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    Production and characterization of spherical thermostable silver nanoparticles from Spirulina platensis (Cyanophyceae)
    (Taylor & Francis Ltd, 2016) Kaliamurthi, Satyavani; Selvaraj, Gurudeeban; Cakmak, Zeynep Elibol; Cakmak, Turgay
    Biological production of silver nanoparticles (SNP) has recently received considerable attention because of their therapeutic applications. The present study reports the production and characterization of spherical-thermostable SNP from Spirulina platensis. Wet biomass harvested from optimized logarithmic-phase culture was used for production of SNP in 1, 3, or 5 mM silver nitrate solution. Formation and concentration of spherical SNP was highest when S. platensis was treated with 3 mM silver nitrate. Fourier transform infrared spectra of SNP indicate that vanillin, coumarins, tannins, amide, and glycogen may act as stabilizing agents for bioreduction. The crystalline nature of the produced SNP was evidenced from X-ray diffractometer analysis. Weight loss of SNP occurred at 210 degrees C, 310 degrees C, and 510 degrees C as shown by thermogravimetric analysis. This study shows that S. platensis may be used as an efficient tool for production of spherical, crystalline, and thermostable SNP.
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    Static magnetic field induced epigenetic changes in wheat callus
    (Wiley, 2016) Aydin, Murat; Taspinar, Mahmut Sinan; Cakmak, Zeynep Elibol; Dumlupinar, Rahmi; Agar, Guleray
    Deoxyribonucleic acid (DNA) is always damaged by endogenous and exogenous factors. Magnetic field (MF) is one of these exogenous factors. When repair mechanisms are not sufficient, mainly because of imbalance in damage or mistakes in repair mechanisms, methylation of DNA results in polymorphism-related abnormalities. In this study, low intensity static magnetic field-induced DNA damage and methylation in wheat calli were investigated by using Random Amplified Polymorphic DNA and Coupled Restriction Enzyme Digestion-Random Amplification techniques. Calli were derived from mature embryos of wheat. Both 7- and 14-day-old wheat calli were exposed to 7mT (millitesla) static MF for 24, 48, 72, 96, or 120h of incubation period. The highest change in polymorphism rate was obtained in calli exposed to 7mT MF for 120h in both 7- and 14-day-old calli. Increase in MF duration caused DNA hypermethylation in both 7- and 14-day-old calli. Polymorphism and DNA methylation ratio were higher in 7-day-old calli. The highest methylation level with a value of 25.1% was found in 7-day-old calli exposed to MF for 120h. Results suggested that low intensity static magnetic field may trigger genomic instability and DNA methylation. Bioelectromagnetics. 37:504-511, 2016. (c) 2016 Wiley Periodicals, Inc.
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    Two pronounced Chlorella strains for efficient biodiesel feedstock production
    (Tubitak Scientific & Technical Research Council Turkey, 2019) Tuzun, Ilhami; Cakmak, Zeynep Elibol; Young, Emmanuel; Cakmak, Turgay
    In this study, two indigenous Chlorella strains were evaluated for triacylglycerol (TAG) production and related parameters during 10 days of N-deprivation. The strains were identified based on morphological characteristics and genomic information, named as Chlorella sp. IMU12 and Chlorella sp. IMU17. Time-dependent reduction of growth was accompanied by decreased chlorophyll content, reduced oxygen evolution ratio, and elevated carotenoid content of both strains cultivated in N-free Bold's basal medium. Nitrogen deprivation induced total lipid and neutral lipid content in both strains, supported by FTIR measurement of TAGs. Chlorella sp. IMU17 showed higher production of TAGs as a response to N-deprivation. Strikingly, relative polysaccharide content showed a rapid increase on the first days and a noticeable reduction was recorded especially after 5 days of N-deprivation while TAG production showed a gradual increase during the whole period of N-deprivation in both strains. Starch might be a predominant form of carbon storage in the short term and the continuous increase of TAG production might be supported by degradation of starch in a longer period of N-deprivation. FAME analysis of lipids showed that the saturation level of the fatty acids of both strains meets the European standard EN 14214 requirements. Lastly, N-deprivation stimulated a significant reduction of PUFA production in Chlorella sp. IMU17. Thus, Chlorella sp. IMU17 might stand as a promising candidate for biodiesel feedstock production with its low PUFA content and a concomitant induction of saturation of fatty acids as a clear response to N-deprivation.