Yazar "Tasdemir, Halil Ugur" 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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    Effects of intramolecular hydrogen bonding on nuclear magnetic resonance, electron paramagnetic resonance and molecular docking studies: Mexiletine molecule
    (Springer, 2024) Tasdemir, Halil Ugur
    ContextIn this study, the molecular structure of the mexiletine molecule was investigated. Since the Mexiletine molecule is a drug active ingredient, its molecular structure and spectroscopic properties are important. The effects of intramolecular hydrogen bonding on Nuclear Magnetic Resonance Parameters (NMR), Electron Paramagnetic Resonance (EPR) parameters and molecular docking studies were examined in the mexiletine molecule. The effects of intramolecular hydrogen bonding on EPR parameters and molecular docking studies are the most important steps for this study.MethodConformational space scanning required for molecular structure calculations was carried out with the Molecular Mechanic Force Field method. DFT method with 6-311 + + G(d,p) basis set level was used to obtain the most stable structure among the conformations. NMR parameters (1H and 13C chemical shift values) were also performed using the same basis set as the DFT method. The radicals created to calculate the Electron Paramagnetic Resonance parameters were modeled using the DFT/B3LYP/6-311 + + G(d,p) method basis set level. Molecular Docking studies were carried out with the Autodock vina program.
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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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    Paramagnetic characterization and dosimetric properties of Airfix drug and its ingredients (Montelukast sodium, Sorbitol): An EPR and DFT study
    (Pergamon-Elsevier Science Ltd, 2022) Ece, Emel; Tasdemir, Halil Ugur; Biyik, Recep; Ozmen, Ayhan; Sayin, Ulku
    In this study, radiation effect on an asthma drug Airfix and its ingredients (Montelukast sodium, Sorbitol) were analyzed by using EPR spectroscopy in the dose range of 10 Gy-30 kGy. The dependence of radiation-induced radicals on irradiation dose, temperature and time was investigated in detail. It has been determined that the radical observed predominantly in the Airfix structure originates from Sorbitol, and the characteristic features of this alkyl-type radical have been clearly defined using both experimental EPR and theoretical DFT methods. Dosimetric properties were investigated for all samples and it was suggested that Airfix drug and Sorbitol could be used as an EPR dosimeter through this radical agent which was determined to be very stable and sensitive to radiation. Moreover, it has been emphasized that other drugs containing Sorbitol excipient can also be used for dosimetric purposes in the dose range studied and even irradiation doses can be detected in case of radiation sterilization.
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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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    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.