than those of the untreated membranes (6.79.10(-3) mu mol m(-2), 1.34.10(-3) mu mol m(-2) and 1.94.10(-3) mu mol m(-2)) respectively. The nonspecific adsorption of the enzymes and the protein on the pHEMA membranes was negligible. (C) 1998 Elsevier Science B.V.
Fluoride release from microporous poly(2-hydroxyethyl methacrylate) membranes
(Elsevier Science Bv, 2003) Yildirmaz, G; Akgol, S; Arica, MY; Sonmez, H; Denizli, A
Fluoride ion is commonly used in the preventive treatment of tooth decay and when provided with extra fluoride, children living in regions that lack fluoride benefit from it. In the present study, the clinical properties of an intraoral controlled release fluoride delivery system were considered. Poly (2-hydroxyethyl methacrylate) (PHEMA) was examined as a fluoride carrier. Membranes were prepared by photopolymerization and then characterised. Contact angles and swelling ratios of fluoride-loaded membranes were determined. The surface morphology of the membranes were examined by using scanning electron microscopy. In vitro fluoride release studies were carried out in an artificial saliva medium. The concentration of fluoride was measured with a fluoride-specific electrode. The amount of released fluoride was determined and the effects of fluoride loading, medium pH and temperature on fluoride release were investigated. The swelling ratio of the PHEMA membrane was 58.5%, that of the fluoride-loaded PHEMA membrane was 17.8%. Increasing in the fluoride loading amount in the PHEMA membrane accelerated the fluoride release. The fluoride release ratio was increased with increasing pH and temperature. (C) 2003 Elsevier B.V. All rights reserved.
Immobilization of glucoamylase onto spacer-arm attached magnetic poly(methylmethacrylate) microspheres: characterization and application to a continuous flow reactor
(Elsevier Science Bv, 2000) Arica, MY; Yavuz, H; Patir, S; Denizli, A
Magnetic poly(methylmethacrylate) microspheres (MPMMA) were prepared by the solvent evaporation method and a 6-carbon spacer-arm (i.e. hexamethylene diamine, HMDA) was covalently attached by the reaction of carbonyl groups of poly(methylmethacrylate). Glucoamylase was then covalently immobilized through the spacer-arm of the MPMMA microspheres by using either carbodiimide (CDI) or cyanogen bromide (CNBr) as a coupling agent. The activity yield of the immobilized glucoamylase was 57% for CDI coupling and 73% for CNBr coupling. Kinetic parameters were determined for both immobilized glucoamylase preparations as well as for the free enzyme. The K-m values for immobilized glucoamylases CDI coupling (12.5 g l(-1) dextrin) and CNBr coupling (9.3 g l(-1) dextrin) were higher than that of the free enzyme (2.1 g l(-1) dextrin) whereas V-max values were smaller for the immobilized glucoamylase preparations. The optimum operational temperature was 5 degreesC higher for both immobilized preparations than that of the free enzyme. Operational, thermal and storage stabilities were found to be increased with immobilization. (C) 2000 Elsevier Science B.V. All rights reserved.
In vitro cadmium removal from human serum by Cibacron Blue F3GA-thionein-complex conjugated affinity membranes
(John Wiley & Sons Ltd, 2000) Denizli, F; Denizli, A; Arica, MY
A new membrane affinity biosorbent carrying thionein has been developed for selective removal of cadmium ions from human serum. Microporous poly(2-hydroxyethyl methacrylate) (pHEMA) membranes were prepared by photopolymerization of HEMA. The pseudo dye ligand Cibacron Blue F3GA (CB) was covalently immobilized on the pHEMA membranes. Then, the cysteine-rich metallopeptide thionein was conjugated onto the CB-immobilized membrane. The maximum amounts of CB immobilized and thionein conjugated on the membranes were 1.07 mu mol cm(-2) and 0.92 mu mol cm(-2), respectively. The hydrophilic pHEMA membrane had a swelling ratio of 58% (w/w) with a contact angle of 45.8 degrees. CB-immobilized and CB-immobilized-thionein-conjugated membranes were used in the Cd(II) removal studies. Cd(II) ion adsorption appeared to reach equilibrium within 30 min and to follow a typical Langmuir adsorption isotherm. The maximum capacity (q(m)) of the CB-immobilized membranes was 0.203 (mu mol Cd(II))cm(-2) membrane and increased to 1.48 (mu mol Cd(II))cm(-2) upon CB-thionein-complex conjugation. The pHEMA membranes retained their cadmium adsorption capacity even after 10 cycles of repeated use. (C) 2000 Society of Chemical Industry.
Invertase immobilized on spacer-arm attached poly(hydroxyethyl methacrylate) membrane: Preparation and properties
(John Wiley & Sons Inc, 2000) Arica, MY; Senel, S; Alaeddinoglu, NG; Patir, S; Denizli, A
Microporous poly(2-hydroxyethyl methacrylate) (pHEMA) membrane was prepared by UV-initiated photopolymerization. The spacer arm (i.e., hexamethylene diamine) was attached covalently and then invertase was immobilized by the condensation reaction of the amino groups of the spacer arm with carboxyl groups of the enzyme in the presence of carbodiimides. The values of the Michael's constant K-m of invertase were significantly larger (ca. 2.5 times) upon immobilization, indicating decreased affinity by the enzyme for its substrate, whereas V-max was smaller for the immobilized invertase. Immobilization improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with immobilization and at 70 degrees C the half times for the activity decay were 12 min for the free enzyme and 41 min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments. (C) 2000 John Wiley & Sons, Inc.
Monosize and non-porous p(HEMA-co-MMA) microparticles designed as dye- and metal-chelate affinity sorbents
(Elsevier Science Bv, 2000) Denizli, A; Yavuz, H; Arica, Y
Congo red was immobilised onto monosize and non-porous poly(2-hydroxyethylmethacrylate-co-methylmethacrylate) [p(HEMA-co-MMA)] copolymer microparticles (4.0 mu m in diameter). Then Fe(III) ions were complexed by chelation with the immobilised congo red molecules. Different amounts of Fe(III) ions were loaded on the dye-derived microparticles by changing the concentration of Fe(III) ions and pH of the reaction medium. Congo red-derived and Fe(III)-complexed microparticles were used in the adsorption of glucose oxidase, catalase, lysozyme and bovine serum albumin. The maximum adsorption capacities of these microparticles were determined by changing pH and the concentration of the proteins in the adsorption medium. Their adsorption behavior can be described at least approximately with the Langmuir equation. Glucose oxidase, catalase, lysozyme and bovine serum albumin adsorption capacities of the Fe(III) complexed microparticles (165.1, 135.2, 67.6 and 44.5 mg g(-1)) were higher than those of the congo red-immobilised microparticles (125.9, 94.2, 35.8 and 21.2 mg g(-1), respectively). The non-specific adsorption of the proteins on the p(HEMA-co-MMA) microparticles was negligible. The resulting dye- and metal-chelate affinity microparticles have excellent reusability and long term storage stability. (C) 2000 Elsevier Science B.V. All rights reserved.
New metal chelate sorbent for albumin adsorption: Cibacron blue F3GA-Zn(II) attached microporous poly(HEMA) membranes
(John Wiley & Sons Inc, 1998) Denizli, A; Salih, B; Senel, S; Arica, MY
Poly(2-hydroxyethyl methacrylate) [poly(HEMA)] membranes were prepared by UV-initiated photopolymerization of HEMA in the presence of an initiator (alpha-alpha'-azobis-isobutyronitrile, AIBN). The triazine dye Cibacron Blue F3GA was attached as an affinity ligand to poly(HEMA) membranes, covalently. These affinity membranes with a swelling ratio of 58% and containing 10.7 mmol Cibacron Blue F3GA/m(2) were used in the albumin adsorption studies. After dye-attachment, Zn(TI) ions were chelated within the membranes via attached-dye molecules. Different amounts of Zn(II) ions [650-1440 mg Zn(II)/m(2)] were loaded on the membranes by changing the initial concentration of Zn(II) ions and pH. Bovine serum albumin (BSA) adsorption on these membranes from aqueous solutions containing different amounts of BSA at different pH was investigated in batch reactors. The nonspecific adsorption of BSA on the poly(HEMA) membranes was negligible. Cibacron Blue F3GA attachment significantly increased the BSA adsorption up to 92.1 mg BSA/m(2). Adsorption capacity was further increased when Zn(II) ions were attached (up to 114.8 mg BSA m(2)). More than 90% of the adsorbed BSA was desorbed in 1 h in the desorption medium containing 0.5M NaSCN at pH 8.0 and 0.025M EDTA at pH 4.9. (C) 1998 John Wiley & Sons, Inc.
Nonporous monosize polymeric sorbents: Dye and metal chelate affinity separation of lysozyme
(John Wiley & Sons Inc, 2000) Denizli, A; Yavuz, H; Garipcan, B; Arica, MY
Lysozyme adsorption onto dye-attached nonporous monosize poly(2-hydroxyethyl-methacrylate-methylmethacrylate) [poly(HEMA-MMA)] microspheres was investigated. Poly(HEMA-MNA) microspheres were prepared by dispersion polymerization. The monochloro-triazine dye, Cibacron Blue F3GA, was immobilized covalently as dye-ligand. These dye-affinity microspheres were used in the lysozyme adsorption-desorption studies. The effect of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye-attached and metal-chelated microspheres were studied in a batch reactor. Effect of Cu(II) chelation on lysozyme adsorption was also studied. The nonspecific adsorption of lysozyme on the poly(HEMA-MMA) microspheres was 3.6 mg/g. Cibacron Blue F3GA attachment significantly increased the lysozyme adsorption up to 247.8 mg/g. Lysozyme adsorption capacity of the Cu(II) incorporated microspheres (318.9 mg/g) was greater than that of the Cibacron Blue F3GA-attached microspheres. Significant amount of the adsorbed lysozyme (up to 97%) was desorbed in 1 h in the desorption medium containing 1.0M NaSCN at pH 8.0 and 25 mM EDTA at pH 4.9. In order to examine the effects of separation conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We conclude that dye-attached and metal-chelate affinity chromatography with poly(HEMA-MMA) microspheres can be applied for lysozyme separation without causing any significant changes and denaturation. Repeated adsorption/desorption processes showed that these novel dye-attached monosize microspheres are suitable for lysozyme adsorption. (C) 2000 John Wiley & Sons, Inc.

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