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Øyen LF, Aalbergsjø SG, Knudtsen IS, Hole EO, Sagstuen E. Direct radiation effects to the amino acid side chain: EMR and periodic DFT of X-irradiated L-asparagine at 6 K. J Phys Chem B 2015; 119:491-502. [PMID: 25514178 DOI: 10.1021/jp5115866] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Radical formation in single crystals of L-asparagine monohydrate following X-irradiation at 6 K has been investigated at 6 K and at elevated temperatures using various electron magnetic resonance (EMR) techniques such as electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and ENDOR-induced EPR (EIE) spectroscopy. Molecular structures of the three free radicals stable at 6 K were assessed by detailed analysis of the experimental data and density functional theory (DFT) calculations in a periodic approach. Radical LI is assumed to result from one-electron reduction at the amide functional group in the asparagine side chain followed by protonation at the amide carbonyl oxygen by proton transfer from a neighboring molecule across a hydrogen bond. Radical LII is assigned to a one-electron reduction of the carboxyl group in the amino acid backbone, followed by proton transfer across a hydrogen bond between a carboxylic oxygen and a neighboring asparagine molecule. Radical LIII is suggested to be formed by a net CO2 abstraction from an initial one-electron oxidized amino acid backbone. For the DFT modeling of LIII at 6 K, it was chosen to include the CO2 group stably embedded in the crystalline lattice. The assignments made are discussed in relation to previous work on L-asparagine. The relevance of these results to possible charge transfer processes in protein:DNA complexes is discussed.
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Affiliation(s)
- Live F Øyen
- Department of Physics, University of Oslo , P.O. Box 1048, Blindern, N-0316 Oslo, Norway
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2
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Knudtsen IS, Aalbergsjø SG, Hole EO, Sagstuen E. Radiation effects on crystalline l-asparagine, revisited: Radical formation by EMR and periodic DFT after X-irradiation at 275K. Radiat Phys Chem Oxf Engl 1993 2015. [DOI: 10.1016/j.radphyschem.2014.07.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Adhikary A, Kumar A, Rayala R, Hindi RM, Adhikary A, Wnuk SF, Sevilla MD. One-electron oxidation of gemcitabine and analogs: mechanism of formation of C3' and C2' sugar radicals. J Am Chem Soc 2014; 136:15646-53. [PMID: 25296262 PMCID: PMC4227712 DOI: 10.1021/ja5083156] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Gemcitabine is a modified cytidine analog having two fluorine atoms at the 2'-position of the ribose ring. It has been proposed that gemcitabine inhibits RNR activity by producing a C3'• intermediate via direct H3'-atom abstraction followed by loss of HF to yield a C2'• with 3'-keto moiety. Direct detection of C3'• and C2'• during RNR inactivation by gemcitabine still remains elusive. To test the influence of 2'- substitution on radical site formation, electron spin resonance (ESR) studies are carried out on one-electron oxidized gemcitabine and other 2'-modified analogs, i.e., 2'-deoxy-2'-fluoro-2'-C-methylcytidine (MeFdC) and 2'-fluoro-2'-deoxycytidine (2'-FdC). ESR line components from two anisotropic β-2'-F-atom hyperfine couplings identify the C3'• formation in one-electron oxidized gemcitabine, but no further reaction to C2'• is found. One-electron oxidized 2'-FdC is unreactive toward C3'• or C2'• formation. In one-electron oxidized MeFdC, ESR studies show C2'• production presumably from a very unstable C3'• precursor. The experimentally observed hyperfine couplings for C2'• and C3'• match well with the theoretically predicted ones. C3'• to C2'• conversion in one-electron oxidized gemcitabine and MeFdC has theoretically been modeled by first considering the C3'• and H3O(+) formation via H3'-proton deprotonation and the subsequent C2'• formation via HF loss induced by this proximate H3O(+). Theoretical calculations show that in gemcitabine, C3'• to C2'• conversion in the presence of a proximate H3O(+) has a barrier in agreement with the experimentally observed lack of C3'• to C2'• conversion. In contrast, in MeFdC, the loss of HF from C3'• in the presence of a proximate H3O(+) is barrierless resulting in C2'• formation which agrees with the experimentally observed rapid C2'• formation.
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Affiliation(s)
- Amitava Adhikary
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
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Aalbergsjø SG, Pauwels E, De Cooman H, Hole EO, Sagstuen E. Structural specificity of alkoxy radical formation in crystalline carbohydrates. Phys Chem Chem Phys 2013; 15:9615-9. [PMID: 23673612 DOI: 10.1039/c3cp50789k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A DFT study of radiation induced alkoxy radical formation in crystalline α-l-rhamnose has been performed to better understand the processes leading to selective radical formation in carbohydrates upon exposure to ionizing radiation at low temperatures. The apparent specificity of radiation damage to carbohydrates is of great interest for understanding radiation damage processes in the ribose backbone of the DNA molecule. Alkoxy radicals are formed by deprotonation from hydroxyl groups in oxidized sugar molecules. In α-l-rhamnose only one alkoxy radical is observed experimentally even though there are four possible sites for alkoxy radical formation. In the present work, the origin of this apparently specific action of radiation damage is investigated by computationally examining all four possible deprotonation reactions from oxygen in the oxidized molecule. All calculations are performed in a periodic approach and include estimates of the energy barriers for the deprotonation reactions using the Nudged Elastic Band (NEB) method. One of the four possible radical sites is ruled out due to the lack of a suitable proton acceptor. For the other three possible sites, the reaction paths and energy profiles from primary cationic radicals to stable, neutral alkoxy radicals are compared. It is found that deprotonation from one site (corresponding to the experimentally observed radical) differs from the others in that the reaction path is less energy demanding. Hence, it is suggested that the alkoxy radical formation is not necessarily site specific, but that the observed radical is formed in much greater abundance than the others due to the different energetics of the processes and reaction products.
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De Cooman H, Keysabyl J, Kusakovskij J, Van Yperen-De Deyne A, Waroquier M, Callens F, Vrielinck H. Dominant Stable Radicals in Irradiated Sucrose: g Tensors and Contribution to the Powder Electron Paramagnetic Resonance Spectrum. J Phys Chem B 2013; 117:7169-78. [DOI: 10.1021/jp400053h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Hendrik De Cooman
- Ghent University, Department of Solid State Sciences, Electron Magnetic Resonance
Research Group, Krijgslaan 281-S1, B-9000 Ghent, Belgium
- Ghent University, Center for Molecular Modeling, Technologiepark 903, B-9052 Zwijnaarde,
Belgium
| | - Joke Keysabyl
- Ghent University, Department of Solid State Sciences, Electron Magnetic Resonance
Research Group, Krijgslaan 281-S1, B-9000 Ghent, Belgium
| | - Jevgenij Kusakovskij
- Ghent University, Department of Solid State Sciences, Electron Magnetic Resonance
Research Group, Krijgslaan 281-S1, B-9000 Ghent, Belgium
- Vilnius University, Institute of Applied Research, Sauletekio
av. 9-III, LT-10222 Vilnius,
Lithuania
| | - Andy Van Yperen-De Deyne
- Ghent University, Center for Molecular Modeling, Technologiepark 903, B-9052 Zwijnaarde,
Belgium
| | - Michel Waroquier
- Ghent University, Center for Molecular Modeling, Technologiepark 903, B-9052 Zwijnaarde,
Belgium
| | - Freddy Callens
- Ghent University, Department of Solid State Sciences, Electron Magnetic Resonance
Research Group, Krijgslaan 281-S1, B-9000 Ghent, Belgium
| | - Henk Vrielinck
- Ghent University, Department of Solid State Sciences, Electron Magnetic Resonance
Research Group, Krijgslaan 281-S1, B-9000 Ghent, Belgium
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De Cooman H, Tarpan MA, Vrielinck H, Waroquier M, Callens F. Room temperature radiation products in trehalose single crystals: EMR and DFT analysis. Radiat Res 2013; 179:313-22. [PMID: 23373902 DOI: 10.1667/rr3179.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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.
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Affiliation(s)
- Hendrik De Cooman
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium
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Tarpan MA, De Cooman H, Hole EO, Waroquier M, Callens F. Radiation products at 77 K in trehalose single crystals: EMR and DFT analysis. J Phys Chem A 2012; 116:3377-87. [PMID: 22390542 DOI: 10.1021/jp300979g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The radicals obtained in trehalose dihydrate single crystals after 77 K X-irradiation have been investigated at the same temperature using X-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and ENDOR-induced EPR (EIE) techniques. Five proton hyperfine coupling tensors were unambiguously determined from the ENDOR measurements and assigned to three carbon-centered radical species (T1, T1*, and T2) based on the EIE spectra. EPR angular variations revealed the presence of four additional alkoxy radical species (T3 to T6) and allowed determination of their g tensors. Using periodic density functional theory (DFT) calculations, T1/T1*, T2, and T3 were identified as H-loss species centered at C4, C1', and O2', respectively. The T4 radical is proposed to have the unpaired electron at O4, but considerable discrepancies between experimental and calculated HFC values indicate it is not simply the (net) H-loss species. No suitable models were found for T5 and T6. These exhibit a markedly larger g anisotropy than T3 and T4, which were not reproduced by any of our DFT calculations.
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Tarpan MA, De Cooman H, Sagstuen E, Waroquier M, Callens F. Identification of primary free radicals in trehalose dihydrate single crystals X-irradiated at 10 K. Phys Chem Chem Phys 2011; 13:11294-302. [PMID: 21566842 DOI: 10.1039/c0cp02616f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Primary free radical formation in trehalose dihydrate single crystals X-irradiated at 10 K was investigated at the same temperature using X-band Electron Paramagnetic Resonance (EPR), Electron Nuclear Double Resonance (ENDOR) and ENDOR-induced EPR (EIE) techniques. The ENDOR results allowed the unambiguous determination of six proton hyperfine coupling (HFC) tensors. Using the EIE technique, these HF interactions were assigned to three different radicals, labeled R1, R2 and R3. The anisotropy of the EPR and EIE spectra indicated that R1 and R2 are alkyl radicals (i.e. carbon-centered) and R3 is an alkoxy radical (i.e. oxygen-centered). The EPR data also revealed the presence of an additional alkoxy radical species, labeled R4. Molecular modeling using periodic Density Functional Theory (DFT) calculations for simulating experimental data suggests that R1 and R2 are the hydrogen-abstracted alkyl species centered at C5' and C5, respectively, while the alkoxy radicals R3 and R4 have the unpaired electron localized mainly at O2 and O4'. Interestingly, the DFT study on R4 demonstrates that the trapping of a transferred proton can significantly influence the conformation of a deprotonated cation. Comparison of these results with those obtained from sucrose single crystals X-irradiated at 10 K indicates that the carbon situated next to the ring oxygen and connected to the CH(2)OH hydroxymethyl group is a better radical trapping site than other positions.
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Shkrob IA, Marin TM, Chemerisov SD, Sevilla MD. Mechanistic aspects of photooxidation of polyhydroxylated molecules on metal oxides. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2011; 115:4642-4648. [PMID: 21532934 PMCID: PMC3083075 DOI: 10.1021/jp110612s] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Polyhydroxylated molecules, including natural carbohydrates, are known to undergo photooxidation on wide-gap transition metal oxides irradiated by ultraviolet light. In this study, we examine mechanistic aspects of this photoreaction on aqueous TiO(2), α-FeOOH, and α-Fe(2)O(3) particles using electron paramagnetic resonance (EPR) spectroscopy and site-selective deuteration. We demonstrate that the carbohydrates are oxidized at sites involved in the formation of oxo-bridges between the chemisorbed carbohydrate molecule and metal ions at the oxide surface. This bridging inhibits the loss of water (which is the typical reaction of the analogous free radicals in bulk solvent) promoting instead a rearrangement that leads to elimination of the formyl radical. For natural carbohydrates, the latter reaction mainly involves carbon-1, whereas the main radical products of the oxidation are radical arising from H atom loss centered on carbon-1, -2, and -3 sites. Photoexcited TiO(2) oxidizes all of the carbohydrates and polyols, whereas α-FeOOH oxidizes some of the carbohydrates, and α-Fe(2)O(3) is unreactive. These results serve as a stepping stone for understanding the photochemistry on mineral surfaces of more complex biomolecules such as nucleic acids.
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Affiliation(s)
- Ilya A. Shkrob
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439
- Corresponding author; , tel. 630-2529516
| | - Timothy M. Marin
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439
- Chemistry Department, Benedictine University, 5700 College Road, Lisle, IL 60532
| | - Sergey D. Chemerisov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439
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Pauwels E, Asher J, Kaupp M, Waroquier M. Cluster or periodic, static or dynamic—the challenge of calculating the g tensor of the solid-state glycine radical. Phys Chem Chem Phys 2011; 13:18638-46. [DOI: 10.1039/c1cp21452g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Pauwels E, Declerck R, Verstraelen T, De Sterck B, Kay CWM, Van Speybroeck V, Waroquier M. Influence of Protein Environment on the Electron Paramagnetic Resonance Properties of Flavoprotein Radicals: A QM/MM Study. J Phys Chem B 2010; 114:16655-65. [DOI: 10.1021/jp109763t] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ewald Pauwels
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Reinout Declerck
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Toon Verstraelen
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Bart De Sterck
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Christopher W. M. Kay
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Veronique Van Speybroeck
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Michel Waroquier
- Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium QCMM - alliance Ghent-Brussels, Belgium, and Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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Tarpan MA, Pauwels E, Vrielinck H, Waroquier M, Callens F. Electron magnetic resonance and density functional theory study of room temperature X-irradiated β-D-fructose single crystals. J Phys Chem A 2010; 114:12417-26. [PMID: 21049978 DOI: 10.1021/jp107777v] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stable free radical formation in fructose single crystals X-irradiated at room temperature was investigated using Q-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and ENDOR induced EPR (EIE) techniques. ENDOR angular variations in the three main crystallographic planes allowed an unambiguous determination of 12 proton HFC tensors. From the EIE studies, these hyperfine interactions were assigned to six different radical species, labeled F1-F6. Two of the radicals (F1 and F2) were studied previously by Vanhaelewyn et al. [Vanhaelewyn, G. C. A. M.; Pauwels, E.; Callens, F. J.; Waroquier, M.; Sagstuen, E.; Matthys, P. J. Phys. Chem. A 2006, 110, 2147.] and Tarpan et al. [Tarpan, M. A.; Vrielinck, H.; De Cooman, H.; Callens, F. J. J. Phys. Chem. A 2009, 113, 7994.]. The other four radicals are reported here for the first time and periodic density functional theory (DFT) calculations were used to aid their structural identification. For the radical F3 a C3 carbon centered radical with a carbonyl group at the C4 position is proposed. The close similarity in HFC tensors suggests that F4 and F5 originate from the same type of radical stabilized in two slightly different conformations. For these radicals a C2 carbon centered radical model with a carbonyl group situated at the C3 position is proposed. A rather exotic C2 centered radical model is proposed for F6.
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Affiliation(s)
- Mihaela Adeluta Tarpan
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium
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Pauwels E, De Cooman H, Waroquier M, Hole EO, Sagstuen E. On the identity of the radiation-induced stable alanine radical. Phys Chem Chem Phys 2010; 12:8733-6. [DOI: 10.1039/c004380j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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De Cooman H, Pauwels E, Vrielinck H, Sagstuen E, Waroquier M, Callens F. Oxidation and Reduction Products of X Irradiation at 10 K in Sucrose Single Crystals: Radical Identification by EPR, ENDOR, and DFT. J Phys Chem B 2009; 114:666-74. [DOI: 10.1021/jp909247z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Hendrik De Cooman
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium, Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Ewald Pauwels
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium, Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Henk Vrielinck
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium, Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Einar Sagstuen
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium, Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Michel Waroquier
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium, Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Freddy Callens
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium, Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
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Tarpan MA, Vrielinck H, Cooman HD, Callens F. Determination of the g Tensors for the Dominant Stable Radicals in X-Irradiated β-d-Fructose Single Crystals. J Phys Chem A 2009; 113:7994-8000. [DOI: 10.1021/jp9017019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mihaela Adeluta Tarpan
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium
| | - Henk Vrielinck
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium
| | - Hendrik De Cooman
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium
| | - Freddy Callens
- Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium
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De Cooman H, Vanhaelewyn G, Pauwels E, Sagstuen E, Waroquier M, Callens F. Radiation-induced radicals in glucose-1-phosphate. I. Electron paramagnetic resonance and electron nuclear double resonance analysis of in situ X-irradiated single crystals at 77 K. J Phys Chem B 2009; 112:15045-53. [PMID: 18973366 DOI: 10.1021/jp804290e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Electron magnetic resonance analysis of radiation-induced defects in dipotassium glucose-1-phosphate dihydrate single crystals in situ X-irradiated and measured at 77 K shows that at least seven different carbon-centered radical species are trapped. Four of these (R1-R4) can be fully or partly characterized in terms of proton hyperfine coupling tensors. The dominant radical (R2) is identified as a C1-centered species, assumedly formed by a scission of the sugar-phosphate junction and the concerted formation of a carbonyl group at the neighboring C2 carbon. This structure is chemically identical to a radical recently identified in irradiated sucrose single crystals. Radical species R1 and R4 most likely are C3- and C6-centered species, respectively, both formed by a net hydrogen abstraction. R3 is suggested to be chemically similar to but geometrically different from R4. Knowledge of the identity of the sugar radicals present at 77 K provides a first step in elucidating the formation mechanism of the phosphoryl radicals previously detected after X-irradiation at 280 K. In paper II, the chemical identity, precise conformation, and possible formation mechanisms of these radical species are investigated by means of DFT calculations and elementary insight into the radiation chemistry of sugar and sugar derivatives is obtained.
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De Cooman H, Pauwels E, Vrielinck H, Sagstuen E, Van Doorslaer S, Callens F, Waroquier M. ENDOR and HYSCORE analysis and DFT-assisted identification of the third major stable radical in sucrose single crystals X-irradiated at room temperature. Phys Chem Chem Phys 2009; 11:1105-14. [DOI: 10.1039/b816641b] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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