1
|
Cadet J, Davies KJA, Medeiros MH, Di Mascio P, Wagner JR. Formation and repair of oxidatively generated damage in cellular DNA. Free Radic Biol Med 2017; 107:13-34. [PMID: 28057600 PMCID: PMC5457722 DOI: 10.1016/j.freeradbiomed.2016.12.049] [Citation(s) in RCA: 210] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Revised: 12/27/2016] [Accepted: 12/31/2016] [Indexed: 12/18/2022]
Abstract
In this review article, emphasis is placed on the critical survey of available data concerning modified nucleobase and 2-deoxyribose products that have been identified in cellular DNA following exposure to a wide variety of oxidizing species and agents including, hydroxyl radical, one-electron oxidants, singlet oxygen, hypochlorous acid and ten-eleven translocation enzymes. In addition, information is provided about the generation of secondary oxidation products of 8-oxo-7,8-dihydroguanine and nucleobase addition products with reactive aldehydes arising from the decomposition of lipid peroxides. It is worth noting that the different classes of oxidatively generated DNA damage that consist of single lesions, intra- and interstrand cross-links were unambiguously assigned and quantitatively detected on the basis of accurate measurements involving in most cases high performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The reported data clearly show that the frequency of DNA lesions generated upon severe oxidizing conditions, including exposure to ionizing radiation is low, at best a few modifications per 106 normal bases. Application of accurate analytical measurement methods has also allowed the determination of repair kinetics of several well-defined lesions in cellular DNA that however concerns so far only a restricted number of cases.
Collapse
Affiliation(s)
- Jean Cadet
- Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
| | - Kelvin J A Davies
- Leonard Davis School of Gerontology of the Ethel Percy Andrus Gerontology Center, The University of Southern California, Los Angeles, CA 90089-0191, United States; Division of Molecular & Computational Biology, Department of Biological Sciences of the Dornsife College of Letters, Arts, and Sciences, The University of Southern California, Los Angeles, CA 90089-0191, United States
| | - Marisa Hg Medeiros
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05508 000 São Paulo, SP, Brazil
| | - Paolo Di Mascio
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05508 000 São Paulo, SP, Brazil
| | - J Richard Wagner
- Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| |
Collapse
|
2
|
Reynisson J, Steenken S. One-electron reduction of 2-aminopurine in the aqueous phase. A DFT and pulse radiolysis study. Phys Chem Chem Phys 2009; 7:659-65. [PMID: 19787883 DOI: 10.1039/b417343k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electron affinity and the subsequent proton affinity of the electron adducts of 2-aminopurine (abbreviated 2AP) and adenine (A) are calculated with density functional theory (DFT). According to these calculations 2AP*- and A*- have similar thermochemical parameters leading to the conclusion that their reaction pathways should be close to analogous. Using the pulse radiolysis technique 2AP*- is formed by reaction with the hydrated electron (e(-)aq) and the resulting transient absorption spectrum is assigned to 2AP(NH)*. Additionally, it was found, employing the laser flash photolysis technique, that the excited singlet state of 2AP is incapable of oxidizing guanine in the aqueous phase. However, the one-electron oxidized 2AP (2AP*+) has sufficient energy to ionize guanine according to the DFT results in agreement with experimental data from the literature.
Collapse
|
3
|
Jaeger HM, Schaefer HF. Characterizing radiation-induced oxidation of DNA by way of the monohydrated guanine-cytosine radical cation. J Phys Chem B 2009; 113:8142-8. [PMID: 19445496 DOI: 10.1021/jp900444k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interaction of one water molecule with the guanine-cytosine radical cation has been studied with ab initio and density functional methods in order to help elucidate the nature of oxidized aqueous DNA. The theoretical spin density of [GC]*(+) reveals that the radical center is localized on guanine. The adiabatic ionization potential lowers from 7.63 to 6.71 eV in concurrence with the formation of the Watson-Crick base pair and hydration by one water molecule. A natural bond orbital analysis of partial charges shows that approximately 80% of the positive charge persists on guanine upon hydration and formation of the Watson-Crick base pair with cytosine. Hydration energies were computed with second-order Z-averaged perturbation theory (ZAPT2) using the aug-cc-pVDZ basis set at 11 stationary points on the B3LYP/DZP++ potential energy surface. The hydration energy at the global minimum is 14.2 kcal mol(-1). The lowest energy structures correspond to hydration near the glycosidic bond sites. Structural changes in the Watson-Crick base pair are predominantly seen for monohydration in the groove regions of double-helix DNA.
Collapse
Affiliation(s)
- Heather M Jaeger
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA.
| | | |
Collapse
|
4
|
Pal C, Hüttermann J. Postirradiation electron transfer vs differential radical decay in X-irradiated DNA and its mixtures with additives. Electron spin resonance spectroscopy in LiBr glass at low temperatures. J Phys Chem B 2007; 110:14976-87. [PMID: 16869613 DOI: 10.1021/jp0583086] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Free radical formation in DNA and in colyophilized mixtures of DNA with the additives mitoxantrone and riboflavin was monitored after X-ray irradiation in frozen aqueous glasses (7 M LiBr/D2O) at 77 K by electron spin resonance (ESR) spectroscopy. Specifically, the postirradiation time course at 77 K of the respective free radical intensity residing on DNA or on the additive was probed in order to test the hypothesis of electron transfer from DNA, e.g., to mitoxantrone after irradiation under these conditions (e.g., Messer, A.; Carpenter, K.; Forzley, K.; Buchanan, J.; Yang, S.; Razskazovskii, Y.; Cai, Z.; Sevilla, M. D. J. Phys. Chem. B 2000, 104, 1128). For both additives, different additive loadings and irradiation doses were employed. The observed relative change in contributions of DNA and of additive radical components to the experimental spectra with time could be ascribed, for both additives, unequivocally to independent, differential fading of component radicals. Transfer from DNA to the additive, e.g., by electron tunneling as proposed before could be ruled out to occur by a detailed, quantitative analysis of the experimental spectra using reconstruction techniques. Additional studies were performed with the nucleotides TMP and dCMP and its mixtures with mitoxantrone in order to describe the time course in systems which are expected to behave independently; the results supported the conclusions arrived at from the analysis of the DNA/additive system. A model was proposed to describe the postirradiation radical fading mechanisms which involve liberation of radiation-induced matrix-trapped defects with time. It was assumed that these defects are ESR-mute and react with radicals by net radical destruction. Some experimental observations are presented concerning influence of temperature and of the matrix on the fading processes. These seem to argue in favor of such a model although a detailed, quantitative description is still not possible.
Collapse
Affiliation(s)
- Chandrima Pal
- Fachrichtung Biophysik, Universität des Saarlandes, Klinikum Bau 76, 66421 Homburg, Germany
| | | |
Collapse
|
5
|
Pramod G, Mohan H, Manoj P, Manojkumar TK, Manoj VM, Mittal JP, Aravindakumar CT. Redox chemistry of 8-azaadenine: a pulse radiolysis study. J PHYS ORG CHEM 2006. [DOI: 10.1002/poc.1100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
6
|
Zierold K, Michel J, Terryn C, Balossier G. The distribution of light elements in biological cells measured by electron probe X-ray microanalysis of cryosections. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2005; 11:138-145. [PMID: 15817143 DOI: 10.1017/s1431927605050130] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2003] [Indexed: 05/24/2023]
Abstract
The intracellular distribution of the elements carbon, nitrogen, and oxygen was measured in cultured rat hepatocytes by energy dispersive electron probe X-ray microanalysis of 100-nm-thick freeze-dried cryosections. Electron irradiation with a dose up to 106 e/nm2 caused no or merely negligible mass loss in mitochondria and in cytoplasm. Cell nuclei lost carbon, nitrogen, and-to a clearly higher extent-oxygen with increasing electron irradiation. Therefore, electron doses less than 3 x 105 e/nm2 were used to measure the subcellular compartmentation of carbon, nitrogen, and oxygen in cytoplasm, mitochondria, and nuclei of the cells. The subcellular distribution of carbon, nitrogen, and oxygen reflects the intracellular compartmentation of various biomolecules. Cells exposed to inorganic mercury before cryofixation showed an increase of oxygen in nuclei and cytoplasm. Concomitantly the phosphorus/nitrogen ratio decreased in mitochondria. The data suggest mercury-induced production of ribonucleic acid (RNA) and decrease of adenosine triphosphate (ATP). Although biomolecules cannot be identified by X-ray microanalysis, measurements of the whole element spectrum including the light elements carbon, nitrogen, and oxygen can be useful to study specific biomolecular activity in cellular compartments depending on the functional state of the cell.
Collapse
Affiliation(s)
- Karl Zierold
- Max-Planck-Institute of Molecular Physiology, 44227 Dortmund, Germany
| | | | | | | |
Collapse
|
7
|
Krivokapić A, Hole EO, Sagstuen E. EPR and ENDOR study of crystalline cytosine x HCl doped with 5-methylcytosine. Radiation-induced radical formation and hole transfer. Radiat Res 2003; 160:340-54. [PMID: 12926993 DOI: 10.1667/rr3048] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Radical formation and hole transfer were investigated in crystals of cytosine.HCl (C.HCl) doped with 0-1.1 mol-% 5-methylcytosine x HCl (5MC x HCl). The doping level was determined by NMR spectroscopy. Crystals and polycrystalline samples were X-irradiated at 295 K, 77 K and 12 K and studied with EPR, ENDOR and FSE spectroscopy at these temperatures. At 295 K the dominant radicals were the so-called 3alphaH radical, formed in 5MC by a net H-abstraction from the methyl group, and the cytosine C6 H-addition (5-yl) radical. At 12 K five radicals were identified. These were the 3alphaH radical, cytosine reduction and oxidation products, and the cytosine C6 and C5 H-addition (5-yl and 6-yl, respectively) radicals. The spectroscopic parameters for the 3alphaH radical are very similar to those of a radical observed previously in the crystalline cytosine derivatives cytidine (CR), 2'deoxycytidine hydrochloride (CdR x HCl), 5'dCMP and 3'CMP as well as in the uracil derivative 2-thiouracil (2-TU). It was shown that amounts of the order of tenths of a percent 5MC x HCl doped into crystals of C.HCl give rise to a considerable yield of 3alphaH radicals after exposure to ionizing radiation both at room temperature and at lower temperatures. This supports a previous suggestion that naturally occurring 5-methylated cytosine impurities may be responsible for the formation of 3alphaH radicals in the crystalline cytosine derivatives CR, CdR.HCl, 5'dCMP and 3'CMP and suggests that the 3alphaH radical in these systems is a 5-methylated base-centered radical. The total radical yield in doped C x HCl crystals increased considerably with the doping level, both at low temperatures and at room temperature, implying that the 3alphaH radical is more stable than the primary cytosine radicals. The relative amounts of the 3alphaH radical were obtained by using simulated benchmark spectra to reconstruct experimental EPR spectra of doped polycrystalline samples. Evidence is presented suggesting that the enhanced yield of the 3alphaH radical in doped samples is due to holes originally formed at cytosine bases and transferred to 5-methylcytosine bases in addition to the 3alphaH radical being less exposed to recombination than other cytosine radicals.
Collapse
|
8
|
A multi-component model for radiation damage to DNA from its constituents. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1380-7323(01)80012-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
9
|
Wetmore SD, Boyd RJ, Eriksson LA. A Comprehensive Study of Sugar Radicals in Irradiated DNA. J Phys Chem B 1998. [DOI: 10.1021/jp9824407] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stacey D. Wetmore
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J6
| | - Russell J. Boyd
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J6
| | - Leif A. Eriksson
- Department of Physics, University of Stockholm, Box 6370, 113 85, Stockholm, Sweden,
| |
Collapse
|
10
|
Close DM, Hole EO, Sagstuen E, Nelson WH. EPR and ENDOR Studies of X-Irradiated Single Crystals of Deoxycytidine 5‘-Phosphate Monohydrate at 10 and 77 K. J Phys Chem A 1998. [DOI: 10.1021/jp981610c] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David M. Close
- Physics Department, East Tennessee State University, P.O. Box 70652, Johnson City, Tennessee 37614
| | - Eli O. Hole
- Department of Physics, University of Oslo, P.O. Box 1048, Blindern N-0316 Oslo, Norway
| | - Einar Sagstuen
- Department of Physics, University of Oslo, P.O. Box 1048, Blindern N-0316 Oslo, Norway
| | - William H. Nelson
- Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303
| |
Collapse
|
11
|
Langman SR, Shohoji MCBL, Telo JP, Vieira AJSC, Novais HM. EPR spectroscopic study of the radical oxidation of hydroxypurines in aqueous solution: acid–base properties of the derived radicals. ACTA ACUST UNITED AC 1996. [DOI: 10.1039/p29960001461] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
12
|
Cullis PM, Elsy D, Fan S, Symons MC. Marked effect of buffers on yield of single- and double-strand breaks in DNA irradiated at room temperature and at 77 K. Int J Radiat Biol 1993; 63:161-5. [PMID: 8094411 DOI: 10.1080/09553009314550211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have shown that the protocol for handling plasmid (pBR 322) DNA for radiation studies, which normally involves using quite high concentrations of Tris or phosphate buffers, is equally satisfactory in the absence of added buffers provided samples are stored at 0 degree C, or used directly. On exposure of aqueous solutions at 77 K, Tris buffer acts as a weak protecting agent, but phosphate buffers at the same pH act as remarkably effective sensitizing agents, giving ca. 100-fold increases in strand breaks. At room temperature there is again a marked difference between the aqueous and buffered systems, but in this case both the Tris and the phosphate systems are protective. Possible reasons for these contrasting results are discussed, and the advantages of using simple aqueous solutions are stressed.
Collapse
Affiliation(s)
- P M Cullis
- Chemistry Department, The University, Leicester, UK
| | | | | | | |
Collapse
|
13
|
|
14
|
Steenken S. Electron-transfer-induced acidity/basicity and reactivity changes of purine and pyrimidine bases. Consequences of redox processes for DNA base pairs. FREE RADICAL RESEARCH COMMUNICATIONS 1992; 16:349-79. [PMID: 1325399 DOI: 10.3109/10715769209049187] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Changes in the oxidation state of the DNA bases, induced by oxidation (ionization) or by reduction (electron capture), have drastic effects on the acidity or basicity, respectively, of the molecules. Since in DNA every base is connected to its complementary base in the other strand, any change of the electric charge status of a base in one DNA strand that accompanies its oxidation or reduction may affect also the other strand via proton transfer across the hydrogen bonds in the base pairs. The free energies for electron transfer to or from a base can be drastically altered by the proton transfer processes that accompany the electron transfer reactions. Electron-transfer (ET) induced proton transfer sensitizes the base opposite to the ET-damaged base to redox damage, i.e., damage produced by separation of charge (ionization) has an increased change of being trapped in a base pair. Of the two types of base pair in DNA, A-T and C-G, the latter is more sensitive to both oxidative and reductive processes than the former. Proton transfer induced by ET does not only occur between the heteroatoms (O and N) of the base pairs (intra-pair proton transfer), but also to and from adjacent water molecules in the hydration shell of DNA (extra-pair proton transfer). These proton transfers can involve carbon and as such are likely to be irreversible. It is the A-T pair which appears to be particularly prone to such irreversible reactions.
Collapse
Affiliation(s)
- S Steenken
- Max-Planck-Institut für Strahlenchemie, Mülheim, Germany
| |
Collapse
|
15
|
Hüttermann J. Radical Ions and Their Reactions in DNA and its Constituents. TOPICS IN MOLECULAR ORGANIZATION AND ENGINEERING 1991. [DOI: 10.1007/978-94-011-3750-8_17] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
16
|
Lin NY. Radiation induced long range electron transfer in biological systems. RESEARCH ON CHEMICAL INTERMEDIATES 1990. [DOI: 10.1163/156856790x00265] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
17
|
Hildenbrand K, Schulte-Frohlinde D. ESR spectra of radicals of single-stranded and double-stranded DNA in aqueous solution. Implications for .OH-induced strand breakage. FREE RADICAL RESEARCH COMMUNICATIONS 1990; 11:195-206. [PMID: 1965722 DOI: 10.3109/10715769009088916] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In situ photolysis at 20 degrees C (argon plasma light source, lambda approximately greater than 200 mm) of oxygen-free solutions containing 2 mM H2O2 and heat-denatured, single-stranded (ss)DNA from calf-thymus resulted in the ESR spectra of the 6-hydroxy-5,6-dihydro-thymin-5-yl (1) and 5-methyleneuracil (3) radicals linked to the sugar-phosphate backbone. They were generated by reaction of OH radicals with DNA. By comparison of the decay characteristics of the ESR signals with rate constants from pulse-conductivity measurements [E. Bothe, G.A. Qureshi and D. Schulte-Frohlinde, Z. Naturforsch., 38c, 1030, (1983)] the thymine-derived radicals (1) and (3) can be excluded as precursors of the fast, dominating component of strand breakage of ssDNA. In the absence of H2O2 from native, double-stranded (ds)DNA an ESR signal was obtained (singlet, g approximately 2.004, delta v1/2 approximately 0.8 mT) which was assigned to the deprotonated guanine radical cation, [G.(-H)] of a DNA subunit. It is assumed that by the UV irradiation the guanine radical cation, (G+.), is generated, either by monophotonic photoionization or by electron transfer to pyrimidine bases. By rapid transfer of the bridging proton from (G+.) to the hydrogen bonded cytosine [G.(-H)] is formed. When photolysis of dsDNA was carried out in the presence of H2O2, reaction of photolytically generated .OH resulted in peroxyl radicals and purine radicals. The oxygen for formation of the peroxyl radicals is probably produced by reaction of [G.(-H)] with H2O2. Photolysis of N2O-saturated solutions containing dsDNA or ssDNA provided another possibility of generation of OH radicals. Under those conditions the .OH-induced radicals (1) and (3) were obtained not only from ssDNA but also from dsDNA.
Collapse
Affiliation(s)
- K Hildenbrand
- Max-Planck-Institut für Strahlenchemie, Mülheim a.d. Ruhr, FRG
| | | |
Collapse
|
18
|
Close DM, Nelson WH, Sagstuen E, Hole EO. ESR and ENDOR studies of X-irradiated single crystals of guanine derivatives. FREE RADICAL RESEARCH COMMUNICATIONS 1989; 6:83-5. [PMID: 2545564 DOI: 10.3109/10715768909073433] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- D M Close
- East Tenn. State University, Johnson City
| | | | | | | |
Collapse
|
19
|
Dubochet J, Adrian M, Chang JJ, Homo JC, Lepault J, McDowall AW, Schultz P. Cryo-electron microscopy of vitrified specimens. Q Rev Biophys 1988; 21:129-228. [PMID: 3043536 DOI: 10.1017/s0033583500004297] [Citation(s) in RCA: 1550] [Impact Index Per Article: 43.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cryo-electron microscopy of vitrified specimens was just emerging as a practical method when Richard Henderson proposed that we should teach an EMBO course on the new technique. The request seemed to come too early because at that moment the method looked more like a laboratory game than a useful tool. However, during the months which ellapsed before the start of the course, several of the major difficulties associated with electron microscopy of vitrified specimens found surprisingly elegant solutions or simply became non-existent. The course could therefore take place under favourable circumstances in the summer of 1983. It was repeated the following years and cryo-electron microscopy spread rapidly. Since that time, water, which was once the arch enemy of all electronmicroscopists, became what it always was in nature – an integral part of biological matter and a beautiful substance.
Collapse
Affiliation(s)
- J Dubochet
- European Molecular Biology Laboratory (EMBL), Heidelberg, FRG
| | | | | | | | | | | | | |
Collapse
|
20
|
Strand P, Sagstuen E, Lehner T, Hüttermann J. Free radical formation in crystals of guanine hydrochloride dihydrate: an ESR and ENDOR study. INTERNATIONAL JOURNAL OF RADIATION BIOLOGY AND RELATED STUDIES IN PHYSICS, CHEMISTRY, AND MEDICINE 1987; 51:303-18. [PMID: 3030948 DOI: 10.1080/09553008714550781] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Radiation-induced free radical formation in single crystals of guanine hydrochloride dihydrate has been studied at temperatures between 20 and 300 K using ESR and ENDOR spectroscopy. At low temperatures three radical species are trapped. Two of these are the C8 H-addition radical R1 previously analysed by Alexander and Gordy (1967) and the O6-protonated anion radical R2. The third species (R4) remains unidentified. Upon annealing at 280 K for an extended period the protonated anion R2 transforms into a new radical R3 which exhibit a well-defined hyperfine pattern but still could not be identified unambiguously. Also radical R4 probably transforms into a new radical (R5) upon such treatment. One proton coupling due to R5 was detected. A scheme of radical reactions incorporating these five radicals is proposed. This scheme also suggests that differences in radical formation between the monohydrate and dihydrate crystals of guanine hydrochloride depends upon differences in the hydrogen bonding network.
Collapse
|
21
|
von Sonntag C, Schuchmann HP. The radiolysis of pyrimidines in aqueous solutions: an updating review. INTERNATIONAL JOURNAL OF RADIATION BIOLOGY AND RELATED STUDIES IN PHYSICS, CHEMISTRY, AND MEDICINE 1986; 49:1-34. [PMID: 3000965 DOI: 10.1080/09553008514552201] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
22
|
Misra M, Egerton RF. Assessment of electron irradiation damage to biomolecules using the Patterson function. J Microsc 1985; 139:197-204. [PMID: 4046015 DOI: 10.1111/j.1365-2818.1985.tb02636.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A method for the assessment of electron radiation damage to 5-iodouracil is described which involves the use of the Patterson function. Changes in Patterson maps computed from the electron diffraction patterns recorded at increasing electron irradiation have been related to structural and chemical damage to 5-iodouracil. The process of radiation damage is also discussed in terms of a disorder parameter which was found to increase with increasing irradiation.
Collapse
|
23
|
|
24
|
|
25
|
Free-radical probes of condensed-phase aspects of radiation damage mechanisms in DNA constituents: 5-halouracils. Ultramicroscopy 1984. [DOI: 10.1016/0304-3991(84)90086-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
26
|
Sagstuen E, Close DM. An ESR study of irradiated 1:1 co‐crystals of 9‐ethyladenine:5,5‐diethylbarbituric acid (barbital) at 295 K. J Chem Phys 1983. [DOI: 10.1063/1.445569] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|