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Copp W, Wilds CJ. O 6 -Alkylguanine DNA Alkyltransferase Mediated Disassembly of a DNA Tetrahedron. Chemistry 2020; 26:14802-14806. [PMID: 32543755 DOI: 10.1002/chem.202002565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Indexed: 11/05/2022]
Abstract
Tetrahedron DNA structures were formed by the assembly of three-way junction (TWJ) oligonucleotides containing O6 -2'-deoxyguanosine-alkylene-O6 -2'-deoxyguanosine (butylene and heptylene linked) intrastrand cross-links (IaCLs) lacking a phosphodiester group between the 2'-deoxyribose residues. The DNA tetrahedra containing TWJs were shown to undergo an unhooking reaction by the human DNA repair protein O6 -alkylguanine DNA alkyltransferase (hAGT) resulting in structure disassembly. The unhooking reaction of hAGT towards the DNA tetrahedra was observed to be moderate to virtually complete depending on the protein equivalents. DNA tetrahedron structures have been explored as drug delivery platforms that release their payload in response to triggers, such as light, chemical agents or hybridization of release strands. The dismantling of DNA tetrahedron structures by a DNA repair protein contributes to the armamentarium of approaches for drug release employing DNA nanostructures.
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Affiliation(s)
- William Copp
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, H4B 1R6, Canada
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, H4B 1R6, Canada
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Copp W, O'Flaherty DK, Wilds CJ. Covalent capture of OGT's active site using engineered human-E. coli chimera and intrastrand DNA cross-links. Org Biomol Chem 2018; 16:9053-9058. [PMID: 30430154 DOI: 10.1039/c8ob02453g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
O 6-Alkylguanine DNA alkyltransferases (AGTs) are proteins found in most organisms whose role is to remove alkylation damage from the O6- and O4-positions of 2'-deoxyguanosine (dG) and thymidine (dT), respectively. Variations in active site residues between AGTs from different organisms leads to differences in repair proficiency: The human variant (hAGT) has a proclivity for removal of alkyl groups at the O6-position of guanine and the E. coli OGT protein has activity towards the O4-position of thymine. A chimeric protein (hOGT) that our laboratory has engineered with twenty of the active site residues mutated in hAGT to those found in OGT, exhibited activity towards a broader range of substrates relative to native OGT. Among the substrates that the hOGT protein was found to act upon was interstrand cross-linked DNA connected by an alkylene linkage at the O6-position of dG to the complementary strand. In the present study the activity of hOGT towards DNA containing alkylene intrastrand cross-links (IaCL) at the O6- and O4-positions respectively of dG and dT, which lack a phosphodiester linkage between the connected residues, was evaluated. The hOGT protein exhibited proficiency at removal of an alkylene linkage at the O6-atom of dG but the O4-position of dT was refractory to protein activity. The activity of the chimeric hOGT protein towards these IaCLs to prepare well defined DNA-protein cross-linked conjugates will enable mechanistic and high resolution structural studies to address the differences observed in the repair adeptness of O4-alkylated dT by the OGT protein relative to other AGT variants.
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Affiliation(s)
- William Copp
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada.
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Sacre L, O'Flaherty DK, Archambault P, Copp W, Peslherbe GH, Muchall HM, Wilds CJ. O 4 -Alkylated-2-Deoxyuridine Repair by O 6 -Alkylguanine DNA Alkyltransferase is Augmented by a C5-Fluorine Modification. Chembiochem 2018; 19:575-582. [PMID: 29243336 DOI: 10.1002/cbic.201700660] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Indexed: 11/10/2022]
Abstract
Oligonucleotides containing various adducts, including ethyl, benzyl, 4-hydroxybutyl and 7-hydroxyheptyl groups, at the O4 atom of 5-fluoro-O4 -alkyl-2'-deoxyuridine were prepared by solid-phase synthesis. UV thermal denaturation studies demonstrated that these modifications destabilised the duplex by approximately 10 °C, relative to the control containing 5-fluoro-2'-deoxyuridine. Circular dichroism spectroscopy revealed that these modified duplexes all adopted a B-form DNA structure. O6 -Alkylguanine DNA alkyltransferase (AGT) from humans (hAGT) was most efficient at repair of the 5-fluoro-O4 -benzyl-2'-deoxyuridine adduct, whereas the thymidine analogue was refractory to repair. The Escherichia coli AGT variant (OGT) was also efficient at removing O4 -ethyl and benzyl adducts of 5-fluoro-2-deoxyuridine. Computational assessment of N1-methyl analogues of the O4 -alkylated nucleobases revealed that the C5-fluorine modification had an influence on reducing the electron density of the O4 -Cα bond, relative to thymine (C5-methyl) and uracil (C5-hydrogen). These results reveal the positive influence of the C5-fluorine atom on the repair of larger O4 -alkyl adducts to expand knowledge of the range of substrates able to be repaired by AGT.
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Affiliation(s)
- Lauralicia Sacre
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Derek K O'Flaherty
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada.,Present address: Howard Hughes Medical Institute, Department of Molecular Biology and, Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA, 02114, USA
| | - Philippe Archambault
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - William Copp
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Gilles H Peslherbe
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Heidi M Muchall
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
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O'Flaherty DK, Wilds CJ. Site-specific covalent capture of human O 6-alkylguanine-DNA-alkyltransferase using single-stranded intrastrand cross-linked DNA. Org Biomol Chem 2018; 15:189-196. [PMID: 27886318 DOI: 10.1039/c6ob02246d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A methodology is reported to conjugate human O6-alkylguanine-DNA-alkyltransferase (hAGT) to the 3'-end of DNA in excellent yields with short reaction times by using intrastrand cross-linked (IaCL) DNA probes. This strategy exploited the substrate specificity of hAGT to generate the desired DNA-protein covalent complex. IaCL DNA linking two thymidine residues, or linking a thymidine residue to a 2'-deoxyguanosine residue (either in a 5'→3' or 3'→5' fashion), lacking a phosphodiester linkage at the cross-linked site, were prepared using a phosphoramidite strategy followed by solid-phase synthesis. All duplexes containing the model IaCL displayed a reduction in thermal stability relative to unmodified control duplexes. The O4-thymidine-alkylene-O4-thymidine and the (5'→3') O6-2'-deoxyguanosine-alkylene-O4-thymidine IaCL DNA adducts were not repaired by any of the AGTs evaluated (human AGT and Escherichia coli homologues, OGT and Ada-C). The (5'→3') O4-thymidine-alkylene-O6-2'-deoxyguanosine IaCL DNA containing a butylene or heptylene tethers were efficiently repaired by the human variant, whereas Ada-C was capable of modestly repairing the heptylene IaCL adduct. The IaCL strategy has expanded the toolbox for hAGT conjugation to DNA strands, without requiring the presence of a complementary DNA sequence. Finally, hAGT was functionalized with a fluorescently-labelled DNA sequence to demonstrate the applicability of this conjugation method.
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Affiliation(s)
- D K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada.
| | - C J Wilds
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada.
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Chen HJC, Chang YL, Teng YC, Hsiao CF, Lin TS. A Stable Isotope Dilution Nanoflow Liquid Chromatography Tandem Mass Spectrometry Assay for the Simultaneous Detection and Quantification of Glyoxal-Induced DNA Cross-Linked Adducts in Leukocytes from Diabetic Patients. Anal Chem 2017; 89:13082-13088. [PMID: 29172486 DOI: 10.1021/acs.analchem.6b04296] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Glyoxal (gx) is a bifunctional electrophile capable of cross-linking DNA. Although it is present in foods and from the environment, endogenous formation of glyoxal occurs through metabolism of carbohydrates and oxidation of lipids and nucleic acids. Plasma concentrations of glyoxal are elevated in in diabetes mellitus patients compared to nondiabetics. The most abundant 2'-deoxyribonucleoside adducts cross-linked by glyoxal are dG-gx-dC, dG-gx-dA, and dG-gx-dG. These DNA cross-links can be mutagenic by damaging the integrity of the DNA structure. Herein, we developed a highly sensitive and specific assay for the simultaneous detection and quantification of the dG-gx-dC and dG-gx-dA cross-links based on stable isotope dilution (SID) nanoflow liquid chromatography nanospray ionization tandem mass spectrometry (nanoLC-NSI/MS/MS) under the highly selected reaction monitoring mode and using a triple quadrupole mass spectrometer. The entire assay procedure involved addition of the stable isotope standards [15N5]dG-gx-dC and [15N5]dG-gx-dA as internal standards, enzyme hydrolysis to release the cross-links as nucleosides, enrichment by a reversed-phase solid-phase extraction column, and nanoLC-NSI/MS/MS analysis. The detection limit is 0.19 amol for dG-gx-dC and 0.89 amol for dG-gx-dA, which is 400 and 80 times more sensitive, respectively, than capillary LC-NSI/MS/MS assay of these adducts. The lower limit of quantification was 94 and 90 amol for dG-gx-dC and dG-gx-dA, respectively, which is equivalent to 0.056 and 0.065 adducts in 108 normal nucleotides in 50 μg of DNA. In type 2 diabetes mellitus (T2DM) patients (n = 38), the levels of dG-gx-dC and dG-gx-dA in leukocyte DNA were 1.94 ± 1.20 and 2.10 ± 1.77 in 108 normal nucleotides, respectively, which were significantly higher than those in nondiabetics (n = 39: 0.83 ± 0.92 and 1.05 ± 0.99 in 108 normal nucleotides, respectively). Excluding the factor of smoking, an exogenous source of glyoxal, levels of these two cross-linked adducts were found to be significantly higher in nonsmoking T2DM patients than in nonsmoking control subjects. Furthermore, the levels of dG-gx-dC and dG-gx-dA correlated with HbA1c with statistical significance. To our best knowledge, this is the first report of the identification and quantification of glyoxal-derived cross-linked DNA adducts in human leukocyte DNA and their association with T2DM. This SID nanoLC-NSI/MS/MS assay is highly sensitive and specific and it requires only 50 μg of leukocyte DNA isolated from 2-3 mL of blood to accurately quantify these two cross-linked adducts simultaneously. Our assay thus provides a useful biomarker for the evaluation of glyoxal-derived DNA damage.
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Affiliation(s)
- Hauh-Jyun Candy Chen
- Department of Chemistry and Biochemistry, National Chung Cheng University , 168 University Road, Ming-Hsiung, Chia-Yi 62102, Taiwan
| | - Ya-Lang Chang
- Department of Chemistry and Biochemistry, National Chung Cheng University , 168 University Road, Ming-Hsiung, Chia-Yi 62102, Taiwan
| | - Yi-Chun Teng
- Department of Chemistry and Biochemistry, National Chung Cheng University , 168 University Road, Ming-Hsiung, Chia-Yi 62102, Taiwan
| | - Chiung-Fong Hsiao
- Department of Chemistry and Biochemistry, National Chung Cheng University , 168 University Road, Ming-Hsiung, Chia-Yi 62102, Taiwan
| | - Tsai-Shiuan Lin
- Department of Chemistry and Biochemistry, National Chung Cheng University , 168 University Road, Ming-Hsiung, Chia-Yi 62102, Taiwan
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O'Flaherty DK, Wilds CJ. AGT Activity Towards Intrastrand Crosslinked DNA is Modulated by the Alkylene Linker. Chembiochem 2017; 18:2351-2357. [PMID: 28980757 DOI: 10.1002/cbic.201700450] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Indexed: 11/12/2022]
Abstract
DNA oligomers containing dimethylene and trimethylene intrastrand crosslinks (IaCLs) between the O4 and O6 atoms of neighboring thymidine (T) and 2'-deoxyguanosine (dG) residues were prepared by solid-phase synthesis. UV thermal denaturation (Tm ) experiments revealed that these IaCLs had a destabilizing effect on the DNA duplex relative to the control. Circular dichroism spectroscopy suggested these IaCLs induced minimal structural distortions. Susceptibility to dealkylation by reaction with various O6 -alkylguanine DNA alkyltransferases (AGTs) from human and Escherichia coli was evaluated. It was revealed that only human AGT displayed activity towards the IaCL DNA, with reduced efficiency as the IaCL shortened (from four to two methylene linkages). Changing the site of attachment of the ethylene linkage at the 5'-end of the IaCL to the N3 atom of T had minimal influence on duplex stability and structure, and was refractory to AGT activity.
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Affiliation(s)
- Derek K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University Montreal, 7141 Sherbrooke Street W., Montreal, Quebec, H4B 1R6, Canada.,Present address: Howard Hughes Medical Institute, Department of Molecular Biology and, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University Montreal, 7141 Sherbrooke Street W., Montreal, Quebec, H4B 1R6, Canada
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Altering Residue 134 Confers an Increased Substrate Range of Alkylated Nucleosides to the E. coli OGT Protein. Molecules 2017; 22:molecules22111948. [PMID: 29137116 PMCID: PMC6150290 DOI: 10.3390/molecules22111948] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 11/01/2017] [Accepted: 11/08/2017] [Indexed: 01/20/2023] Open
Abstract
O6-Alkylguanine-DNA alkyltransferases (AGTs) are proteins responsible for the removal of mutagenic alkyl adducts at the O6-atom of guanine and O4-atom of thymine. In the current study we set out to understand the role of the Ser134 residue in the Escherichia coli AGT variant OGT on substrate discrimination. The S134P mutation in OGT increased the ability of the protein to repair both O6-adducts of guanine and O4-adducts of thymine. However, the S134P variant was unable, like wild-type OGT, to repair an interstrand cross-link (ICL) bridging two O6-atoms of guanine in a DNA duplex. When compared to the human AGT protein (hAGT), the S134P OGT variant displayed reduced activity towards O6-alkylation but a much broader substrate range for O4-alkylation damage reversal. The role of residue 134 in OGT is similar to its function in the human homolog, where Pro140 is crucial in conferring on hAGT the capability to repair large adducts at the O6-position of guanine. Finally, a method to generate a covalent conjugate between hAGT and a model nucleoside using a single-stranded oligonucleotide substrate is demonstrated.
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Framski G, Goslinski T, Januszczyk P, Golankiewicz B, Ostrowski T. Alkylation of 9-substituted guanine derivatives with α,ω-dihaloalkanes. HETEROATOM CHEMISTRY 2017. [DOI: 10.1002/hc.21399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Grzegorz Framski
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznan Poland
| | - Tomasz Goslinski
- Department of Chemical Technology of Drugs; Poznan University of Medical Sciences; Poznan Poland
| | - Piotr Januszczyk
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznan Poland
| | | | - Tomasz Ostrowski
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznan Poland
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O'Flaherty DK, Wilds CJ. Preparation of Intrastrand {G}O(6) -Alkylene-O(6) {G} Cross-Linked Oligonucleotides. ACTA ACUST UNITED AC 2016; 66:5.17.1-5.17.24. [PMID: 27584704 DOI: 10.1002/cpnc.14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This unit describes the preparation O(6) -2'-deoxyguanosine-butylene-O(6) -2'-deoxyguanosine dimer phosphoramidites and precursors for incorporation of site-specific intrastrand cross-links (IaCL) into DNA oligonucleotides. Protected 2'-deoxyguanosine dimers are produced using the Mitsunobu reaction. IaCL DNA containing the intradimer phosphodiester are first chemically phosphorylated, followed by a ring-closing reaction using the condensing reagent 1-(2-mesitylenesulfonyl)-3-nitro-1H-1,2,4-triazole. Phosphoramidites are incorporated into oligonucleotides by solid-phase synthesis and standard deprotection and cleavage protocols are employed. This approach allows for the preparation of IaCL DNA substrates in amounts and purity amenable for biophysical characterization, and biochemical studies as substrates to investigate DNA repair and bypass pathways. © 2016 by John Wiley & Sons, Inc.
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Affiliation(s)
- Derek K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, Canada
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, Canada
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O'Flaherty DK, Wilds CJ. O
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-Alkylguanine DNA Alkyltransferase Repair Activity Towards Intrastrand Cross-Linked DNA is Influenced by the Internucleotide Linkage. Chem Asian J 2016; 11:576-83. [PMID: 26692563 DOI: 10.1002/asia.201501253] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Indexed: 01/12/2023]
Affiliation(s)
- Derek K. O'Flaherty
- Department of Chemistry&Biochemistry; Concordia University; 7141 Sherbrooke St. West Montréal Québec (Canada
| | - Christopher J. Wilds
- Department of Chemistry&Biochemistry; Concordia University; 7141 Sherbrooke St. West Montréal Québec (Canada
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O'Flaherty DK, Guengerich FP, Egli M, Wilds CJ. Backbone Flexibility Influences Nucleotide Incorporation by Human Translesion DNA Polymerase η opposite Intrastrand Cross-Linked DNA. Biochemistry 2015; 54:7449-56. [PMID: 26624500 DOI: 10.1021/acs.biochem.5b01078] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Intrastrand cross-links (IaCL) connecting two purine nucleobases in DNA pose a challenge to high-fidelity replication in the cell. Various repair pathways or polymerase bypass can cope with these lesions. The influence of the phosphodiester linkage between two neighboring 2'-deoxyguanosine (dG) residues attached through the O(6) atoms by an alkylene linker on bypass with human DNA polymerase η (hPol η) was explored in vitro. Steady-state kinetics and mass spectrometric analysis of products from nucleotide incorporation revealed that although hPol η is capable of bypassing the 3'-dG in a mostly error-free fashion, significant misinsertion was observed for the 5'-dG of the IaCL containing a butylene or heptylene linker. The lack of the phosphodiester linkage triggered an important increase in frameshift adduct formation across the 5'-dG by hPol η, in comparison to the 5'-dG of IaCL DNA containing the phosphodiester group.
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Affiliation(s)
- Derek K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
| | - F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Martin Egli
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
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