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    An EPR study on single crystals of dimethyl-1,3-cyclohexanedione by gamma-rays
    (TAYLOR & FRANCIS LTD, 2012) Aras, Erdal; Usta, Ayhan; Erturk, Serkan; Asik, Biray
    Single crystals of dimethyl-1,3-cyclohexanedione (C8H12O2) were produced by slow evaporation of the concentrated ethyl acetate solutions. These single crystals were exposed to Co-60 gamma-rays with a dose speed of 0.950 kGy/h at room temperature for 24, 48, and 72 h. The free radicals of the samples irradiated for 48 and 72 h were detected using electron paramagnetic resonance (EPR)-X-band spectrometer. EPR measurements were performed between 120 and 300 K. The sample irradiated for 48 h by gamma-rays was rotated in steps of 10 degrees at 298 K. The spectrum parameters were found to be dependent on the temperature. Two radicals were determined in the molecular structure irradiated. These radiation damage centers were called R1 and R2. The average values of g and the hyperfine coupling constants were calculated as follows: a(Ha) = 6.84 G, a(Hb) = 3.60 G, g = 2.0040 for R1, a(H) = 28 G, g = 2.0062 for R2.
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    Screening of free radical formation in crystals of guanosine by ESR study
    (ELSEVIER SCIENCE BV, 2011) Usta, Ayhan; Vural, Hasibe Cingilli; Asik, Biray; Usta, Keziban
    In this study, to obtain guanosine polycrystalline, novel crystallization method was performed on powder guanosine material. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial acetic acid, nitric oxide, perchloric acid, glutamic acid, and pH of buffer. Behaviors of the guanosine polycrystal samples exposed to high-energy values were investigated using ESR method. The polycrystal samples were exposed to gamma-rays for 48 and 72 h. ESR signals were not recorded from the non-irradiated sample and the sample irradiated for 48 h, but the polycrystalline sample irradiated for 72 h exhibited complex ESR spectra. ESR measurements were taken on the irradiated sample in temperature range from 300 to 450 K. On the basis of all these measurements dependence temperature, it can be said that the shape of the spectrum was to be dependent on temperature slightly. Hence, we assume that the radical structure occurred was resistance to high temperature. Two radicals were determined in the structure irradiated and these were called radical I and radical II. The g, hyperfine constants, and spin density were found to be rho = 0.96, a(NNH)(N) = 2.7 mT, a(NNH)(N) = 1.155 mT, a(N) = 0.35 ml and g(1) = 2.0093 for the radical 1; a(N) = 4.7 ml and g(2) = 2.0094 for the radical II. (C) 2011 Elsevier B.V. All rights reserved.