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Now showing items 1 - 8 of 8

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

    Ulku Sayin   ?mer Dereli   Ercan Türkkan   Ayhan Ozmen  

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of alpha-benzoinoxime (ABO) have been examined between 120 and 440K. 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. [All rights reserved Elsevier].
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  • Effects of gamma irradiation on the single crystal ergosterol: An EPR study

    Ulku Sayin   ?mer Dereli   Ercan Türkkan  

    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 380K, 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, CH 2alphaH beta, and radical B, CH alphaH betaH gammaH sigma, were produced in the host crystal. The EPR parameters; spectroscopic splitting factor, g, and hyperfine coupling constant, a, were determined for each radical. [All rights reserved Elsevier].
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  • CW-EPR study of 2,2,4,4-tetramethyl-3-pentanone oxime single crystals

    Ulku Sayin   Huseyin Yuksel   Ayhan Ozmen   Mehmet Birey  

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of 2,2,4,4-tetramethyl-3-pentanone oxime (TPO) have been examined between temperatures of 125 and 450 K. The spectra were found to be both dependent on temperature and orientation of single crystals with magnetic field. We attributed radiation damage centers to iminoxy radicals (). There are two similar group of splitting in the spectra because of conformational isomers (R1, R2) of iminoxy radicals produced by gamma irradiation of TPO. Determined g-factor and hyperfine coupling constants for R1 and R2 conformers were found anisotropic with the average values (giso)R1=2.01057, (giso)R2=2.009337, [(aN)iso]R1=28.09 G, [(aN)iso]R2=36.34 G, [(aH)iso]R2=9.15 G, respectively.
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  • ESR analysis of natural and gamma irradiated coriander (

    M. Özgür Sezer   Necati Kaplan   Ulku Sayin  

    Electron spin resonance (ESR) is a powerful technique to detect radicals trapped in cellulosic food products and has been suggested as a useful method for identification of irradiated herbal foodstuffs. Coriander spice which has important medicinal properties was investigated using ESR spectroscopy. Radicals in natural and irradiated coriander samples were determined at room temperature. ESR spectra of natural sample were characterized by a single central signal with value and gamma irradiation produced satellite peaks attributed to cellulose-like radical which is used as a marker for detection of irradiated cellulosic plant products. The spectroscopic splitting values of radicals were determined. Dose dependency and stability of this center were analyzed by dose response and kinetic measurements. The reported results about activation energy, thermal life time and dose response relationship of the cellulose-like radical accurately prove that ESR can be used for identification of irradiated coriander spice seeds.
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  • EPR analysis of gamma irradiated single crystal cimetidine

    Ulku Sayin  

    The magnetic properties of gamma irradiated single crystal cimetidine were investigated between temperatures of 123 K and 418 K and between microwave power of 0.01 mW and 150 mW by electron paramagnetic resonance. Magnetic field orientation in each of the three perpendicular axes, microwave power, and temperature dependence of the EPR spectra has led to more than one radical being produced by gamma irradiation in the host crystal. The distinctive radical was attributed to being a ring type radical; however, the other radicals could not be identified because of the superimposition. The EPR parameters of the ring type radical were determined to be: a(Hα)av = 2.42 mT, a(Nα)av = 0.62 mT, a(Hβ)av = 1.08 mT, a(Hγ)av = 0.2 mT, a(Nβ)av = 0.3 mT, and (g)av = 2.0030, respectively.
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  • EPR analysis of gamma irradiated single crystal cimetidine

    Ulku Sayin  

    The magnetic properties of gamma irradiated single crystal cimetidine were investigated between temperatures of 123 K and 418 K and between microwave power of 0.01 mW and 150 mW by electron paramagnetic resonance. Magnetic field orientation in each of the three perpendicular axes, microwave power, and temperature dependence of the EPR spectra has led to more than one radical being produced by gamma irradiation in the host crystal. The distinctive radical was attributed to being a ring type radical; however, the other radicals could not be identified because of the superimposition. The EPR parameters of the ring type radical were determined to be: a(Hα)av = 2.42 mT, a(Nα)av = 0.62 mT, a(Hβ)av = 1.08 mT, a(Hγ)av = 0.2 mT, a(Nβ)av = 0.3 mT, and (g)av = 2.0030, respectively.
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  • Magnetic properties of gamma irradiated single crystals of cholesteryl chloride: An EPR study

    Ulku Sayin   Huseyin Yuksel   Mehmet Birey  

    The cholesteryl chloride compound has been irradiated with 60Co-gamma ray at room temperature. The radical produced by gamma irradiation has been investigated in the range of temperatures 123-450K for different orientations of the crystal in a magnetic field by electron paramagnetic resonance (EPR). Radiation damage center was attributed to radical CdotH alphaCH 2betaCH 2gamma. The g factor and hyperfine coupling constants have slight dependency on temperature and evident dependency on the orientation of the magnetic field. Determined g factor and hyperfine coupling constants for the radical CdotH alphaCH 2betaCH 2gamma were found to be anisotropic with the average values g av=2.003222,(a CHalpha) av=16.82G and (a CH2beta) av=23.94G measured in all axes and (a CH2gamma) av=8G, which was measured only in one axis. [All rights reserved Elsevier].
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  • CW-EPR study of 2,2,4,4-tetramethyl-3-pentanone oxime single crystals

    Ulku Sayin   Huseyin Yuksel   Ayhan Ozmen   Mehmet Birey  

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of 2,2,4,4-tetramethyl-3-pentanone oxime (TPO) have been examined between temperatures of 125 and 450K. The spectra were found to be both dependent on temperature and orientation of single crystals with magnetic field. We attributed radiation damage centers to iminoxy radicals (RC=NO). There are two similar group of splitting in the spectra because of conformational isomers (R1, R2) of iminoxy radicals produced by gamma irradiation of TPO. Determined g-factor and hyperfine coupling constants for R1 and R2 conformers were found anisotropic with the average values (g iso) R1=2.01057, (g iso)R2=2.009337, [(a N)iso] R1=28.09G, [(a N)iso] R2=36.34G, [(a H)iso] R2=9.15G, respectively. [All rights reserved Elsevier].
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