Browsing by Author "Tepe, M"

Now showing 1 - 7 of 7
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    Surface-induced textures in lyotropic liquid crystalline mesophases
    Nesrullajev, A; Tepe, M; Kazanci, N; Çakmak, HM; Abukay, D
    In the present work the investigation of the effect of YBa2Cu3O7-x complex compounds thin films on the mesomorphic, morphologic and orientational properties of lyotropic nematics have been carried out. The thin films of YBa2Cu3O7-x lead to an increase in number of morphologies of investigated nematics and promote the obtaining of tilted oriented and homeotropic textures of these nematics. The coating of YBa2Cu3O7-x thin films by inverted cylindrical DC magnetron sputtering system has been shown in this work to be a useful method for obtaining oriented textures of lyotropic nematics. (C) 2000 Elsevier Science S.A. All rights reserved.
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    Effects of thermal oxidation temperature on vacuum evaporated tin dioxide film
    Çakmak, HM; Çetinkara, HA; Kahraman, S; Bayansal, F; Tepe, M; Güder, HS; Çipiloglu, MA
    In order to investigate the effect of thermal oxidation temperature on tin dioxide (SnO2), tin dioxide films were obtained on quartz substrates by vacuum evaporation of tin metal. The films were characterized by X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM), temperature dependent electrical resistivity measurement and optical absorption spectroscopy. The SEM images showed that the films are dense, continuous and are composed of nanoparticles and particle sizes are increased after thermal oxidation. From the X-ray measurement results, the films indicated two strong reflection peaks of tetragonal structure in the orientations of (101) and (200) at 20 = 33.8 degrees and 37.95 degrees, respectively. Intensity of the peaks increased with increasing thermal oxidation temperature. We found resistivity values of about 10(-4) Omega-cm. Optical absorption spectra of the films in the UV-Vis spectral range revealed that optical band gap (E-g) value of the films increases with increasing thermal oxidation temperature. (C) 2012 Elsevier Ltd. All rights reserved.
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    Phenolic Compounds, Fatty Acid Contents, and Antibacterial Properties of Ozonated and Non-Ozonated Tobacco Seed Oils
    Yemis, F; Alp, H; Ay, E; Tepe, M; Ay, K
    In this study, the fatty acid content, phenolic compounds, and antimicrobial activity of seed oils from Ege & Ouml;zba & scedil; (EO), Sar & imath;ba & gbreve;lar 407 (S407) and Akhisar 98 (A98) tobacco plants grown in the Aegean region were investigated. The ozonation process altered fatty acid and phenolic compound compositions and affected antimicrobial activities against Gram-positive and Gram-negative bacteria in the oils. Tobacco seed oils (TSOs) were extracted via cold pressing (CP) and Soxhlet extraction (SE). Fatty acids and phenolic compounds were analyzed using GC-FID and LC-MS/MS, respectively. Non-ozonated oils averaged 73% linoleic acid, 13% oleic acid, 9% palmitic acid, and 3% stearic acid, while ozonated oils contained 41% linoleic acid, 18% oleic acid, 22% palmitic acid, and 11% stearic acid. The presence of 33 phenolic compounds was investigated and 22 common phenolic compounds were detected in both ozonated and non-ozonated TSOs, including gallic acid, protocatechuic acid, chlorogenic acid, 3-hydroxybenzoic acid, (-)-epicatechin, 2,5-dihydroxybenzoic acid, caffeic acid, verbascoside, luteolin-7-glucoside, hesperidin, and rosmarinic acid. The increased antimicrobial activity of fatty acids and phenolic compounds following ozonation suggests the potential for developing creams to treat skin diseases and wounds caused by antibiotic-resistant pathogens, and to reduce the effects of aging skin wrinkles.
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    Chemistry of plant extracts directs the silver nanostructures' crystal structure into hexagonally close-packed: a comparative study using elecampane and blueberry extracts
    Tepe, M; Zeybek, MS
    In this study, silver nanostructures (AgNSs) were obtained using aqueous extracts of elecampane (Inula viscosa) and blueberry (Vaccinium arctostaphylos L.). The synthesized AgNSs were characterized using UV-visible spectrophotometers, Fouriertransformed infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray analysis, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The optimization studies revealed that pH and the extract/AgNO3 ratio played significant roles in the morphology and size of the AgNSs, while temperature did not show any significant role. Both the blueberry and elecampane extracts resulted in a mixture of spherical and aspherical silver nanoparticles (AgNPs). In contrast, utilization of a relatively high extract/AgNO3 ratio accompanied by an extended incubation period (i.e., 10 days) caused the formation of larger spherical (e.g., up to micron-sized) and large 1D AgNPs for the blueberry and elecampane extracts, respectively. The major difference related to the crystal structures was obtained, as the blueberry extracts resulted in face-centric cubic crystals, and the elecampane extracts allowed the formation of hexagonally close-packed (hcp) crystalline structures. The AgNPs were tested for their antibacterial activities using gram (-) and gram (+) bacterial species, where the elecampane-synthesized AgNPs possessed higher antibacterial activity that can be attributed to the hcp crystalline structure of the AgNPs.
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    Antioxidant responses of lentil and barley plants to boron toxicity under different nitrogen sources
    Tepe, M; Aydemir, T
    In this study, the effects of different nitrogen sources on lentil (Lens clunaris) and barley (Hordeum vulgare) plants, exposed to 5 and 10 mM boron stress previously, were studied. After ten-day germination, the lentil (native) and barley (Tokak157/37) were incubated 16 h light and 8 h dark per day for 7-day growth cycle under the conditions of boron stress via different nitrogen sources (10 mM nitrogen in NH4 Cl, KNO3 and urea). As a result of the changes in the nitrogen sources of the plants, there were determined decreases in the relative growth rate (%) and total chlorophyll content related to boron stress, (p < 0.05) and (p < 0.01), respectively. The changes in the lentil were obtained much more than those in the barley. In addition, the changes in the groups in which NH4+ was used as nitrogen source were obtained at lowest levels. The concentrations of MDA, H2O2 and proline showed increases under boron stress (p < 0.05). The effect of boron toxicity on the activities of SOD, GPX and LOX was similar in the two species but the levels of CAT and APX activities were different in both species under 5 and 10 mM boron stress (p < 0.01). SOD, GPX and LOX activities increased in the roots and shoots of boron treated plants as compared with the controls (p < 0.01). Although, lentil CAT and APX, activities decreased; in barley, CAT and APX, activities increased under boron toxicity. In conclusion, the fertilizers which contain NH4+ should be used in the boron stressed farmlands.
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    Modification of chitosan-bead support materials with l-lysine and l-asparagine for α-amylase immobilization
    Yazgan, I; Turner, EG; Cronmiller, LE; Tepe, M; Ozturk, TK; Elibol, M
    Maltose syrups have got wide-range utilizations in a variety of applications from bakery to drug-development. alpha-Amylases are among the most widely utilized industrial enzymes due to their high specificity in production of maltose syrup from starch. However, enzymes are not stable in ex vivo conditions towards alteration in pH, temperature, and such other parameters as high salt concentrations and impurities, where immobilization is required to advance the stability of the enzyme with which approach the requirement of isolation of the enzyme from media is eliminated as well. In this study, Termamyl(A (R)) alpha-amylase was immobilized on the none-modified chitosan beads (NMCB), l-lysine-modified chitosan beads (LMCB), and l-asparagine-modified chitosan beads (AMCB) to assess effects of the support material on optimum conditions and kinetic parameters of the alpha-amylase activity in production of maltose from starch. Immobilization on NMCB, LMCB, and AMCB puts a strong influence on optimum pH, optimum temperature, stability, and kinetic parameters of alpha-amylase. Modification of chitosan beads with l-lysine and l-asparagine dramatically altered the overall immobilization yield, and enzyme's response to pH and temperature variations and the kinetic parameters. AMCB provided the best immobilization yield (49%), while LMCB only improved the yield by 2% from 22 to 24%.
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    Doxorubicin functionalized metallic nanoparticles for anticancer and antibacterial applications
    Yesil, I; Atmaca, H; Degirmenci, S; Çamli-Pulat, C; Ari, M; Tepe, M; Küçük, A; Salmanoglu, DS; Sancak, Z; Kilinç, C; Ilhan, S; Yazgan, I
    In this study, we used Doxorubicin, an FDA approved drug possessing anticancer and antibacterial activity, as a model drug to functionalize sugar ligand synthesized silver/gold bimetallic nanoparticles (Ag/AuNPs) to test simultaneous antibacterial and anticancer activities under in vitro conditions. DU-145 prostate cancer cells were used as the main target while T98G glioblastoma and MDA-MB-231 breast cancer cell lines were used for selectivity test, and HEK-293 epithelial cell line was used as non-cancerous cells to test toxicity of these formulations. Three Ag/AuNP and corresponding Doxorubicin (D) functionalized ones and free Doxorubicin were tested for these four cell lines. Plain Ag/AuNP showed the highest toxicities on HEK-293 cell lines while DU-145 cell line showed the greatest vulnerability for Ag/AuNP-D formulations. However, DU-145 cells showed the lowest susceptibility for free Doxorubicin at all the tested concentrations. The antiproliferative activity was not dose dependent while an inverse relationship was obtained for a certain concentration range. Two Doxorubicin functionalized gold nanoparticles (AuNP-D) were then synthesized and applied on DU-145 cells. Interestingly, a better anticancer activity was obtained even at the minimum applied concentration (1.8 x 10-5 mu g/mL D). Antibacterial activities of these formulations were also tested for multidrug-resistant gram (-) and gram (+) bacterial species. Depending on the sugar ligand chemistry, antibacterial activity of Doxorubicin functionalized Ag/AuNPs showed a better performance in comparison to the plain Ag/AuNPs and vice-versa. Based on the results, it can be claimed that selective or semi-selective formulations targeting cancer cells and bacterial species as anti-neutropenia formulations can be developed using carbohydrate derivatives synthesized metallic nanoparticles as drug delivery agents.