Radiation-induced defects in sucrose single crystals, revisited: a combined electron magnetic resonance and density functional theory study.

Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium.
Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy (Impact Factor: 1.98). 06/2008; 69(5):1372-83. DOI: 10.1016/j.saa.2007.09.033
Source: PubMed

ABSTRACT The results are presented of an electron magnetic resonance analysis at 110 K of radiation-induced defects in sucrose single crystals X-irradiated at room temperature, yielding a total of nine (1)H hyperfine coupling tensors assigned to three different radical species. Comparisons are made with results previously reported in the literature. By means of electron paramagnetic resonance and electron nuclear double resonance temperature variation scans, most of the discrepancies between the present 110 K study and a previous 295 K study by Sagstuen and co-workers are shown to originate from the temperature dependence of proton relaxation times and hyperfine coupling constants. Finally, radical models previously suggested in the literature are convincingly refuted by means of quantum chemical density functional theory calculations.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Crystalline sucrose irradiated with C and Si ions is investigated with EPR and UV spectroscopy. Samples are treated at different doses of radiation in the region 20–300 Gy and linear energy transfer (LET) values of 39.6, 49 and 58 keV μm−1 for C ions and 60 keV μm−1 for Si ions. All samples exhibit identical EPR spectra due to radiation-induced stable sucrose radicals. At given constant LET the EPR signal responses are linear to the absorbed doses of Si and C ions. Water solutions of irradiated sucrose exhibit UV absorption maximum at 267 nm due to the product of radical recombination. The intensity of this band is stronger at irradiation with Si than with C ions. UV absorption is more sensitive to heavy-ion species irradiation than the EPR signals.
    Radiation Measurements. 01/2010;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Radicals generated in trehalose single crystals by X radiation at room temperature were investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and ENDOR-induced EPR measurements, together with periodic density functional theory calculations. In the first days after irradiation, three radical species (I1, I2 and I3) were detected, two of which (I1 and I2) dominate the EPR spectrum and could be identified as H-abstracted species centered at C3' (I1) and C2 (I2), the latter with additional formation of a carbonyl group at C3. Annealing the sample at 40°C for 3 days or storing it in ambient conditions for three months resulted in another, more stable EPR spectrum. Two major species could be characterized in this stage (S1 and S2), only one of which was tentatively identified as an H-abstracted, C2-centered species (S1). Our findings disagree with a previous EPR study [Gräslund and Löfroth (23)] on several accounts. This work stresses the need for caution when interpreting composite EPR spectra and thermally induced spectral changes of radiation-induced species, even in these relatively simple carbohydrates. It also provides further evidence that the pathways for radiation damage critically depend on the specific conformation of a molecule and its environment, but also that carbonyl group formation is a common process in the radiation chemistry of sugars and related compounds.
    Radiation Research 01/2013; · 2.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Solid state/EPR (SS/EPR) dosimeters of carbon ions irradiated sucrose are studied with EPR, and their water solutions – with UV spectroscopy. Doses between 20 and 200 Gy are used with linear energy transfer (LET) values for carbon ions of 63, 77, 96 and 230 keV μm−1. After irradiation all samples show typical for irradiated sucrose EPR and UV spectra. The obtained data are compared with those previously reported for nitrogen particles and gamma rays irradiated sucrose. The identical shape of both the EPR and UV spectra of irradiated with various type radiation samples suggests that generated free radicals are not influenced by the nature of radiation. The lack of difference in the line width of the separate lines or the whole EPR spectrum, obtained for gamma and heavy particles irradiation, suggests negligible spin–spin interaction among the radiation-generated free radicals in the samples. The linear dependence of the EPR response on the absorbed dose radiation is found to be higher when generated by gamma rays, than by the same absorbed dose of heavy particles. In addition, the EPR response for carbon ions is higher than that for nitrogen ions. Water solutions of irradiated sucrose exhibit UV spectrum with absorption maximum at 267 nm, attributed to the recombination products of free radicals. The UV band intensity depends on the absorbed dose radiation. The UV spectra obtained for carbon, nitrogen and gamma rays irradiated sucrose are also compared.
    Radiation Measurements. 01/2010;