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Zima V, Liu Y, Tureček F. Radical Cascade Dissociation Pathways to Unusual Nucleobase Cation Radicals. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1038-1047. [PMID: 35536606 DOI: 10.1021/jasms.2c00098] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We report unusual dissociations of protonated RNA nucleosides tagged with radical initiator groups at ribose 5'-O and furnished with a 2',3'-O-isopropylidene protecting group. The ions undergo collision-induced radical cascade dissociations starting at the radical initiator that break down the dioxolane ring and trigger the formation of nucleobase cations and cation radicals. The adenine cation radical that was formed by radical cascade dissociations was identified by MS5 UV-vis photodissociation action spectroscopy to be a higher-energy N-3-H tautomer of the canonical ionized nucleobase. The guanine cation radical was formed by radical cascade dissociations as the N-7-H tautomer. In contrast to adenosine and guanosine, radical cascade dissociations of the tagged ribocytidine ion produced protonated cytosine, whereas tagged ribothymidine showed yet different dissociations resulting in predominant thymine loss. Reaction mechanisms were suggested for the cascade dissociations that were based on Born-Oppenheimer molecular dynamics and density functional theory calculations that were used to map the relevant parts of the potential energy surfaces for adenosine, guanosine, and cytidine radical ions. The reported radical cascade dissociations represent a new, nonredox approach to nucleobase and nucleoside cation radicals that has the potential of being expanded to the generation of various oligonucleotide cation radicals.
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Affiliation(s)
- Václav Zima
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 981195-1700, United States
| | - Yue Liu
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 981195-1700, United States
| | - František Tureček
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 981195-1700, United States
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Wang SD, Eriksson LA, Zhang RB. Dynamics of 5R-Tg Base Flipping in DNA Duplexes Based on Simulations─Agreement with Experiments and Beyond. J Chem Inf Model 2022; 62:386-398. [PMID: 34994562 PMCID: PMC8790752 DOI: 10.1021/acs.jcim.1c01169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Damaged or mismatched
DNA bases are normally thought to be able
to flip out of the helical stack, providing enzymes with access to
the faulty genetic information otherwise hidden inside the helix.
Thymine glycol (Tg) is one of the most common products of nucleic
acid damage. However, the static and dynamic structures of DNA duplexes
affected by 5R-Tg epimers are still not clearly understood, including
the ability of these to undergo spontaneous base flipping. Structural
effects of the 5R-Tg epimers on the duplex DNA are herein studied
using molecular dynamics together with reliable DFT based calculations.
In comparison with the corresponding intact DNA, the cis-5R,6S-Tg epimer base causes little perturbation to the duplex DNA,
and a barrier of 4.9 kcal mol–1 is obtained by meta-eABF
for cis-5R,6S-Tg base flipping out of the duplex
DNA, comparable to the 5.4 kcal mol–1 obtained for
the corresponding thymine flipping in intact DNA. For the trans-5R,6R-Tg epimer, three stable local structures were
identified, of which the most stable disrupts the Watson–Crick
hydrogen-bonded G5/C20 base pair, leading to conformational distortion
of the duplex. Interestingly, the relative barrier height of the 5R-Tg
flipping is only 1.0 kcal mol–1 for one of these trans-5R,6R-Tg epimers. Water bridge interactions were identified
to be essential for 5R-Tg flipping. The study clearly demonstrates
the occurrence of partial trans-5R,6R-Tg epimer flipping
in solution.
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Affiliation(s)
- Shu Dong Wang
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, South Street no 5, Zhongguancun, Haidian District, 100081 Beijing, China
| | - Leif A Eriksson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan 9c, 405 30 Göteborg, Sweden
| | - Ru Bo Zhang
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, South Street no 5, Zhongguancun, Haidian District, 100081 Beijing, China
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Wang Y, Zhao H, Yang C, Jie J, Dai X, Zhou Q, Liu K, Song D, Su H. Degradation of Cytosine Radical Cations in 2′-Deoxycytidine and in i-Motif DNA: Hydrogen-Bonding Guided Pathways. J Am Chem Soc 2019; 141:1970-1979. [DOI: 10.1021/jacs.8b10743] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Yinghui Wang
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P. R. China
- University of Chinese Academy of Science, Beijing 100049, P. R. China
| | - Hongmei Zhao
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P. R. China
| | - Chunfan Yang
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Jialong Jie
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Xiaojuan Dai
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Qian Zhou
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Kunhui Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Di Song
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P. R. China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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Cadet J, Wagner JR, Angelov D. Biphotonic Ionization of DNA: From Model Studies to Cell. Photochem Photobiol 2018; 95:59-72. [PMID: 30380156 DOI: 10.1111/php.13042] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 10/16/2018] [Indexed: 12/13/2022]
Abstract
Oxidation reactions triggered by low-intensity UV photons represent a minor contribution with respect to the overwhelming pyrimidine base dimerization in both isolated and cellular DNA. The situation is totally different when DNA is exposed to high-intensity UVC radiation under conditions where biphotonic ionization of the four main purine and pyrimidine bases becomes predominant at the expense of singlet excitation processes. The present review article provides a critical survey of the main chemical reactions of the base radical cations thus generated by one-electron oxidation of nucleic acids in model systems and cells. These include oxidation of the bases with the predominant formation of 8-oxo-7,8-dihydroguanine as the result of preferential hole transfer to guanine bases that act as sinks in isolated and cellular DNA. In addition to hydration, other nucleophilic addition reactions involving the guanine radical cation give rise to intra- and interstrand cross-links together with DNA-protein cross-links. Information is provided on the utilization of high-intensity UV laser pulses as molecular biology tools for studying DNA conformational features, nucleic acid-protein interactions and nucleic acid reactivity through DNA-protein cross-links and DNA footprinting experiments.
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Affiliation(s)
- Jean Cadet
- Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - J Richard Wagner
- Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Dimitar Angelov
- Laboratoire de Biologie et Modélisation de la Cellule LBMC, CNRS-UMR 5239, Université de Lyon, École Normale Supérieure de Lyon, Lyon, France
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Sun H, Zheng L, Greenberg MM. Independent Generation of Reactive Intermediates Leads to an Alternative Mechanism for Strand Damage Induced by Hole Transfer in Poly(dA-T) Sequences. J Am Chem Soc 2018; 140:11308-11316. [PMID: 30169029 DOI: 10.1021/jacs.8b05484] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Purine radical cations (dA•+ and dG•+) are the primary hole carriers of DNA hole migration due to their favorable oxidation potential. Much less is known about the reactivity of higher energy pyrimidine radical cations. The thymidine radical cation (T•+) was produced at a defined position in DNA from a photochemical precursor for the first time. T•+ initiates hole transfer to dGGG triplets in DNA. Hole localization in a dGGG sequence accounts for ∼26% of T•+ formed under aerobic conditions in 9. Reduction to yield thymidine is also quantified. 5-Formyl-2'-deoxyuridine is formed in low yield in DNA when T•+ is independently generated. This is inconsistent with mechanistic proposals concerning product formation from electron transfer in poly(dA-T) sequences, following hole injection by a photoexcited anthraquinone. Additional evidence that is inconsistent with the original mechanism was obtained using hole injection by a photoexcited anthraquinone in DNA. Instead of requiring the intermediacy of T•+, the strand damage patterns observed in those studies, in which thymidine is oxidized, are reproduced by independent generation of 2'-deoxyadenosin- N6-yl radical (dA•). Tandem lesion formation by dA• provides the basis for an alternative mechanism for thymidine oxidation ascribed to hole migration in poly(dA-T) sequences. Overall, these experiments indicate that the final products formed following DNA hole transfer in poly(dA-T) sequences do not result from deprotonation or hydration of T•+, but rather from deprotonation of the more stable dA•+, to form dA•, which produces tandem lesions in which 5'-flanking thymidines are oxidized.
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Affiliation(s)
- Huabing Sun
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Liwei Zheng
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Marc M Greenberg
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
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