Dye-affinity hollow-fibres and their lysozyme adsorption-desorption characteristics

Akgol, Sinan/0000-0002-8528-1854; AKGOL, Sinan/0000-0003-2836-7181WOS: 000171435700013Dye-affinity adsorption is increasingly used for protein separation. Hollow-fibres have advantages as adsorbents in comparison to conventional bead supports because they are not compressible and can eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow-fibres to which Reactive Green HE-4BD was attached for adsorption of lysozyme. The hollow-fibre was characterized by scanning electron microscopy. These dye-carrying hollow-fibres (26.3 mu mol g(-1)) were used in the lysozyme adsorption-elution studies. The effect of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye-attached hollow-fibres was studied in a batch system. The non-specific adsorption of lysozyme on the polyamide hollow-fibres was 1.8 mgg(-1). Reactive Green HE-4BD attachment significantly increased the lysozyme adsorption up to 41.1 mgg(-1). Langmuir adsorption model was found to be applicable in interpreting lead adsorption by Reactive Green HE-4BD attached hollow fibres. Significant amount of the adsorbed lysozyme (up to 95%) was eluted in lh in the elution medium containing 1.0M NaSCN at pH 8.0. In order to determine the effects of adsorption conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We concluded that polyamide dye-affinity hollow-fibres can be applied for lysozyme adsorption without causing any significant conformational changes. Repeated adsorption-elution processes showed that these dye-attached hollow-fibres are suitable for lysozyme adsorption. (C) 2001 Society of Chemical Industry

Concanavalin a immobilized affinity adsorbents for reversible use in yeast invertase adsorption

Akgol, Sinan/0000-0002-8528-1854; AKGOL, Sinan/0000-0003-2836-7181WOS: 000222909600006PubMed: 15468261Concanavalin A (Con A) immobilized poly(2-hydroxyethyl methacrylate) (PHEMA) beads were investigated for specific adsorption of yeast invertase from aqueous solutions. PHEMA beads were prepared by a suspension polymerization technique with an average size of 150-200 mum, and activated by epichlorohydrin. Con A was then immobilized by covalent binding onto these beads. The maximum Con A immobilization was found to be 10 mg/g. The invertase-loading capability of the PHEMA/Con A beads was observed at pH 5.0. The values of the Michaelis constant K-m of invertase were significanly larger upon adsorption, indicating decreased smaller for the adsorbed invertase. Adsorption improved the pH stability of the enzyme activity was found to be quite stable in repeated experiments

Hydrolysis of sucrose by invertase immobilized onto novel magnetic polyvinylalcohol microspheres

Akgol, Sinan/0000-0002-8528-1854; Kacar, Yasemin/0000-0002-8682-9228; AKGOL, Sinan/0000-0003-2836-7181WOS: 000170507600004The magnetic polyvinylalcohol (PVAL) microspheres were prepared by crosslinking glutaraldehyde. 1,1 ' -Carbonyldiimidazole (CDI), a carbonylating agent was used for the activation of hydroxyl groups of polyvinylalcohol, and invertase immobilized onto the magnetic PVAL microspheres by covalent bonding through the amino group. The retained activity of the immobilized invertase was 74%. Kinetic parameters were determined for immobilized invertase, as well as for the free enzyme. The K-m values for immobilized invertase (55 mM sucrose) were higher than that of the free enzyme (24 mM sucrose), whereas V-max values were smaller for the immobilized invertase. The optimum operational temperature was 5 degreesC higher for immobilized enzyme than that of the free enzyme. The operational inactivation rate constant (k(opi)) of the immobilized invertase at 35 degreesC with 200 mM sucrose was 5.83 x 10(-5) min(-1). Thermal and storage stabilities were found to increase with immobilization. (C) 2001 Elsevier Science Ltd. All rights reserved

Phe-graft-poly(Hema) polymeric nanoparticle: A promising tool to design new agrochemicals

###EgeUn###In this study, L-phenylalanine grafted 2-hydroxyethyl methacrylate (Phe-graft-Poly(HEMA))polymericnanoparticles(PNPs)weresynthesizedandtheir using potential for agricultural purposes was evaluated through the assessment ofthe PNPs characterization and phytotoxicityon wheat(Triticum aestivum L. cv. Gonen). Characterization of Phe-graft-Poly(HEMA) PNPs was carried out by FT-IR spectroscopy, Zeta-Size analysis and SEM. FT-IR analysis showed L-phenylalanine amino acids incorporation into poly(HEMA) nanoparticles and theparticlesizewasmeasuredabout168nmbyZeta-Sizeanalysis. SEMimages showed spherical shape and narrow distribution of the PNPs. Surface area of the PNP was calculated to be 2723 m 2 g -1 . The phytotoxicity of the PNPs on wheat was explored in seed germination and seedling stage. Treated seedlings maintained high germination rate, fresh-dry weights and shoot-root lengths in early growth period. Leaves of 14-days-old wheat seedlings did not present any decrement on photosynthetic efficiency (Fv/Fm) and pigment contents in comparison to control. Hydrogen peroxide and reactive oxygen species (ROS) induced lipid peroxidation levels were measured similar to control level. These results show that Phe-graft-Poly(HEMA)PNPs may be used as non-phytotoxic hydrophobic carrier system to design unique nanoagrochemicals for different agricultural purposes. © 2019, Academic Publishing House. All rights reserved

Reversible immobilization of urease onto Procion Brown MX-5BR-Ni(II) attached polyamide hollow-fibre membranes

Akgol, Sinan/0000-0002-8528-1854; AKGOL, Sinan/0000-0003-2836-7181WOS: 000179722300006Urease was immobilized onto Procion Brown MX-5BR attached and Ni(II) incorporated microporous polyarnide hollow-fibre membrane via adsorption. Urease immobilization onto the polyamide hollow-fibre membrane from aqueous solutions containing different amounts of urease at different pH was investigated in a batch system. The maximum urease immobilization capacity of the polyamide hollow-fibre membrane was 78 mg g(-1) fibre. The retained adsorbed enzyme activity was found to be 37%. However, the urease adsorption onto the polyamide fibre resulted in a threefold increase in enzyme stability with time at 50 degreesC. The Km values were 18 and 22 mM for the free and the immobilized enzymes, respectively. The V-max values were 59.7 U mg(-1) for the free and 25.9 U mg(-1) for the immobilized enzyme. The optimum pH (7.0) apparently was shifted 1.0 unit acidic region upon immobilization via adsorption. The optimum reaction temperature for the free and the immobilized enzymes were determined to be 45 and 55 degreesC, respectively. The dye-Ni(II) attached polyamide hollow-fibre membranes could be repeatedly used for the adsorption/desorption of enzyme without any significant loss in adsorption capacity. (C) 2002 Elsevier Science Ltd. All rights reserved

Immobilization of catalase via adsorption onto L-histidine grafted functional pHEMA based membrane

Kacar, Yasemin/0000-0002-8682-9228; Akgol, Sinan/0000-0002-8528-1854; AKGOL, Sinan/0000-0003-2836-7181WOS: 000171658200011Poly(2-hydroxyethylmethacrylate) (pHEMA) based flat sheet membrane was prepared by UV-initiated photopolymerization technique. The membrane was then grafted with L-histidine. Catalase immobilization onto the membrane from aqueous solutions containing different amounts of catalase at different pH was investigated in a batch system. The maximum catalase immobilization capacity of the pHEMA-histidine membrane was 86 mug cm(-2). The activity yield was decreased with the increase of the enzyme loading. It was observed that there was a significant change between V-max value of the free catalase and V-max value of the adsorbed catalase on the pHEMA-histidine membrane. The K-m value of the immobilized enzyme was higher 1.5 times than that of the free enzyme. Optimum operational temperature was 5 degreesC higher than that of the free enzyme and was significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed without loss of adsorption capacity or enzyme activity. (C) 2001 Elsevier Science B.V. All rights reserved

Can eculizumab be discontinued in aHUS? Case report and review of the literature

Nephrolog