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ÇAKMAKÇI, EMRAH

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2017 - 201922020 - 20231
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Author: DEMİR, SERAP × Subject: Thiol-ene ×

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Now showing 1 - 3 of 3
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    Nonhydrolytic sol-gel synthesized oligosiloxane resin reinforced thiol-ene photocured coatings for the immobilization of acetylcholinesterase
    (SPRINGER, 2019) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Demir, Serap
    Acetylcholinesterase (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.
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    Immobilization of acetylcholinesterase onto pyrrole-containing photocured thermosets
    (2023-04-01) DEMİR, SERAP; ÇAKMAKÇI, EMRAH; OGAN, AYŞE; ALI K. K., DEMİR S., ÇAKMAKÇI E., OGAN A.
    Acetylcholinesterase (AChE; EC 3.1.1.7) is a group of enzymes that catalyzes the hydrolysis of the neurotransmitter acetylcholine (ACh) into choline and acetate. AChE inhibition is commonly utilized as a biomarker for pesticides. In membrane based AChE biosensors the enzyme immobilization onto an electrode surface is of prime importance. In previous studies, conducting polymers-based supports have been used for the immobilization of AChE. In this study, a novel immobilization platform was developed. The simultaneous polymerization of pyrrole and functional thiol/ene monomers was performed to prepare conductive thermosets. AchE was covalently immobilized onto the membranes through the epoxy functional groups. After the immobilization process, the optimal temperature increased to 50 °C, displaying a better thermal stability and the optimum pH was elevated to 8.5. The activity of the immobilized enzyme was tested in the presence of several metals, and it was found that Cu2+ ions caused a noticable inhibition. After 10 cycles, the immobilized enzyme retained 51% of its original activity. In accordance with our results; the durability and the stability of the immobilized enzyme were improved. In future studies, the method applied here can be used in the design of an AchE biosensor.
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    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, Serap
    In 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.