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Öğe Biosorption of mercury(II), cadmium(II) and lead(II) ions from aqueous system by microalgae Chlamydomonas reinhardtii immobilized in alginate beads(Elsevier, 2006) Bayramoğlu, Gülay; Tüzün, İlhami; Çelik, Gökçe; Yilmaz, Meltem; Arica, M. YakupThe potential use of the immobilized microalgae (in Ca-alginate) of Chlamydomonas reinhardtii to remove Hg(II), Cd(II) and Pb(II) ions from aqueous solutions was evaluated using bare Ca-alginate bead as a control system. Ca-alginate beads containing immobilized microalgae were incubated for the uniform growth at 22 degrees C for 5 days. Effects of pH, temperature, initial concentration of metal ions and biosorbent dosages on the adsorption of Hg(II), Cd(II) and Pb(II) ions were studied. Adsorption of Hg(II), Cd(II) and Pb(II) ions on the immobilized microalgae showed highest values at around pH 5.0 to 6.0. The adsorption equilibrium was represented with Langnmir and Freundlich adsorption isotherms. The adsorption of these ions on the immobilized microalgae followed second-order kinetics and equilibrium was established in about 60 min. The temperature change in the range of 5-40 degrees C did not affect the adsorption capacities of the immobilized microalgae. The immobilized-algal systems can be regenerated using 2 M NaCl for Hg(II), Cd(II) and Pb(II) ions. (c) 2006 Elsevier B.V. All rights reserved.Öğe Covalent immobilization of chloroperoxidase onto magnetic beads: Catalytic properties and stability(Elsevier, 2008) Bayramoglu, Guelay; Kiralp, Senem; Yilmaz, Meltem; Toppare, Levent; Arica, M. YakupAmino groups containing magnetic beads were used in covalent immobilization of the enzyme "chloroperoxidase (CPO)" which is one of a few enzymes that can catalyse the peroxide dependent oxidation of a wide spectrum of organic and inorganic compounds. The magnetic poly(glycidylmethacrylate-methylmethacrylate-etbyleneglycol dimethacrylate), magnetic p(GMA-MMA-EGDMA) beads were prepared via suspension polymerization in the presence of ferric ions. The magnetic beads were characterized with scanning electron microscope (SEM), Fourier transform infrared (FTIR), Mossbauer spectroscopy and vibrating sample magnetometer (VSM). The magnetic beads were derivatized sequentially with ammonia and glutaraldehyde, and CPO was covalently immobilized on the support via reaction of the amino groups of the enzyme under mild conditions. The effect of various parameters including pH, temperature and enzyme concentration on the immobilization efficiency of CPO onto glutaric dialdhyde activated magnetic beads was evaluated. Magnetic measurement revealed that the resultant CPO-immobilized magnetic beads were superparamagnetic with a saturation magnetization of 18.2 emu/g. The analysis of FTIR spectra confirmed the binding of CPO on the magnetic beads. The maximum amount of immobilized CPO on the magnetic beads was 2.94 mg/g support. The values of Michaelis constants Km for immobilized CPO was significantly larger, indicating decreased affinity by the enzyme for its substrate, whereas V-max values were smaller for the immobilized CPO. However, the CPO immobilized on the magnetic beads resulted in an increase in enzyme stability with time. (c) 2007 Elsevier B.V. All rights reserved.Öğe Heparin-coated poly(hydroxyethyl methacrylate/albumin) hydrogel networks: In vitro hemocompatibility evaluation for vascular biomaterials(Wiley, 2008) Bayramoglu, Gülay; Yilmaz, Meltem; Batislam, Ertan; Arica, M. YakupHuman serum albumin (AL) containing poly(hydroxyethyl methacrylate) (pHEMA; in tube form with an inner diameter of 6 mm) was synthesized for blood-contacting hydrogel networks via UV-initiated photopolymerization. at 25 degrees C. Tensile and breaking tests of pHEMA and pHEMA-AL-1-4 hydrogel networks were studied at their equilibrium water content. The mechanical strength of the hydrogel networks was found to be lowered by an increase in the ratio of AL in the polymer networks. To increase the blood compatibility and prevent thrombus formation, the surface of the pHEMA and pHEMA-AL-3 hydrogel compositions were coated with heparin (HEP). Contact-angle studies showed that the polarities (%) of the pHEMA-AL-3 and pHEMA-AL-3-HEP hydrogel networks were significantly increased in comparison with that of pure pHEMA. The fibrinogen adsorption and platelet adhesion were also reduced after the incorporation of AL and HEP into/onto hydrogel networks in comparison with the pure pHEMA control. Blood compatibility tests of the prepared hydrogel networks, which were intended to be used as blood-contacting materials, were examined with various parameters, such as the hemolytic activity, prothrombin time, activated thromboplastin time, and loss of blood cells in blood. (C) 2008 Wiley Periodicals, Inc.Öğe Preparation of nanofibrous polymer grafted magnetic poly(GMA-MMA)-g-MAA beads for immobilization of trypsin via adsorption(Elsevier, 2008) Bayramoglu, Guelay; Yilmaz, Meltem; Senel, Ayseguel Uelkue; Arica, M. YakupPoly (glycidylmethacrylate-methylmethacrylate), poly(GMA-MMA) beads were prepared via suspension polymerization in the presence of ferric ions. The epoxy groups of the poly(GMA-MMA) beads were converted into amino groups during magnetization reaction, and then were grafted with methacrylic acid (MAA) via graft copolymerization. The magnetic beads were characterized by surface area measurement, swelling test, scanning electron microscope (SEM), electron spin resonance (ESR) and Mossbauer spectroscopy. The enzyme "trypsin" was immobilized on the magnetic beads via adsorption. The maximum adsorption was obtained at pH 7.0. At 2.0 mg/mL initial trypsin concentration, the maximum immobilization capacity was 123.2 mg trypsin/g beads and retained about 84.2% of its initial activity. The immobilized trypsin could not be desorbed by enzyme reaction solution in the pH range of 5.0-9.0, and could be desorbed by 1.0 M formic acid solution containing 1 M NaCl. (C) 2007 Elsevier B.V. All rights reserved.
