Powder ENDOR study of the fourth stable radical species
in X-irradiated sucrose
J. Kusakovskij, F. Callens, H. Vrielinck
EMR research group, Department of Solid State Sciences, Ghent University
Electron Paramagnetic Resonance (EPR) studies of radiation-induced radicals in sucrose
present a twofold interest. From a practical point of view, the intensity of the EPR spectrum is
proportional to the absorbed dose in a considerable range, making it an attractive
solid-state/EPR dosimetric system [1]. It is very likely that dose assessment protocols could
be further improved if the spectrum was fully understood. On the other hand, knowledge of
occurring radical structures and reaction pathways may provide more insight into the
radiation chemistry of other carbohydrates and sugar-containing macrobiomolecules, e.g.
DNA or RNA. Even though this is foremost important from a fundamental point of view, in the
long run this knowledge can also lead to practical advances, e.g. improvements in radiation
therapy.
It is known that at least four radical species contribute to the stable EPR spectrum of
irradiated sucrose. Three of those are well-known [2]; the fourth has been thoroughly
characterized, but not yet identified [3]. In this contribution the experimental data on the
fourth stable radical species is summarized and its chemical structure is discussed. Special
attention is devoted to the powder Electron-Nuclear Double Resonance (ENDOR) spectrum
of its largest hyperfine interaction. Its isolation from other spectral components made it
possible to extract the radical’s EPR absorption spectrum from a multicomponent powder
pattern, which (to our knowledge) has not been done before with cw-ENDOR. Comparison to
single crystal data showed that this approach can be useful in studies of disordered systems,
where single crystals are not available.
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Magnetic Field (mT)
Figure 1: Simulated Q-band (34 GHz) absorption spectrum (black line) and integrated
ENDOR field sweep (grey line) of the fourth stable radical species in X-irradiated sucrose.
1. Karakirova, Y. and Yordanov, N. D., Radiat. Phys. and Chem., 2015, 110, 42-50.
2. Vrielinck, H.; de Cooman, H.; Callens, F.; Sagstuen, E. In Applications of EPR in Radiation
Research; Lund, A., Shiotani, M., Eds.; Springer International Publishing: New York, 2014;
189−254.
3. J. Kusakovskij, I. Caretti, S. Van Doorslaer, F. Callens, H. Vrielinck, poster at the IXth EF EPR
conference, Marseille, 2014