Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2021Scopus SJRQ1Photovoltaic performance of non-covalent functionalized single-layer graphene in dye-sensitized solar cells (DSSCs)
Igman, Erdal; Bayram, Ozkan; Mavi, Ahmet; Hasar, Ugur Cem; Simsek, Onder
In this study, it was aimed to fabricate new effective alternative counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). For this purpose, firstly, single-layer graphene (SLG) thin films were grown by chemical vapor deposition (CVD) method. Then, these films were separately functionalized with 1,8-cineole (ppCin/SLG), D-Limonene (ppLim/SLG) and Thiophene (ppTh/SLG) by plasma polymerization. Number of layers in CVD-grown graphene determined by Raman, transmission electron microscope (TEM) and ultraviolet–visible (UV–Vis) spectroscopy. Chemical structures of plasma polymerised (pp) thin films were investigated by Fourier transform infrared (FTIR) spectroscopy. Photovoltaic parameters of DSSCs were calculated, and electrocatalytic properties of CEs were investigated by electrochemical impedance spectroscopy (EIS). Polymer functionalization greatly enhanced the electrical conductivity and electrocatalytic activity properties of graphene compared to that of SLG. The efficiencies of DSSCs with ppCin/SLG and ppLim/SLG CEs were 1.10% and 1.02%, respectively. As a result, the cell efficiencies of ppCin/SLG and ppLim/SLG could be as alternative materials to platinum (Pt) counter electrode.
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İncele - MakaleYalnız künye2020Scopus SJRQ1Thin films derived from Zn(Al)O mixed metal oxides nanoparticles dispersed in polyethylene glycol: Structural, morphological and optical properties
El Hassani, Kaoutar; Bayram, Ozkan; Anouar, Abdellah; Mavi, Ahmet
In this study, Zn(Al)O thin films were produced using colloidal solution of Zn(Al)O nanoparticles dispersed in polyethylene glycol (PEG). Zn(Al)O mixed metal oxides were obtained by a simple pyrolysis of Zn–Al containing layered double hydroxide materials with different Al content. Survey of textural analysis of Zn(Al)O mixed oxides displayed characteristic peaks of ZnO structure. The calculated ratios of lattice parameters c/a were found to be 1.61 and 1.60 for 3-ZAO and 5-ZAO, respectively. The optical transmittance of the prepared thin films was not significantly affected by the increase in Al content; however, this increase changed the optical band gap from 3.27 eV to 3.33 eV. ZAO thin films, which are both cost-effective with good optical properties, have the potential to be an alternative to those used in many optical devices lately.
AtıfScopus4WoS3OpenAlex4İncele - MakaleAçık Erişim2019Scopus SJRQ2Characterization of an interesting selenium-dependent glutathione peroxidase (Se-GPx) protecting cells against environmental stress: The Camelus dromedarius erythrocytes Se-GPx
Chafik, Abdelbasset; Essamadi, Abdelkhalid; Çelik, Safinur Yildirim; Solak, Kübra; Mavi, Ahmet
Camel lives most of its life under high environmental stress in the desert. Glutathione peroxidase plays a key role in protecting cells against oxidative stress. For the first time, selenium-dependent glutathione peroxidase (Se-GPx) was purified from camel erythrocytes, biochemically characterized, and some of its properties were studied. The enzyme was purified using ethanol-chloroform treatment, acetone precipitation and ion exchange chromatography. A purification fold of 33.72 with 0.19% yield were obtained. The native molecular weight of the enzyme was estimated to be about 69 kDa. On SDS-PAGE, the enzyme was composed of two different subunits with a molecular weight of approximately 53 and 21 kDa. An optimum temperature of 47 °C and an optimum pH of 7.2 were found. The activation energy was 41.71 kJ/mol. This enzyme was inhibited by thiol reagents, D,L-Dithiothreitol and β-Mercaptoethanol, and was sensitive to bivalent cations. The enzyme had a general specificity toward hydroperoxides, and high specificity for reduced glutathione. The purified enzyme contained 3.06 mol of selenium per mol of protein. The Km and Vmax values for hydrogen peroxide and reduced glutathione were 0.72 and 1.58 mM, and 25.33 and 31.03 U/mg, respectively. The biochemical properties of camel Se-GPx were different comparing to those of mammalian species. Lower molecular weight, heterodimeric structure, higher optimum temperature, relatively lower optimum pH, lower content of selenium and higher affinity for hydrogen peroxide at low reduced glutathione concentration, these could be explained by the fact that camel is able to live in the intense environmental stress in the desert.
AtıfScopus11WoS10OpenAlex10İncele - MakaleAçık Erişim2019Scopus SJRQ3Plasma polymerized linalool (ppLin): An antimicrobial and biocompatible coating
Çakmak, Kenan; Bayram, Özkan; Solak, Kübra; Kaban, Güzin; Şimşek, Önder; Mavi, Ahmet
Bacterial infections in medical devices and drug resistance of bacteria can cause chaos in the world due to loss of lives in addition to the cost of device revisions, quarantine, disinfection of infected areas, and patient treatment. Antibacterial coatings of essential oils on medical devices can prevent bacterial attachment and reduce costs. Linalool is an antibacterial constituent of essential oils. Herein, we examine for the first time the fabrication and characterization of radio frequency (RF) plasma polymerized hydrophilic thin films from linalool (ppLin) by varying deposition parameters (RF power and deposition time) and the behavior of ppLin with two bacteria (Escherichia coli and Staphylococcus aureus) commonly related to microbial contamination of medical devices. While a dramatic reduction in E. coli and S. aureus attachment was observed on ppLin films, their hydrophilic surface was also bactericidal to S. aureus. Additionally, ppLin films were shown to be adherent and noncytotoxic to human fibroblast cells. ppLin can be potentially integrated into medical and other clinical devices as a promising low-cost biocompatible antimicrobial coating.
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İncele - MakaleYalnız künye2019Scopus SJRQ1Purification and biochemical characterization of a novel copper, zinc superoxide dismutase from liver of camel (Camelus dromedarius): An antioxidant enzyme with unique properties
Chafik, Abdelbasset; Essamadi, Abdelkhalid; Çelik, Safinur Yildirim; Mavi, Ahmet
A novel copper, zinc superoxide dismutase (CuZnSOD) was purified to homogeneity from the liver of an animal well adapted to the stressful living conditions of the desert, the camel (Camelus dromedarius). The biochemical properties of camel liver CuZnSOD were examined. The purified enzyme had a native molecular weight of 28 kDa, as judged by gel filtration chromatography, and showed a single band at 27 kDa on SDS-PAGE, indicating that it is a monomeric protein. Optimal activity of the purified enzyme occurred at 43 °C and pH 6.0, and the activation energy was 1.42 kJ/mol. CuZnSOD activity was strongly inhibited by β-ME, DTT, H 2 O 2 and SDS and slightly inhibited by EDTA, NaN 3 and PMSF. Al 3+ , Ca 2+ , Cd 2+ , Mg 2+ and Zn 2+ stimulated CuZnSOD activity, whereas Ba 2+ , Co 2+ , Fe 2+ and Ni 2+ inhibited it. The purified enzyme contained 0.010 µg of Cu and 0.69 µg of Zn per mg of protein. K m , V max , k cat and k cat /K m values for NBT and riboflavin were 16.27 and 0.16 µM, 20.85 and 21.54 U/mg, 9.65 and 9.97 s −1 , and 0.59 and 62.33 s -1 µM −1 , respectively. Camel liver CuZnSOD exhibited unique biochemical properties compared to those of other CuZnSODs, including lower molecular weight with a monomeric structure, higher optimum temperature, very low E a , very low optimum pH, very low contents of Cu and Zn, and higher affinity, turnover number and catalytic efficiency for riboflavin. These unique properties of camel liver CuZnSOD might be related to the ability of this animal to inhabit stressful desert conditions.
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İncele - Proje2018Sülfanilamid Bağlanmış Manyetik Nanopartiküllerle (Fe 3 O 4 @SiO 2 -PA-SA) Karbonik Anhidraz Enziminin Saflaştırması
Çelik, Safinur; Mavi, Ahmet
Enzimler, endüstriyel süreçlerde ve bilimsel çalışmalarda oldukça yaygın olarak kullanılmaktadır. Bu sebeple enzimlerin hızlı ve ucuz bir yolla yüksek saflıkta saflaştırılması, ekonomik bir önem arz etmektedir. Bu projede amaç, karbonik anhidraz (CA) enzimini kısa sürede yüksek verimle saflaştırmak için ucuz, tekrar kullanılabilir ve manyetik temelli yeni bir materyal geliştirmektir. Projenin birinci bölümünde ilk olarak Fe3O4 MNP sentezlenmiştir. MNP?nin kararlılığını sağlamak için ikinci basamakta tetraetilortosilikat (TEOS) kullanılarak MNP?ler silika ile kaplanmış ve Fe3O4@SiO2 elde edilmiştir. Üçüncü basamakta Fe3O4@SiO2 yüzeyine APTES ((3-Aminopropil) trietoksisilan) ile -NH2 grubu ilave edilerek Fe3O4@SiO2-NH2 üretilmiştir. Dördüncü basamakta ise Fe3O4@SiO2-NH2 yüzeyinde bulunan -NH2 ile Phloretik asitin (PA, 3-(4-hidroksifenil) propiyonik asit) -COOH grubu, EDC (N-(3- Dimetilaminopropil)-N?-etilcarbodiimid hidroklorid) ve NHS (N-hidroksi süksinimid) aktivatörlüğünde, kovalent olarak bağlanmış ve Fe3O4@SiO2-PA elde edilmiştir. Son olarak karbonik anhidraz enziminin ilgisinin bulunduğu sülfonamidin (SA) diazonyum tuzu, Fe3O4@SiO2-PA?de bulunan Phloretik asitin aromatik halkasına bağlanarak Fe3O4@SiO2- PA-SA sentezlenmiştir. Nihai partikül (Fe3O4@SiO2-PA-SA) SEM, TEM, XRD ve FT-IR ile karakterize edilmiştir. TEM analiz sonuçları, hekzagonal şekle sahip monodispers ve ortalama 10 nm boyutlarında Fe3O4 MNP?ler üretildiğini göstermektedir. Silika kaplama ve APTES modifikasyonu yapılan nanopartiküllere ait TEM görüntüleri; Fe3O4@SiO2-NH2 MNP?lerin multi-çekirdek içerdiğini, SEM görüntüleri ise MNP?lerin 100 nm?den küçük ve küresel morfolojiye sahip olduğunu göstermektedir. Projenin ikinci bölümünde Fe3O4@SiO2-PA-SA kullanılarak hemolizattan karbonik anhidraz (CA) enzimi saflaştırılmıştır. Fe3O4@SiO2-PA-SA partikülleri hemolizat ile karıştırılıp CA?nın sülfanilamite bağlanması sağlanmıştır. Daha sonra bir mıknatıs ile Fe3O4@SiO2-PA-SA:::CA partikülleri toplanarak hemolizat ortamından uzaklaştırılmıştır. Fe3O4@SiO2-PA-SA:::CA partikülleri yıkanarak safsızlıklar ortamdan uzaklaştırılmıştır. Fe3O4@SiO2-PA-SA:::CA partiküllerinin üzerine elüsyon tamponu ilave edilerek CA, partiküllerden ayrılmış ve çözelti ortamına alınmıştır. Ortamda kalan Fe3O4@SiO2-PA-SA partiküller tekrar kullanılmak üzere mıknatısla geri kazanılmıştır. Sentezlenen MNP?ler ile CA, 2 saat gibi kısa bir zamanda ve basit bir şekilde hemolizattan saflaştırılabilmiştir. MNP?lerin maksimum enzim tutma kapasitesi 19,5 ± 1,1 mg CA/g MNP olarak hesaplanmıştır. Elde edilen CA?ın SDS-PAGE ile saflığı kontrol edilmiş ve enzimin yüksek saflıkta olduğu görülmüştür. Sentezlenen MNP?leri tekrar kullanılabilirliği test edilmiş ve üç kullanıma kadar MNP?lerin etkinliğini kaybetmediği görülmüştür.
- MakaleYalnız künye2018Scopus SJRQ4Partial Purification and Some Interesting Properties of Glutathione Peroxidase from Liver of Camel (Camelus dromedarius)
Chafik, Abdelbasset; Essamadi, Abdelkhalid; Çelik, Safinur Yildirim; Solak, Kübra; Mavi, Ahmet
Climate change and increasing temperatures are global concerns. Well adapted to desert life, the camel (Camelus dromedarius) lives most of its life under high environmental stress and represents an ideal model for studying desert adaptation among mammals. Glutathione peroxidase is the principal antioxidant defense system capable of protecting cells from oxidative stress. Glutathione Peroxidase from camel liver was purified (11.64-fold purification with 1.73% yield) and characterized The molecular weight of the enzyme was estimated to be about 69 kDa by gel filtration and 34 kDa by SDS-PAGE, implying dimeric structure of the protein. An optimum temperature of 47°C and an optimum pH of 7.8 were found. This enzyme is a typical SH-enzyme that is inhibited by D,L-dithiothreitol and β-mercaptoethanol and sensitive to bivalent cations. The enzyme had common specificity toward hydroperoxides and high specificity for reduced glutathione. The Km and Vmax values for hydrogen peroxide and reduced glutathione were 0.57 and 2.10 mM and 1.11 and 0.87 U/mg, respectively. The purified enzyme contained 16 ng of selenium per mg of protein. Our results show that the camel glutathione peroxidse exhibits properties different of those reported for other mammalian species. Lower molecular weight, homodimeric structure, higher optimum temperature, relatively low optimum pH, high affinity for hydrogen peroxide at low concentration of reduced glutathione and very low content of selenium could be explained by adaptation of the camel to living in the desert under intense environmental stress.
AtıfScopus12WoS9OpenAlex11İncele - MakaleYalnız künye2017Scopus SJRQ1Purification 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.
AtıfScopus9WoS9OpenAlex10İncele