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Öğe Maltose functionalized magnetic core/shell Fe3O4@Au nanoparticles for an efficient L-asparaginase immobilization(Elsevier, 2020) Tarhan, Tuba; Ulu, Ahmet; Saricam, Melike; Culha, Mustafa; Ates, BurhanIn this study, maltose-functionalized magnetic core/shell nanoparticles (Fe3O4@Au NPs) as a promising carrier matrix for a simple and effective immobilization of L-asparaginase (L-ASNase) were prepared and characterized using imaging techniques including atomic force microscopy (AFM) and transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results indicate that the NPs are monodispersed with an average diameter of 10 nm and magnetization of 9.0 emu g(-1). Under the optimal conditions, 77.2 +/- 2.3% of the total L-ASNase was immobilized. It was found that the acid-base tolerance and thermal stability of immobilized L-ASNase were significantly improved in comparison to the free form of the enzyme in solution. For instance, while only 10% of the immobilized enzyme was lost its activity, the free form was lost its activity more than 50% after 3 h incubation at 55 degrees C. After 13 times recycling, the immobilized L-ASNase retained about 50% of its initial activity. Moreover, the free and immobilized L-ASNase maintained their initial activities about 25 and 64% after 28 days storage at 25 degrees C, respectively. Km value of immobilized L-ASNase decreased to 1.59 from 2.95 mM as an indication of increased enzyme affinity for the substrate. The results of this study suggest that the maltose-coated magnetic nanoparticles are excellent nanovehicles to carry enzymes for a range of industrial applications. (C) 2019 Elsevier B.V. All rights reserved.Öğe Newly Synthesized Multifunctional Biopolymer Coated Magnetic Core/Shell Fe3O4@Au Nanoparticles for Evaluation of L-asparaginase Immobilization(Springer/Plenum Publishers, 2023) Tarhan, Tuba; Dik, Gamze; Ulu, Ahmet; Tural, Bilsen; Tural, Servet; Ates, BurhanThe immobilization strategy can promote greater enzyme utilization in applications by improving the overall stability and reusability of the enzyme. In this work, the L-asparaginase (L-ASNase) obtained from Escherichia coli was chosen as a model enzyme and immobilized onto the Fe3O4@Au-carboxymethyl chitosan (CMC) magnetic nanoparticles (MNPs) through adsorption. TEM, SEM, FT-IR, XRD, EDS, and TGA analyses were performed to examine the structure with and without L-ASNase. The yield of immobilized L-ASNase on Fe3O4@Au-CMC was found to be 68%. The biochemical properties such as optimum pH, optimum temperature, reusability, and thermal stability of the Fe3O4@Au-CMC/L-ASNase were comprehensively investigated. For instance, Fe3O4@Au-CMC/L-ASNase reached maximum activity at pH 7.0 and the optimum temperature was found to be 50 degrees C. The noticeably lower Ea value of the Fe3O4@Au-CMC/L-ASNase revealed the enhanced catalytic activity of this enzyme after immobilization. The Km and Vmax values were 3.27 +/- 0.48 mM, and 51.54 +/- 0.51 mu mol min(-1) for Fe3O4@Au-CMC/L-ASNase, respectively, which means good substrate affinity. The Fe3O4@Au-CMC/L-ASNase retained 65% of its initial activity even after 90 min at 60 degrees C. Moreover, it maintained more than 75% of its original activity after 10 cycles, indicating its excellent reusability. The results obtained suggested that this investigation highlights the use of MNPs as a support for the development of more economical and sustainable immobilized enzyme systems.