Electron magnetic resonance study of stable radicals in irradiated D-fructose single crystals

Vanhaelewyn, Gauthier; Lahorte, Philippe; Proft, Frank De; Mondelaers, W.; Geerlings, Pau̧l; Callens, Freddy

doi:10.1039/b008248l

Cited by 26 publications

(36 citation statements)

References 20 publications

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“… direction is the difference (in degrees) between the anisotropic principal axes calculated with both basis sets not present and also possible vibrational averaging effects related to pyramidal inversion at the radical centre are not taken into account. We therefore conclude that both radical species F1 and F2, found in the experiments of Vanhaelewyn et al 5 can be identified as having the radical structure F A , possibly with a O6-C6-C5-C4 torsional angle at about 234°.…”

Section: Model Structure F Amentioning

confidence: 89%

“…Vanhaelewyn et al performed a combined experimental and theoretical study on the EPR properties of irradiated D-fructose crystals. 5 In their contribution, the identification of two dominant radicals, which will be indicated as F1 and F2, is reported. 5 Both of these radicals are characterized by threeˇ-type hyperfine couplings, as detected by the EI-EPR experiment, given in Table 3.…”

Section: Tentative Structures For Radicals Derived From Crystalline Bmentioning

confidence: 99%

“…5 In their contribution, the identification of two dominant radicals, which will be indicated as F1 and F2, is reported. 5 Both of these radicals are characterized by threeˇ-type hyperfine couplings, as detected by the EI-EPR experiment, given in Table 3. This suggests that the unpaired electron of both the fructose radicals interacts with three protons yielding six hydrogen hyperfine tensors.…”

Section: Tentative Structures For Radicals Derived From Crystalline Bmentioning

confidence: 99%

“…glucose, fructose, sucrose) by Vanhaelewyn et al 5 The accurate calculation of hfccs in several candidate fructose radicals provides the experimentalist with valuable information on their possible structure but in turn requires a validated computational approach owing to its highly exploratory nature, as relatively few EPR studies are available. In addition to the computation of the isotropic and anisotropic components of the hyperfine interaction tensor, the eigenvectors of the proton hyperfine tensors also had to be investigated in order to elucidate the structure of the radicals involved.…”

Section: Prologuementioning

confidence: 99%

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Density functional theory as a tool for the structure determination of radiation-induced bioradicals

et al. 2004

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The use of density functional methods for the elucidation of the structure of radiation-induced bio-radicals by comparison of computed and experimental EPR properties is discussed. Three case studies, radiation induced radicals of the amino acid alanine, steroid hormones and b-D-fructose, with increasing degree of uncertainty about the proposed radical structures, are investigated. Next to the analysis of the isotropic and anisotropic components of the hyperfine tensor, also the direction cosines of the principal axes of this tensor were investigated in greater detail in the case of the b-D-fructose radicals. Since all radicals considered in this contribution are formed in a solid matrix, also the question as to how to incorporate the effect of the molecular environment is addressed. It is concluded that the methodology outlined represents a powerful tool to aid experimentalists in the assignment of the contributions of various radicals contributing to the observed EPR spectra. Copyright  2004 John Wiley & Sons, Ltd. KEYWORDS: EPR; density functional theory; bioradicals; radiation; structure; alanine; fructose INTRODUCTION PrologueIn this contribution, which is of a review type, electron paramagnetic resonance (EPR) properties are discussed as a source of information on the structure of radiation-induced bioradicals in the solid state. More precisely, we will show, via three case studies, how the comparison of the computed and experimental EPR properties of a series of radiationinduced radicals can be used to confirm or propose the structure of these radicals.A large number of the studies on amino acids (in particular alanine) and sugars are motivated by their potential dosimetric applications. L-˛-Alanine, for example, is currently used as a reference dosimeter suitable over a wide dose range.1 In the first part, the hyperfine coupling constants for various candidate alanine radicals are discussed.2 For this system, many studies are available yielding a substantial amount of structural information and EPR spectroscopic properties of irradiated solid L-˛-alanine. As a result, this system represents and ideal test case for the purpose of exploring and validating the DFT calculation of hfccs in † Dedicated to Professor M. Barfield on the occasion of his 70th birthday. Ł Correspondence to: F. De Proft, Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Faculteit Wetenschappen, Pleinlaan 2, 1050 Brussels, Belgium. E-mail: fdeprof@vub.ac.be radiation-induced bioradicals for the purpose of structure elucidation. At the end of this section, we will briefly mention the results of a study on the EPR properties of steroid radicals, 3 where various experimental studies available agree on the identity of two different radicals whereas another two radicals form the subject of ongoing debate, to which the results of the theoretical analysis presented here can contribute significantly.In the final section, a theoretical study is discussed on the tentative structures of fructose radicals, 4 following an earlier ...

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Section: Model Structure F Amentioning

confidence: 89%

Section: Tentative Structures For Radicals Derived From Crystalline Bmentioning

confidence: 99%

Section: Tentative Structures For Radicals Derived From Crystalline Bmentioning

confidence: 99%

Section: Prologuementioning

confidence: 99%

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Density functional theory as a tool for the structure determination of radiation-induced bioradicals

et al. 2004

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“…Both as model systems for studying the effects of radiation on the DNA sugar unit and for applications in dosimetry, irradiated mono and disaccharides, such as glucose 1,2 , fructose [3][4][5] , sucrose [6][7] and rhamnose [8][9][10][11][12][13] , have been intensively studied with electron paramagnetic resonance (EPR) over the past few decades. By now it is well-established that such EPR spectra are multi-composite.…”

Section: Introductionmentioning

confidence: 99%

Determination of the g Tensors for the Dominant Stable Radicals in X-Irradiated β-d-Fructose Single Crystals

et al. 2009

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In spite of recent successful identifications of radicals produced after X-ray irradiation at 10 K and 77 K in β-D-fructose, the structure of the two stable radicals dominating the electron paramagnetic resonance (EPR) spectrum after room temperature irradiation is still unclear. Based on the agreement between proton hyperfine (HF) tensors obtained in electron nuclear double resonance (ENDOR) experiments and the results of single molecule density functional calculations, a model for these radicals, involving OH abstraction at the C2 ring position, had previously been proposed, but this assignment could not be confirmed when the radical was embedded in a crystal environment. In this paper, we therefore provide additional experimental information for these radicals. First, their g tensors are determined from angular dependent ENDOR-induced EPR experiments.The relatively large anisotropy of these tensors is indicative of delocalization of the unpaired electron onto a neighboring oxygen atom. Second, EPR spectra of fructose powders, selectively enriched in 13 C on various ring positions, are presented, demonstrating that the HF interaction with the carbon atom C3 is larger than with the C2.Combining the g tensor, proton and 13 C HF data, we conclude that the structure of the stable radicals differs strongly from that of intact molecules and that further advanced quantum chemical modeling will be required to fully identify them.

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Chemical Reactivity Within the Spin‐Polarized Framework of Density Functional Theory

Chamorro

Pérez²

2021

Chemical Reactivity in Confined Systems

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Electron magnetic resonance study of stable radicals in irradiated D-fructose single crystals

Cited by 26 publications

References 20 publications

Density functional theory as a tool for the structure determination of radiation-induced bioradicals

Density functional theory as a tool for the structure determination of radiation-induced bioradicals

Determination of the g Tensors for the Dominant Stable Radicals in X-Irradiated β-d-Fructose Single Crystals

Chemical Reactivity Within the Spin‐Polarized Framework of Density Functional Theory

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