Person: DEMİR, SERAP
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DEMİR
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SERAP
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Publication Metadata only Preparation and characterization of UV-curable polymeric support for covalent immobilization of xylanase enzyme(ELSEVIER, 2011) KAHRAMAN, MEMET VEZİR; Akdemir, Zumrut Seden; Demir, Serap; Kahraman, M. Vezir; Apohan, Nilhan KayamanThe hydroxyl group of poly(ethylene glycol) monoacrylate (PEGMA) was activated by 1 1'-carbonyldiimidazole (CDI) and then a xylanase enzyme was immobilized to amine active PEGMA UV-curable polymeric support formulation was prepared by mixing the xylanase bonded PEGMA aliphatic polyester 2-hydroxyethyl methacrylate (HEMA) poly(ethylene glycol) diacrylate (PEGDA) and photoinitiator After UV irradiation the enzymatic activity of the polymeric matrix was evaluated and compared with the corresponding free enzyme By immobilization the temperature resistance of the enzyme was improved and showed maximum activity at 60 C pH dependent activities of the free and immobilized enzymes were also investigated and it was found that the pH of maximum activity for the free enzyme was 60 while for the optimal pH of the immobilized enzyme was 65 The immobilized enzyme retained 75% of its activity after 33 runs The morphology of the polymeric support was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) coupled with SEM was used to explore the chemical composition The results have confirmed the evidence of enzyme in the structure of the polymeric material (c) 2010 Elsevier B V All rights reservedPublication Metadata only alpha-Amylase immobilization on functionalized nano CaCO3 by covalent attachment(WILEY-V C H VERLAG GMBH, 2012) KAHRAMAN, MEMET VEZİR; Demir, Serap; Gok, Sevda Burcu; Kahraman, Memet VezirIn this study, a-amylase was immobilized on glutaraldehyde activated silanized calcium carbonate nanoparticles by a using covalent binding method. The surface modified nano calcium carbonate (CaCO3) were characterized using FTIR and SEM. Immobilization yield was found as 199.43 mg/g of calcium carbonate nanoparticles. The maximum activity was observed at pH 6.5. The immobilized enzyme had a higher activity at elevated temperature (5090 degrees C) than the free one. Reuse studies demonstrated that the immobilized enzyme could reuse 25 times while retaining 18.2% of its activity. Free enzyme lost its activity completely within 15 days. Vmax values for the free and immobilized enzymes were calculated as 10 and 0.35 mg/mL/min, respectively.Publication Metadata only Immobilization of alpha-amylase onto poly(glycidyl methacrylate) grafted electrospun fibers by ATRP(ELSEVIER, 2015) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanIn this study, novel alpha-amylase immobilized poly(vinyl alcohol) (PVA) nanofibers were prepared. The PVA nanofiber surfaces were functionalized with 2-bromoisobutyryl bromide (BiBBr) and followed by surface initiated atom transfer radical polymerization (SI-ATRP) of glycidyl methacrylate (GMA). The morphology of the poly(glycidyl methacrylate) (PGMA) grafted PVA nanofibers was characterized by scanning electron microscopy (SEM). Also PGMA brushes were confirmed by X-ray photo electron microscopy (XPS). alpha-Amylase was immobilized in a one step process onto the PGMA grafted PVA nanofiber. The characteristic properties of the immobilized and free enzymes were examined. The thermal stability of the enzyme was improved and showed maximum activity at 37 degrees C by immobilization, pH values of the maximum activity of the free and immobilized enzymes were also found at 6.0 and 6.5, respectively. Free enzyme lost its activity completely within 15 days. The immobilized enzyme lost only 23.8% of its activity within 30 days. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only İnsan monoamin oksidaz a ve b inhibitörleri olarak benzokumarin türevlerinin sentezi ve biyolojik olarak değerlendirilmesi(2015-05-07) DANIŞ, ÖZKAN; DEMİR, SERAP; OGAN, AYŞE; ERDEM, SAFİYE; Danış Ö., Yüce Dursun B., Demir S., Alparslan M., Ogan A., Erdem S.Publication Metadata only Preparation and characterization of sol-gel hybrid coating films for covalent immobilization of lipase enzyme(ELSEVIER, 2016) OGAN, AYŞE; Yuce-Dursun, Basak; Cigil, Asli Beyler; Dongez, Dilek; Kahraman, M. Vezir; Ogan, Ayse; Demir, SerapIn this study UV-curable hybrid epoxy-silica polymer films were prepared via sol-gel method. Lipase (EC 3.1.1.3) from Candida rugosa was covalently immobilized onto hybrid epoxy-silica polymer films and immobilization capacity of polymer films was found 7.22 mg g(-1). The morphology of the polymeric support was characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Immobilized and free enzymes were used in two different reaction systems: hydrolysis of p-nitrophenyl palmitate in aqueous medium and synthesis of p-nitrophenyl linoleate (from p-nitrophenol and linoleic acid) in n-hexane medium. The effect of temperature on hydrolytic and synthetic activities was investigated and observed maximum activities at 50 degrees C and 45 degrees C for immobilized enzyme, orderly. Km values for free enzyme were determined 0.71 and 1.12 mM by hydrolytic and synthetic activity assays, respectively, while these values were observed as 0.91 mM and 1.19 mM for immobilized enzyme. At the end of 30 repeated cycles, 56% and 59% of initial activities remained for hydrolytic and synthetic assays, respectively. Native enzyme lost its activity completely within 20 days, whereas the immobilized enzyme retained for hydrolytic and synthetic activities was approximately 82% and 72%, respectively, under the same storage time. (C) 2016 Elsevier B.V. All rights reserved.Publication Metadata only Nonhydrolytic sol-gel synthesized oligosiloxane resin reinforced thiol-ene photocured coatings for the immobilization of acetylcholinesterase(SPRINGER, 2019) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Demir, SerapAcetylcholinesterase (AChE), which is responsible for the hydrolysis of neurotransmitter acetylcholine, is a critical enzyme for the nervous system and also a biomarker for organophosphorous pesticide detection. The immobilization of AChE is an active area of research and recently the use of sol-gel-derived materials for enzyme immobilization has gained a lot of attraction. In this work, AChE was covalently immobilized onto a photocured substrate which was reinforced with an oligosiloxane resin. The oligosiloxane resin was designed to have both vinyl and epoxide groups and prepared via nonhydrolytic sol-gel technique. The strategy employed in this study offered a platform that has good mechanical and thermal properties and also suitable for modification. Thus, AChE was also immobilized onto these substrates after amine modification of the epoxy groups and followed by glutaraldehyde activation. Over 80% enzyme immobilization yield was achieved. At certain pH values (5.5 and 8.5) and under relatively higher temperatures (above 40 degrees C) the immobilized enzymes were found to have higher catalytic activity than the free enzyme. Furthermore, by immobilization the reuse and the storage stability of the enzyme was improved and the stability of the immobilized enzyme against the inhibitory effects of certain metal cations was enhanced [GRAPHICS] . Nonhydrolytic sol-gel synthesized oligosiloxane resin reinforced thiol-ene photocured coatings for the immobilization of acetylcholinesterase. Emrah CAKMAKCI, Serap DEMIR. HighlightsAn oligosiloxane resin was prepared via nonhydrolytic sol-gel technique.The oligosiloxane resin was used to reinforce thiol-ene photocured coatings.Acetylcholinesterase was immobilized onto the photocured coatings.By immobilization, storage stability, reuse and metal ion resistance were improved.Publication Metadata only Magnetic nanoparticle containing thiol-ene crosslinked hydrogels for controlled and targeted release of hydrophobic drugs(WILEY, 2018) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanThis study reports a straightforward but very effective method to produce nanocomposite hydrogels for targeted drug delivery system. An organic network containing both hydrophilic and hydrophobic components was obtained using thiol-ene cross-linking. Magnetite nanoparticles (MNPs) were synthesized by chemical co-precipitation. The surface of the MNPs was modified with allyl groups to avoid agglomeration. Composite hydrogels were prepared by addition of surface modified MNPs to hydrogel formulation at different ratios. The prepared composite hydrogels were investigated for their ability to loading and release hydrophobic drugs tamoxifen and clarithromycin. The morphological and structural characterizations of MNPs were performed by Fourier transform infrared spectroscopy (FT-IR) and Environmental scanning electron microscopy (SEM) and Environmental scanning transmission electron microscopy (STEM). Moreover the superparamagnetic behavior of the hydrogels was studied by a vibrating sample magnetometer (VSM). The saturation magnetization values increased with the magnetite content. Swelling, gel content and degradation of the hydrogels were examined. According to the loading of drugs, the maximum loading efficiency was 91% for tamoxifen and 70% for clarithromycin due to the stronger hydrophobic interactions. In vitro release studies showed that controlled release of the drugs occurred over a prolonged period of time. Therefore, drug loaded hydrogels can be considered as potential long-term sustained drug release systems. POLYM. COMPOS., 39:E200-E209, 2018. (c) 2016 Society of Plastics EngineersPublication Metadata only Physical and Covalent Immobilization of Lipase onto Amine Groups Bearing Thiol-Ene Photocured Coatings(HUMANA PRESS INC, 2017) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Muhsir, Pelin; Demir, SerapIn this study, amine groups containing thiol-ene photocurable coating material for lipase immobilization were prepared. Lipase (EC 3.1.1.3) from Candida rugosa was immobilized onto the photocured coatings by physical adsorption and glutaraldehyde-activated covalent bonding methods, respectively. The catalytic efficiency of the immobilized and free enzymes was determined for the hydrolysis of p-nitrophenyl palmitate and also for the synthesis of p-nitrophenyl linoleate. The storage stability and the reusability of the immobilized enzyme and the effect of temperature and pH on the catalytic activities were also investigated. The optimum pH for free lipase and physically immobilized lipase was determined as 7.0, while it was found as 7.5 for the covalent immobilization. After immobilization, the optimum temperature increased from 37 A degrees C (free lipase) to 50-55 A degrees C. In the end of 15 repeated cycles, covalently bounded enzyme retained 60 and 70 % of its initial activities for hydrolytic and synthetic assays, respectively. While the physically bounded enzyme retained only 56 % of its hydrolytic activity and 67 % of its synthetic activity in the same cycle period. In the case of hydrolysis V (max) values slightly decreased after immobilization. For synthetic assay, the V (max) value for the covalently immobilized lipase was found as same as free lipase while it decreased dramatically for the physically immobilized lipase. Physically immobilized enzyme was found to be superior over covalent bonding in terms of enzyme loading capacity and optimum temperature and exhibited comparable re-use values and storage stability. Thus, a fast, easy, and less laborious method for lipase immobilization was developed.Publication Metadata only Preparation, characterization, and in vitro evaluation of isoniazid and rifampicin-loaded archaeosomes(WILEY, 2018) OGAN, AYŞE; Attar, Azade; Bakir, Ceren; Yuce-Dursun, Basak; Demir, Serap; Cakmakci, Emrah; Danis, Ozkan; Birbir, Meral; Ogan, AyseThe ability of Archaea to adapt their membrane lipid compositions to extreme environments has brought in archaeosomes into consideration for the development of drug delivery systems overcoming the physical, biological blockades that the body exhibits against drug therapies. In this study, we prepared unilamellar archaeosomes, from the polar lipid fraction extracted from Haloarcula 2TK2 strain, and explored its potential as a drug delivery vehicle. Rifampicin and isoniazid which are conventional drugs in tuberculosis medication were loaded separately and together in the same archaeosome formulation for the benefits of the combined therapy. Particle size and zeta potential of archaeosomes were measured by photon correlation spectroscopy, and the morphology was assessed by with an atomic force microscope. Encapsulation efficiency and loading capacities of the drugs were determined, and in vitro drug releases were monitored spectrophotometrically. Our study demonstrates that rifampicin and isoniazid could be successfully loaded separately and together in archaeosomes with reasonable drug-loading and desired vesicle-specific characters. Both of the drugs had greater affinity for archaeosomes than a conventional liposome formulation. The results imply that archaeosomes prepared from extremely halophilic archaeon were compatible with the liposomes for the development of stable and sustained release of antituberculosis drugs.Publication Metadata only Preparation of a Poly(ethylene glycol)-Based Cross-Linked Network from a Click Reaction for Enzyme Immobilization(WILEY-V C H VERLAG GMBH, 2019) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanIn this study, a polyethylene glycol (PEG)-maleimide film was prepared by a thiol-ene click reaction. The covalent immobilization of amylase was carried out onto the PEG-maleimide based photo-curable network via epoxy and C=O groups without any linker. The epoxy and carbonyl groups on the PEG backbone improved the affinity of the enzyme. The immobilization yield of amylase onto the film was 72.46%. The immobilization capacity was also determined as 313 mg/g. The thermal stability of amylase improved via covalent attachment. Immobilized amylase showed maximum activity at 40 degrees C and pH 6.5. The immobilized amylase continued to retain 66% of its initial activity after 30 days.
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