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    Biosorption of dye crystal violet on Tragopogon sp. leaf powder: Equilibrium, kinetics, thermodynamics, and DFT calculations
    (Elsevier, 2024) Eyupoglu, Volkan; Aksu, Aysun; Cetinkaya, Huseyin Fatih; Cetintas, Halil Ibrahim; Cetinkaya, Serap; Tuzun, Burak
    Crystal violet, CV, was adsorbed on dead mass of Tragopogon sp. in aqueous solutions and the adsorption process was evaluated by analytical, visual, and theoretical means. The functional groups on the biosorbent surface were detected by FT-IR (Fourier Transform Infrared Spectrophotometry), and the surface morphology was visualized by SEM (Scanning Electron Microscopy), and EDX (Energy Dispersive X-Ray Analysis). Some of the biosorption conditions, pH, time, adsorbent mass, and temperature, were optimized. Three isotherm models, Langmuir, Freundlich, and Dubinin-Radushkevich, employed for the understanding of the reaction kinetics, suggested a spontaneous endothermic reaction that took place on the surface of Tragopogon sp cells. Iterative usability experiments, involving four biosorption-desorption rounds, showed that Tragopogon sp. biomass retained approximately 42% of its sorbent activity. Calculations, using the Gaussian software packages B3LYP, HF, and M06-2x, indicated a very high biosorption capacity of Tragopogon sp. for crystal violet. Crystal violet had -7.2067 HOMO and 0.1921 LUMO values.
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    Equilibrium and DFT modeling studies for the biosorption of Safranin O dye from water samples using Bacillus subtilis biosorbent
    (Elsevier, 2023) Çetinkaya, Serap; Kaya,Savaş; Aksu, Aysun; Çetintaş, Halil İbrahim; Jalbani, Nida Shams; Erkan Sultan; Marzouki, Riadh
    Current study deals with the biosorption of Safranin O dye from water by using high potential Bacil- lus subtilis biosorbent material. The presence of functional groups and surface morphology of biosor- bent was analyzed by using sophisticated analytical techniques such as FT-IR (Fouirer Transform Infrared Spectrophotometer), SEM (Scanning Electron Microscopy), EDX (Energy Dispersive X-Ray Analysis), and TGA (Thermogravimetric Analysis). To check the dye removal potential of Bacillus subtilis sorbent, batch adsorption experiments were performed under the optimized conditions. The biosorption experiments showed that the Bacillus subtilis sorbents remove 80% of safranin O dye from water. The biosorption mechanism is depends upon the solution pH thus the maximum biosorption was observed at (5.5–6.5). Moreover, the biosorbent dose has been optimized and it has observed that the maximum concentra- tion of safranin O dye has been removed using the 50 mg.L −1 of Bacillus subtilis . The biosorption equi- librium data were well fitted by the Langmuir adsorption isotherm due to good regression coefficient value ( R 2 = 0.98) and better Langmuir capacity (0.383 mmol.g −1 ), while the kinetic studies indicated that the biosorption followed the pseudo-second-order model. The thermodynamic parameters values showed that the biosorption is process is endothermic and spontaneous nature. In addition, molecular docking was also performed to examine the interaction between the safranin O dye molecule and the Bacillus subtilis bacterial cell line.
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    Experimental and Theoretical Evidence on the Amoebicidal Activity of Synthesized tRNA-Palmitic Acid Esters
    (Jihad Daneshgahi, 2024) Aksu, Aysun; Celik, Muhammed Safa; Polat, Zubeyde Akin; Yenidunya, Ali Fazil; Cetinkaya, Serap; Tuzun, Burak
    Synthesis of tRNA-palmitic acid esters was carried out in dimethyl sulfoxide (DMSO) and tert-butanol, %20 and %80 (v/v), respectively, for 24h at 55oC. These conditions have been to be optimal in the synthesis of monosaccharide-fatty acid esters in previous studies. The majority of the ester product (89.19%) was phthalic acid, butyl undecyl ester, as identified by GC-MS. This finding hinted that the ester bond took place between tRNA ribose unit(s) and carboxyl group of the palmitic acid. NMR (Nuclear Magnetic Resonance) was also used for the characterization of the ester product (data not shown). The ester product (O1) exerted remarkable amoebicidal activity, at 4mg/ml, on the trophozoites and cysts of Acanthamoeba castellanii. No live trophozoites or cysts could be detected after the 24th and 72th of incubation, respectively. The study included all the necessary control experiments. Interactions between the substrate molecules were scrutinized by molecular docking calculations. Activities of the studied molecules against various Acanthamoeba castellanii proteins (PDB ID: 1PRQ and 6UX0), in crystal form, were compared, and finally, ADME/T analyses were carried out.
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    MXenes and their composites as corrosion prevention
    (De Gruyter, 2023) Aksu, Aysun; Çetinkaya, Hüseyin Fatih; Çetinkaya, Serap; Tüzün, Gamze; Tüzün, Burak
    MXene, an advanced metal-based 2D ceramic material family, has had a sig- nificant impact in the field of corrosion prevention due to its unique physicochemical properties. Due to the need for further advancement and improvement in MXene ma- terials, studies have turned to the manufacture of composites that help strengthen MXene composites in terms of their properties and applications in various fields. MXenes have excellent filling properties. Anticorrosive application of MXene-filled polymer coatings has been extensively reported. Although modified graphene oxide is widely used as a filler in boron nitride and epoxy-based coatings, its applications as filler in other polymers with new properties are needed. This chapter focuses on MXenes as corrosion inhibitors, the properties of their composites and their applica- tion in industry.
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    Purification and characterisation of 1-dodecanol from an isolate of Streptomyces viridodiastaticus
    (Elsevier, 2021) Cetinkaya, Serap; Yenidunya, Ali Fazil; Aksu, Aysun; Celik, Muhammed Safa
    One-dodecanol was identified as the predominant secondary metabolite produced by a novel isolate of Streptomyces viridodiastaticus. A total secondary metabolite extract was electrophoresed, along with a prestained protein ladder (from 10 to 180 kDa), in a 10% SDS-polyacrylamide gel. Two prominent bands obtained were aligned with 25 and 10 kDa bands of the protein marker. These two secondary metabolite bands were also visualized by thin layer chromatography. The two bands, lower band (C1) and upper band (C2), in the polyacrylamide gel were sliced off and their metabolite content was eluted in n-butanol. Elution samples were analysed by GC-MS. Results indicated that the lower C1 band mostly contained 1-dodecanol, approximately 93%. The lower band also contained a 1-dodecanol-like metabolite, approximately 55%. The elution samples were also analysed by FTIR and the results were in accordance with those of the GC-MS.
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    Theoretically supported experimental analyses on Safranin O biosorption from textile wastewater via dead biomass of Spirogyra porticalis
    (Springer Heidelberg, 2024) Aksu, Aysun; Kutuk, Nursah; Caylak, Osman; Kasaka, Erguen; Cetinkaya, Serap; Maslov, Mikhail M.; Kaya, Savas
    High-performance chemical systems designed to eliminate pollution caused by dyestuffs are still among the focuses of interest of chemists. Non-toxic biological materials especially have begun to be widely used in this field. Fourier transform infrared spectrometry, SEM (scanning electron microscopy), EDS (energy-dispersive X-ray analysis), and TGA (thermogravimetric analysis) were performed. Adsorption was performed in batch-adsorption experiments. Optimization processes involved pH, amounts of the sorbent and Safranin O, adsorption kinetics, desorption, and reusability. To highlight the mechanism of the interaction between Safranin O and S. porticalis and to predict the power and nature interactions, density functional theory computations were performed. Optimization processes included pH, amounts of sorbent and Safranin O, adsorption kinetics, desorption, and reusability. Experimental results were re-evaluated using Langmuir and Freundlich isotherm models and the biosorption process followed Freundlich isotherm kinetics. The biosorption mechanism was understood by pseudo-first-order (PFO), intraparticle diffusion (IPD), and Elovich models. Adsorption was determined to follow PFO kinetics: physical, endothermic, and spontaneous. The highest recovery was obtained in NaOH. Density functional theory (DFT) finding calculations were also performed to prove the high adsorption capacity for Safranin O of the material used.