Mechanisms of Radiation-Induced DNA Damage: Direct Effects

Becker, Dávid; Adhikary, Amitava; Sevilla, Michael D.

doi:10.1142/9789814282093_0018

Cited by 29 publications

(76 citation statements)

References 54 publications

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“…Furthermore, we note here that formation of C3' dephos • has been reported to occur via dissociative electron attachment owing to the attack of low energy electron (LEE) at the DNA sugar phosphate C3'-O bond (Becker et al 2003, 2007, 2010a, 2010b) and supported by product analyses in LEE (4 to 15 electron volt (eV))-induced damaged oligomers (Li et al 2008). On the other hand, this work provides the first evidence of distinct line components owing to C3' dephos • production via excited one-electron oxidized base radicals.…”

Section: Resultssupporting

confidence: 65%

“…91 G). Our work (Adhikary et al 2008; Becker et al 2010a,b) have shown that the β-proton HFCC values for C3′• ranges from ca. 84 to ca.…”

Section: Resultsmentioning

confidence: 83%

“…Previous ESR spectral studies carried out by our laboratory have established that the photoexcited purine cation radical in DNA model systems (nucleosides, nucleotides, single and double stranded oligomers), in RNA model systems (nucleosides, nucleotides, single stranded oligomers) and in highly polymerized DNA (salmon sperm) lead to formation of sugar radicals (Adhikary et al 2005, 2008, 2010, 2012; Becker et al 2007, 2010a, 2010b; Khanduri et al 2011). Simultaneously, theoretical calculations employing time-dependent density functional theory (TD-DFT) (Kumar and Sevilla, 2006, 2008, 2009) supported these experimental results.…”

Section: Resultsmentioning

confidence: 93%

“…Following our ongoing studies with the DNA and RNA monomers (Becker et al 2007, 2010a, 2010b; Adhikary et al 2012, 2013b) and DNA and RNA oligomers (Becker et al 2007, 2010a, 2010b; Adhikary et al 2009, 2010, 2012, 2013a; Khanduri et al 2011), homogeneous solution of each monomer was prepared by dissolving ~ 2 to 3 mg of it in 1 ml of 7.5 M LiCl in D 2 O; whereas to prepare a homogeneous solution of a dsDNA oligomer, ~ 1.5 to 2 mg of it was dissolved in 1 ml of 7.5 M LiCl in D 2 O. K 2 S 2 O 8 (5 to 6 mg/ml) was added to each solution as an electron scavenger to investigate only the formation of the one-electron oxidized species and its subsequent reactions. Following the procedure by Sevilla and co-workers (Sevilla et al 1972), homogeneous solution of 5-Me-2'-dC (0.5 mg/ml) was prepared in 8 M NaClO 4 in D 2 O.…”

Section: Methodsmentioning

confidence: 99%

“…Following our works (Kumar and Sevilla 2006, 2008; Becker et al 2007, 2010a,b; Adhikary et al 2005, 2008), the excited states of 5-Me-2'-dC cation radical were calculated using the TD-DFT (time dependent density functional theory) for determining the transition energy and the nature of the molecular orbitals involved in transitions. Calculations were performed using the TD- B3LYP/6-31G(d) method as implemented in Gaussian 09.…”

Section: Methodsmentioning

confidence: 99%

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Reactions of 5-methylcytosine cation radicals in DNA and model systems: Thermal deprotonation from the 5-methyl group vs. excited state deprotonation from sugar

Adhikary

Kumar

Palmer

et al. 2014

International Journal of Radiation Biology

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Purpose To study the formation and subsequent reactions of the 5-methyl-2′-deoxycytidine cation radical (5-Me-2′-dC•+) in nucleosides and DNA-oligomers and compare to one electron oxidized thymidine. Materials and methods Employing electron spin resonance (ESR), cation radical formation and its reactions were investigated in 5-Me-2′-dC, thymidine (Thd) and their derivatives, in fully double stranded (ds) d[GC*GC*GC*GC*]2 and in the 5-Me-C/A mismatched, d[GGAC*AAGC:CCTAATCG], where C* = 5-Me-C. Results We report 5-Me-2′-dC•+ production by one-electron oxidation of 5-Me-2′-dC by Cl2•− via annealing in the dark at 155 K. Progressive annealing of 5-Me-2′-dC•+ at 155 K produces the allylic radical (C-CH2•). However, photoexcitation of 5-Me-2′-dC•+ by 405 nm laser or by photoflood lamp leads to only C3′• formation. Photoexcitation of N3-deprotonated thyminyl radical in Thd and its 5′-nucleotides leads to C3′• formation but not in 3′-TMP which resulted in the allylic radical (U-CH2•) and C5′• production. For excited 5-Me-2′,3′-ddC•+, absence of the 3′-OH group does not prevent C3′• formation. For d[GC*GC*GC*GC*]2 and d[GGAC*AAGC:CCTAATCG], intra-base paired proton transferred form of G cation radical (G(N1-H)•:C(+H+)) is found with no observable 5-Me-2′-dC•+ formation. Photoexcitation of (G(N1-H)•:C(+H+)) in d[GC*GC*GC*GC*]2 produced only C1′• and not the expected photoproducts from 5-Me-2′-dC•+. However, photoexcitation of (G(N1-H)•:C(+H+)) in d[GGAC*AAGC:CCTAATCG] led to C5′• and C1′• formation. Conclusions C-CH2• formation from 5-Me-2′-dC•+ occurs via ground state deprotonation from C5-methyl group on the base. In the excited 5-Me-2′-dC•+ and 5-Me-2′,3′-ddC•+, spin and charge localization at C3′ followed by deprotonation leads to C3′• formation. Thus, deprotonation from C3′ in the excited cation radical is kinetically controlled and sugar C-H bond energies are not the only controlling factor in these deprotonations.

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Section: Resultssupporting

confidence: 65%

“…91 G). Our work (Adhikary et al 2008; Becker et al 2010a,b) have shown that the β-proton HFCC values for C3′• ranges from ca. 84 to ca.…”

Section: Resultsmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Reactions of 5-methylcytosine cation radicals in DNA and model systems: Thermal deprotonation from the 5-methyl group vs. excited state deprotonation from sugar

Adhikary

Kumar

Palmer

et al. 2014

International Journal of Radiation Biology

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Radiation‐Induced Radical Reactions

Bobrowski

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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This article reports on radiation‐induced radical reactions in gases, liquids, and solids. A brief summary of specific features of high‐energy radiation and its interaction with matter is given as a base for better understanding of reaction mechanisms initiated by radiation. The first section describes the most important features of radiolysis in a gas phase with presentation of the commonly used gas systems for inducing and studying radical reactions. Relevant examples include radical reactions connected with atmospheric and environmental chemistry, combustion, and electric discharges. The second section focuses on radiation‐induced radical reactions in water and aqueous solutions with a special emphasis on procedures that allow induction of radical reactions in a controlled manner. Relevant examples include radical reactions initiated by primary and secondary radicals from water radiolysis with a variety of compounds. Application of various organic solvents and ionic liquids offering a convenient method of generation and also some control over the nature of radical ions and excited states formed in the irradiated solvents and derived from the solutes is also presented. The last section briefly summarizes the most commonly applied solid systems and highlights radiation‐induced radical reactions in zeolites, a new matrix used recently for radiation generation of radicals and radical ions in the solid state.

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Understanding DNA Radicals Employing Theory and Electron Spin Resonance Spectroscopy

Adhikary

Kumar

Becker

et al. 2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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Ionizing radiation, such as γ‐rays, X‐rays, or ion beam radiation, results in the formation of cation and anion radicals in DNA and neutral radicals by secondary reactions. These DNA radicals are stable at low temperatures and, therefore, can be studied by electron spin resonance (ESR) spectroscopy. In these DNA radicals, the unpaired spin on the radical site interacts with nuclei with a magnetic moment, such as, 1 H, 2 H, and 14 N. This electron spin–nuclear spin interaction gives rise to hyperfine coupling, which is characterized by the hyperfine coupling constant (HFCC) values. The HFCC values along with the g ‐values determine the ESR spectra of these radicals. Calculations based on density functional theory (DFT) allow for identification of these DNA radicals via the prediction of stabilization energies and, most importantly, accurate values of the HFCCs. These calculations elucidate radical conformational structures as well. Thus, the combination of ESR with DFT calculations is a powerful approach to the investigation of DNA radicals and is the main focus of this article. This is illustrated in this article by specific examples—such as the prediction of sites of deprotonation in the DNA base cation radicals, intra‐base pair proton transfer processes in DNA base radicals, and excited state‐induced reactions of the DNA base cation and anion radicals leading to sugar radical formation.

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Mechanisms of Radiation-Induced DNA Damage: Direct Effects

Cited by 29 publications

References 54 publications

Reactions of 5-methylcytosine cation radicals in DNA and model systems: Thermal deprotonation from the 5-methyl group vs. excited state deprotonation from sugar

Reactions of 5-methylcytosine cation radicals in DNA and model systems: Thermal deprotonation from the 5-methyl group vs. excited state deprotonation from sugar

Radiation‐Induced Radical Reactions

Understanding DNA Radicals Employing Theory and Electron Spin Resonance Spectroscopy

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