DFT‐EPR study of radiation‐induced radicals in α‐D‐glucose

Abstract

ABSTRACT:The structures of two radiation-induced radicals in solid-state ␣-dglucose have been identified by means of single-molecule density function theory (DFT) calculations. Using the original crystalline structure as input, several radical models were created and their geometries optimized. Subsequently, electron paramagnetic resonance (EPR) parameters were calculated. During these calculations, the global orientation of the radical structure was kept fixed with respect to the crystal axes reference frame. This was essential to allow for an easy analysis of the hyperfine tensor principal directions, besides the isotropic and anisotropic coupling constants. By comparing these calculated EPR parameters with their experimentally determined counterparts, a plausible identification of two carbon-centered glucose radicals was possible.

Selenium-induced protection of photosynthesis activity in rape (Brassica napus) seedlings subjected to cadmium stress. Fluorescence and EPR measurements

“…EPR experimental data and DFT calculations performed for D-fructose in pyranose form showed that the HFS constants A for b hydrogen equal to 1.4 and 0.3 mT [68], very similar to those observed in this paper (1.6 and 0.2 mT). On the other hand, it was found by several authors from experiment and theoretical calculations that abstraction of hydrogen or a hydroxyl group from a carbon atom, C(3), C(5), C(6) of a-glucose or b-fructose led to radicals with g-factors of about 2.005, lower than those found in this article (Gräslund and Löfroth 1975;Bernhard 1979, 1982;Pauwels et al 2002Pauwels et al , 2004Pauwels et al , 2006. The higher values of g-factor are probably connected with the localization of an unpaired electron at a carbon atom situated in the vicinity of the strongly electronegative oxygen atom.…”

“…As the glucose molecule is a structural unit of many saccharides, it can be considered that the formation of the radical species occur by abstraction of hydrogen or OH group from a C(1) atom, especially one surrounded by the greatest number of oxygen atoms. This process can proceed upon supplying of various kinds of energy (mechanical, thermal or radiative; Dyrek et al 2007;Flores et al 2000;Kuzuya et al 1999;Bernhard 1979, 1982;Pauwels et al 2004;Vanhaelewyn et al 2000;Yamauchi et al 1999;Sasai et al 2004). It should be emphasized that radicals generated in biological materials, such as starch or cane sugar, exhibited higher values of the g-factor than those produced in chemical compounds, which confirms the localization of an unpaired electron at different carbon atoms in both systems.…”

Identification of primary free radicals in trehalose dihydrate single crystals X-irradiated at 10 K

“…Other studies, like ours, aim at determining the identity and understanding the structural properties of the radicals involved in the various stages of radiation action. For this purpose, model systems such as glucose 3,4 , sucrose [5][6][7][8] , fructose [9][10][11][12][13] and rhamnose [14][15][16][17] single crystals have previously been experimentally investigated using Electron Paramagnetic Resonance (EPR), Electron…”

Radiation Chemistry of Solid-State Carbohydrates Using EMR

“…Such comparisons later on proved insufficient for credible radical model assignments. In a better approach, the orientation of the molecule in the crystal was properly taken into account, which allowed more complete comparisons between experimental and calculated HF tensors and already proved quite successful in radical model identification [10,90].…”