Yazarlar
- Korkmaz, Şadan(6)
- Pat, Suat(6)
- Özen, Soner(6)
- Şenay, Volkan(6)
- Akdemir, A.O.(5)
- Dadasoglu, F.(5)
- Ekinci, A.(5)
- Han, I.(5)
- Karagoz, K.(5)
- Oztekin, A.(5)
- Set, E.(5)
- Cuce, Erdem(4)
- Allm, Bünyamin(3)
- Saricaoglu, Furkan Turker(3)
- Yudar, H. Hakan(3)
- Abdioglu, M.(2)
- Abuşoǧlu, A.(2)
- Celik, S.(2)
- Cuce, Pinar Mert(2)
- Demir, Lütfü(2)
- Dertli, Enes(2)
- Erdem, O.(2)
- Gul, Osman(2)
- Tozlu, A.(2)
- Turhan, Sadettin(2)
- Çolak, M.(2)
- Özahi, E.(2)
- Şahin, Engin(2)
- Adiyaman, G.(1)
- Adıyaman, Gökhan(1)
- Akbulut, Mustafa(1)
- Akkuş, Tuba(1)
- Alim, Zuhal(1)
- Alisoy, Gulizar(1)
- Alım, Bünyamin(1)
- Artar, Musa(1)
- Atalar, Ilyas(1)
- Atalay, F.(1)
- Ates, I.(1)
- Ayazoglu Mashiyev, Rabil(1)
Yayınlar
- MakaleYalnız künye2017Optimum design of steel bridges including corrosion effect using TLBO
Artar, Musa; Catar, Recep; Daloglu, Ayse T.
This study presents optimum design of plane steel bridges considering corrosion effect by using teaching-learning based optimization (TLBO) method. Optimum solutions of three different bridge problems are linearly carried out including and excluding corrosion effect. The member cross sections are selected from a pre-specified list of 128 W profiles taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB to carry out optimum design interacting with SAP2000 using OAPI (Open Application Programming Interface). The stress constraints are incorporated as indicated in AISC Allowable Stress Design (ASD) specifications and also displacement constraints are applied in optimum design. The results obtained from analysis show that the corrosion effect on steel profile surfaces causes a crucial increase on the minimum steel weight of bridges. Moreover, the results show that the method proposed is applicable and robust to reach the destination even for complex problems.
AtıfScopus9WoS9
İncele - MakaleYalnız künye2017Characterization of functional properties of Enterococcus spp. isolated from Turkish white cheese
İspirli, Hümeyra; Demirbaş, Fatmanur; Dertli, Enes
Enterococcus species was isolated from Turkish white cheese and genotypic characterization of these isolates revealed the presence of 12 distinct strains belonging to 5 different species: Enterococcus faecium, E. faecalis, E. durans, E. gallinarum and E. italicus. All strains showed good survival ability under bile salt conditions. The antibiotic resistance of these strains was low but two strains showed high levels of resistance including resistance to vancomycin. PCR detection of virulence determinant in these isolates revealed that cheese isolate enterococci contained virulence genes common in gut and food originated enterococci and importantly two strains harboured cylB gene related to cytolysin metabolism. No complete hemolytic activity was observed for Enterococcus strains but partial hemolytic activity was observed 8 out of 12 strains. Additionally, all strains showed important levels of antimicrobial activity against food-borne pathogens and PCR screening of genes encoding enterocin A and B indicated the presence of enterocin B gene in all tested strains. The antimicrobial activities of the tested strains were lost after proteolytic enzyme treatments but no alteration was observed at different pHs and after heat treatments. In summary, this study reflected characteristics of Enterococcus strains presented in Turkish white cheese in terms of functional and safety perspectives.
AtıfScopus56İncele - BildiriYalnız künye2017Effect of chemical dosage on color parameters of hydrophobic calcium carbonate obtained in aqueous solution
Uçurum, M.; Bayraktar, I.; Ozyurt, M.; Atalay, F.; Torun Bilgic, E.; Karadeniz, M.; Gulsun Kilic, M.; Onel, O.
Ultra-fine ground calcium carbonate is widely utilized as a performance mineral in rubber, plastics and paper industries. Both micronized calcium carbonate and a chemical (sodium oleate) treated calcium carbonate products, obtained in the aqueous solution, were used in the experiments. The color property is an important factor that affects the acceptability of the industrial mineral products. The current study describes the relationship between micronized calcium carbonate and coated calcium carbonate on the basis color parameters (L∗, a∗, b∗), whiteness index (WI), saturation index (SI), hue angle (H) and total color difference (ΔE). The results showed that the processing variables (chemical dosage) did not have a significant effect on the color parameters of hydrophobic calcium carbonate products.
- MakaleYalnız künye2017Zn/ZnSe thin films deposition by RF magnetron sputtering
Yudar, H. Hakan; Pat, Suat; Korkmaz, Şadan; Özen, Soner; Şenay, Volkan
In this paper, Zn/ZnSe thin films were deposited on glass substrates by RF magnetron sputtering system. XRD analyses were done. Zn and ZnSe phases were obtained. Miller indices of obtained Zn phases were detected in (320), (620) and (112) crystal formation. For the ZnSe phases, only one peak of (110)/(220) was observed. The surface morphology of the samples was investigated by an atomic force microscopy tools. It found that average roughness of the films was increased by raised RF power. The thin films around 80 % of high transmittance were measured. The band gap values were calculated as to be ~2.80 eV by the Cauchy model. The calculated refractive indices values were approximately 2.25 by a relation between the refractive index and the band gap.
AtıfScopus31WoS24İncele - MakaleYayıncıda açık erişim2017Delocalization and charge transfer studies of PERMENDUR49, KOVAR and Ti50Co50 alloys from relative K X-ray intensity ratios
Uğurlu, Mine; Alım, Bünyamin; Han, İbrahim; Demir, Lütfü
Kβ-to-Kα X-ray intensity ratios of Fe, Ni, Co, Ti, V in pure form and PERMENDUR49 (Fe49Co49V2), KOVAR (Fe54Ni29Co17) and Ti50Co50 alloys were calculated in order to determine valence-electron structure of the samples. The obtained experimental Kβ-to-Kα X-ray intensity ratios were found to be 0.1252 ± 0.0025, 0.1256 ± 0.0027, 0.1298 ± 0.0026, 0.1327 ± 0.0028, 0.1346 ± 0.0027 for pure Ti, V, Fe, Co and Ni, respectively. These values of present pure metals have increased with the increment in atomic number of these pure metals. Also, although the obtained these values for metal atoms in PERMENDUR49, Ti50Co50 and for Fe, Ni metal atoms in KOVAR approximately compatible with respect to results same pure metals, the obtained experimental Kβ-to-Kα X-ray intensity ratios for Co in KOVAR are significantly different from the appropriate values for pure Co metal. Then, the valence-electron populations of these alloys were calculated in order to answer as to why the characteristic properties of the studied alloys are distinct from each other. The valence-electron structures of these metals in pure form and alloys were determined by comparison of the calculated Kβ-to-Kα X-ray intensity ratios with the results of multi-configurations Dirac-Fock (MCDF) calculations to understand the charge-transfer and/or delocalization phenomena of these alloys. The experimental n3d values were found to be 3.2694, 4.7905, 7.7941, 7.9618, 8.500 for pure Ti, V, Fe, Co and Ni, respectively. The calculated 3d and 4s, 4p electron population values for Ti, V and Co in pure form have shown very little deviation from the appropriate values of Ti in Ti50Co50 and Co, V in PERMENDUR49. Also, the deviation for these values is greater for Fe, Ni, in KOVAR, Co in Ti50Co50, Fe in PERMENDUR49 with respect to the corresponding values of pure metals and the largest deviation for these values is observed for Co metal atoms in KOVAR alloy. We have also calculated the weighted average numbers of 3d and 4s, 4p electrons per one atom as well as the superposition of 3d and 4s, 4p electrons, as obtained from pure metal values. While the obtained superposition 3d electron numbers of present alloys exhibit a decreasing tendency as S3d(Ti50Co50) < S3d(PERMENDUR49) < S3d(KOVAR), the obtained weighted average 3d electron numbers of present alloys has opposite tendency (A3d(KOVAR) < A3d(PERMENDUR49) < A3d(Ti50Co50)). The analysis show that valance-electron population of elements in these alloys indicated differences with respect to the pure metal and each other. These differences can be related to type of alloy elements, concentration of alloy elements, charge transfer and/or delocalization phenomena between of individual metal atoms in alloys. Also, the obtained results show that there are alloying effect on valence-electron population due to charge transfer and/or delocalization phenomena.
AtıfScopus15WoS15İncele - BildiriYalnız künye2017Examination of absorption effects at the Compton to coherent scattering intensities X-rays using Fe-Ca and Fe-Ti binary compounds with WDXRF
Boydaş, Elif; Boydaş, Mustafa Gökalp; Allm, Bünyamin; Akdemir, A.O.; Ekinci, A.; Han, I.; Oztekin, A.; Set, E.; Dadasoglu, F.; Karagoz, K.
Matrix absorption effects have been examined with scattered X-rays by using WDXRF system for Fe-Ca and Fe-Ti binary compounds. Fe as analyte and elements which some of them the K absorption edge just below the characteristic K X-ray energies of the analyte (Fe) as matrix have been chosen. Pure and binary with Fe ratio ranging from 10% to 90% samples were prepared with these elements. These samples have been analyzed in WDXRF system. At the end of measurement, the coherent and Compton scattering X-rays data of Rh Kα X-rays from these samples have been obtained. Matrix absorption effects have been examined by calculating coherent / Compton scattered X-rays intensity ratio.
AtıfScopus3İncele - MakaleYalnız künye2017Continuous and discontinuous contact problem of a functionally graded layer resting on a rigid foundation
Adıyaman, Gökhan; Öner, Erdal; Birinci, Ahmet
In this study, the continuous and discontinuous contact problem of a functionally graded (FG) layer resting on a rigid foundation is considered. The top of the FG layer is subjected to normal tractions over a finite segment. The graded layer is modeled as a non-homogenous medium with a constant Poissons’ ratio and exponentially varying shear modules and density. For continuous contact, the problem was solved analytically using plane elasticity and integral transform techniques. The critical load that causes first separation and contact pressures is investigated for various material properties and loadings. The problem reduced to a singular integral equation using plane elasticity and integral transform techniques in case of discontinuous contact. The obtained singular integral equation is solved numerically using Gauss–Jacobi integral formulation, and an iterative scheme is employed to obtain the correct separation distance. The separation distance and contact pressures between the FG layer and the foundation are analyzed for various material properties and loading. The results are shown in Tables and Figures. It is seen that decreasing stiffness and density at the top of the layer result in an increment in both critical load in case of continuous contact and separation distance in case of discontinuous contact.
AtıfScopus24WoS24İncele - MakaleYalnız künye2017Role of airtightness in energy loss from windows: Experimental results from in-situ tests
Cuce, Erdem
The rate of air leakage related energy loss from glazed areas is unequivocal especially in older and poorly installed windows. Therefore, in this research, a comprehensive experimental investigation is done to analyse the importance of air leakage on overall heat transfer coefficient (U-value) of conventional air filled double glazed windows. The tests are conducted in a typical UK dwelling of Nottingham fitted with traditional air filled double glazed windows. One sash of the test window is sealed internally with a special transparent cover to provide excellent airtightness whereas the second window sash is left as it is to represent the ordinary case. The experiments are conducted in April 2016, and dynamic co-heating test methodology is applied to evaluate the rate of enhancement in the U-value of airtight window sash. The results indicate that the airtight window sash has a notably lower U-value compared to the ordinary window sash due to the impact of airtightness and reverse heat flux during noon time owing to the greenhouse effect between transparent cover and internal glazing. The overall U-value of ordinary window sash is found to be 2.67 W/m2K, whereas it is 1.79 W/m2K for airtight window sash. It is observed that about 33% of reduction in heat losses can be achieved via airtight windows.
AtıfScopus60İncele - MakaleYayıncıda açık erişim2017Efficiency improvement of gas turbine cogeneration systems; [Poboljšanje učinkovitosti kogeneracijskih sustava plinske turbine]
Karaali, Rabi; Öztürk, İlhan Tekin
In this study eight methods are evaluated for a gas turbine cogeneration cycle to improve the efficiency. These methods are increasing gas turbine inlet air temperature, cooling the inlet air of the compressor, air preheating, fuel preheating, increasing compressor inlet air pressure, increasing air excess rates, steam injection, and humidification of the inlet air of the compressor. These methods are studied in order to compare their effects on the performance of the systems. The effects of these methods on the exergetic efficiency depend on the kind of the cogeneration cycle. By combining recuperation, preheating fuel and steam injection methods high efficiency can be achieved. The combined methods give the best results under variable heat demands of the market. An appropriate combination of the efficiency improvement methods may increase the exergetic efficiency about 20 %. The results show that efficiency improvement methods must be applied together whenever it is possible.
AtıfScopus8İncele - BildiriYayıncıda açık erişim2017Thermal and Acoustic Properties of Aerogels: Preliminary Investigation of the Influence of Granule Size
Moretti, Elisa; Merli, Francesca; Cuce, Erdem; Buratti, Cinzia; Capozzoli, A.; Serra, V.; Howlett, R.
The influence of granules size in silica aerogels is experimentally investigated in terms of thermal and acoustic performance characteristics. The transmission loss (TL) is measured at normal incidence in a traditional impedance tube, whereas the thermal conductivity (λ) is evaluated using a Hot Plate apparatus, setting up an appropriate methodology, due to the nature of the sample. The results reveal that the small granules (granules size in the 0.01-1.2 mm range), which have the highest density, have the best performance both in terms of thermal and acoustic properties. Depending on the granules size, λ varies in 19-22 mW/mK range at 10°C, whereas a TL equal to 13 dB at about 6400 Hz for 20 mm thickness is obtained for small granules.
AtıfScopus58İncele - BildiriYayıncıda açık erişim2017Effect of copper addition to aluminium alloys on surface roughness in terms of turning operation
Özen, F.; Fiçici, F.; Dündar, M.; Çolak, M.
Aluminium alloys have found usage in numerous industries due to some superior properties, such as high strength-to-weight ratios and high oxidation resistance. Aluminum alloys can be strengthened by some techniques. One of them, the most practical one, is precipitation hardening in aluminum alloys. By adding Cu, aluminum gains strength and hardness. In this work the machinability of unalloyed aluminum and aluminum alloyed with 4% and 8% of Cu have been investigated. Machinability assessment was executed in terms of surface roughness during turning operation. Specimens were manufactured by sand casting method, which is a commonly utilized casting operation. In machinability experiments, three different cutting tool materials were employed. Three different cutting speeds and three different feed rates have been used. Effect of these feeds, speeds and cutting tool materials on surface roughness has been studied. In addition, effect of Cu addition to aluminum alloys on surface roughness has been examined.
AtıfScopus9WoS6İncele - MakaleYalnız künye2017Harvesting of microalgae via submerged membranes: Flux, fouling and its reversibility
Elcik, Harun; Cakmakci, Mehmet
The purpose of this study was to investigate membrane fouling caused by microalgal cells in submerged membrane systems consisting of polymeric and ceramic microfiltration membranes. In this study, one polymeric (flat-sheet, pore size: 0.2 μm) and two ceramic (flat-sheet, pore size: 0.2 μm and cylindrical, pore size: 1 μm) membranes were used. Physical cleaning was performed with water and air to determine the potential for reversible and irreversible membrane fouling. The study results showed that substantial irreversible membrane fouling (after four filtration cycles, irreversible fouling degree 27% (cleaning with water) and 38% (cleaning with air)) occurs in the polymeric membrane. In cleaning studies performed using water and air on ceramic membranes, it was observed that compressed air was more effective (recovery rate: 87-91%) for membrane cleaning. The harvesting performance of the membranes was examined through critical flux experiments. The critical flux values for polymeric membrane with a pore size of 0.20 μm and ceramic membranes with a pore size of 0.20 μm and 1 μm were ≤ 95 L/m2hour, ≤ 70 L/m2hour and ≤ 55 L/m2hour, respectively. It was determined that critical flux varies depending on the membrane material and the pore size. To obtain more information on membrane fouling caused by microalgal cells, the characterization of the fouled polymeric membrane was performed. This study concluded that ceramic membranes with a pore size of 0.2-1 μm in the submerged membrane system could be efficiently used for microalgae harvesting by cleaning the membrane with compressed air at regular intervals.
AtıfScopus9WoS7İncele - MakaleYalnız künye2017An accurate model for photovoltaic (PV) modules to determine electrical characteristics and thermodynamic performance parameters
Cuce, Erdem; Cuce, Pinar Mert; Karakas, Ibrahim Hakki; Bali, Tulin
Accurate and reliable modelling of photovoltaic (PV) modules is necessary for design and performance estimation of PV systems. Manufacturers of PV modules usually provide some basic electrical parameters specified at only one single operating condition, which is commonly known as standard test conditions (STCs). However, PV systems operate over a wide range of outdoor conditions, and the manufacturers’ reports do not cover sufficient information about how the PV modules react with respect to changes in the two most important environment-oriented conditions, which are solar intensity and operating cell temperature. In this respect, an accurate and reliable tool is required by designers to predict electrical characteristics and thermodynamic performance parameters of PV modules. Therefore in this research, a novel mathematical model is developed to determine solar intensity and cell temperature dependency of PV module parameters and thermodynamic efficiency figures. A simple one-diode model is proposed considering series resistance and shunt conductance. Mitsubishi PV-UJ225GA6 225 W polycrystalline silicon PV module and Kyocera KD205GH-2P 205 W multicrystal PV module are utilised for model assessment. Model results are compared with environmental chamber tests and manufacturers’ performance reports, and a very good agreement is achieved.
AtıfScopus97WoS85İncele - MakaleYayıncıda açık erişim2017Multiple small solutions for p(x)-Schrödinger equations with local sublinear nonlinearities via genus theory
Ayazoglu Mashiyev, Rabil; Ekincioglu, Ismail; Alisoy, Gulizar
In this paper, we deal with the following p(x)-Schrödinger problem: (Formula Presented) where the nonlinearity is sublinear. We present the existence of infinitely many solutions for the problem. The main tool used here is a variational method and Krasnoselskii’s genus theory combined with the theory of variable exponent Sobolev spaces. We also establish a Bartsch-Wang type compact embedding theorem for the variable exponent spaces.
AtıfScopus7WoS7İncele - MakaleYayıncıda açık erişim2017Comparison of writing anxiety and writing dispositions of sixth, seventh and eighth grade students
Berk, Rifat Ramazan; Ünal, Emre
The purpose of this study is to determine sixth, seventh and eighth grade students' writing anxiety and dispositions and to examine to what extent they predict each other. The basis of this study is to determine whether writing disposition is the significant predictor of writing anxiety or not and whether students' grade levels and genders are significant predictor of writing anxiety and dispositions or not. The research was designed according to survey model. The study group, selected through simple sampling method, is made up of 860 students studying at 6th, 7th and 8th grades in elementary schools of Sarkisla District, Sivas. While "Writing Anxiety Scale", adapted into Turkish by özbay and Zorbay (2011), was administered to determine the study group's writing anxiety level, "Writing Disposition Scale", adapted into Turkish by Iseri and ünal (2010), was used to determine the writing disposition level. At the end of the study, it was found that writing disposition is a significant predictor of writing anxiety and students' grade levels and genders are significant predictors of writing anxiety and dispositions. An education environment to create a strong writing disposition for students is recommended. Also, similar studies on different dimensions of the issue can be conducted.
AtıfScopus9İncele - BildiriYalnız künye2017Analysis of turbulent convective heat transfer from rectangular baffles by Taguchi method
Sahin, B.; Bayrakceken, A.; Manay, E.; Ates, I.
In this study, the effects of the rectangular baffles mounted on the bottom surface of a heat exchanger on the heat and pressure drop characteristics were investigated using the Taguchi experimental-design method. Nusselt number and friction factor were considered as performance parameters. An L18(2135) orthogonal array was selected as an experimental plan for the six parameters: corner angle (α), inclination angle (β), baffle height (H), baffle length (L), baffle width (S) and Reynolds number. First of all, each goal was optimized, separately. Then, all the goals were optimized together, considering the priority of the goals. The presence of the rectangular cross sectioned baffles caused higher pressure drop than that of the smooth channel. It was concluded that increasing inclination angle and corner angle caused heat transfer to decrease. The length of the baffle was found to be the most influential parameter on friction factor. Likewise, it was concluded that the most affected parameter on the heat transfer was Reynolds number.
- MakaleYalnız künye2017Bioactive content of Rosa canina biotypes from Turkey
Beyhan, O.; Koc, A.; Ercisli, S.; Jurikova, T.; Cakir, O.
Rose hips have been used as medicinal and aromatic plants for a long time throughout Turkey. The plant has been the focus of many recent studies due to its potential effects on treatment and prevention of several diseases. However, there are few in vitro studies concerning its composition and antioxidant capacity. The aim of the present study was to determine bioactive content including ascorbic acid, total phenolics, total flavonoids, total carotenoids and antioxidant activity of Rosa canina biotypes growing wild in Sivas province located eastern Anatolia. The results revealed that fruits of Rosa canina biotypes rich in terms of Vitamin C which ranged from 360 to 482 mg/100 g fresh weight base. The total phenolic content varied from 340 to 464 mg/100 g fresh weight. The biotype S-07 had the highest total flavonoids content (241 mg quercetin equivalent/100 g fresh weight) and the lowest value attributed to biotype S-01 as 151 mg/quercetin equivalent/100 g fresh weight. The antioxidant activity of the biotypes was between 14.2-30.7 μg Trolox/ml sample. The results revealed that there was enough diversity among Rosa canina biotypes for bioactive content and promising biotypes with high bioactive content are ready material for future breeding activities.
AtıfScopus4İncele - BildiriYayıncıda açık erişim2017Thermodynamic performance assessment of different fluids in a typical organic Rankine cycle for usage in municipal solid waste power plant
Özahi, E.; Tozlu, A.; Abuşoǧlu, A.
This paper presents the energy and exergy analyses of some different organic fluids which can be used in an organic Rankine cycle adapted to a municipal solid waste power plant in the frame of energy recovery. The novelty of the study is to adapt a well-known organic Rankine cycle system theoretically to the existing municipal solid waste power plant where the exhaust gas with a temperature of almost 560 °C is sent to atmosphere causing both energy loss and air pollution, and also violating the related legislation. The efficient organic fluid that can be used in such a plant is estimated by means of the thermodynamic analyses. It is known that, in a typical municipal solid waste power plant, a considerable amount of energy is sent up from a plant chimney to the atmosphere. This waste energy can be utilized by using an adapted organic Rankine cycle system with a proper organic fluid. In this frame, some different organic fluids were examined and compared thermodynamically in this study. The optimal operation conditions of some organic fluids, R141b, isobutane, R245fa, n-pentane and n-hexane have been evaluated by means of ASPEN and EES software programs. The effects of the outlet temperature of heat source on the energetic and exergetic efficiencies and the net power output at a given pinch point temperature difference were investigated. It can be deduced from the analyses that n-hexane has the highest energetic and exergetic efficiencies at all outlet temperatures of the heat source such as 8.92% and 34.47% at 82.08°C, respectively. It can also be stated that the maximum net power output is obtained by using the organic fluid n-hexane.
AtıfScopus14İncele - MakaleYayıncıda açık erişim2017Lateral Position Effect of Auxiliary Permanent Magnets on the Magnetic Force Properties of Cylindrical YBCO
Abdioglu, M.; Kabaer, M.; Ozturk, K.; Erdem, O.; Celik, S.
The magnetic levitation force (MLF) and the guidance force (GF) should be improved for loading capacity and stability of Maglev systems, respectively. Although there are some ways to increase these properties, using of auxiliary onboard permanent magnets (PMs) can be considered as the most efficient one. The auxiliary PMs increase the MLF significantly but, at the same time, decrease the GF. We have searched a solution to overcome this problem in this study. Firstly, we have determined the optimum vertical positions of the auxiliary PMs and then we have investigated the vertical levitation force and lateral guidance force of hybrid Maglev system depending on lateral position of auxiliary PMs in different cooling heights (CHs). A cylindrical YBCO superconductor, fabricated by a top seeding method with the diameter of 45 mm and the height of 15 mm, was used as a high-temperature superconductor (HTS). The maximum increment rate in MLF and the minimum decrement rate in GF were observed as 277 and 54 %, respectively. The increment in MLF was obtained five times more than the decrement in GF, and this reality points out that the results of this study can be useful for improving the loading capacity and thus enhancing the practical applicability of Maglev systems.
AtıfScopus16WoS14İncele - MakaleYalnız künye2017Purification of camel liver catalase by zinc chelate affinity chromatography and pH gradient elution: An enzyme with interesting properties
Chafik, Abdelbasset; Essamadi, Abdelkhalid; Çelik, Safinur Yildirim; Mavi, Ahmet
Climate change and increasing temperatures are global concerns. Camel (Camelus dromedarius) lives most of its life under high environmental stress in the desert and represent ideal model for studying desert adaptation among mammals. Catalase plays a key role in protecting cells against oxidative stress. For the first time, catalase from camel liver was purified to homogeneity by zinc chelate affinity chromatography using pH gradient elution, a better separation was obtained. A purification fold of 201.81 with 1.17% yield and a high specific activity of 1132539.37 U/mg were obtained. The native enzyme had a molecular weight of 268 kDa and was composed of four subunits of equal size (65 kDa). The enzyme showed optimal activity at a temperature of 45 °C and pH 7.2. Thiol reagents, β-Mercaptoethanol and D,L-Dithiothreitol, inhibited the enzyme activity. The enzyme was inhibited by Al3+, Cd2+ and Mg2+, whereas Ca2+, Co2+ and Ni2+ stimulated the catalase activity. Reduced glutathione has no effect on catalase activity. The Km and Vmax of the enzyme for hydrogen peroxide were 37.31 mM and 6185157 U/mg, respectively. Sodium azide inhibited the enzyme noncompetitively with Ki value of 14.43 μM, the IC50 was found to be 16.71 μM. The properties of camel catalase were different comparing to those of mammalian species. Relatively higher molecular weight, higher optimum temperature, protection of reduced glutathione from hydrogen peroxide oxidation and higher affinity for hydrogen peroxide and sodium azide, these could be explained by the fact that camel is able to live in the intense environmental stress in the desert.
AtıfScopus9WoS9
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