1
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Wilbanks B, Garcia B, Byrne S, Dedon P, Maher LJ. Phenoxy Radical Reactivity of Nucleic Acids: Practical Implications for Biotinylation. Chembiochem 2021; 22:1400-1404. [PMID: 33368926 PMCID: PMC8052304 DOI: 10.1002/cbic.202000854] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Indexed: 01/10/2023]
Abstract
Recent advances in peroxidase-mediated biotin tyramide (BT) signal amplification technology have resulted in high-resolution and subcellular compartment-specific mapping of protein and RNA localization. Horseradish peroxidase (HRP) in the presence of H2 O2 is known to activate phenolic compounds for phenoxy radical reaction with nucleic acids, where biotinylation by BT is a practical example. BT reactivity with RNA and DNA is not understood in detail. We report that BT phenoxy radicals react in a sequence-independent manner with guanosine bases in RNA. In contrast, DNA reactivity with BT cannot be detected by our methods under the same conditions. Remarkably, we show that fluorescein conjugates DNA rapidly and selectively reacts with BT phenoxy radicals, allowing convenient and practical biotinylation of DNA on fluorescein with retention of fluorescence.
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Affiliation(s)
- Brandon Wilbanks
- Department of Biochemistry and Molecular BiologyMayo Clinic College of Medicine and Science200 First St SWRochesterMinnesota 55905USA
| | - Brian Garcia
- Department of Biochemistry and Molecular BiologyMayo Clinic College of Medicine and Science200 First St SWRochesterMinnesota 55905USA
| | - Shane Byrne
- Department of Biological EngineeringMassachusetts Institute of TechnologyBostonMA 02139USA
| | - Peter Dedon
- Department of Biological EngineeringMassachusetts Institute of TechnologyBostonMA 02139USA
| | - L. James Maher
- Department of Biochemistry and Molecular BiologyMayo Clinic College of Medicine and Science200 First St SWRochesterMinnesota 55905USA
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2
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Vidović M, Ćuković K. Isolation of high-quality RNA from recalcitrant leaves of variegated and resurrection plants. 3 Biotech 2020; 10:286. [PMID: 32550105 DOI: 10.1007/s13205-020-02279-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 05/25/2020] [Indexed: 01/16/2023] Open
Abstract
Resurrection plant Ramonda serbica is a suitable model to investigate mechanisms of desiccation tolerance, while variegated Pelargonium zonale has been proven to serve as an excellent model for the metabolite allocation between sink tissue and source tissue within the same organ. However, the genomes of these plants are still not sequenced, limiting their application in molecular studies. To investigate the transcript abundance by next-generation sequencing, high-quality RNA input is required. Leaves of both P. zonale and R. serbica are rich in polyphenols that interfere with high-quality RNA extraction by common protocols. Moreover, low water content and high amount of sugars and other osmoprotectants in desiccated R. serbica leaves present the additional challenge in total RNA extraction. Here, we evaluated and compared several already established TRIzol- and CTAB-based protocols aiming to develop the efficient, simple and low-cost methods for the extraction of the satisfactory yield RNA of great purity and integrity, required for the construction of high-quality cDNA libraries. Our results show that the CTAB-based protocol (i.e. CTAB 1b) enabled the extraction of high-quality RNA from photosynthetically active and non-photosynthetically active leaf sectors of P. zonale, with high RIN values. On the other hand, TRIzol-based protocol provided a high RNA yield with low contamination and high RNA integrity even in desiccated leaves of R. serbica. We envisage that the proposed protocol would be suitable for the RNA extractions from other desiccated organs (e.g. seeds, grains, pollen grains).
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Affiliation(s)
- Marija Vidović
- Department of Life Science, University of Belgrade, Institute for Multidisciplinary Research, Kneza Višeslava 1, Belgrade, 11030 Serbia
| | - Katarina Ćuković
- Department of Plant Physiology, Institute for Biological Research "Siniša Stanković"-National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
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3
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Zhou Y, Wang G, Wang P, Li Z, Yue T, Wang J, Zou P. Expanding APEX2 Substrates for Proximity‐Dependent Labeling of Nucleic Acids and Proteins in Living Cells. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905949] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Ying Zhou
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
| | - Gang Wang
- Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
| | - Pengchong Wang
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- School of Life Sciences Tsinghua University Beijing 100084 China
| | - Zeyao Li
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- Peking-Tsinghua-NIBS Joint Graduate Program Tsinghua University Beijing 100084 China
| | - Tieqiang Yue
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
| | - Jianbin Wang
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- School of Life Sciences Tsinghua University Beijing 100084 China
| | - Peng Zou
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- PKU-IDG/McGovern Institute for Brain Research Beijing 100871 China
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4
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Zhou Y, Wang G, Wang P, Li Z, Yue T, Wang J, Zou P. Expanding APEX2 Substrates for Proximity‐Dependent Labeling of Nucleic Acids and Proteins in Living Cells. Angew Chem Int Ed Engl 2019; 58:11763-11767. [DOI: 10.1002/anie.201905949] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/24/2019] [Indexed: 01/19/2023]
Affiliation(s)
- Ying Zhou
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
| | - Gang Wang
- Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
| | - Pengchong Wang
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- School of Life Sciences Tsinghua University Beijing 100084 China
| | - Zeyao Li
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- Peking-Tsinghua-NIBS Joint Graduate Program Tsinghua University Beijing 100084 China
| | - Tieqiang Yue
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
| | - Jianbin Wang
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- School of Life Sciences Tsinghua University Beijing 100084 China
| | - Peng Zou
- College of Chemistry and Molecular Engineering Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education Peking University Beijing 100871 China
- Peking-Tsinghua Center for Life Sciences Beijing 100871 China
- PKU-IDG/McGovern Institute for Brain Research Beijing 100871 China
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5
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Berger FD, Sturla SJ, Kung RW, Montina T, Wetmore SD, Manderville RA. Conformational Preference and Fluorescence Response of a C-Linked C8-Biphenyl-Guanine Lesion in the NarI Mutational Hotspot: Evidence for Enhanced Syn Adduct Formation. Chem Res Toxicol 2017; 31:37-47. [DOI: 10.1021/acs.chemrestox.7b00266] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Florence D. Berger
- Department
of Health Sciences and Technology, Institute of Food, Nutrition, and
Health, ETH Zürich, 8092 Zürich, Switzerland
| | - Shana J. Sturla
- Department
of Health Sciences and Technology, Institute of Food, Nutrition, and
Health, ETH Zürich, 8092 Zürich, Switzerland
| | - Ryan W. Kung
- Department
of Chemistry and Biochemistry, and the Canadian Centre for Research
in Advanced Fluorine Technologies, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Tony Montina
- Department
of Chemistry and Biochemistry, and the Canadian Centre for Research
in Advanced Fluorine Technologies, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Stacey D. Wetmore
- Department
of Chemistry and Biochemistry, and the Canadian Centre for Research
in Advanced Fluorine Technologies, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Richard A. Manderville
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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6
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Manderville RA, Wetmore SD. Understanding the Mutagenicity of O-Linked and C-Linked Guanine DNA Adducts: A Combined Experimental and Computational Approach. Chem Res Toxicol 2016; 30:177-188. [DOI: 10.1021/acs.chemrestox.6b00323] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Richard A. Manderville
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Stacey D. Wetmore
- Department of Chemistry & Biochemistry, University of Lethbridge, Lethbridge, AB, Canada T1K 3M4
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7
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Toxicology of DNA Adducts Formed Upon Human Exposure to Carcinogens. ADVANCES IN MOLECULAR TOXICOLOGY 2016. [DOI: 10.1016/b978-0-12-804700-2.00007-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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8
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Sproviero M, Verwey AMR, Witham AA, Manderville RA, Sharma P, Wetmore SD. Enhancing Bulge Stabilization through Linear Extension of C8-Aryl-Guanine Adducts to Promote Polymerase Blockage or Strand Realignment to Produce a C:C Mismatch. Chem Res Toxicol 2015. [PMID: 26225720 DOI: 10.1021/acs.chemrestox.5b00233] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Aryl radicals can react at the C8-site of 2'-deoxyguanosine (dG) to produce DNA adducts with a C8-C linkage (denoted C-linked). Such adducts are structurally distinct from those possessing a flexible amine (N-linked) or ether (O-linked) linkage, which separates the C8-aryl moiety from the guanine nucleobase. In the current study, two model C-linked C8-dG adducts, namely, C8-benzo[b]thienyl-dG ([BTh]G) and C8-(pyren-1-yl)-dG ([Py]G), were incorporated into the NarI (12mer, NarI(12) and 22mer, NarI(22)) hotspot sequence for frameshift mutations in bacteria. For the first time, C-linked C8-dG adducts are shown to stabilize the -2 deletion duplex within the NarI sequence. Primer-elongation assays employing Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4) demonstrates the influence of C8-aryl ring size and shape in promoting Dpo4 blockage or strand realignment to produce a C:C mismatch downstream of the adduct site. Molecular dynamics simulations of the -2 deletion duplex suggest that both anti and syn adduct structures are energetically accessible. These findings provide a rationale for describing the biochemical outcome induced by C-linked C8-dG adducts when processed by Dpo4.
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Affiliation(s)
- Michael Sproviero
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
| | - Anne M R Verwey
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
| | - Aaron A Witham
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
| | - Richard A Manderville
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
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9
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Sharma P, Majdi Yazdi M, Merriman A, Manderville RA, Wetmore SD. Influence of the Linkage Type and Functional Groups in the Carcinogenic Moiety on the Conformational Preferences of Damaged DNA: Structural and Energetic Characterization of Carbon- and Oxygen-Linked C8-Phenolic-Guanine Adducts. Chem Res Toxicol 2015; 28:782-96. [DOI: 10.1021/tx500527p] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Purshotam Sharma
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Mohadeseh Majdi Yazdi
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Ashlyn Merriman
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Richard A. Manderville
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G2W1
| | - Stacey D. Wetmore
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
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10
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Witham AA, Sharma P, Wetmore SD, Gabryelski W, Manderville RA. Chlorine substitution promotes phenyl radical loss from C8-phenoxy-2'-deoxyguanosine adducts: implications for biomarker identification from chlorophenol exposure. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:81-87. [PMID: 25601678 DOI: 10.1002/jms.3475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 08/21/2014] [Accepted: 08/21/2014] [Indexed: 06/04/2023]
Abstract
Chlorophenols are persistent organic pollutants, which undergo peroxidase-mediated oxidation to afford phenolic radical intermediates that react at the C8-site of 2'-deoxyguanosine (dG) to generate oxygen-linked C8-dG adducts. Such adducts are expected to contribute to chlorophenol toxicity and serve as effective dose biomarkers for chlorophenol exposure. Electrospray ionization mass spectrometry (ESI-MS) was employed to study collision induced dissociation (CID) for a family of such phenolic O-linked C8-dG adducts. Fragmentation of the deprotonated nucleosides demonstrates that an unexpected homolytic cleavage of the ether linkage to release phenyl radicals and a nucleoside distonic ion with m/z 281 competes effectively with commonly observed breakage of the glycosidic bond to release the deprotonated nucleobase. Increased chlorination of the phenyl ring enhances phenyl radical loss. Density functional theory calculations demonstrate that Cl-substitution decreases phenyl radical stability but promotes homolytic breakage of the C8-phenyl bond in the C8-dG adduct. The calculations suggest that phenyl radical loss is driven by destabilizing steric (electrostatic repulsion) interactions between the ether oxygen atom and ortho-chlorines on the phenyl ring. The distonic ion at m/z 281 represents a unique dissociation product for deprotonated O-linked C8-dG adducts and may prove useful for selective detection of relevant biomarkers for chlorophenol exposure by tandem mass spectrometry using selective reaction monitoring.
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Affiliation(s)
- Aaron A Witham
- Department of Chemistry and Toxicology, University of Guelph, Guelph, ON, N1G 2W1, Canada
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11
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Kuska MS, Witham AA, Sproviero M, Manderville RA, Majdi Yazdi M, Sharma P, Wetmore SD. Structural Influence of C8-Phenoxy-Guanine in the NarI Recognition DNA Sequence. Chem Res Toxicol 2013; 26:1397-408. [DOI: 10.1021/tx400252g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Michael S. Kuska
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Aaron A. Witham
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Michael Sproviero
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Richard A. Manderville
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Mohadeseh Majdi Yazdi
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Purshotam Sharma
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Stacey D. Wetmore
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
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12
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Sharma P, Manderville RA, Wetmore SD. Modeling the conformational preference of the carbon-bonded covalent adduct formed upon exposure of 2'-deoxyguanosine to ochratoxin A. Chem Res Toxicol 2013; 26:803-16. [PMID: 23560542 DOI: 10.1021/tx4000864] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The conformational flexibility of the C8-linked guanine adduct formed from attachment of ochratoxin A (OTA) was analyzed using a systematic computational approach and models ranging from the nucleobase to the adducted DNA helix. A focus was placed on the influence of the C8-modification of 2'-deoxyguanosine (dG) on the preferred relative arrangement of the nucleobase and the C8-substituent and, more importantly, the anti/syn conformational preference with respect to the glycosidic bond. Although OTA is twisted with respect to the base in the nucleobase model, addition of the deoxyribose sugar induces a further twist and restricts rotation about the C-C linkage due to close contacts between OTA and the sugar. The nucleoside model preferentially adpots a syn orientation (by 10-20 kJ mol(-1) depending on the OTA conformation) due to the presence of an O5'-H···N3 interaction. However, when this hydrogen bond is eliminated, which better mimics the DNA environment, a small (<5 kJ mol(-1)) anti/syn energy difference is predicted. Inclusion of the 5'-monophosphate group leads to an up to 20 kJ mol(-1) preference for the syn (nucleotide) conformation due to stabilizing base-phosphate interactions involving the amino group of guanine. Nevertheless, MD simulations and free energy analysis predict that both syn- and anti-conformations of OTB-dG are equally stable in helices when paired opposite cytosine. These results indicate that the adduct will likely adopt a syn conformation in an isolated nucleoside and nucleotide, while a mixture of syn and anti conformations will be observed in DNA duplexes. Since the syn conformation could stabilize base mismatches upon DNA replication or Z-DNA structures with varied biological outcomes, future computational and experimental work should elucidate the consequences of the conformational preference of this potentially harmful DNA lesion.
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Affiliation(s)
- Purshotam Sharma
- Department of Chemistry and Biochemistry, University of Lethbridge , 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
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13
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Lenz SAP, Kellie JL, Wetmore SD. Glycosidic bond cleavage in deoxynucleotides: effects of solvent and the DNA phosphate backbone in the computational model. J Phys Chem B 2012; 116:14275-84. [PMID: 23167947 DOI: 10.1021/jp3096677] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Density functional theory (B3LYP) was employed to examine the hydrolysis of the canonical 2'-deoxynucleotides in varied environments (gas phase or water) using different computational models for the sugar residue (methyl or phosphate group at C5') and nucleophile (water activated through full or partial proton abstraction). Regardless of the degree of nucleophile activation, our results show that key geometrical parameters along the reaction pathway are notably altered upon direct inclusion of solvent effects in the optimization routine, which leads to significant changes in the reaction energetics and better agreement with experiment. Therefore, despite the wide use of gas-phase calculations in the literature, small model computational work, as well as large-scale enzyme models, that strive to understand nucleotide deglycosylation must adequately describe the environment. Alternatively, although inclusion of the phosphate group at C5' also affects the geometries of important stationary points, the effects cancel to yield unchanged deglycosylation barriers, and therefore smaller computational models can be used to estimate the energy associated with nucleotide deglycosylation, with the 5' phosphate group included if full (geometric) details of the reaction are desired. Hydrogen-bonding interactions with the nucleobase can significantly reduce the barrier to deglycosylation, which supports suggestions that discrete hydrogen-bonding interactions with active-site amino acid residues can play a significant role in enzyme-catalyzed nucleobase excision. Taken together with previous studies, the present work provides vital clues about the components that must be included in future studies of the deglycosylation of isolated noncanonical nucleotides, as well as the corresponding enzyme-catalyzed reactions.
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Affiliation(s)
- Stefan A P Lenz
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, Canada T1K 3M4
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14
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C8-linked bulky guanosine DNA adducts: experimental and computational insights into adduct conformational preferences and resulting mutagenicity. Future Med Chem 2012; 4:1981-2007. [PMID: 23088278 DOI: 10.4155/fmc.12.138] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Bulky DNA adducts are formed through the covalent attachment of aryl groups to the DNA nucleobases. Many of these adducts are known to possess conformational heterogeneity, which is responsible for the variety of mutagenic outcomes associated with these lesions. The present contribution reviews several conformational and mutagenic themes that are prevalent among the DNA adducts formed at the C8-site of the guanine nucleobase. The most important conclusions obtained (to date) from experiments are summarized including the anti/syn conformational preference of the adducts, their potential to inflict DNA mutations and mismatch stabilization, and their interactions with DNA polymerases and repair enzymes. Additionally, the unique role that computer calculations can play in understanding the structural properties of these adducts are highlighted.
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15
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Omumi A, McLaughlin CK, Ben-Israel D, Manderville RA. Application of a fluorescent C-linked phenolic purine adduct for selective N7-metalation of DNA. J Phys Chem B 2012; 116:6158-65. [PMID: 22607044 DOI: 10.1021/jp303138s] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The C-linked phenolic adduct, C8-(2″-hydroxyphenyl)-2'-deoxyguanosine (o-PhOHdG), has been employed to study the impact of N7-metalation of 2'-deoxyguanosine (dG) within duplex DNA. The phenolic group of o-PhOHdG assists selective metal ion coordination by the N7-site of the attached dG moiety, which is the most important metal binding site in duplex DNA. The biaryl nucleobase probe o-PhOHdG is highly fluorescent in water (Φ(fl) = 0.44), and changes in its absorption and emission were used to determine apparent association constants (K(a)) for binding to Cu(II), Ni(II), and Zn(II). The nucleoside was found to bind Cu(II) (log K(a) = 4.59) and Ni(II) (log K(a) = 3.65) effectively, but it showed relatively poor affinity for Zn(II) (log K(a) = 2.55). The fluorescent nucleobase o-PhOHdG was incorporated into a pyrimidine-rich oligonucleotide substrate (ODN1) and a purine-rich (ODN2) substrate to monitor selective binding of Cu(II) through fluorescence quenching of the enol emission of o-PhOHdG within the DNA substrates. The pyrimidine-rich substrate ODN1 was found to possess greater affinity for Cu(II) than the free nucleobase, while the purine-rich substrate ODN2 exhibited diminished Cu(II) binding affinity. The impact of Cu(II) on duplex stability and structure was determined using UV melting temperature analysis and circular dichroism (CD) measurements. These studies highlight the syn preference for Cu(II)-bound o-PhOHdG within ODN1 duplexes and demonstrate competitive Cu(II) binding by other natural dG nucleobases within ODN2. The metal binding properties of o-PhOHdG are compared to the structurally similar 2-(2'-hydroxyphenyl)benzoxazole (HBO) derivatives and the nucleoside C8-(2-pyridyl)-dG (2PydG) that has also been used to control N7-metal coordination in DNA. Our results show certain advantages to the use of o-PhOHdG that stem from its highly fluorescent nature in aqueous media and provide additional tools for studying the effects of N7-metalation on the structure and stability of duplex DNA.
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Affiliation(s)
- Alireza Omumi
- Department of Chemistry, University of Guelph, Ontario, Canada
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16
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Millen AL, Kamenz BL, Leavens FMV, Manderville RA, Wetmore SD. Conformational flexibility of C8-phenoxylguanine adducts in deoxydinucleoside monophosphates. J Phys Chem B 2011; 115:12993-3002. [PMID: 21942470 DOI: 10.1021/jp2057332] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
M06-2X/6-31G(d,p) is used to calculate the structure of all natural deoxydinucleoside monophosphates with G in the 5' or 3' position, the anti or syn conformation, and each natural (A, C, G, T) base in the corresponding flanking position. When the ortho or para C8-phenoxyl-2'-deoxyguanosine (C8-phenoxyl-dG) adduct replaces G in each model, there is little change in the relative base-base orientation or backbone conformation. However, the orientation of the C8-phenoxyl group can be characterized according to the position (5' versus 3'), conformation (anti versus syn), and isomer (ortho versus para) of damage. Although the degree of coplanarity between the phenoxyl ring and G base in the ortho adduct is highly affected by the sequence since the hydroxyl group can interact with neighboring bases, the para adduct generally does not exhibit discrete interactions with flanking bases. For both adducts, steric clashes between the phenoxyl group and the backbone or flanking base destabilize the anti conformation preferred by the natural nucleotide and thereby result in a clear preference for the syn conformation regardless of the sequence or position. This contrasts the conclusions drawn from smaller (nucleoside, nucleotide) models previously used in the literature, which stresses the importance of using models that address the steric constraints present due to the surrounding environment. Since replication errors for other C8-dG bulky adducts have been linked to a preference for the syn conformation, our findings provide insight into the possible mutagenicity of phenolic adducts.
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Affiliation(s)
- Andrea L Millen
- Department of Chemistry, University of Lethbridge, Lethbridge, Alberta, Canada
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17
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Omumi A, Millen AL, Wetmore SD, Manderville RA. Fluorescent properties and conformational preferences of C-linked phenolic-DNA adducts. Chem Res Toxicol 2011; 24:1694-709. [PMID: 21905681 DOI: 10.1021/tx200247f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phenolic toxins and mutagenic diazoquinones generate C-linked adducts at the C8 site of 2'-deoxyguanosine (dG) through the intermediacy of radical species. We have previously reported the site-specific incorporation of these adducts into oligonucleotides using a postsynthetic palladium-catalyzed cross-coupling strategy [Omumi (2011 ) J. Am. Chem. Soc. 133 , 42 - 50 ]. We report here the structural impact of these lesions within two decanucleotide sequences containing either 5'- and 3'-flanking pyrimidines or purines. In the complementary strands, the base opposite (N) the C-linked adduct was varied to determine the possibility of mismatch stabilization by the modified nucleobases. The resulting adducted duplex structures were characterized using UV thermal denaturation studies, circular dichroism, fluorescence spectroscopy, and molecular dynamics (MD) simulations. The experimental data showed the C-linked adducts to destabilize the duplex when base paired with its normal partner C but to increase duplex stability within a G:G mismatch. The stabilization within the G:G mismatch was sequence dependent, with flanking purine bases playing a key role in the stabilizing influence of the adduct. MD simulations showed no large structural changes to the B form double helix, regardless of the (anti/syn) adduct preference. Consideration of H-bonding and stacking interactions derived from the MD simulations together with the thermal melting data and changes in fluorescent emission of the adducts upon hybridization to the complementary strands implied that the C-linked phenolic adducts preferentially adopt the syn-conformation within both duplexes regardless of the opposite base N. Given that biological outcome in terms of mutagenicity appears to be strongly correlated to the conformational preference of the corresponding N-linked C8-dG adducts, the potential biological implications of phenolic C-linked adducts are discussed.
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Affiliation(s)
- Alireza Omumi
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada
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Sagoo S, Beach DG, Manderville RA, Gabryelski W. Tautomerization in gas-phase ion chemistry of isomeric C-8 deoxyguanosine adducts from phenol-induced DNA damage. JOURNAL OF MASS SPECTROMETRY : JMS 2011; 46:41-9. [PMID: 21184435 DOI: 10.1002/jms.1869] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Collision-induced dissociation (CID) of 8-(4''-hydroxyphenyl)-2'-deoxyguanosine and 8-(2''-hydroxyphenyl)-2'-deoxyguanosine was investigated using sequential tandem mass spectrometry. These adducts represent biomarkers of DNA damage linked to phenolic radicals and were investigated to gain insight into the effects of chemical structure of a C-8 modification on fragmentation pathways of modified 2'-deoxyguanosine (dG). CID in MS(2) of the deprotonated molecules of both the isomers generated the same product ion having the same m/z values. CID in MS(3) of the product ion at m/z 242 and CID in MS(4) experiments carried out on the selected product ions at m/z 225 and m/z 218 afford distinct fragmentation patterns. The conformational properties of isomeric product ions from CID showed that the ortho-isomers possess the unique ability to tautomerize through an intramolecular proton transfer between the phenolic OH group and the imine nitrogen (N7). Tautomerization of ortho-isomers to their keto-tautomers led to differences in their system of conjugated double bonds compared with either their enol-tautomer or the para-isomer. The charge redistribution through the N-7 site on the imidazole ring is a critical step in guanosine adduct fragmentation which is disrupted by the formation of the keto-tautomer. For this reason, different reaction pathways are observed for 8-(4''-hydroxyphenyl)-2'-deoxyguanosine and 8-(2''-hydroxyphenyl)-2'-deoxyguanosine. We present herein the dissociation and the gas-phase ion-molecule reactions for highly conjugated ions involved in the CID ion chemistry of the investigated adducts. These will be useful for those using tandem mass spectrometry for structural elucidation of C-8 modified dG adducts. This study demonstrates that the modification at the C-8 site of dG has the potential to significantly alter the reactivity of adducts. We also show the ability of tandem mass spectrometry to completely differentiate between the isomeric dG adducts investigated.
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Affiliation(s)
- Sandeep Sagoo
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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Omumi A, Beach DG, Baker M, Gabryelski W, Manderville RA. Postsynthetic guanine arylation of DNA by Suzuki-Miyaura cross-coupling. J Am Chem Soc 2010; 133:42-50. [PMID: 21067186 DOI: 10.1021/ja106158b] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Direct radical addition reactions at the C(8)-site of 2'-deoxyguanosine (dG) can afford C(8)-Ar-dG adducts that are produced by carcinogenic arylhydrazines, polycyclic aromatic hydrocarbons, and certain phenolic toxins. Such modified nucleobases are also highly fluorescent for sensing applications and possess useful electron transfer properties. The site-specific synthesis of oligonucleotides containing the C(8)-Ar-G adduct can be problematic. These lesions are sensitive to acids and oxidants that are commonly used in solid-phase DNA synthesis and are too bulky to be accepted as substrates for enzymatic synthesis by DNA polymerases. Using the Suzuki-Miyaura cross-coupling reaction, we have synthesized a number of C(8)-Ar-G-modified oligonucleotides (dimers, trimers, decamers, and a 15-mer) using a range of arylboronic acids. Good to excellent yields were obtained, and the reaction is insensitive to the nature of the bases flanking the convertible 8-Br-G nucleobase, as both pyrimidines and purines are tolerated. The impact of the C(8)-Ar-G lesion was also characterized by electrospray ionization tandem mass spectrometry, UV melting temperature analysis, circular dichroism, and fluorescence spectroscopy. The C(8)-Ar-G-modified oligonucleotides are expected to be useful substrates for diagnostic applications and understanding the biological impact of the C(8)-Ar-G lesion.
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Affiliation(s)
- Alireza Omumi
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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Millen AL, Churchill CDM, Manderville RA, Wetmore SD. Effect of Watson−Crick and Hoogsteen Base Pairing on the Conformational Stability of C8-Phenoxyl-2′-deoxyguanosine Adducts. J Phys Chem B 2010; 114:12995-3004. [DOI: 10.1021/jp105817p] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Andrea L. Millen
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Cassandra D. M. Churchill
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Richard A. Manderville
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Stacey D. Wetmore
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
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Martín JMP, Peropadre A, Herrero Ó, Freire PF, Labrador V, Hazen MJ. Oxidative DNA damage contributes to the toxic activity of propylparaben in mammalian cells. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2010; 702:86-91. [DOI: 10.1016/j.mrgentox.2010.07.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 06/23/2010] [Accepted: 07/16/2010] [Indexed: 01/09/2023]
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Ochratoxin A and aristolochic acid involvement in nephropathies and associated urothelial tract tumours. Arh Hig Rada Toksikol 2010; 60:465-83. [PMID: 20061248 DOI: 10.2478/10004-1254-60-2009-2000] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
This review addresses the unresolved aetiology of several nephropathies and associated upper tract tumours diagnosed all over the world, but especially in the Balkan regions. Studies conducted over the last 35 years point to mycotoxins, mainly ochratoxin A (OTA) as the main culprit. Recent theories however have implicated aristolochic acids (AA). The aim of this review is to put forward arguments in favour of the mycotoxin theory and to show the incoherence of the AA theory. It discusses the differences between the epidemiology of Balkan endemic nephropathy (BEN) and aristolochic acid nephropathy (AAN); OTA and AA carcinogenicity; clinical and pathological effects induced by OTA and AA; sources of OTA contamination (food, air, drinking water); OTA- and AA-DNA adduct formation; the role of genetic polymorphisms; and the risk for young children.
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Millen AL, Manderville RA, Wetmore SD. Conformational Flexibility of C8-Phenoxyl-2′-deoxyguanosine Nucleotide Adducts. J Phys Chem B 2010; 114:4373-82. [DOI: 10.1021/jp911993f] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Andrea L. Millen
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Richard A. Manderville
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Stacey D. Wetmore
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
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Structural and biological impact of radical addition reactions with DNA nucleobases. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2009. [DOI: 10.1016/s0065-3160(08)00005-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Manderville R, Pfohl-Leszkowicz A. Bioactivation and DNA adduction as a rationale for ochratoxin A carcinogenesis. WORLD MYCOTOXIN J 2008. [DOI: 10.3920/wmj2008.x039] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ochratoxin A (OTA) is a para-chlorophenolic mycotoxin produced by strains of Aspergillus and Penicillium that is widely found as a contaminant of improperly stored food products. The toxin is a potent renal carcinogen in rats, especially male, and has an implicated role in the etiology of Balkan endemic nephropathy and its associated urinary tract tumours. Although the mechanism of OTA-mediated tumour formation is not fully understood, and represents a hotly debated topic, bioactivation and subsequent DNA adduction through covalent attachment of electrophilic OTA species remains a viable mechanism for OTA-mediated carcinogenesis. In this paper we outline the established chemistry for the bioactivation of chlorophenol carcinogens and demonstrate how this chemistry relates to the bioactivation of OTA. From this basis it is predicted that OTA will form a benzoquinone electrophile following activation by cytochrome P450 enzymes and radical species following activation by enzymes with peroxidase activities. These electrophiles react preferentially with deoxyguanosine (dG) to form benzetheno adducts and C8- dG adducts, respectively. Analysis of OTA-mediated DNA adduction using the 32P-postlabelling method correlates with OTA chemistry and adduct spots derived from the quinone electrophile are generated following activation by cytochrome P450, while a C8-OTA adduct is formed following activation of OTA by peroxidase enzymes. These same adduct spots are also produced in animal (rat and pig) and human tumoral kidney tissue. This model for OTAmediated carcinogenesis is consistent with established structure-activity relationships for covalent attachment of OTA analogues and OTA toxicity. The model also provides a rationale for the synergistic effect observed for OTA in the presence of the mycotoxin citrinin and for the sexual differences observed in rat carcinogenesis where the male is particularly susceptible to OTA-mediated tumour formation.
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Affiliation(s)
- R. Manderville
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, N1G 2W1 Ontario, Canada
| | - A. Pfohl-Leszkowicz
- ENSAT, Laboratory Chemical Engineering, UMR CNRS/INPT/UPS n° 5503, 1 avenue agrobiopole, 31326 Auzeville-Tolosane, France
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Weishar JL, McLaughlin CK, Baker M, Gabryelski W, Manderville RA. Oxidation of a Biomarker for Phenol Carcinogen Exposure: Expanding the Redox Chemistry of 2′-Deoxyguanosine. Org Lett 2008; 10:1839-42. [DOI: 10.1021/ol8004694] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jennifer L. Weishar
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | | - Michael Baker
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Wojciech Gabryelski
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Richard A. Manderville
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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Millen AL, McLaughlin CK, Sun KM, Manderville RA, Wetmore SD. Computational and Experimental Evidence for the Structural Preference of Phenolic C-8 Purine Adducts. J Phys Chem A 2008; 112:3742-53. [DOI: 10.1021/jp712058a] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrea L. Millen
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and the Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Christopher K. McLaughlin
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and the Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Kewen M. Sun
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and the Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Richard A. Manderville
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and the Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Stacey D. Wetmore
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and the Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
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Xu X, Muller JG, Ye Y, Burrows CJ. DNA−Protein Cross-links between Guanine and Lysine Depend on the Mechanism of Oxidation for Formation of C5 Vs C8 Guanosine Adducts. J Am Chem Soc 2007; 130:703-9. [DOI: 10.1021/ja077102a] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Xiaoyun Xu
- Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112-0850
| | - James G. Muller
- Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112-0850
| | - Yu Ye
- Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112-0850
| | - Cynthia J. Burrows
- Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112-0850
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Sun KM, McLaughlin CK, Lantero DR, Manderville RA. Biomarkers for Phenol Carcinogen Exposure Act as pH-Sensing Fluorescent Probes. J Am Chem Soc 2007; 129:1894-5. [PMID: 17256942 DOI: 10.1021/ja068416l] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kewen M Sun
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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McLaughlin CK, Lantero DR, Manderville RA. Conformational Properties of a Phototautomerizable Nucleoside Biomarker for Phenolic Carcinogen Exposure. J Phys Chem A 2006; 110:6224-30. [PMID: 16686455 DOI: 10.1021/jp0617571] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have characterized the conformational properties of the C8-deoxyguanosine (C8-dG) nucleoside adduct, 8-(2"-hydroxyphenyl)-2'-dG (1), which is a potential biomarker for exposure to phenolic carcinogens. Adduct 1 possesses the unique ability to phototautomerize, through an excited-state intramolecular proton transfer (ESIPT) process, to generate its keto form. This tautomerization depends on the presence of an intramolecular hydrogen (H)-bond between the phenolic OH and the imine nitrogen (N7) and has permitted insight into the equilibrium ground states of adduct 1. The results of our studies demonstrate that adduct 1 undergoes an ESIPT despite preferring a nonplanar "twisted" conformation that is imposed by the deoxyribose (dR) sugar moiety. Interestingly, a planar conformation of adduct 1 is also formed in certain aprotic solvents due to the anchoring effect of the intramolecular H-bond. Our results provide a basis for future studies aimed at determining the conformations of adduct 1 within DNA that will aid in our understanding of phenol-mediated carcinogenesis.
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