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Now showing items 1 - 10 of 10

  • Theoretical EPR Study of 6-Mercaptopurine

    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.
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  • EPR study of gamma-irradiated 2-Bromo-4 '-methoxyacetophenone single crystals

    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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  • Magnetic properties of single crystal alpha-benzoin oxime: An EPR study

    Sayin, Ulku   Dereli, Omer   Turkkan, Ercan   Ozmen, Ayhan  

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of alpha-benzoinoxime (ABO) have been examined between 120 and 440 K. Considering the dependence on temperature and the orientation of the spectra of single crystals in the magnetic field, we identified two different radicals formed in irradiated ABO single crystals. To theoretically determine the types of radicals, the most stable structure of ABO was obtained by molecular mechanic and B3LYP/6-31G(d,p) calculations. Four possible radicals were modeled and EPR parameters were calculated for the modeled radicals using the B3LYP method and the TZVP basis set. Calculated values of two modeled radicals were in strong agreement with experimental EPR parameters determined from the spectra. Additional simulated spectra of the modeled radicals, where calculated hyperfine coupling constants were used as starting points for simulations, were well matched with experimental spectra. (C) 2011 Elsevier Ltd. All rights reserved.
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  • Effects of gamma irradiation on the single crystal ergosterol: An EPR study

    Sayin, Ulku   Dereli, Omer   Turkkan, Ercan  

    Single crystals of ergosterol were investigated by Electron Paramagnetic Resonance (EPR) technique, with gamma irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 380 K, and the spectra were found to be slightly dependent on temperature. Because of the importance of ergosterol it is important to determine the irradiation effects on this molecule. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal ergosterol, we found that two paramagnetic species which were labeled as radical A. (center dot)CH2(alpha)H(beta), and radical B-1 (CH alpha H beta H gamma H sigma)-C-center dot, were produced in the host crystal. The EPR parameters; spectroscopic splitting factor, g, and hyperfine coupling constant, a, were determined for each radical. (C) 2011 Elsevier B.V. All rights reserved.
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  • (2-Hydroxyethyl)triphenylphosphonium chloride

    Ceylan, Umit   Tanak, Hasan   Turkkan, Ercan   Dereli, Omer   Buyukgungor, Orhan  

    In the crystal structure of the title compound, C(20)H(20)OP(+)center dot Cl(-), the cations and anions are linked by intermolecular CH center dot center dot center dot Cl and O-H center dot center dot center dot Cl hydrogen bonds into chains running parallel to the b axis. In the cation, the hydroxyethyl group is disordered over two orientations with site-occupancy factors of 0.554 (4) and 0.446 (4).
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  • Electron Paramagnetic Resonance Study of Gabapentin and Pregabalin Molecules with Density Functional Theory

    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 investigation of gamma irradiated single crystal guaifenesin:A combined experimental and computational study

    Tasdemir, Halil Ugur   Sayin, Ulku   Turkkan, Ercan   Ozmen, Ayhan  

    Gamma irradiated single crystal of Guaifenesin (Glyceryl Guaiacolate), an important expectorant drug, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy between 123 and 333 K temperature at different orientations in the magnetic field. Considering the chemical structure and the experimental spectra of the gamma irradiated single crystal of guaifenesin sample, we assumed that alkoxy or alkyl-type paramagnetic species may be produced by irradiation. Depending on this assumption, eight possible alkoxy and alkyl-type radicals were modeled and EPR parameters of these modeled radicals were calculated using the B3LYP/6-311+ +G(d,p)-level of density functional theory (DFT). Theoretically calculated values of alkyl-type modeled radical(R3) are in good agreement with experimentally determined EPR parameters of single crystal. Furthermore, simulation spectra which are obtained by using the thepretical initial values are well matched with the experimental spectra. It was determined that a stable C alpha H2 alpha C beta H beta C gamma H2 gamma (R3) alkyl radical was produced in the host crystal as a result of gamma irradiation. (C) 2015 Elsevier Ltd. All rights reserved.
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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

    Turkkan, Ercan   Sayin, Ulku   Erbilen, Nesibe   Pehlivanoglu, Suray   Erdogan, Gokce   Tasdemir, Halil Ugur   Saf, Ahmet Ozgur   Guler, Leyla   Akgemci, Emine Guler  

    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

    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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  • Spectrophotometric, voltammetric and cytotoxicity studies of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its N(4)-substituted derivatives: a combined experimental-computational study.

    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 B3LYP/6-311++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 MTT 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. Copyright =C2=A9 2014 Elsevier B.V. All rights reserved.
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