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• MakaleYalnız künye2026/r/gumushane/13816
  Covalent Immobilization of Glutathione-S-Transferase onto Magnetic Iron Nanoparticles via Epichlorohydrin Spacer Arm

  Kemal Caglar, M.; Gulesci, Nuri; Bilgin, Ramazan; Yucebilgic, Guzide

  This study examined the synthesis of Fe₃O₄ magnetic nanoparticles (MNPs) and the covalent immobilization of glutathione-S-transferase (GSTs) onto these nanoparticles using an epichlorohydrin (ECH) spacer arm, as well as the optimal reaction conditions for both free and immobilized enzymes and the reusability of the immobilized enzyme. The optimal pH values for free and immobilized enzymes were established as 7.0 and 6.0, respectively. It was found that the ideal temperature for both free and immobilized enzymes was 37 and 40°C, respectively. Under the optimum conditions, the values of V_max for glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB) substrates of free GSTs enzyme were measured as 204.8 U/mg prot. and 194.3 U/mg prot., respectively. The immobilized GSTs enzyme's CDNB and GSH substrates had V_max values of 33.29 U/mg prot. and 33.08 U/mg prot., respectively. The free GSTs enzyme's CDNB and GSH substrates have K_m values of 0.201 mM and 0.1873 mM, respectively. GSH and CDNB have K_m values of 0.3042 mM and 0.2523 mM, respectively. At various temperatures, we contrasted the thermal stability of free and immobilized GSTs. The immobilized GSTs enzyme retained 50% of its activity after 20 reuses. After 30 days of storage at 25°C and 4°C, it was discovered that 18% and 32% of the free GSTs enzyme activity were preserved, and 30 days of storage at 25°C and 4°C resulted in 20% and 41% preserved enzyme activity for the immobilized enzyme, respectively.

  İncele
• MakaleAçık Erişim2026/r/gumushane/13623
  Layered Polymeric Carbon Nitride as a Green Support for Cellulase Immobilization: Improved Stability, Activity, and Reusability

  Gulesci, Nuri; Altan, Orhan; Toprak, Ali; Yalçın, M. Serkan; Bilgin, Ramazan; Yildirim, Deniz

  Polymeric carbon nitride (PCN) has attracted considerable attention in recent years due to its layered structure and donor groups such as terminal amines and triazine units. In this study, PCN was synthesized from melamine and employed for the first time as a support material for the immobilization of cellulase, a key enzyme used in numerous industrial applications. Transmission electron microscopy (TEM) analysis revealed that ranged from 219 to 375 nm in size, thereby confirming their nanoscale layered morphology. Cellulase from Aspergillus sp. was immobilized onto PCN using three methods. In the first approach, cellulase was adsorbed onto PCN to form PCN@cellulase. In the second method, PCN@cellulase was cross-linked with glutaraldehyde (PCN@cellulase/Glu). Finally, the primary amino group of PCN was modified with glutaraldehyde, and the cellulase was immobilized onto this support via covalent attachment (PCN/Glu@cellulase). Each cellulase preparation was assessed for its optimal pH, temperature conditions, thermal stability, and enzyme kinetics. The optimal pH was 5.5 for all cellulase preparations, while the optimal temperature was 45 °C for free cellulase and 55 °C for all immobilized cellulase preparations. Thermal stability of PCN@cellulase, PCN@cellulase/Glu, and PCN/Glu@cellulase increased by 2.1-, 2.7-, and 3.7-fold, respectively, compared to the free cellulase. PCN/Glu@cellulase showed a 1.4-fold higher catalytic efficiency than the free cellulase and retained 80% of its initial activity after 10 reuses. This work highlights PCN as a green, metal-free, and easy-to-prepare support for enzyme immobilization, thereby opening new possibilities for sustainable bioprocessing applications.

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  İncele
• MakaleYalnız künye2026/r/gumushane/13616
  Purification of catalase enzyme from Thymus nummularius and examination of the effects of varying glucose concentrations on catalase activity

  Toprak, Esma; Güleşci, Nuri

  Catalase (EC 1.11.1.6), an antioxidant enzyme, breaks down reactive oxygen species, hydrogen peroxide (H2O2), into water and oxygen. In this study, the partial purification of catalase was obtained from Thymus nummularius M. Bieb. through ammonium sulfate (NH4)2SO4 precipitation, dialysis, and desalting/buffer exchange by using a PD-10 Sephadex G-25 M column. The isolated enzyme had a specific activity of 1294.45 U/mg protein and a purification fold of 7.80. The SDS-PAGE analysis indicated a molecular weight ranging between 37 and 50 kDa. The optimal pH and temperature for catalase activity were determined to be pH 8.0 and 25 °C, respectively. The kinetic parameters, maximum velocity (Vmax) 277.78 U/mL and Michaelis constant (KM) 34.17 mM were estimated from Lineweaver-Burk plots. Furthermore, catalase activity was evaluated at glucose concentrations ranging between 25 and 500 ppm. Enzyme activity increased at 25–100 ppm, significantly decreased at 250 ppm, and then increased again at 500 ppm. These results suggest that glucose may modulate catalase activity in a concentration-dependent manner. Even though the exact regulatory mechanism remains unclear, this effect could have potential implications for glucose-sensitive metabolic systems.

  İncele
• MakaleAçık Erişim2022/r/gumushane/12834
  Different spacer-arm attached magnetic nanoparticles for covalent immobilization of Jack bean urease

  Gulesci, Nuri; Yucebilgic, Guzide; Yildirim, Deniz

  Objectives: This study aims the covalent immobilization of Jack bean urease on Fe3O4 magnetic nanoparticles via glutaraldehyde (urease@MNPs-Si-Glu) and epichlorohydrin (urease@MNPs-ECH) spacer arms. Methods: The optimum pH and temperature, thermal, storage and reuse stability of free and immobilized urease preparations were investigated. Thermodynamics characterizations of free and immobilized urease preparations were also studied. Results: The free urease and both immobilized urease preparations showed maximal catalytic activity at pH 7.5. The free urease had a maximal catalytic activity at 50 °C, while the both immobilized urease preparations exhibited their maximal catalytic activities at 70 °C. The urease@MNPs-Si-Glu and urease@MNP-ECH showed 2.7- and 1.9-fold higher thermal stability than the free urease at 60 °C, respectively. The free urease remained 30% of their initial activity at 4 °C, while urease@MNPs-Si-Glu and urease@MNPs-ECH retained 72 and 60% of their initial activities at the same conditions. The urease@MNPs-Si-Glu and urease@MNPs-ECH preserved 53 and 52% of their initial activities, respectively for urea hydrolysis after 20 reuses. Conclusions: The urease@MNPs-Si-Glu and urease@MNPsECH may find a potential application area in urea hydrolysis.

  İncele
• BildiriYalnız künye2016/r/gumushane/16835
  Immobilization and characterization of urease onto different spacer arms attached magnetic nanoparticles

  Yucebilgic, Guzide; Gulesci, Nuri; Yildirim, Deniz

  İncele
• MakaleYalnız künye2015/r/gumushane/15571
  Effectiveness of levamisole and tarantula cubensis extract in the treatment of teat Papillomatosis of cows

  Paksoy, Zahid; Gülesci, Nuri; Kandemir, Fatih Mehmet; Dinçel, Güngör Çagdas

  Papillomatosis is widespread in cattle and is often observed on the skin of udders. For treatment, anthelmintic, immunomodulator and homeopathic drugs are administered. The objective of the study was to examine the therapeutic effect of levamisole and tarantula cubensis extract in the treatment of papilloma observed in the teats of cows. Sixteen Holstein cows between the age of 2-3 years were used as study material. The cows with Papillomatosis were randomly assigned into two equal groups. The animals in the first group (n=8) were treated with intramuscular double doses of levamisole (5 mg/kg) applied one week apart. The second group of animals (n=8) was treated with two subcutaneous doses of 10 ml of Tarantula cubensis extract one week apart. Four animals in the first group recovered while 8 animals in the second group recovered. The total serum oxidant levels of the animals treated with Tarantula cubensis extract and levamisole on the 15th day was found to be significantly lower than the serum levels of same animals on day 0 of the treatment (P<0.05). The results of this study revealed that tarantula cubensis extract applied in normal therapeutic doses was more effective in the treatment of teat papillomatosis than levamisole.

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