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Arthur-Baidoo E, Schöpfer G, Ončák M, Chomicz-Mańka L, Rak J, Denifl S. Electron Attachment to 5-Fluorouracil: The Role of Hydrogen Fluoride in Dissociation Chemistry. Int J Mol Sci 2022; 23:8325. [PMID: 35955461 PMCID: PMC9369043 DOI: 10.3390/ijms23158325] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/22/2022] [Accepted: 07/25/2022] [Indexed: 12/03/2022] Open
Abstract
We investigate dissociative electron attachment to 5-fluorouracil (5-FU) employing a crossed electron-molecular beam experiment and quantum chemical calculations. Upon the formation of the 5-FU- anion, 12 different fragmentation products are observed, the most probable dissociation channel being H loss. The parent anion, 5-FU-, is not stable on the experimental timescale (~140 µs), most probably due to the low electron affinity of FU; simple HF loss and F- formation are seen only with a rather weak abundance. The initial dynamics upon electron attachment seems to be governed by hydrogen atom pre-dissociation followed by either its full dissociation or roaming in the vicinity of the molecule, recombining eventually into the HF molecule. When the HF molecule is formed, the released energy might be used for various ring cleavage reactions. Our results show that higher yields of the fluorine anion are most probably prevented through both faster dissociation of an H atom and recombination of F- with a proton to form HF. Resonance calculations indicate that F- is formed upon shape as well as core-excited resonances.
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Affiliation(s)
- Eugene Arthur-Baidoo
- Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria; (E.A.-B.); (G.S.)
- Center for Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
| | - Gabriel Schöpfer
- Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria; (E.A.-B.); (G.S.)
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria; (E.A.-B.); (G.S.)
| | - Lidia Chomicz-Mańka
- Laboratory of Biological Sensitizers, Physical Chemistry Department, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (L.C.-M.); (J.R.)
| | - Janusz Rak
- Laboratory of Biological Sensitizers, Physical Chemistry Department, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (L.C.-M.); (J.R.)
| | - Stephan Denifl
- Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria; (E.A.-B.); (G.S.)
- Center for Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
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Fong CW. Platinum based radiochemotherapies: Free radical mechanisms and radiotherapy sensitizers. Free Radic Biol Med 2016; 99:99-109. [PMID: 27417937 DOI: 10.1016/j.freeradbiomed.2016.07.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 06/18/2016] [Accepted: 07/08/2016] [Indexed: 12/22/2022]
Abstract
The radiosensitizing ability of Pt drugs can in the first instance be predicted based on the ease that they undergo activation by electron attachment accompanied by structural modification prior to forming Pt-DNA adducts. Unlike cisplatin, carboplatin and nedaplatin, oxaliplatin does not undergo a facile dissociative electron transfer reaction when an electron is attached. However, oxaliplatin undergoes a facile nucleophilic assisted proton coupled electron transfer (NAPCET), which may be key element of the success of FOLFOX radiochemotherapy against certain cancers. Under acidic conditions, oxaliplatin is a superior radiosensitizer to cisplatin or carboplatin, in the presence of nucleophiles such as water, chloride ions or thiols. Oxaliplatin may also be activated as a platinating agent and radiosensitizer by a minor hydrogen radical free radical mechanism as well as the more dominant NAPCET mechanism. The radiosensitizing synergism that is shown when oxaliplatin is combined with 5-fluorouracil can be due to the formation of a π complex between the two drugs, which is more potent under acidic conditions. These factors have a bearing on Pt based chemotherapy clinical regimes as well as clinical radiochemotherapy regimes, and could be a basis for optimizing how such drug schedules are administered.
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Wang S, Zhao P, Zhang C, Bu Y. Mechanisms Responsible for High Energy Radiation Induced Damage to Single-Stranded DNA Modified by Radiosensitizing 5-Halogenated Deoxyuridines. J Phys Chem B 2016; 120:2649-57. [PMID: 26913546 DOI: 10.1021/acs.jpcb.5b11432] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Experimental studies showed that high energy radiation induced base release and DNA backbone breaks mainly occur at the neighboring 5' nucleotide when a single-stranded DNA is modified by radiosensitizing 5-halogenated deoxyuridines. However, no mechanism can be used to interpret these experimental observations. To better understand the radiosensitivity of 5-halogenated deoxyuridines, mechanisms involving hydrogen abstraction by the uracil-5-yl radical from the C2' and C3' positions of an adjacent nucleotide separately followed by the C3'-O3' or N-glycosidic bond rupture and the P-O3' bond breakage are investigated in the DNA sequence 5'-TU(•)-3' employing density functional theory calculations in the present study. It is found that hydrogen abstractions from both positions are comparable with the one from the C2' site slightly more favorable. The N-glycosidic bond cleavage in the neighboring 5' nucleotide following the internucleotide C2'-Ha abstraction is estimated to have the lowest activation free energies, indicating that the adjacent 5' base release dominates electron induced damage to single-stranded DNA incorporated by 5-halogenated deoxyuridines. Relative to the P-O3' bond breakage after the internucleotide C3'-H abstraction, the C3'-O3' bond rupture in the neighboring 5' nucleotide following the internucleotide C2'-Ha abstraction is predicted to have a lower activation free energy, implying that single-stranded DNA backbone breaks are prone to occur at the C3'-O3' bond site. The 5'-TU(•)-3' species has substantial electron affinity and can even capture a hydrated electron, forming the 5'-TU(-)-3' anion. However, the electron induced C3'-O3' bond rupture in 5'-TU(-)-3' anion via a pathway of internucleotide proton abstraction is only minor in both the gas phase and aqueous solution. The present theoretical predictions can interpret rationally experimental observations, thereby demonstrating that the mechanisms proposed here are responsible for high energy radiation induced damage to single-stranded DNA incorporated by radiosensitizing 5-halogenated deoxyuridines. By comparing with previous results, our work proves that the radiosensitizing action of 5-bromo-2-deoxyuridine is not weaker but stronger than its isomer 6-bromo-2-deoxyuridine on the basis of the available data.
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Affiliation(s)
- Shoushan Wang
- School of Chemistry and Chemical Engineering, Institute of Theoretical Chemistry, Shandong University , Jinan 250100, P. R. China
| | - Peiwen Zhao
- School of Chemistry and Chemical Engineering, Institute of Theoretical Chemistry, Shandong University , Jinan 250100, P. R. China
| | - Changzhe Zhang
- School of Chemistry and Chemical Engineering, Institute of Theoretical Chemistry, Shandong University , Jinan 250100, P. R. China
| | - Yuxiang Bu
- School of Chemistry and Chemical Engineering, Institute of Theoretical Chemistry, Shandong University , Jinan 250100, P. R. China
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Rak J, Chomicz L, Wiczk J, Westphal K, Zdrowowicz M, Wityk P, Żyndul M, Makurat S, Golon Ł. Mechanisms of Damage to DNA Labeled with Electrophilic Nucleobases Induced by Ionizing or UV Radiation. J Phys Chem B 2015; 119:8227-38. [PMID: 26061614 DOI: 10.1021/acs.jpcb.5b03948] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hypoxia--a hallmark of solid tumors--makes hypoxic cells radioresistant. On the other hand, DNA, the main target of anticancer therapy, is not sensitive to the near UV photons and hydrated electrons, one of the major products of water radiolysis under hypoxic conditions. A possible way to overcome these obstacles to the efficient radio- and photodynamic therapy of cancer is to sensitize the cellular DNA to electrons and/or ultraviolet radiation. While incorporated into genomic DNA, modified nucleosides, 5-bromo-2'-deoxyuridine in particular, sensitize cells to both near-ultraviolet photons and γ rays. It is believed that, in both sensitization modes, the reactive nucleobase radical is formed as a primary product which swiftly stabilizes, leading to serious DNA damage, like strand breaks or cross-links. However, despite the apparent similarity, such radio- and photosensitization of DNA seems to be ruled by fundamentally different mechanisms. In this review, we demonstrate that the most important factors deciding on radiodamage to the labeled DNA are (i) the electron affinity (EA) of modified nucleoside (mNZ), (ii) the local surroundings of the label that significantly influences the EA of mNZ, and (iii) the strength of the chemical bond holding together the substituent and a nucleobase. On the other hand, we show that the UV damage to sensitized DNA is governed by long-range photoinduced electron transfer, the efficiency of which is controlled by local DNA sequences. A critical review of the literature mechanisms concerning both types of damage to the labeled biopolymer is presented. Ultimately, the perspectives of studies on DNA sensitization in the context of cancer therapy are discussed.
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Affiliation(s)
- Janusz Rak
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Lidia Chomicz
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Justyna Wiczk
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Kinga Westphal
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Magdalena Zdrowowicz
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Paweł Wityk
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Michał Żyndul
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Samanta Makurat
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Łukasz Golon
- Faculty of Chemistry University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
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Golon Ł, Chomicz L, Rak J. Electron-induced single strand break in the nucleotide of 5- and 6-bromouridine. A DFT study. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.08.049] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Castrovilli MC, Bolognesi P, Cartoni A, Catone D, O'Keeffe P, Casavola AR, Turchini S, Zema N, Avaldi L. Photofragmentation of halogenated pyrimidine molecules in the VUV range. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:351-367. [PMID: 24385396 DOI: 10.1007/s13361-013-0783-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 11/11/2013] [Accepted: 11/17/2013] [Indexed: 06/03/2023]
Abstract
In the present work, we studied the photoinduced ion chemistry of the halogenated pyrimidines, a class of prototype radiosensitizing molecules, in the energy region 9-15 eV. The work was stimulated by previous studies on inner shell site-selective fragmentation of the pyrimidine molecule, which have shown that the fragmentation is governed by the population/formation of specific ionic states with a hole in valence orbitals, which in turn correlate to accessible dissociation limits. The combined experimental and theoretical study of the appearance energies of the main fragments provides information on the geometric structure of the products and on the role played by the specific halogen atom and the site of halogenation in the dissociation process. This information can be used to gain new insights on the elementary mechanisms that could possibly explain the enhanced radiation damage to the DNA bases or to the medium in which the bases are embedded, thereby contributing to their radiosensitizing effect.
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Chomicz L, Rak J, Storoniak P. Electron-induced elimination of the bromide anion from brominated nucleobases. A computational study. J Phys Chem B 2012; 116:5612-9. [PMID: 22510158 DOI: 10.1021/jp3008738] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The enhancement of radiodamage to DNA labeled with halonucleobases is attributed to the reactive radical produced from a halonucleobase by the attachment of an electron. We examined at the B3LYP/6-31++G** level electron capture by four brominated nucleobases (BrNBs): 8-bromo-9-methyladenine, 8-bromo-9-methylguanine, 5-bromo-1-methylcytosine, and 5-bromo-1-methyluracil followed by the release of the bromide anion and a nucleobase radical. We demonstrate that neutral BrNBs in both gas and aqueous phases are better electron acceptors than unsubstituted NBs and that resulting anion radicals, BrNBs(•-), can easily transform into the product complex of the bromide anion and the nucleobase radical ([Br(-)···NB(•)]). The overall thermodynamic stimulus for the process starting with the neutral BrNB and ending with the isolated bromide anion and the NB(•) radical is similar in the case of all four BrNBs studied, which suggests their comparable radiosensitizing capabilities.
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Affiliation(s)
- Lidia Chomicz
- Department of Chemistry, University of Gdańsk , Sobieskiego 18, 80-952 Gdańsk, Poland
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Polska K, Rak J, Bass AD, Cloutier P, Sanche L. Electron stimulated desorption of anions from native and brominated single stranded oligonucleotide trimers. J Chem Phys 2012; 136:075101. [PMID: 22360262 PMCID: PMC3813477 DOI: 10.1063/1.3685587] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We measured the low energy electron stimulated desorption (ESD) of anions from thin films of native (TXT) and bromine monosubstituted (TBrXT) oligonucleotide trimers deposited on a gold surface (T = thymidine, X = T, deoxycytidine (C), deoxyadenosine (A) or deoxyguanosine (G), Br = bromine). The desorption of H(-), CH(3)(-)/NH(-), O(-)/NH(2)(-), OH(-), CN(-), and Br(-) was induced by 0 to 20 eV electrons. Dissociative electron attachment, below 12 eV, and dipolar dissociation, above 12 eV, are responsible for the formation of these anions. The comparison of the results obtained for the native and brominated trimers suggests that the main pathways of TBrXT degradation correspond to the release of the hydride and bromide anions. Significantly, the presence of bromine in oligonucleotide trimers blocks the electron-induced degradation of nuclobases as evidenced by a dramatic decrease in CN(-) desorption. An increase in the yields of OH(-) is also observed. The debromination yield of particular oligonucleotides diminishes in the following order: BrdU > BrdA > BrdG > BrdC. Based on these results, 5-bromo-2(')-deoxyuridine appears to be the best radiosensitizer among the studied bromonucleosides.
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Affiliation(s)
- Katarzyna Polska
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
| | - Janusz Rak
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
| | - Andrew D. Bass
- Research Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Pierre Cloutier
- Research Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Léon Sanche
- Research Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Li X, Chen J, Bowen KH. Photoelectron spectroscopic study of the negative ions of 4-thiouracil and 2,4-dithiouracil. J Chem Phys 2011; 134:074304. [DOI: 10.1063/1.3555177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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