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Öğe Combined voltammetric and spectroscopic investigation of binding interaction between nifedipine and human serum albumin on polyelectrolyte modified ITO electrode(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Ozmen, Mustafa; Maltas, Esra; Patir, Imren Hatay; Bayrakci, MevlutThe binding interaction between the drug molecule, nifedipine (Nf), and the human serum albumin (HSA) on polyelectrolyte modified indium tin oxide (ITO) electrode has been investigated by the combination of electrochemical and fluorescence spectroscopy techniques. Surface modification has also been characterized by scanning electron microscopy (SEM) and Contact Angle (CA) measurements in each step. The cyclic voltammetry, electrochemical impedance parameters (peak potential difference (Delta E-p)), peak current difference (Delta I-p) and charge-transfer resistance (R-ct) indicate that nifedipine strongly interacted with human serum albumin molecule on the polyelectrolyte modified ITO electrode surface. Stern-Volmer quenching constant K-a is inversely correlated with the temperature, which indicates that the probable quenching mechanism of the nifedipine-human serum albumin binding reaction is initiated by complex formation. The results obtained from these techniques showed that Nf could bind to HSA. The binding constant (K-b) and the number of binding sites (n) of the drug with HSA at different temperatures were determined. At 298 K, K-b was found as 4.04 x 10(-3) and n was 1.08 for Nf-HSA. According to the van't Hoff equation, the thermodynamic parameters, Delta G, Delta H and Delta S, were obtained, showing the involvement of hydrophobic and electrostatic force in this interaction. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Humic-makeup approach for simultaneous functionalization of polyacrylonitrile nanofibers during electrospinning process, and dye adsorption study(TAYLOR & FRANCIS INC, 2016) Gezici, Orhan; Guven, Idris; Ozcan, Fatih; Ertul, Seref; Bayrakci, MevlutA useful methodology is represented to functionalize polyacrylonitrile nanofibers by using humic acid as a makeup agent in electrospinning process. Both morphology and surface chemistry of polyacrylonitrile nanofiber mats were understood to be influenced by incorporation of humic acid into the structure. Physicochemical changes were evidenced by Fourier transform infrared spectroscopy, scanning electron microscope, and surface charge measurements. Unlike some anionic dyes (i.e., methyl orange, methyl red, and Congo red), there was an enhancement in crystal violet (a cationic dye) adsorption after incorporation of humic acid. The Langmuir model fitted well to crystal violet data, and monolayer adsorption capacity was calculated as 81.6 mg/g (r(2) = 0.998).Öğe A new calix[4]azacrown ether based boradiazaindacene (Bodipy): Selective fluorescence changes towards trivalent lanthanide ions(ELSEVIER SCI LTD, 2013) Bayrakci, Mevlut; Kursunlu, Ahmed Nuri; Guler, Ersin; Ertul, SerefWe report on the synthesis and photophysical properties of a new calix[4]azacrown derivative, capped with two amide bridges, in the cone conformation bearing two boradiazaindacene (Bodipy) groups at the narrow rim. Its binding properties towards trivalent lanthanide ions such as La3+, Gd3+, Tb3+, Dy3+, Er3+ and Yb3+ were investigated by using spectroscopic techniques. With respect to fluorescence intensity changes upon trivalent lanthanide ion complexation, calix[4]azacrown ether based Bodipy showed higher selectivity towards Yb3+ ion over other ions. Presence of proximal two amide groups in calix[4] azacrown ether based Bodipy were observed to play an important role in exhibiting its lanthanide ion binding. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Novel humic acid-bonded magnetite nanoparticles for protein immobilization(ELSEVIER SCIENCE BV, 2014) Bayrakci, Mevlut; Gezici, Orhan; Bas, San Zeki; Ozmen, Mustafa; Maltas, EsraThe present paper is the first report that introduces (i) a useful methodology for chemical immobilization of humic acid (HA) to aminopropyltriethoxysilane-functionalized magnetite iron oxide nanoparticles (APS-MNPs) and (ii) human serum albumin (HSA) binding to the obtained material (HA-APS-MNPs). The newly prepared magnetite nanoparticle was characterized by using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and elemental analysis. Results indicated that surface modification of the bare magnetite nanoparticles (MNPs) with aminopropyltriethoxysilane (APS) and HA was successfully performed. The protein binding studies that were evaluated in batch mode exhibited that HA-APS-MNPs could be efficiently used as a substrate for the binding of HSA from aqueous solutions. Usually, recovery values higher than 90% were found to be feasible by HA-APS-MNPs, while that value was around 2% and 70% in the cases of MNPs and APS-MNPs, respectively. Hence, the capacity of MNPs was found to be significantly improved by immobilization of HA. Furthermore, thermal degradation of HA-APS-MNPs and HSA bonded HA-APS-MNPs was evaluated in terms of the Horowitz-Metzger equation in order to determine kinetic parameters for thermal decomposition. Activation energies calculated for HA-APS-MNPs (20.74 kJ mol(-1)) and HSA bonded HA-APS-MNPs (33.42 kJ mol(-1)) implied chemical immobilization of HA to APS-MNPs, and tight interactions between HA and HA-APS-MNPs. (C) 2014 Elsevier B.V. All rights reserved.Öğe Synthesis and application of novel magnetite nanoparticle based azacrown ether for protein recognition(POLYMER SOC KOREA, 2013) Bayrakci, Mevlut; Maltas, Esra; Yigiter, Sengul; Ozmen, MustafaThis article is the first report showing the human serum albumin (HSA) binding studies by using a new magnetite nanoparticle containing azacrown ether moieties via solid-liquid extraction process. The structure of the newly prepared magnetite nanoparticle was clarified by using attenuated total reflectance (ATR) infrared spectroscopy, scanning electron microscopy (SEM), UV-vis and elemental analysis. Analytic results indicated that modification of the surface of the magnetite nanoparticles with azacrown ether derivative was successfully carried out. The protein binding studies exhibited that the modified magnetite nanoparticles could be efficiently used for the binding of the human serum albumin (HSA) in aqueous solutions via non-covalent interaction between crown ether cavity and amino group of the protein.Öğe Synthesis and Preparation of Novel Magnetite Nanoparticles Containing Calix[4]arenes With Different Chelating Group Towards Uranium Anions(TAYLOR & FRANCIS INC, 2015) Ozcan, Fatih; Bayrakci, Mevlut; Ertul, SerefIn this study, four new magnetite nanoparticle containing different chelating groups as ester, amide and azacrown moieties at the lower rim of calix[4]arenes were prepared by the reaction of formylated calix[4]arenes and amino propyl modified magnetite nanoparticles (APTMS-MN). All of the newly synthesized and prepared compounds were characterized by using different analytical techniques such as nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). Furthermore, uranium binding abilities of newly prepared magnetite nanoparticles were evaluated by using solid-liquid phase extraction process and obtained results showed that magnetite nanoparticles containing picolinamide units exhibited superior and more efficient extraction percentage for uranium ions at lower pH values.Öğe Synthesis and Spectroscopic Studies of Novel Rhodanine Azo Dyes: An Excellent Selective Chemosensor for Naked-eye Detecting of Cu2+ Ion(SLOVENSKO KEMIJSKO DRUSTVO, 2012) Ceylan, Abdullah; Bas, Salih Zeki; Bayrakci, Mevlut; Ertul, Seref; Uysal, AhmetThis study is first report on the synthesis of novel rhodanine based azo dyes and their fluorogenic and chromogenic sensing behaviors with metal ions (Li+, Na+, K+, Rb+, Pb2+, Ni2+, Zn2+, Cu2+) by using UV-vis and fluorescence spectroscopy techniques. The results of spectroscopic experiments for rhodanine based azo dye 1a exhibited excellent selectivity for Cu2+ over the other metal ions. Furthermore, anti-bacterial studies of rhodanine azo dyes were performed towards some selected bacteria via microbroth dilution method. Obtained results showed that rhodanine ionophore 1a showed strong antibacterial activity against S. aureus.Öğe Synthesis and trivalent lanthanide ion complexation studies of new macrocyclic receptors based lactam ionophores(SPRINGER, 2014) Gullu, Fadime; Bayrakci, Mevlut; Kursunlu, Ahmed Nuri; Yigiter, Sengul; Ertul, SerefThis study is the first report on the design, synthesis and photophysical properties of three new macrocyclic receptors based receptors containing two amide bridges. Their binding properties towards trivalent lanthanide ions such as La3+, Gd3+, Tb3+, Dy3+, Er3+ and Yb3+ were investigated by using spectroscopic techniques. With respect to emission intensity changes upon trivalent lanthanide ion complexation, macrocyclic receptors based lactam ionophores showed higher selectivity towards Yb3+ and/or Er3+ ion over other ions. Presence of proximal two amide groups in macrocyclic lactam receptors having different cavity size were observed to play an important role in exhibiting its lanthanide ion binding.Öğe Synthesis of calixamide nanofibers by electrospinning and toxic anion binding to the fiber structures(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Bayrakci, Mevlut; Ozcan, Fatih; Ertul, SerefThis study reports the synthesis of three novel polyacrylonitrile (PAN) nanofibers based calixamide containing pyridine groups by electrospinning. The structures of the newly prepared nanofibers were clarified using spectroscopic techniques. Analysis indicated that preparation of nanofibers based calixamide was successfully achieved. The presence of calixarene molecules in the nanofiber backbones was confirmed by Fourier transform infrared (FTIR-ATR), scanning electron microscope (SEM), and thermogravimetric analyses (TGA and DSC). The toxic anion binding studies exhibited that the nanofiber-based calixamide could be efficiently used for the binding of chromate anions as a model toxic oxoanion. Nanofiber based calixamide may be a good candidate as a filter material for water purification and waste treatment owing to their very large surface area as well as the inclusion complexation capability of all surfaces associated with the calixarene skeleton. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Synthesis of tetra-substituted calix[4]arene ionophores and their recognition studies toward toxic arsenate anions(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Bayrakci, Mevlut; Yigiter, SengulThe article displays the synthesis of a family of novel tetra-substituted calix[4]arene ionophores bearing furyl, phenyl, and pyridyl units in the cone conformation. In the synthesis, the lower rims of calix[4]arene scaffold were modified in order to establish the influence of the molecular structure of calixarene on recognition of toxic anions as arsenate by liquid-liquid extraction process. In addition, the effects of solvent, solution conditions (mainly pH), and counter ions (Cl-, NO3-, and SO42-) on the extraction abilities of the ionophores were studied. From the liquid-liquid phase extraction studies, it was observed that the structures of the tetra-substituted calix[4]arenes influenced the extraction percentage of selected toxic anion. Also, thermodynamic parameters, such as the free energy (Delta G degrees) and enthalpy (Delta H degrees) indicated an exothermic nature of extraction and a spontaneous and favorable process. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Synthesis, Characterization, and Spectroscopic Properties of a Symmetrical Schiff Base Ligand and its Bimetallic Complexes(TAYLOR & FRANCIS INC, 2011) Bayrakci, Mevlut; Ertul, Seref; Bas, Salih Zeki; Demir, IbrahimThis article presents the synthesis of new Schiff base ligand and preparation of its transition metal complexes with copper (II), nickel (II), zinc (II), and cobalt (II). Furthermore, absorption and fluorescence properties of ligand and its metal complexes are investigated. The effect of the solvents, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, methanol, 1,4-dioxane on fluorescence properties of metal complexes, are performed and obtained results are summarized. All of the structures were characterized by using spectroscopic techniques.
