Yazar "Turkkan, Ercan" seçeneğine göre listele

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    Anticancer, antimicrobial, spectral, voltammetric and DFT studies with Cu(II) complexes of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its N(4)-substituted derivatives
    (Elsevier Science Sa, 2017) Turkkan, Ercan; Sayin, Ulku; Erbilen, Nesibe; Pehlivanoglu, Suray; Erdogan, Gokce; Tasdemir, Halil Ugur; Saf, Ahmet Ozgur
    New copper complexes of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its N(4)-substituted derivatives were synthesized and characterized by theoretical DFT studies and experimental UV-Vis, FT-IR, EPR spectral analysis, cyclic voltammetry, magnetic susceptibility and conductivity measurements. The DFT calculation results have been used to predict and interpret the experimental results. The geometric parameter G within the range of 7.61-7.86 for all complexes confirms the mononuclear nature of the complexes. The EPR, UV-Vis, DFT studies and obtained bonding parameters show that all the complexes have square planar geometry and their M-L bonds have strong ionic and some in-plane a-bond character. In addition, the experimental and DFT studies showed that HOMO and LUMO energy levels of the complexes may present good electron transporting properties. Also, the investigated Cu(II) complexes were tested for biological activity, proving both in vitro antibacterial and anticancer activity. The complexes exhibited antibacterial activity against Gram positive bacteria S. aureus while exhibiting no activities against gram negative bacteria E. toll and S. gallinarum. The f parameters obtained experimentally by EPR support the antimicrobial activity properties results of the complexes. The evaluations of potential anticancer activity of these complexes were carried out against highly metastatic MDA-MB-231 breast adenocarcinoma cell line by MTT assay. Our results suggest that all tested copper complexes have high cytotoxic effects with the range of 1.76-3.53 mu M IC50 values in vitro. These copper complexes could be considered as potential anticancer agents to counteract drug resistance of metastatic cancer cells. (C) 2016 Elsevier B.V. All rights reserved.
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    An electron paramagnetic resonance and density-functional theory study on the methyl isotropic hyperfine coupling constants in gamma-irradiated 2,6-di-tert-butyl-4-methylphenol
    (Taylor & Francis Ltd, 2013) Turkkan, Ercan; Dereli, Omer; Sayin, Ulku; Tapramaz, Recep
    Single crystal of gammairradiated 2,6-di-tert-butyl-4-methylphenol (BHT) was investigated using an electron paramagnetic resonance (EPR) technique at different orientations in the magnetic field at room temperatures. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal of BHT, we assumed that one phenoxyltype paramagnetic species was produced having an unpaired electron localized at the methyl fragment side of the phenyl ring. Depending on this assumption, one possible radical was modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radical using the B3LYP/TZVP and B3LYP/EPR-III level. The averaged value of isotropic hydrogen hyperfine coupling constants of rotating methyl functional group of phenoxyl radical is calculated for the first time. Theoretically calculated values of the modeled radical are in reasonably good agreement with the experimental data determined from the spectra (differences in averaged coupling constant values smaller than 5%, and differences in isotropic g values fall into 1ppt).
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    Electron Paramagnetic Resonance Study of Gabapentin and Pregabalin Molecules with Density Functional Theory
    (Amer Inst Physics, 2018) Tasdemir, Halil Ugur; Turkkan, Ercan
    The conformational analysis was performed using the molecular mechanics method to determine the molecular structure of the Gabapentin and Pregabalin molecules. The most stable structures of Gabapentin and Pregabalin molecules were determined using the combination of the DFT/B3LYP/6-31+ G(d, p) method basis set combination. Four possible radicals were modeled with DFT/B3LYP/6-31+ G(d, p) method and basis set combination for Gabapentin and Pregabalin molecules. Electron Paramagnetic Resonance parameters of Gabapentin and Pregabalin molecules were determined with the same method and basis set combination.
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    EPR study of gamma-irradiated 2-Bromo-4?-methoxyacetophenone single crystals
    (Taylor & Francis Ltd, 2016) Tasdemir, Halil Ugur; Turkkan, Ercan; Sayin, Ulku; Ozmen, Ayhan
    The gamma-irradiated single crystals of 2-Bromo-4'-methoxyacetophenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA.
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    New copper(II) complex based-thiosemicarbazone and phenanthroline: DNA/BSA binding, antiproliferative activity, DFT and docking studies
    (Elsevier, 2023) Findik, Mukerrem; Turkkan, Ercan; Pehlivanoglu, Suray; Sayin, Ulku; Ceylan, Umit; Akgemci, Emine Guler
    A new copper(II) complex {Cu(HPP)}, bromo(1,10-phenanthroline)(triphenylphosphine)copper(I) with 2-hydroxy-5-methoxyacetophenone thiosemicarbazone (HMAT) was synthesized and characterized by experimental FT-IR, Raman, UV-vis, TGA and EPR spectral analysis. The Cu(HPP) was theoretically modeled using the B3LYP/VTZ method/basis set and the values of the spectroscopic parameters were calculated by the DFT method. The coordination geometry around the Cu(II) in the compound was predicted as an elongated octahedral. Spectroscopic investigations showed the intercalative binding mechanism of the Cu(HPP) with calf-thymus deoxyribonucleic acid (ct-DNA). Spectroscopic techniques were also used to evaluate the interaction of the Cu (HPP) with bovine serum albumin (BSA), which revealed that the Cu(HPP) could bind to BSA significantly. In addition, the molecular docking between the Cu(HPP) and BSA was investigated to support the bonding mechanism. Further, we studied the anticancer activity of the Cu(HPP) in drug resistant breast cancer cell line (MDA-MB-231), with a focus on the proliferative characteristics. Our findings emphasize that this newly synthetized complex has a significant cytotoxic effect on the cells and can be utilized as a candidate chemotherapeutic agent to effectively target breast cancer.
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    Spectrophotometric, voltammetric and cytotoxicity studies of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its N(4)-substituted derivatives: A combined experimental-computational study
    (Pergamon-Elsevier Science Ltd, 2015) Akgemci, Emine Guler; Saf, Ahmet Ozgur; Tasdemir, Halil Ugur; Turkkan, Ercan; Bingol, Haluk; Turan, Suna Ozbas; Akkiprik, Mustafa
    In this study, 2-hydroxy-5-methoxyacetophenone thiosemicarbazone (HMAT) and its novel N(4) substituted derivatives were synthesized and characterized by different techniques. The optical band gap of the compounds and the energy of HOMO were experimentally examined by UV-vis spectra and cyclic voltammetry measurements, respectively. Furthermore, the conformational spaces of the compounds were scanned with molecular mechanics method. The geometry optimization, HOMO and LUMO energies, the energy gap of the HOMO LUMO, dipole moment of the compounds were theoretically calculated by the density functional theory B3LY10/6-3114-+G(d,p) level. The minimal electronic excitation energy and maximum wavelength calculations of the compounds were also performed by TD-DFT//B3LYP/6-311++G(d,p) level of theory. Theoretically calculated values were compared with the related experimental values. The combined results exhibit that all compounds have good electron-donor properties which affect anti-proliferative activity. The cytotoxic effects of the compounds were also evaluated against HeLa (cervical carcinoma), MCF-7 (breast carcinoma) and PC-3 (prostatic carcinoma) cell lines using the standard MIT assay. All tested compounds showed antiproliferative effect having IC50 values in different range. In comparison with that of HMAT, it was obtained that while ethyl group on 4(N)-substituted position decreased in potent anti-proliferative effect, the phenyl group on the position increased in anti-proliferative effect for the tested cancer cell line. Considering the molecular energy parameters, the cytotoxicity activities of the compounds were discussed. (C) 2014 Elsevier B.V. All rights reserved.
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    Synthesis of anti-4-phenoxyphenylaminoglyoxime and its some transition metal complexes: Spectral, DFT, electrochemical and anticancer activity studies
    (Elsevier, 2020) Findik, Mukerrem; Ucar, Asuman; Turkkan, Ercan; Pehlivanoglu, Suray; Ozcan, Emine
    anti-4-phenoxyphenylaminoglyoxime (LH2) was synthesized starting from 4-aminodiphenylether and anti-chloroglyoxime in absolute ethanol. Then, mononuclear complexes [Ni(II) and Cu(II)] of LH2 were synthesized with the metal:ligand ratio of 1:2. The LH2 and its complexes [Ni(LH)(2) and Cu(LH)(2)] were characterized by elemental analysis, FT-IR, Raman, UV-vis, thermogravimetric analysis (TGA), H-1 NMR, C-13 NMR, heteronuclear multiple bond correlation (HMBC) spectroscopy and theoretical DFT studies. Also, redox properties of the ligand and its complexes were investigated by cyclic voltammetry in DMSO solution at room temperature. Conformational space was scanned with molecular mechanic simulations and then the possible stable conformers of LH2 ligand were determined by B3LYP/6-311++G (d,p) level calculations. The Ni(LH)(2) and Cu(LH)(2) metal complexes were modeled theoretically using B3LYP/LanL2DZ level. The theoretical vibrational frequencies were calculated by using optimization calculation levels. The NMR parameters of LH2 ligand, Cu(LH)(2) and Ni(LH)(2) metal complexes were calculated at mPW1PW91/6-311 + G (2d,p) level. Theoretically calculated values were compared with the related experimental values. The DFT calculation results have been used to predict and interpret the molecular structures of LH2 ligand and its complexes. The geometry around nickel in Ni(LH)(2) and around cupper in Cu(LH)(2) complex are almost square planar. In addition, we evaluated the efficacy of LH2 ligand and its Ni(LH)(2) and Cu(LH)(2) complexes in the breast adenocarcinoma cell line (MCF7). Our data showed that the metal compounds affect positively the cytotoxic activity of the ligand (LH2). The metal complexes, especially Ni(LH)(2) complex, exhibited noteworthy biological activity against the viability of MCF7 cells. (C) 2020 Elsevier B.V. All rights reserved.
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    Theoretical EPR Study of 6-Mercaptopurine
    (Amer Inst Physics, 2017) Tasdemir, Halil Ugur; Turkkan, Ercan
    6-Mercaptopurine is important antineoplastics agent and it is used for immuno suppressive and anti inflammatory. Experimental EPR parameters of 6-Mercaptopurine molecules powder were studied in the literature. The aim of this study EPR parameters of 6 Mercaptopurine molecules were calculated with theoretical calculations and define the possible radicals of 6 Mercaptopurine molecules. Firstly the X-ray structure of 6-Mercaptopurine molecules were found in the literature (1). EPR parameters and possible radicals of 6 Mercaptopurine molecules were calculated from this X-ray structure. Possible radicals of gamma-irradiated 6-Mercaptopurine molecules were constituted. EPR parameters of possible radicals were calculated with 1331XP/6-31.1++ G (d,p) basis set in MT methods for 6 Mercaptopurine molecules.