1
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Lee EM, Setterholm NA, Hajjar M, Barpuzary B, Chaput JC. Stability and mechanism of threose nucleic acid toward acid-mediated degradation. Nucleic Acids Res 2023; 51:9542-9551. [PMID: 37650628 PMCID: PMC10570051 DOI: 10.1093/nar/gkad716] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 07/21/2023] [Accepted: 08/18/2023] [Indexed: 09/01/2023] Open
Abstract
Xeno-nucleic acids (XNAs) have gained significant interest as synthetic genetic polymers for practical applications in biomedicine, but very little is known about their biophysical properties. Here, we compare the stability and mechanism of acid-mediated degradation of α-l-threose nucleic acid (TNA) to that of natural DNA and RNA. Under acidic conditions and elevated temperature (pH 3.3 at 90°C), TNA was found to be significantly more resistant to acid-mediated degradation than DNA and RNA. Mechanistic insights gained by reverse-phase HPLC and mass spectrometry indicate that the resilience of TNA toward low pH environments is due to a slower rate of depurination caused by induction of the 2'-phosphodiester linkage. Similar results observed for 2',5'-linked DNA and 2'-O-methoxy-RNA implicate the position of the phosphodiester group as a key factor in destabilizing the formation of the oxocarbenium intermediate responsible for depurination and strand cleavage of TNA. Biochemical analysis indicates that strand cleavage occurs by β-elimination of the 2'-phosphodiester linkage to produce an upstream cleavage product with a 2'-threose sugar and a downstream cleavage product with a 3' terminal phosphate. This work highlights the unique physicochemical properties available to evolvable non-natural genetic polymers currently in development for biomedical applications.
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Affiliation(s)
- Erica M Lee
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Noah A Setterholm
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Mohammad Hajjar
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Bhawna Barpuzary
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - John C Chaput
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
- Department of Chemistry, University of California, Irvine, CA 92697-3958, USA
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3958, USA
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, CA 92697-3958, USA
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2
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Bell M, Kumar A, Sevilla MD. Electron-Induced Repair of 2'-Deoxyribose Sugar Radicals in DNA: A Density Functional Theory (DFT) Study. Int J Mol Sci 2021; 22:ijms22041736. [PMID: 33572317 PMCID: PMC7916153 DOI: 10.3390/ijms22041736] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/01/2021] [Accepted: 02/05/2021] [Indexed: 12/19/2022] Open
Abstract
In this work, we used ωB97XD density functional and 6-31++G** basis set to study the structure, electron affinity, populations via Boltzmann distribution, and one-electron reduction potentials (E°) of 2′-deoxyribose sugar radicals in aqueous phase by considering 2′-deoxyguanosine and 2′-deoxythymidine as a model of DNA. The calculation predicted the relative stability of sugar radicals in the order C4′• > C1′• > C5′• > C3′• > C2′•. The Boltzmann distribution populations based on the relative stability of the sugar radicals were not those found for ionizing radiation or OH-radical attack and are good evidence the kinetic mechanisms of the processes drive the products formed. The adiabatic electron affinities of these sugar radicals were in the range 2.6–3.3 eV which is higher than the canonical DNA bases. The sugar radicals reduction potentials (E°) without protonation (−1.8 to −1.2 V) were also significantly higher than the bases. Thus the sugar radicals will be far more readily reduced by solvated electrons than the DNA bases. In the aqueous phase, these one-electron reduced sugar radicals (anions) are protonated from solvent and thus are efficiently repaired via the “electron-induced proton transfer mechanism”. The calculation shows that, in comparison to efficient repair of sugar radicals by the electron-induced proton transfer mechanism, the repair of the cyclopurine lesion, 5′,8-cyclo-2′-dG, would involve a substantial barrier.
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3
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A theoretical study towards understanding the origin of DNA oxidation products. J PHYS ORG CHEM 2020. [DOI: 10.1002/poc.4176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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4
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Kao MH, Venkatraman RK, Ashfold MNR, Orr-Ewing AJ. Effects of ring-strain on the ultrafast photochemistry of cyclic ketones. Chem Sci 2020; 11:1991-2000. [PMID: 34123294 PMCID: PMC8148387 DOI: 10.1039/c9sc05208a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ring-strain in cyclic organic molecules is well-known to influence their chemical reactivity. Here, we examine the consequence of ring-strain for competing photochemical pathways that occur on picosecond timescales. The significance of Norrish Type-I photochemistry is explored for three cyclic ketones in cyclohexane solutions at ultraviolet (UV) excitation wavelengths from 255–312 nm, corresponding to an π* ← n excitation to the lowest excited singlet state (S1). Ultrafast transient absorption spectroscopy with broadband UV/visible probe laser pulses reveals processes common to cyclobutanone, cyclopentanone and cyclohexanone, occurring on timescales of ≤1 ps, 7–9 ps and >500 ps. These kinetic components are respectively assigned to prompt cleavage of an α C–C bond in the internally excited S1-state molecules prepared by UV absorption, vibrational cooling of these hot-S1 molecules to energies below the barrier to C–C bond cleavage on the S1 state potential energy surface (with commensurate reductions in the energy-dependent α-cleavage rate), and slower loss of thermalized S1-state population. The thermalized S1-state molecules may competitively decay by activated reaction over the barrier to α C–C bond fission on the S1-state potential energy surface, internal conversion to the ground (S0) electronic state, or intersystem crossing to the lowest lying triplet state (T1) and subsequent C–C bond breaking. The α C–C bond fission barrier height in the S1 state is significantly reduced by the ring-strain in cyclobutanone, affecting the relative contributions of the three decay time components which depend systematically on the excitation energy above the S1-state energy barrier. Transient infra-red absorption spectra obtained after UV excitation identify ring-opened ketene photoproducts of cyclobutanone and their timescales for formation. Ultrafast spectroscopy of ring-opening in three cyclic ketones reveals how ring-strain affects Norrish Type-I α-cleavage mechanisms.![]()
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Affiliation(s)
- Min-Hsien Kao
- School of Chemistry, University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | | | - Michael N R Ashfold
- School of Chemistry, University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close Bristol BS8 1TS UK
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5
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Wang SD, Zhang RB, Cadet J. Enhanced reactivity of the pyrimidine peroxyl radical towards the C–H bond in duplex DNA – a theoretical study. Org Biomol Chem 2020; 18:3536-3543. [DOI: 10.1039/d0ob00302f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The peroxyl radical exhibits a much stronger reactivity towards C1′–H1′ in duplex DNA with respect to single-stranded DNA.
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Affiliation(s)
- Shu-dong Wang
- School of Chemistry and Chemical Engineering
- Beijing Institute of Technology
- Beijing
- China
| | - Ru-bo Zhang
- School of Chemistry and Chemical Engineering
- Beijing Institute of Technology
- Beijing
- China
| | - Jean Cadet
- Département de Médecine Nucléaire et Radiobiologie
- Faculté de Médecine
- Université de Sherbrooke
- Sherbrooke
- Canada JIH 5N4
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6
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Robert G, Wagner JR. Tandem Lesions Arising from 5-(Uracilyl)methyl Peroxyl Radical Addition to Guanine: Product Analysis and Mechanistic Studies. Chem Res Toxicol 2019; 33:565-575. [PMID: 31820932 DOI: 10.1021/acs.chemrestox.9b00407] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction of hydroxyl radical (HO•) with thymine in DNA generates 5-(uracilyl)-methyl radicals (T•) and the corresponding methylperoxyl radical (TOO•) in the presence of O2, which in turn propagates damage by reacting with a vicinal nucleobase. This leads to so-called double or tandem lesions. Because methyl oxidation products of thymine are major products, we investigated the reactivity of TOO• using a photolabile precursor: 5-(phenylthiomethyl)uracil (TSPh). The precursor was prepared and incorporated into a DNA trinucleotide: 5'-d(GpTSPhpA)-3' (G-TSPh-A). Upon photolysis, the resulting products were characterized by LC-MS/MS. Thereby, we identified four tandem lesions involving GpT, which include either 2,6-diamino-4-hydroxy-5-formamidopyrimidine (fapyG) or 8-oxo-7,8-dihydroguanine (oxoG) in tandem with either 5-formyluracil (fU) or 5-hydroxymethyluracil (hmU). The formation of these tandem lesions is explained by initial addition of TOO• to the C8 of guanine moiety, giving an N7-guanine cross-linked radical. The latter radical undergoes either reduction to an 7,8-saturated endoperoxide or oxidation to an 7,8-unsaturated endoperoxide, which transform into fapyG-fU-A and oxoG-fU-A, respectively. This is supported by the effect of a reducing (dithiothreitol) and oxidizing agent (Fe3+) on product formation. This study expands the repertoire of tandem lesions that can occur at GpT sequences and underlines the importance of redox environment.
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Affiliation(s)
- Gabriel Robert
- Département de Biochimie, Faculté de Médecine et des Sciences de la Santé , Université de Sherbrooke , Sherbrooke , Québec J1H 5N4 , Canada
| | - J Richard Wagner
- Département de Biochimie, Faculté de Médecine et des Sciences de la Santé , Université de Sherbrooke , Sherbrooke , Québec J1H 5N4 , Canada.,Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la Santé , Université de Sherbrooke , Sherbrooke , Québec J1H 5N4 , Canada
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7
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Zhao S, Eriksson LA, Zhang RB. Theoretical Insights on the Inefficiency of RNA Oxidative Damage under Aerobic Conditions. J Phys Chem A 2017; 122:431-438. [PMID: 29206039 DOI: 10.1021/acs.jpca.7b10711] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Oxidative damage to RNA has been linked to change or loss of RNA function and development of many human age-related diseases. However, knowledge on the nature of RNA oxidative damage is relatively limited. In this study, oxidative damage to RNA is investigated under anaerobic and aerobic conditions by exploring the properties and reactions of 5-hydroxyl-2'-uridin-6-yl and its peroxyl diastereoisomers in the RNA strand, respectively. Selective addition of OH to the nucleic base from the 5'-end is studied at the molecular level for the first time, explaining the large number of the 5S-isomer available for further reactions. Our results provide clear evidence that the efficiency of C2'-H2' bond activation in the peroxyl isomers is lower than in the carbon radical species. An exception is observed for the isomer cis-(5S,6R)-A1, whose internucleotidyl H2'-abstraction barrier is far smaller than that in the corresponding C6-yl radical. However, analysis of the equilibrium species distribution reveals that the amount of cis-(5S,6R)-A1 is very small among the peroxyl diastereoisomers, and hence the resulting products from direct strand scission should be a less important component in RNA oxidative damage. The species with maximum distribution is the cis-(5S,6R)-B1 isomer, which is derived from cis-(5S,6R)-A1 and has a moderate intranucleotidyl H2'-abstraction barrier. More importantly, the reaction is mildly exothermic. These results show that the main fraction of the intranucleotidyl H2'-abstraction intermediates can be formed from the cis-(5S,6R)-B1 isomer. The absolute reduction potentials, the hydrogen atom binding energies, and the key structural parameters of the C6-peroxyl species are used to understand the diverse reactivity of the cis-(5S,6R) diastereoisomers toward the C2'-H2' bonds activation. The present study shows that in addition to the selectivity of the OH radical addition, there is a strong correlation between the conformation of the modified uracil base and its reactivity in RNA oxidative damage.
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Affiliation(s)
- Shuang Zhao
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology , South Street No. 5, Zhongguancun, Haidian District, Beijing 100081, China
| | - Leif A Eriksson
- Department of Chemistry and Molecular Biology, University of Gothenburg , Box 462, 405 30 Göteborg, Sweden
| | - Ru-Bo Zhang
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology , South Street No. 5, Zhongguancun, Haidian District, Beijing 100081, China
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8
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Zheng L, Griesser M, Pratt DA, Greenberg MM. Aminyl Radical Generation via Tandem Norrish Type I Photocleavage, β-Fragmentation: Independent Generation and Reactivity of the 2'-Deoxyadenosin- N6-yl Radical. J Org Chem 2017; 82:3571-3580. [PMID: 28318253 DOI: 10.1021/acs.joc.7b00093] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Formal hydrogen atom abstraction from the nitrogen-hydrogen bonds in purine nucleosides produces reactive intermediates that are important in nucleic acid oxidation. Herein we describe an approach for the independent generation of the purine radical resulting from hydrogen atom abstraction from the N6-amine of 2'-deoxyadenosine (dA•). The method involves sequential Norrish Type I photocleavage of a ketone (7b) and β-fragmentation of the initially formed alkyl radical (8b) to form dA• and acetone. The formation of dA• was followed by laser flash photolysis, which yields a transient with λmax ≈ 340 nm and a broader weaker absorption centered at ∼560 nm. This transient grows in at ≥2 × 105 s-1; however, computations and reactivity data suggest that β-fragmentation occurs much faster, implying the consumption of dA• as it is formed. Continuous photolysis of 7b in the presence of ferrous ion or thiophenol produces good yields of dA, whereas less reactive thiols afford lower yields presumably due to a polarity mismatch. This tandem photochemical, β-fragmentation method promises to be useful for site-specific production of dA• in nucleic acid oligomers and/or polymers and also for the production of aminyl radicals, in general.
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Affiliation(s)
- Liwei Zheng
- Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Markus Griesser
- Department of Chemistry & Biomolecular Sciences, University of Ottawa , 10 Marie Curie Pvt., Ottawa, Canada
| | - Derek A Pratt
- Department of Chemistry & Biomolecular Sciences, University of Ottawa , 10 Marie Curie Pvt., Ottawa, Canada
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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9
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Wrigstedt P, Iashin V, Lagerblom K, Keskiväli J, Chernichenko K, Repo T. Syntheses of C-6 Aryl- and Alkynyl-Substituted Thymidines from Thymidine trans-5,6-Bromohydrins. European J Org Chem 2017. [DOI: 10.1002/ejoc.201601219] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Pauli Wrigstedt
- Department of Chemistry; University of Helsinki; P. O. Box 55 (A. I. Virtasen aukio 1) 00014 Helsinki Finland
| | - Vladimir Iashin
- Department of Chemistry; University of Helsinki; P. O. Box 55 (A. I. Virtasen aukio 1) 00014 Helsinki Finland
| | - Kalle Lagerblom
- Department of Chemistry; University of Helsinki; P. O. Box 55 (A. I. Virtasen aukio 1) 00014 Helsinki Finland
| | - Juha Keskiväli
- Department of Chemistry; University of Helsinki; P. O. Box 55 (A. I. Virtasen aukio 1) 00014 Helsinki Finland
| | - Konstantin Chernichenko
- Department of Chemistry; University of Helsinki; P. O. Box 55 (A. I. Virtasen aukio 1) 00014 Helsinki Finland
| | - Timo Repo
- Department of Chemistry; University of Helsinki; P. O. Box 55 (A. I. Virtasen aukio 1) 00014 Helsinki Finland
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10
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Paul R, Greenberg MM. Mechanistic Studies on RNA Strand Scission from a C2'-Radical. J Org Chem 2016; 81:9199-9205. [PMID: 27668445 DOI: 10.1021/acs.joc.6b01760] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The C2'-carbon-hydrogen bond in ribonucleotides is significantly weaker than other carbohydrate carbon-hydrogen bonds in RNA or DNA. Independent generation of the C2'-uridine radical (1) in RNA oligonucleotides via Norrish type I photocleavage of a ketone-substituted nucleotide yields direct strand breaks via cleavage of the β-phosphate. The reactivity of 1 in different sequences and under a variety of conditions suggests that the rate constant for strand scission is significantly greater than 106 s-1 at pH 7.2. The initially formed C2'-radical (1) is not trapped under a variety of conditions, consistent with computational studies ( Chem.-Eur. J. 2009 , 15 , 2394 ) that suggest that the barrier to strand scission is very low and that synchronous proton transfer from the 2'-hydroxyl to the departing phosphate group facilitates cleavage. The C2'-radical could be a significant contributor to RNA strand scission by the hydroxyl radical, particularly under anaerobic conditions where 1 can be produced from nucleobase radicals.
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Affiliation(s)
- Rakesh Paul
- 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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11
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Abstract
Nucleobase radicals are major products of the reactions between nucleic acids and hydroxyl radical, which is produced via the indirect effect of ionizing radiation. The nucleobase radicals also result from hydration of cation radicals that are produced via the direct effect of ionizing radiation. The role that nucleobase radicals play in strand scission has been investigated indirectly using ionizing radiation to generate them. More recently, the reactivity of nucleobase radicals resulting from formal hydrogen atom or hydroxyl radical addition to pyrimidines has been studied by independently generating the reactive intermediates via UV-photolysis of synthetic precursors. This approach has provided control over where the reactive intermediates are produced within biopolymers and facilitated studying their reactivity. The contributions to our understanding of pyrimidine nucleobase radical reactivity by this approach are summarized.
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Affiliation(s)
- Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218
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12
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Wrigstedt P, Kavakka J, Heikkinen S, Nieger M, Räisänen M, Repo T. The Reactivity of Thymine and Thymidine 5,6-Epoxides with Organometallic Reagents - A Route to Thymidine (6-4) Photoproduct Analogues. J Org Chem 2016; 81:3848-59. [PMID: 27080560 DOI: 10.1021/acs.joc.6b00495] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This report describes an efficient procedure for the generation and isolation of various thymine and thymidine 5,6-epoxides from the corresponding trans-5,6-bromohydrins by reaction with triethylamine. The quantitative isolation of the epoxides, accomplished by solvent precipitation of triethylamine hydrobromide, enabled their regiospecific ring-opening at C6 position by organometallic nucleophiles. The reaction was amenable to a broad range of alkyl, aryl, alkenyl, and alkynyl organomagnesium, -zinc, -aluminum, or -boron reagents, although the reactivity was strongly affected by the electronic effects of N3 protecting group. Additionally, the reaction featured excellent cis-diastereoselectivity providing access to C6-carbon-functionalized dihydrothymidine cis-alcohols, which are synthetic derivatives of UV-induced DNA lesions, namely, thymidine (6-4) photoproducts.
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Affiliation(s)
- Pauli Wrigstedt
- Department of Chemistry, †Laboratory of Inorganic Chemistry and ‡Laboratory of Organic Chemistry, University of Helsinki , P.O. Box 55, Helsinki FIN-00014, Finland
| | - Jari Kavakka
- Department of Chemistry, †Laboratory of Inorganic Chemistry and ‡Laboratory of Organic Chemistry, University of Helsinki , P.O. Box 55, Helsinki FIN-00014, Finland
| | - Sami Heikkinen
- Department of Chemistry, †Laboratory of Inorganic Chemistry and ‡Laboratory of Organic Chemistry, University of Helsinki , P.O. Box 55, Helsinki FIN-00014, Finland
| | - Martin Nieger
- Department of Chemistry, †Laboratory of Inorganic Chemistry and ‡Laboratory of Organic Chemistry, University of Helsinki , P.O. Box 55, Helsinki FIN-00014, Finland
| | - Minna Räisänen
- Department of Chemistry, †Laboratory of Inorganic Chemistry and ‡Laboratory of Organic Chemistry, University of Helsinki , P.O. Box 55, Helsinki FIN-00014, Finland
| | - Timo Repo
- Department of Chemistry, †Laboratory of Inorganic Chemistry and ‡Laboratory of Organic Chemistry, University of Helsinki , P.O. Box 55, Helsinki FIN-00014, Finland
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13
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Zhao S, Zhang RB, Li ZS. A new understanding towards the reactivity of DNA peroxy radicals. Phys Chem Chem Phys 2016; 18:23763-8. [DOI: 10.1039/c6cp04720c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
New radical reaction paths for the formation of DNA oxidation products are suggested, which are strongly different from the previously suggested paths with the tetraoxide intermediate.
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Affiliation(s)
- Shuang Zhao
- School of Chemistry
- Beijing Institute of Technology
- 100081 Beijing
- China
| | - Ru-bo Zhang
- School of Chemistry
- Beijing Institute of Technology
- 100081 Beijing
- China
| | - Ze-sheng Li
- School of Chemistry
- Beijing Institute of Technology
- 100081 Beijing
- China
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14
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Greenberg MM. Reactivity of Nucleic Acid Radicals. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2016; 50:119-202. [PMID: 28529390 DOI: 10.1016/bs.apoc.2016.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Nucleic acid oxidation plays a vital role in the etiology and treatment of diseases, as well as aging. Reagents that oxidize nucleic acids are also useful probes of the biopolymers' structure and folding. Radiation scientists have contributed greatly to our understanding of nucleic acid oxidation using a variety of techniques. During the past two decades organic chemists have applied the tools of synthetic and mechanistic chemistry to independently generate and study the reactive intermediates produced by ionizing radiation and other nucleic acid damaging agents. This approach has facilitated resolving mechanistic controversies and lead to the discovery of new reactive processes.
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15
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Paul R, Greenberg MM. Rapid RNA strand scission following C2'-hydrogen atom abstraction. J Am Chem Soc 2015; 137:596-9. [PMID: 25580810 DOI: 10.1021/ja511401g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
C2'-Nucleotide radicals have been proposed as key intermediates in direct strand break formation in RNA exposed to ionizing radiation. Uridin-2'-yl radical (1) was independently generated in single- and double-stranded RNA via photolysis of a ketone precursor. Direct stand breaks result from heterolytic cleavage of the adjacent C3'-carbon-oxygen bond. Trapping of 1 by O2 or β-mercaptoethanol (1 M) does not compete with strand scission, indicating that phosphate elimination is >10(6) s(-1). Uracil loss also does not compete with strand scission. When considered in conjunction with reports that nucleobase radicals produce 1, this chemistry explains why RNA is significantly more susceptible to strand scission by ionizing radiation (hydroxyl radical) than is DNA.
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Affiliation(s)
- Rakesh Paul
- Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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16
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Abstract
The uridin-2'-yl radical (1) has been proposed as an intermediate during RNA oxidation. However, its reactivity has not been thoroughly studied due to the complex conditions under which it is typically generated. The uridin-2'-yl radical was independently generated from a benzyl ketone (2a) via Norrish type I photocleavage upon irradiation at λmax = 350 nm. Dioxygen and β-mercaptoethanol are unable to compete with loss of uracil from 1 in phosphate buffer. Thiol trapping competes with uracil fragmentation in less polar solvent conditions. This is ascribed mostly to a reduction in the rate constant for uracil elimination in the less polar solvent. Hydrogen atom transfer to 1 from β-mercaptoethanol occurs exclusively from the α-face to produce arabinouridine. Mass balances range from 72 to 95%. Furthermore, the synthesis of 2a is amenable to formation of the requisite phosphoramidite for solid-phase oligonucleotide synthesis. This and the fidelity with which the urdin-2'-yl radical is generated from 2a suggest that this precursor should be useful for studying the radical's reactivity in synthetic oligonucleotides.
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Affiliation(s)
- Rakesh Paul
- 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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17
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Abstract
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Nucleobase radicals are a major family
of reactive species produced
in DNA as a result of oxidative stress. Two such radicals, 5-hydroxy-5,6-dihydrothymidin-6-yl
radical (1) and 5,6-dihydrouridin-6-yl radical (5), were independently generated within chemically synthesized
oligonucleotides from photochemical precursors. Neither nucleobase
radical produces direct strand breaks or alkali-labile lesions in
single or double stranded DNA. The respective peroxyl radicals, resulting
from O2 trapping, add to 5′-adjacent nucleobases,
with a preference for dG. Distal dG’s are also oxidatively
damaged by the peroxyl radicals. Experiments using a variety of sequences
indicate that distal damage occurs via covalent modification of the
5′-adjacent dG, but there is no evidence for electron transfer
by the nucleobase peroxyl radicals.
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Affiliation(s)
- Joanna Maria N San Pedro
- Department of Chemistry, Johns Hopkins University , 3400 N. Charles St., Baltimore, Maryland 21218, United States
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18
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Insight into reaction mechanism and product formation a C8-purine radical in RNA: a theoretical perspective. Theor Chem Acc 2013. [DOI: 10.1007/s00214-013-1355-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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19
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Morinaga H, Kizaki S, Takenaka T, Kanesato S, Sannohe Y, Tashiro R, Sugiyama H. Photoreactivities of 5-Bromouracil-containing RNAs. Bioorg Med Chem 2013; 21:466-9. [DOI: 10.1016/j.bmc.2012.11.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Revised: 11/10/2012] [Accepted: 11/10/2012] [Indexed: 11/16/2022]
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20
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Abstract
In this chapter, most of the reported work deals with the photochemistry of carbonyl compounds; however, the photoreactions of other functions, such as the photo-Claisen rearrangement or the photocleavage of cyclic ethers, are also included. In the present volume, time coverage is 2010–2011, and only original research articles are quoted. In general, reviews or purely theoretical calculations are not systematically included. As usually, the material is organized according to established types of reactions (e.g., Norrish I/II, hydrogen abstraction, Paternò-Büchi, photoelimination, photo-Fries/photo-Claisen, etc.). After presenting the basic photochemical aspects, more specific findings are reported. They include synthetic applications, stereoselectivity, and biological or technological implications. Next, the attention is focused on photochemical reactions in anisotropic media, including (micro)heterogeneous or supramolecular systems, solid matrixes or fully organized crystals. Finally, mechanistic studies based on direct experimental evidence are highlighted, especially when transient absorption spectroscopy or related ultrafast detection are employed.
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Affiliation(s)
- M. Consuelo Jiménez
- Departamento de Química, Instituto de Tecnología Química UPV-CSIC Universidad Politécnica de Valencia camino de Vera s/n, E-46022 Valencia Spain
| | - Miguel A. Miranda
- Departamento de Química, Instituto de Tecnología Química UPV-CSIC Universidad Politécnica de Valencia camino de Vera s/n, E-46022 Valencia Spain
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21
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Geiermann AS, Micura R. Selective desulfurization significantly expands sequence variety of 3'-peptidyl-tRNA mimics obtained by native chemical ligation. Chembiochem 2012; 13:1742-5. [PMID: 22786696 PMCID: PMC3430856 DOI: 10.1002/cbic.201200368] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Indexed: 12/30/2022]
Affiliation(s)
- Anna-Skrollan Geiermann
- Institute of Organic Chemistry, CCB: Center for Chemistry and Biomedicine, University of Innsbruck6020 Innsbruck (Austria) E-mail:
| | - Ronald Micura
- Institute of Organic Chemistry, CCB: Center for Chemistry and Biomedicine, University of Innsbruck6020 Innsbruck (Austria) E-mail:
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22
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Kumar A, Pottiboyina V, Sevilla MD. One-electron oxidation of neutral sugar radicals of 2'-deoxyguanosine and 2'-deoxythymidine: a density functional theory (DFT) study. J Phys Chem B 2012; 116:9409-16. [PMID: 22793263 DOI: 10.1021/jp3059068] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One electron oxidation of neutral sugar radicals has recently been suggested to lead to important intermediates in the DNA damage process culminating in DNA strand breaks. In this work, we investigate sugar radicals in a DNA model system to understand the energetics of sugar radical formation and oxidation. The geometries of neutral sugar radicals C(1')(•), C(2')(•), C(3')(•), C(4')(•), and C(5')(•) of 2'-deoxyguanosine (dG) and 2'-deoxythymidine (dT) were optimized in the gas phase and in solution using the B3LYP and ωB97x functionals and 6-31++G(d) basis set. Their corresponding cations (C(1')(+), C(2')(+), C(3')(+), C(4')(+), and C(5')(+)) were generated by removing an electron (one-electron oxidation) from the neutral sugar radicals, and their geometries were also optimized using the same methods and basis set. The calculation predicts the relative stabilities of the neutral sugar radicals in the order C(1')(•) > C(4')(•) > C(5')(•) > C(3')(•) > C(2')(•), respectively. Of the neutral sugar radicals, C(1')(•) has the lowest vertical ionization potential (IP(vert)), ca. 6.33 eV in the gas phase and 4.71 eV in solution. C(2')(•) has the highest IP(vert), ca. 8.02 eV, in the gas phase, and the resultant C(2') cation is predicted to undergo a barrierless hydride transfer from the C(1') site to produce the C(1') cation. One electron oxidation of C(2')(•) in dG is predicted to result in a low lying triplet state consisting of G(+•) and C(2')(•). The 5',8-cyclo-2'-deoxyguanosin-7-yl radical formed by intramolecular bonding between C(5')(•) and C(8) of guanine transfers spin density from C(5') site to guanine, and this structure has IP(vert) 6.25 and 5.48 eV in the gas phase and in solution.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA
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23
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San Pedro JMN, Greenberg MM. Photochemical generation and reactivity of the major hydroxyl radical adduct of thymidine. Org Lett 2012; 14:2866-9. [PMID: 22616940 DOI: 10.1021/ol301109z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
5,6-Dihydro-5-hydroxythymidin-6-yl radical (1), the major reactive intermediate resulting from hydroxyl radical addition to C5 of the pyrimidine, is produced via 350 nm photolysis of a 2,5-dimethoxyphenylsulfide precursor (2). Competition between O(2) and thiol for 1 suggests that the radical reacts relatively slowly with β-mercaptoethanol compared to other alkyl radicals. Overall, aryl sulfide 2 should be an effective precursor for the major hydroxyl radical adduct of thymidine in DNA.
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Affiliation(s)
- Joanna Maria N San Pedro
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
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24
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Adhikary A, Becker D, Palmer BJ, Heizer AN, Sevilla MD. Direct formation of the C5'-radical in the sugar-phosphate backbone of DNA by high-energy radiation. J Phys Chem B 2012; 116:5900-6. [PMID: 22553971 DOI: 10.1021/jp3023919] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Neutral sugar radicals formed in DNA sugar-phosphate backbone are well-established as precursors of biologically important damage such as DNA strand scission and cross-linking. In this work, we present electron spin resonance (ESR) evidence showing that the sugar radical at C5' (C5'(•)) is one of the most abundant (ca. 30%) sugar radicals formed by γ- and Ar ion-beam irradiated hydrated DNA samples. Taking dimethyl phosphate as a model of sugar-phosphate backbone, ESR and theoretical (DFT) studies of γ-irradiated dimethyl phosphate were carried out. CH(3)OP(O(2)(-))OCH(2)(•) is formed via deprotonation from the methyl group of directly ionized dimethyl phosphate at 77 K. The formation of CH(3)OP(O(2)(-))OCH(2)(•) is independent of dimethyl phosphate concentration (neat or in aqueous solution) or pH. ESR spectra of C5'(•) found in DNA and of CH(3)OP(O(2)(-))OCH(2)(•) do not show an observable β-phosphorus hyperfine coupling (HFC). Furthermore, C5'(•) found in DNA does not show a significant C4'-H β-proton HFC. Applying the DFT/B3LYP/6-31G(d) method, a study of conformational dependence of the phosphorus HFC in CH(3)OP(O(2)(-))OCH(2)(•) shows that in its minimum energy conformation, CH(3)OP(O(2)(-))OCH(2)(•), has a negligible β-phosphorus HFC. On the basis of these results, the formation of radiation-induced C5'(•) is proposed to occur via a very rapid deprotonation from the directly ionized sugar-phosphate backbone, and the rate of this deprotonation must be faster than that of energetically downhill transfer of the unpaired spin (hole) from ionized sugar-phosphate backbone to the DNA bases. Moreover, C5'(•) in irradiated DNA is found to be in a conformation that does not exhibit β-proton or β-phosphorus HFCs.
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Affiliation(s)
- Amitava Adhikary
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA
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25
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Resendiz MJE, Pottiboyina V, Sevilla MD, Greenberg MM. Direct strand scission in double stranded RNA via a C5-pyrimidine radical. J Am Chem Soc 2012; 134:3917-24. [PMID: 22335525 DOI: 10.1021/ja300044e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nucleobase radicals are the major family of reactive intermediates produced when nucleic acids are exposed to γ-radiolysis. The 5,6-dihydrouridin-5-yl radical (1), the formal product of hydrogen atom addition and a model for hydroxyl radical addition, was independently generated from a ketone precursor via Norrish Type I photocleavage in single and double stranded RNA. Radical 1 produces direct strand breaks at the 5'-adjacent nucleotide and only minor amounts of strand scission are observed at the initial site of radical generation. Strand scission occurs preferentially in double stranded RNA and in the absence of O(2). The dependence of strand scission efficiency from the 5,6-dihydrouridin-5-yl radical (1) on secondary structure under anaerobic conditions suggests that this reactivity may be useful for extracting additional RNA structural information from hydroxyl radical reactions. Varying the identity of the 5'-adjacent nucleotide has little effect on strand scission. Internucleotidyl strand scission occurs via β-elimination of the 3'-phosphate following C2'-hydrogen atom abstraction by 1. The subsequently formed olefin cation radical yields RNA fragments containing 3'-phosphate or 3'-deoxy-2'-ketonucleotide termini from competing deprotonation pathways. The ketonucleotide end group is favored in the presence of low concentrations of thiol, presumably by reducing the cation radical to the enol. Competition studies with thiol show that strand scission from the 5,6-dihydrouridin-5-yl radical (1) is significantly faster than from the 5,6-dihydrouridin-6-yl radical (2) and is consistent with computational studies using the G3B3 approach that predict the latter to be more stable than 1 by 2.8 kcal/mol.
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Affiliation(s)
- Marino J E Resendiz
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
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26
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Abstract
The past several years have seen numerous reports of new chemical modifications for use in RNA. In addition, in that time period, we have seen the discovery of several previously unknown naturally occurring modifications that impart novel properties on the parent RNAs. In this review, we describe recent discoveries in these areas with a focus on RNA modifications that introduce spectroscopic tags, reactive handles, or new recognition properties.
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Affiliation(s)
- Kelly Phelps
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Alexi Morris
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Peter A. Beal
- Department
of Chemistry, University of California, Davis, California 95616, United States
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27
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Bietti M, Martella R, Salamone M. Understanding kinetic solvent effects on hydrogen abstraction reactions from carbon by the cumyloxyl radical. Org Lett 2011; 13:6110-3. [PMID: 22026478 DOI: 10.1021/ol202561z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A kinetic study of the hydrogen abstraction reactions from tetrahydrofuran (THF) and cyclohexane (CHX) by the cumyloxyl radical was carried out in different solvents. With THF, a 4.5-fold decrease in rate constant (k(H)) was observed on going from isooctane to 2,2,2-trifluoroethanol. An opposite behavior was observed with CHX, where k(H) increased by a factor 4 on going from isooctane to 2,2,2-trifluoroethanol. The important role of substrate structure and of the solvent hydrogen bond donor ability is discussed.
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Affiliation(s)
- Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università Tor Vergata, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
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28
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Ariza-Mateos A, Prieto-Vega S, Díaz-Toledano R, Birk A, Szeto H, Mena I, Berzal-Herranz A, Gómez J. RNA self-cleavage activated by ultraviolet light-induced oxidation. Nucleic Acids Res 2011; 40:1748-66. [PMID: 21989404 PMCID: PMC3287179 DOI: 10.1093/nar/gkr822] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A novel UV-C-light-induced ribozyme activity was discovered within the highly structured 5'-genomic regions of both Hepatitis C Virus (HCV) and the related Classic Swine Fever Virus (CSFV). Cleavage is mediated by exposure to UV-C light but not by exogenous oxygen radicals. It is also very selective, occurring at base positions HCV C(79) and CSFV A(45) in some molecules and at the immediately adjacent 5'-positions HCV U(78) and CSFV U(44) in others. Among other reaction products, the majority of biochemically active products detected contained 3'-phosphate and 5'-phosphate-end groups at the newly generated termini, along with a much lower amount of 3'-hydroxyl end group. While preservation of an E-loop RNA structure in the vicinity of the cleavage site was a requisite for HCV RNA self-cleavage, this was not the case for CSFV RNA. The short size of the reactive domains (~33 nt), which are compatible with primitive RNA motifs, and the lack of sequence homology, indicate that as-yet unidentified UV-activated ribozymes are likely to be found throughout structured RNAs, thereby providing clues to whether early RNA self-cleavage events were mediated by photosensitive RNA structures.
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Affiliation(s)
- Ascensión Ariza-Mateos
- Laboratory of RNA Archeology, Instituto de Parasitología y Biomedicina 'López-Neyra', CSIC, Armilla, 18100 Granada, Spain
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29
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Salamone M, DiLabio GA, Bietti M. Hydrogen atom abstraction selectivity in the reactions of alkylamines with the benzyloxyl and cumyloxyl radicals. The importance of structure and of substrate radical hydrogen bonding. J Am Chem Soc 2011; 133:16625-34. [PMID: 21895002 DOI: 10.1021/ja206890y] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A time-resolved kinetic study on the hydrogen abstraction reactions from a series of primary and secondary amines by the cumyloxyl (CumO(•)) and benzyloxyl (BnO(•)) radicals was carried out. The results were compared with those obtained previously for the corresponding reactions with tertiary amines. Very different hydrogen abstraction rate constants (k(H)) and intermolecular selectivities were observed for the reactions of the two radicals. With CumO(•), k(H) was observed to decrease on going from the tertiary to the secondary and primary amines. The lowest k(H) values were measured for the reactions with 2,2,6,6-tetramethylpiperidine (TMP) and tert-octylamine (TOA), substrates that can only undergo N-H abstraction. The opposite behavior was observed for the reactions of BnO(•), where the k(H) values increased in the order tertiary < secondary < primary. The k(H) values for the reactions of BnO(•) were in all cases significantly higher than those measured for the corresponding reactions of CumO(•), and no significant difference in reactivity was observed between structurally related substrates that could undergo exclusive α-C-H and N-H abstraction. This different behavior is evidenced by the k(H)(BnO(•))/k(H)(CumO(•)) ratios that range from 55-85 and 267-673 for secondary and primary alkylamines up to 1182 and 3388 for TMP and TOA. The reactions of CumO(•) were described in all cases as direct hydrogen atom abstractions. With BnO(•) the results were interpreted in terms of the rate-determining formation of a hydrogen-bonded prereaction complex between the radical α-C-H and the amine lone pair wherein hydrogen abstraction occurs. Steric effects and amine HBA ability play a major role, whereas the strength of the substrate α-C-H and N-H bonds involved appears to be relatively unimportant. The implications of these different mechanistic pictures are discussed.
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Affiliation(s)
- Michela Salamone
- Dipartimento di Scienze e Tecnologie Chimiche, Università Tor Vergata, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
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