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Öğe Assessment of oxidative stress in plants by EPR spectroscopy(Elsevier, 2023) İşlek, YaseminFree radicals are chemically active and destructive molecules. Free radicals contain one or more unpaired electrons that interact with other molecules within the cell. These interactions can cause oxidative stress during biological processes. Oxidative stress is defined as a disturbance between reactive oxygen species and antioxidant balance in an organism. Reactive oxygen species that increase with the disturbance in this balance cause oxidative stress formation. Oxidative stress damages biological macromolecules such as proteins, lipids, and DNA. Electron paramagnetic resonance (EPR) technique is a tool used for identifying the effects of various oxidative stresses in biological samples. The EPR is a unique technique capable of providing a direct identification of free radicals. This method is one of the most powerful and sensitive methods for detailed analysis of free radicals and provides complete information about the structures. © 2023 Elsevier Inc. All rights reserved.Öğe Bjerkandera adusta Collected from Niğde: Analysis of Total Phenolic Compound, Antioxidant, vnd Antimicrobial Properties(2022) Ildız, Elif; Canpolat, Şükrü; İşlek, Cemil; Canpolat, Elif; İşlek, Yasemin; Akata, IlgazMacrofungi have long been used as food and medicinal purposes by humankind. This study aimed to identify a macrofungus sample collected from Niğde, Türkiye in 2019 via molecular techniques and determine the content of total phenolic compounds, antioxidant and antimicrobial activities. According to data obtained from the sequence analysis of ITS fragment of rDNA the macrofungus sample was identified as Bjerkandera adusta (Willd.) P. Karst (1880). The sample was extracted with ethanol and methanol. Total phenolic compound content, antioxidant activity via DPPH scavenging method and antimicrobial activity via disc diffusion method of B. adusta was determined by using these extracts. The amount of total phenolic compounds was found as 772.28 ?g GAE/mL for a methanolic extract of B. adusta. The ethanol extract of B. adusta showed 79.66% scavenging activity of 0.1 mM DPPH solution. The highest inhibition zone diameter was measured as 28±1 mm against P. aeruginosa by ethanolic extract, while the lowest antimicrobial activity was found in 15 ?L methanol extract against S. typhimurium with an inhibition zone diameter of 8.7±1.2 mm.Öğe Elektron paramanyetik rezonans (EPR) spektroskopisi kullanılarak organik maddelerde oluşturulan serbest radikallerin incelenmesi(Niğde Ömer Halisdemir Üniversitesi / Fen Bilimleri Enstitüsü, 2016) İşlek, Yasemin; Canımoğlu, AdilBu tez çalışmasında tıpta önem arzeden ve pek çok ilacın etken maddesini oluşturan bazı organik maddelerin hem toz formları hem de bunlardan elde edilen tek kristaller Elektron Paramanyetik Rezonans (EPR) yöntemiyle incelenmiştir. Toz maddeler ile yapılan çalışmalarda farklı mikrodalga frekanslarına sahip X-band (9.7 GHz), Q-band (34 GHz) ve W-band (94 GHz) tipleri kullanılarak yapıda oluşabilecek radikal tipleri öngörülmüştür. 60Co-? ile ışınlanan ve antioksidan özellik taşıyan 3-methyl-1-phenyl-2-pyrazoline-5-one tek kristalinde R-C ?HCH_2 radikalinin oluştuğu tespit edilmiştir. X-ışınları ile ışınlanan ve bir pirazolon türevi olan 1-(4-Sulfophenyl)-3-methyl-5-pyrazolone tek kristalinde R-N ? ve R-S ? olarak adlandırılan iki farklı radikalin oluştuğu görülmüştür. 60Co-? ile ışınlanan methyl 4-methyl benzoate tek kristali ile yapılan çalışmalar neticesinde ise tek kristalde R-C ?H_4 CH_3 radikalinin oluştuğu tespit edilmiştir. X-ışınları ile ışınlanan cholesteryl chloroformate tek kristali ile sıcaklık çalışmaları yürütülmüş, 20K gibi çok düşük sıcaklıklarda EPR spektrumlarındaki değişim incelenmiştir.Öğe Morphological and Thermal Characterization of Low-Cost Graphene Produced by Electrochemical Exfoliation Method(2024) Güzel, Tamer; İşlek, Yasemin; Yıldız, OğuzhanThe low-cost and mass production of graphene has gained importance in recent years. The electrochemical exfoliation method, one of the graphene production methods, is an efficient technique used to obtain low-cost-effective and large quantities of graphene nanosheets. Exfoliation parameters affect the properties of exfoliated graphene nanosheets. In this study, graphene production is fabricated by the method of exfoliation using electrolyte and voltage parameters. For this, a pen tip was used instead of pure platinum, which is very expensive, at the cathode. The structural research was done by X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Fourier Transform Infrared Spectrometer (F-TIR). Morphological analyses were carried out by Scanning Electron Microscopy (SEM). The number of layers and crystallite of graphene layers were estimated. The obtained results were compared with the results of the other similar studies. Analysis results show that low-cost multilayer graphene can be produced by the electrochemical exfoliation method with the electrical parameters.Öğe Total Phenolics, Antioxidative and Antimicrobial Activities of Some Edible Ascomycota Collected from Niğde(2021) Canpolat, Şükrü; Akata, Ilgaz; İşlek, Yasemin; Canpolat, Elif; İşlek, CemilMushrooms have been used as food and medicinal purposes for centuries. In this study, some edible\rAscomycota were collected in 2018 and 2019 from Niğde, Turkey. Molecular identifications of the\rsamples were performed afterward. PCR products were sent for sequence analysis after ITS\rfragments were amplified with suitable primers concerning DNA isolation of samples. The obtained\rdata were compared with the Genbank database for samples’ determination. The mushroom samples\rwere determined to be Terfezia claveryi Chatin and Morchella esculenta (L.) Pers. Samples were\rextracted by ethanol and methanol to determine antimicrobial activity using the disc diffusion\rmethod. Antimicrobial zones against microorganisms were measured. Then DPPH radical\rscavenging effects and total phenolic content of T. claveryi and M. esculenta mushroom samples\rwere studied. The highest antimicrobial activity was observed in ethanol extracts of M. esculenta.\rWhen the DPPH radical scavenging activities are taken into account, the activity is increased\rdepending on the concentration. The highest DPPH scavenging activity was found in the extract of\rM. esculenta with 40.86%. It was determined that the total phenolic substances in methanol extracts\rof mushroom samples varies between 533.28 ± 1,15-537.34 ±2.20 ?g GAE / mg extract.
