Browsing by Author "Aydemir, T"
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Item Effects of antioxidant vitamins A, C, E and trace elements Cu, Se on CuZnSOD, GSH-Px, CAT and LPO levels in chicken erythrocytesAydemir, T; Öztürk, R; Bozkaya, LA; Tarhan, LThe biologically damaging effects of reactive oxygen species are controlled in vivo by a wide spectrum of antioxidant defence mechanisms. Dietary constituents of antioxidant vitamins and trace elements may play an important role in protecting against oxidant damage. The effects of supplementation of vitamins A, C, E and trace elements Cu and Se on the activities of antioxidant enzymes and lipid peroxide levels in chicken erythrocytes were investigated depend on the time. CuZnSOD activity and plasma Cu levels in the Cu group were increased by 39 and 37 per cent respectively. CuZnSOD activity in vitamin C groups was also increased by 20 per cent. The GSH-Px activity in Se, Se + E and Se + Ca groups was raised by 35, 46 and 69 per cent respectively. Also, the GSH-Px activity in the vitamin C group was increased by 33 per cent. Catalase activity in all of these groups was not significantly different when compared with controls (p < 0.01). The maximum decrease in LFO levels of 42 per cent was obtained for the Se + E group. Copyright (C) 2000 John Wiley & Sons, Ltd.Item Glucose sensing employing fluorescent pH indicatorErtekin, K; Cinar, S; Aydemir, T; Alp, SThe proton sensitive azlactone derivative; 4-[(p-N,N-dimethylamino)benzylidene]-2-phenyloxazole-5-one (DPO) exhibits high quantum yield, excellent photostability, and high molar absorptivity in a sol-gel matrix. In this work, two different DPO containing constructions were tested and evaluated as glucose sensors. In the first, both glucose oxidase (GOx) and azlactone derivative were incorporated into a single tetraethylorthosilicate (TEOS) based sol-gel phase. In the second, TEOS and 3-aminopropyltriethoxysilane (APTEOS) containing dye-doped sol-gel layer was covered with GOx entrapped sol-gel (the two-layer configuration). The monolayer configuration has the fastest response time (tau(90) = 20 s) but suffers from leaching upon prolonged use. Response time and dynamic working range of the cross-linking agent containing two-layer configuration are 40 s and 0.1-15 mM glucose, respectively. The resulting glucose sensor was characterized by high sensitivity, low interference from acidogenic species, and a working lifetime of at least 90 days. (c) 2004 Elsevier Ltd. All rights reserved.Item Effects of Se, Cu and Se plus vitamin E deficiency on the activities of CuZnSOD, GSH-Px, CAT and LPO levels in Chicken ErythrocytesBozkaya, LA; Öztürk-Ürek, R; Aydemir, T; Tarhan, LAntioxidant enzymes and vitamins provide a defence against the damage of cells by reactive oxygen species in living systems. The effect of Cu, Se and vitamin E deficiencies on the antioxidant enzyme activities and lipid peroxide levels of chicken erythrocytes were investigated during 6 weeks of a depletion diet. CuZnSOD activity and the plasma Cu level of the Cu-deficient group which was fed a diet containing 0.2 mg Cu kg(-1) were reduced to 62 and 71% respectively. GSH-Px activity of the Se-deficient group was decreased by 46% but by 21% in the Cu-deficient group. CAT activity values of Se- and Cu-deficient groups were increased by 28 and 10% respectively. The maximum increase of LPO levels in erythrocyte membranes was observed as 32% for the Se + E-deficient group. The LPO level of the Cu-deficient group which had decreased CuZnSOD and GSH-Px activity, was also observed to be significantly increased when compared with the controls (p < 0.05). Copyright (C) 2001 John Wiley & Sons, Ltd.Item ANTIMICROBIAL AND SOD-LIKE ACTIVITIES OF N,N'-BIS(FERROCENYLMETHYLENE)ETHYLENEDIAMINE SCHIFF BASE AND IT'S METAL COMPLEXESÖzbek, HA; Çinar, S; Oskay, M; Aydemir, T; Demirhan, FThe synthesized N,N'-bis(ferrocenylmethylene)ethylenediamine Schiff base and it's metal complexes were screened in vitro for antimicrobial activity against two Gram-positive (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 7064), four Gram-negative (Escherichia coli ATCC 25922, Citrobacter koseri DBCC 01, Entorebacter aeruginosa ATCC 13048, Salmonella typhimurium DBCC 02) and antifungal activity against a Candida albicans. MIC values of the compounds ranged from 27 to 533 mu g/mL. Compound (5) showed very strong activity against S. aureus with the best MIC (27 mu g/mL). The lowest MIC for C. albicans was obtained 107 mu g/mL. The superoxide dismutase activity of Schiff base and it's metal complexes has been measured and discussed. SOD-like activities of bis ferrocenyl Schiff base ligand metal complexes were investigated using NBT. While only the Cu (II) complex showed SOD-like (40 mu m IC50) activity, the SOD-like activity value was not determined in the other complex and ligand.Item An investigation on the seasonal variations of the biomarkers of oxidative stress response and their correlations to Polonium-210 in mussel (Mytilus galloprovincialis) and common sole (Solea solea) from Izmir Bay, TurkeyAslan, E; Görgün, AU; Katalay, S; Filizok, I; Becerik, S; Aydemir, TIt is well known that the marine organisms are used as biological indicators for environmental pollution studies. Among these studies, the research on oxidative stress has been increasing in recent years. In this study, mussels (Mytilus galloprovincialis) and fish (Solea solea) samples were collected seasonally from inciralti, Izmir, Turkey. This station was in an area where fishing is carried out for human consumption. The relationship between Po-210 and oxidative stress markers (lipid peroxidation (LPO), H2O2 and proline) was investigated in the mussel tissue (digestive gland, gills) and fish tissue (liver, gills) samples. The present study indicated that H2O2 accumulated with increasing Po-210 concentration in mussel samples. Statistically significant correlation were found between H2O2 and Po-210 and LPO and proline in mussel samples. This correlation between LPO and proline can be attributed to common environmental parameters (other than Po-210) affecting expression of both LPO and proline levels. There was not a significant correlation between Po-210 and LPO levels. Similarly, a significant correlation was not found between Po-210 and proline.Item Purification and partial characterisation of superoxide dismutase from chicken erythrocytesAydemir, T; Tarhan, LSuperoxide dismutase (SOD), which plays a very important role in protecting organisms from oxygen toxicity, was purified from chicken erythrocyte and partially characterised. Erythrocyte membranes were disintegrated via freeze-thaw methods in the presence of Triton X-100. Following ethanol precipitation, SOD-containing solution was applied to DEAE-cellulose and then Sephadex G-100 gel columns. Chicken erythrocyte SOD was purified 508-fold with a specific activity of 8,480 units per mg. The molecular weight was estimated to be 30.6 kDa +/- 0.4 by gel filtration. The enzyme was composed of two subunits of equal size and contained one atom of copper and one atom of zinc per molecule. Maximum SOD activity was observed between pH 7.0 to 9.0 at 25 degreesC. The enzyme has high thermal stability.Item Voltammetric determination of timolol maleateTürkdemir, MH; Erdögdu, G; Aydemir, T; Karagözler, AA; Karagözler, AETimolol as a beta -adrenoceptor antagonist is a potent antihypertensive and antianginal drug, which was also proved to be effective for the secondary prevention of myocardial infarction. The analysis of timolol, as with other oxprenolols, in ophthalmic solutions and biological liquids using sensitive instrumental methods has gained importance. Investigation of the electrochemical behavior of timolol maleate on a mercury drop electrode reveals the presence of a specific reduction peak of analytical significance. Analysis conditions affecting the properties of this peak were optimized by a systematic study. The limit of detection of about 2.5 ppb, obtained for the DPV technique using SMDE, is comparable with the most sensitive techniques. This method is suitable for routine analysis in that it is simpler and requires no preconcentration step for the analysis of therapeutic doses of the drug.Item Pulsed Deposited Manganese and Vanadium Oxide Film Modified with Carbon Nanotube and Gold Nanoparticle: Chitosan and Ionic Liquid-based BiosensorAkogullari, S; Çinar, S; Özdokur, KV; Aydemir, T; Ertas, FN; Koçak, SPresent study describes the synthesis of mixed oxide films of manganese and vanadium by electrochemical pulsed deposition technique on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT). The film was further decorated with gold nanoparticles to enhance the reduction signal of dissolved oxygen in pH 5.17 acetate buffer solution. All of the electrochemical synthesized modified electrodes have been characterized with Scanning electron microscopy(SEM), High-resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD) techniques. The electrode obtained (AuNPs/MnOx-VOx/CNT/GCE) was utilized as a platform for glucose biosensor where the glucose oxidase enzyme was immobilized on the composite film with the aid of chitosan and an ionic liquid. The electrochemical performance of the biosensor was investigated by cyclic voltammetry and the relative parameters have been optimized by amperometric measurements in pH 5.17 acetate buffer solution. The developed biosensor exhibited a linear range for glucose between 0.1-1.0 mM and the limit of detection was calculated as 0.02 mM.Item Immobilization of Subtilisin Carlsberg and its use for transesterification of N-acetyl-L-phenylalanine ethyl ester in organic mediumEser, A; Aydemir, TIn this study, inorganic-based carrier perlite (PER) and cyclodextrin-modified perlite (PER-CD) were used for Subtilisin Carlsberg (SC) immobilization. For enzyme immobilization, the supports aminated with 3-aminotriethoxysilane were first activated with glutaraldehyde (GA) and genipin (GE), and then, the immobilized enzymes (PER-SC and PER-CD-SC) were obtained. The reaction medium for SC immobilization consisted of 500 mg carrier and 5 ml (1 mg/ml) enzyme solution. The immobilization conditions were pH 8.0, 25 degrees C, and 2 h incubation time. Free and immobilized SC were used for transesteri-fication of N-acetyl-L-phenylalanine ethyl ester (APEE) with 1-propanol in tetrahydrofuran (THF). The transesterification activity of the enzyme and the yield of the transesterification reaction were determined by gas chromatography (GC). 50 mg of immobilized or 2.5 mg of free SC was added to the reaction medium, which was prepared as 1 mmol APEE and 10 mmol alcohol in 10 mL of THF. The conditions for the transesterification reaction were 60 degrees C and 24 h of incubation. The structure and surface morphology of the prepared carriers were characterized using scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). Casein substrate was used in the optimization study. The optimum temperature and pH for SC activity were found to be 50 degrees C and pH 8.0, respectively, for free and immobilized SC. The thermal stability of immobilized SC was found to be greater than that of free SC. At the end of 4 h of exposure to high temperature, the immobilized enzyme maintained its activity at approximately 50%, while the free enzyme was maintained at approximately 20%. However, modi-fication with cyclodextrin did not alter the thermal stability. The transesterification yield was found to be approximately 55% for the free enzyme, while it was found to be approximately 68% and 77% for PER-SC and PER-CD-SC, respectively. The effect of metal ions and salts on transesterification yield was examined. The results showed that the addition of metal ions decreased the percentage of transesterification by approximately 10% compared to the control group, whereas the addition of salt significantly decreased the percentage of transesterification by 60-80% compared to the control group.Item Removal of nickel(II) ions by histidine modified chitosan beadsEser, A; Tirtom, VN; Aydemir, T; Becerik, S; Dinçer, AIn order to increase the nickel adsorption capacity of raw chitosan beads (CB), they were chemically modified with histidine (HIS-ECH-CB) by using crosslinking agent, epichlorohydrine (ECH). The nature and morphology of the sorbent were characterized using FTIR, TGA and SEM analysis. For optimization of adsorption conditions, sorption experiments were performed by varying contact time, pH, temperature and initial nickel concentration. Based on the adsorption experiment, the HIS-ECH-CB showed the significant adsorption capacity of 55.6 mg/g under the optimal adsorption condition. Nickel adsorption isotherms data were fitted to Freundlich isotherm. Thermodynamic parameters namely Delta G degrees. Delta H degrees and Delta S degrees of the Ni(II) adsorption process were calculated. The negative values of Gibbs free energy of adsorption (Delta G degrees) indicated the spontaneity of the adsorption of Ni(II) ions on the histidine modified chitosan. Desorption of Ni(II) ions from HIS-ECH-CB could be done rapidly by using 0.1 M HCl, HNO3 and EDTA solutions and the beads could be used again to adsorb Ni(II) ions. (C) 2012 Elsevier B.V. All rights reserved.Item Removal of erythrosine dye from aqueous solutions using magnetic chitosan with erythrosine as imprinted moleculesEser, A; Aydemir, T; Becerik, S; Dinçer, AA novel, chitosan coating on the surface of magnetite (Fe3O4) (erythrosine-imprinted magnetic chitosan (EIMC)) was successfully synthesized using erythrosine (ER) as a template for adsorption and the removal of ER from aqueous solutions. Characterization of the obtained EIMC was achieved by FTIR spectra, SEM micrographs, and TGA analysis. Batch adsorption experiments of EIMC and non-imprinted magnetic chitosan (NIMC) were performed to investigate the adsorption conditions. The results showed that the maximum adsorption capacity for EIMC and NIMC was observed at pH 6 and temperature 40 degrees C. Equilibrium adsorption was achieved within 3 h. Adsorption process could be well described by Freundlich adsorption isotherms. Thermodynamic parameters namely Delta G degrees, Delta H degrees, and Delta S degrees of the ER adsorption process were calculated. The negative values of Gibbs free energy of adsorption (Delta G degrees) indicated the spontaneity of the adsorption of ER dye on the EIMC and NIMC. Desorption of ER from EIMC and NIMC could be done rapidly using 0.1 M NaOH solution and the beads could be used again to remove ER. Results show that imprinting technique increases the removal amount of ER dye from aqueous solutions.Item Purification and partial characterization of catalase from chicken erythrocytes and the effect of various inhibitors on enzyme activityAydemir, T; Kuru, KCatalase plays a major role in the protection of tissues from the toxic effects of H2O2 and partially reduced oxygen species. A nearly 136-fold enzyme purification was obtained from chicken erythrocyte by acetone precipitation, ethanol-chloroform treatment, CM-cellulose and Sephadex G-200 chromatography. The specific activity of purified enzyme was 42,556 U/mg. The molecular weight of the native chicken erythrocyte catalase was estimated at 240 kDa by gel filtration. SDS-gel electrophoresis results indicated that chicken erythrocyte catalase consists of four apparently identical subunits, with a molecular weight of around 57.5 kDa. The optical spectrum of the purified enzyme shows a Soret band at 406 nm, which is the characteristic for the heme group. Dithionite treatment of the enzyme resulted in the reduction of enzyme. The Km of chicken erythrocyte catalase was 33 mM H2O2. The maximal activity of catalase was observed between pH 6.0 and 8.0. Enzyme activity was stable at temperatures between 10 and 30degreesC. The activity of purified catalase was inhibited by azide, cyanide, beta-mercaptoethanol, dithiotreitol (DTT) and iodoacetamide.Item Removal of lead (II) ions from aqueous solution by using crosslinked chitosan-clay beadsTirtom, VN; Dinçer, A; Becerik, S; Aydemir, T; Çelik, AA simple and effective biodegradable material known as chitosan-clay composite beads were prepared to remove Pb(II) ions from aqueous solution. For this purpose, various important parameters such as contact time, pH and temperature were examined on the adsorption of Pb(II) ions onto crosslinked chitosan-clay composite beads. Maximum adsorption capacity of Pb(II) was observed at pH 4.5 and 25 degrees C and calculated as 7.93 mg/g according to Langmuir isotherm model. Thermodynamic parameters namely Delta G degrees, Delta H degrees and Delta S degrees of the Pb(II) adsorption process have been calculated as 7.889 kJ/mol, -15.131 kJ/mol and -0.0785 kJ/molK respectively. EDTA was the best eluent for the desorption of Pb(II) ions from the crosslinked chitosan-clay beads. Scanning electron microscope (SEM) was used to characterize the surface morphology of the crosslinked chitosan-clay beads.Item Subtilisin Carlsberg immobilization and its application for eco-friendly leather processingEser, A; Aydemir, TConventional dehairing based on application of huge amount of chemicals is the most polluting process of all leather manufacturing processes. In this study, Subtilisin Carlsberg (SC) was immobilized on magnetic chitosan (mCTS) using two different crosslinkers: 2% glutaraldehyde (GA) and 0.5% genipin (GE). The reaction medium for SC immobilization consisted of 500 mg carrier and 5 ml (1 mg/ml) enzyme solution. Also, the immobilization conditions were pH 8, 25 degrees C and 2 h incubation period. The hydrolysis activity of immobilized SC has been extensively investigated. The structure and surface morphology of the prepared carriers were characterized by Scanning Electron Microscop (SEM), Thermogravimetric Analyzis (TGA) and Energy Dispersive X-Ray Spec-troscopy (EDX). Optimum temperature and pH values of SC activity were found to be 50 degrees C and pH 8.0, respectively for free and immobilized SC. Higher activity of SC at around pH 8 and 50 degrees C makes it suitable for industrial applications. Thermal stability of immobilized SC was found greater than free SC. At the end of 4 h of exposure to high temperature, while the immobilized enzyme can maintain its activity around 50%, the free enzyme can maintain around 20%. Enzymatic hair removal from leather skin with SC was carried out as an alternative eco-benign deharing process. In enzymatic hair removal, a softer and smoother skin surface was obtained compared to the chemical method. Leather skins was characterized by SEM images.Item Application of Exogenous Sodium Nitroprussid Alleviates Boron Toxicity in Wheat Seedlings: Investigation of Thiol Compounds, Macro/Micronutrient, and Polyamine ContentsTepe, HD; Aydemir, THigh boron (B) levels in the soil reduce plant growth and yield production in crop plants. Nitric oxide (NO) is a highly reactive signaling molecule involved in stress response in plants. The aim of the study was to investigate the role of sodium nitroprussid (SNP), a NO donor, in alleviating the B-induced toxicity in two wheat cultivars. Both cultivars were treated with 10 mM B, 10 mM B + 0.1 mM SNP, 10 mM B + 0.2 mM SNP, and 10 mM B + 0.5 mM SNP. The nutrient contents were investigated via inductively coupled plasma mass-spectrometry. Contents of polyamines and thiol compounds were analyzed by high-performance liquid chromatography. The B toxicity caused a significant decrease in nutrient contents and thiol compounds, but increased polyamine contents. However, exogenous application of 0.2 mM SNP increased nutrient contents and thiol compounds, but lowered polyamine contents. The study clearly revealed that exogenous SNP can overcome the toxic effects of B on wheat seedlings.Item Purification and characterization of catalase from chard (Beta vulgaris var. cicla)Dinçer, A; Aydemir, TCatalase is a major primary antioxidant defence component that primarily catalyses the decomposition of H2O2 to H2O Here we report the purification and characterization of catalase from chard (Beta vulgaris var. cicla). Following a procedure that involved chloroform treatment, ammonium sulfate precipitation and three chromatographic steps (CM-cellulose, Sephadex G-25, and Sephadex G-200), catalase was purified about 250-fold to a final specific activity of 56947 U/mg of protein. The molecular weight of the purified catalase and its subunit were determined to be 235000 and 58500 daltons, indicating that the chard catalase is a tetramer. The absorption spectra showed a soret peak at 406 nm, and there was slightly reduction by dithionite. The ratio of absorption at 406 and 275 nanometers was 1.5, the value being similar to that obtained for catalase from other plant sources. In the catalytic reaction, the apparent Km value for chard catalase was 50 mM. The purified protein has a broad pH optimum for catalase activity between 6.0 and 8.0. The enzyme had an optimum reaction temperature at 30 degreesC. Heme catalase inhibitors, such as azide and cyanide, inhibited the enzyme activity markedly and the enzyme was also inactivated by beta -mercaptoethanol, dithiothreitol and iodoacetamide.Item SELECTED KINETIC PROPERTIES OF POLYPHENOL OXIDASE EXTRACTED FROM ROSMARINUS OFFICINALIS L.Aydemir, TPolyphenol oxidase from Rosmarinus officinalis L. (PPO, EC 1:14:18.1) was extracted and partially purified by using (NH4)(2)SO4 precipitation and dialysis. Stable and highly active PPO extracts were obtained using 0.5% (w/v) PEG and 0.5% (w/v) Triton X-100 in 0.1 M phosphate buffer 7.0. K-M values were found to be as 14.3 mM for catechol. Four isoenzymes of Rosemary PPO were detected by PAGE with DL-dopa substrate. The enzyme was strongly inhibited by dithiotreitol, sodium metasulfite, sodium thiosulfate, ascorbic acid, and L-cysteine. Metal ions Ca++, Mg++, and Mn++ were poor inhibitors of rosemary PPO at 10 Mm.Item Characterization of β-glucosidase immobilized on chitosan-multiwalled carbon nanotubes (MWCNTS) and their application on tea extracts for aroma enhancementÇelik, A; Dinçer, A; Aydemir, Tbeta-Glucosidase was covalently immobilized on chitosan-MWCNTs carrier and its aroma enhancement effect in different tea samples was investigated. Chitosan-MWCNTs carrier was prepared by mixing chitosan with MWCNTs (5:1 w/w) and characterization of prepared composite carrier was done by FTIR, TGA and SEM analysis. beta-Glucosidase was covalently immobilized on the composite carrier after glutaraldeyde activation. After optimization of the immobilization conditions, immobilization yield was achieved as 95.22%. Optimum pH was found as pH 6.0 and pH 5.0 for free and immobilized enzyme, respectively. Optimum temperature of the enzyme was shifted from 35 degrees C to 45 degrees C after immobilization. The K-m and V-max values for immobilized beta-glucosidase calculated as 5.55 mM and 7.14 Wing protein respectively. Immobilized beta-glucosidase showed better pH and storage stability than free enzyme. After storage at +4 degrees C for 50 days, the immobilized enzyme retained its 68.4% of the initial activity. The calculated half-life (t(1/2)) of immobilized enzyme was 115.8 min. After 10 cycles of reuse, immobilized beta-glucosidase showed 72.83% of its initial activity. (C) 2016 Elsevier B.V. All rights reserved.Item Poly(methyl methacrylate-ethylene glycol dimethacrylate) copolymer for adsorptive removal of erythrosine dye from aqueous solutionAltindag, IG; Dinçer, A; Becerik, S; Eser, A; Aydemir, TThe preparation and characterization of poly(methyl methacrylate-ethylene glycol dimethacrylate), (poly(MMA-EGDMA)) polymer for erythrosine adsorption has been investigated. Erythrosine is a synthetic red dye used to color food. Water-soluble acid dyes have caused serious water pollution. Poly(MMA-EGDMA) polymer showed better adsorption performance for erythrosine at acidic region and at 30 degrees C. The adsorption process had also been verified by Langmuir and Freundlich adsorption isotherms at 30, 40, and 50 degrees C. Free energy of adsorption ( increment G degrees), enthalpy ( increment H degrees), and entropy ( increment S degrees) changes were calculated to predict the nature of adsorption. The estimated value for increment G degrees was calculated as -125.6 kJ/mol at 303 K (30 degrees C). The estimated value for increment H degrees was found as -60.69 kJ/mol at 303 K. The negative value for increment H degrees indicated that the adsorption of erythrosine on poly(MMA-EGDMA) polymer was an exothermic process.Item Partial purification and characterisation of polyphenol oxidase from celery root (Apium graveolens L.) and the investigation of the effects on the enzyme activity of some inhibitorsAydemir, T; Akkanli, GPolyphenol oxidase (PPO) of celery root was extracted and partially purified by (NH4)(2)SO4 fractionation and dialysis. Optimum pH and temperature were found at pH 7.0 and 30 degrees C, and K-m and V-max values were 29 mm and 5560 U mL(-1) min(-1) with catechol, respectively. The activation energy of the enzyme with catechol was 17.9 kJ mol(-1) at pH 7.0. In electrophoretic seperation, six isoenzymes were detected with DL-dopa substrate. PPO showed activity to catechol, 4-methylcatechol, pyrogallol, gallic acid, DL-dopa. l-Tyrosine was also tested but was not oxidised by celery root PPO. beta-Mercaptoethanol was found to be the most effective inhibitor. (NH4)(2)SO4, NaCl, KCl and sucrose appeared to be protective agents of celery root PPO against thermal denaturation. Metal ions (Cu2+, Zn2+, Mn2+) were poor inhibitors of the celery root PPO at 1 mm. PPO activity was also inhibited by CaCl2, NaCl, BaCl2, FeSO4 and NiCl2.