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Martínez-Fernández L, Kohl FR, Zhang Y, Ghosh S, Saks AJ, Kohler B. Triplet Excimer Formation in a DNA Duplex with Silver Ion-Mediated Base Pairs. J Am Chem Soc 2024; 146:1914-1925. [PMID: 38215466 DOI: 10.1021/jacs.3c08793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2024]
Abstract
The dynamics of excited electronic states in self-assembled structures formed between silver(I) ions and cytosine-containing DNA strands or monomeric cytosine derivatives were investigated by time-resolved infrared (TRIR) spectroscopy and quantum mechanical calculations. The steady-state and time-resolved spectra depend sensitively on the underlying structures, which change with pH and the nucleobase and silver ion concentrations. At pH ∼ 4 and low dC20 strand concentration, an intramolecularly folded i-motif is observed, in which protons, and not silver ions, mediate C-C base pairing. However, at the higher strand concentrations used in the TRIR measurements, dC20 strands associate pairwise to yield duplex structures containing C-Ag+-C base pairs with a high degree of propeller twisting. UV excitation of the silver ion-mediated duplex produces a long-lived excited state, which we assign to a triplet excimer state localized on a pair of stacked cytosines. The computational results indicate that the propeller-twisted motifs induced by metal-ion binding are responsible for the enhanced intersystem crossing that populates the triplet state and not a generic heavy atom effect. Although triplet excimer states have been discussed frequently as intermediates in the formation of cyclobutane pyrimidine dimers, we find neither computational nor experimental evidence for cytosine-cytosine photoproduct formation in the systems studied. These findings provide a rare demonstration of a long-lived triplet excited state that is formed in a significant yield in a DNA duplex, demonstrating that supramolecular structural changes induced by metal ion binding profoundly affect DNA photophysics.
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Affiliation(s)
- Lara Martínez-Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemical Science (IADCHEM), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Forrest R Kohl
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Yuyuan Zhang
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Supriya Ghosh
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Andrew J Saks
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Bern Kohler
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
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Jin P, Wang JN, Wang X, Jia M, Pan H, Mei Y, Chen J. Tracking the Early Stage of Triplet-Induced Photodamage in a DNA Dimer and Oligomer Containing 5-Methylcytosine. J Phys Chem B 2023; 127:6878-6886. [PMID: 37490365 DOI: 10.1021/acs.jpcb.3c02454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Methylation at the C5 position of cytosine, a naturally occurring epigenetic modification on DNA, shows a high correlation with mutational hotspots in disease such as skin cancer. Due to its essential biological relevance, numerous studies were devoted to confirming that the methylated sites favor the formation of the cyclobutane pyrimidine dimer (CPD), a well-known UV-induced lesion. However, photophysical and photochemical properties of dinucleotides and polynucleotides containing 5-methylcytosine (5mC) remain elusive. Herein, a charge transfer (CT) triplet state, generated via intersystem crossing (ISC) from a CT singlet state that enhanced after methylation on cytosine, is directly observed by using femtosecond transient absorption (TA) and time-resolved mid-infrared (TRIR) spectroscopy together with quantum chemical calculations for the first time in the T5mC dimer. Such an ISC process is quenched due to limitations of the ground-state geometries in 5mC-containing single-strand oligomer d(T5mC)9. This mechanistic information is important for understanding the early stage of triplet state-induced CPD formation in 5mC containing DNA.
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Affiliation(s)
- Peipei Jin
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Jia-Ning Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Menghui Jia
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Haifeng Pan
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Ye Mei
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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Wu P, Wang X, Pan H, Chen J. Direct Observation of Excitation Wavelength-Dependent Ultrafast Intersystem Crossing in Cytosine Nucleoside Solution. J Phys Chem B 2022; 126:7975-7980. [PMID: 36179273 DOI: 10.1021/acs.jpcb.2c05865] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A triplet excited state can lead to different DNA photolesions, especially in cytosine and its nucleoside/nucleotide as they are hotspots for DNA mutations. However, the triplet state generation mechanism is in controversy, and experimental evidence of ultrafast intersystem crossing (ISC) has not been registered in these molecules. In this work, ultrafast ISC is directly observed in 2'-deoxycytidine (dCyd) solution by using femtosecond transient absorption spectroscopy. Surprisingly, we demonstrate that ISC in dCyd is sensitive to the excitation wavelength, and a spin-vibronic ISC mechanism is proposed. This finding is the last piece of the dCyd excited-state deactivation mechanism puzzle and sets the base for further investigation of triplet state-involved photophysics and photochemistry in dCyd-containing DNA.
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Affiliation(s)
- Peicong Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Haifeng Pan
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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Jakhlal J, Denhez C, Coantic-Castex S, Martinez A, Harakat D, Douki T, Guillaume D, Clivio P. SN- and NS-puckered sugar conformers are precursors of the (6-4) photoproduct in thymine dinucleotide. Org Biomol Chem 2022; 20:2300-2307. [PMID: 35253821 DOI: 10.1039/d2ob00044j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Some amount of furanose in a southern conformation, possibly in both, but certainly in one of the two adjacent nucleotides of a dipyrimidine site, is necessary for (6-4) photoproduct formation in oligonucleotides. To explore the necessity, role, and most favorable location of each South sugar conformer in the formation of the (6-4) adduct in the thymine dinucleotide TpT, the photochemical behavior of two synthetic analogues, in which the South sugar conformation is prohibited for one of their two sugars, has been examined. Herein, we experimentally demonstrate that the presence of one sugar presenting some amount of South puckering, at any of the extremities, is sufficient to trigger (6-4) adduct formation. Nonetheless, the photochemical behavior of the dinucleotide with a South-puckered conformation at the 5'-end, mimics more closely that of TpT. In addition, using the 5' North 3' South-dilocked dinucleotide, we demonstrate that the flexibility of the South pucker at the 3'-end has little influence on the (6-4) adduct formation.
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Affiliation(s)
- Jouda Jakhlal
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR de Pharmacie, 51100 Reims, France.
| | - Clément Denhez
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR de Pharmacie, 51100 Reims, France.
- MaSCA, P3M, UFR des Sciences Exactes et Naturelles, 51100 Reims, France
| | - Stéphanie Coantic-Castex
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR de Pharmacie, 51100 Reims, France.
| | - Agathe Martinez
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR des Sciences Exactes et Naturelles, 51100 Reims, France
| | - Dominique Harakat
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR des Sciences Exactes et Naturelles, 51100 Reims, France
| | - Thierry Douki
- Université Grenoble Alpes, CEA, CNRS, IRIG, SyMMES, 38000 Grenoble, France
| | - Dominique Guillaume
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR de Pharmacie, 51100 Reims, France.
| | - Pascale Clivio
- Université de Reims Champagne Ardenne, Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, UFR de Pharmacie, 51100 Reims, France.
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Wagenknecht H. Remote Photodamaging of DNA by Photoinduced Energy Transport. Chembiochem 2022; 23:e202100265. [PMID: 34569126 PMCID: PMC9292490 DOI: 10.1002/cbic.202100265] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 09/14/2021] [Indexed: 12/11/2022]
Abstract
Local DNA photodamaging by light is well-studied and leads to a number of structurally identified direct damage, in particular cyclobutane pyrimidine dimers, and indirect oxidatively generated damage, such as 8-oxo-7,8-hydroxyguanine. Similar damages have now been found at remote sites, at least more than 105 Å (30 base pairs) away from the site of photoexcitation. In contrast to the established mechanisms of local DNA photodamaging, the processes of remote photodamage are only partially understood. Known pathways include those to remote oxidatively generated DNA photodamages, which were elucidated by studying electron hole transport through the DNA about 20 years ago. Recent studies with DNA photosensitizers and mechanistic proposals on photoinduced DNA-mediated energy transport are summarized in this minireview. These new mechanisms to a new type of remote DNA photodamaging provide an important extension to our general understanding to light-induced DNA damage and their mutations.
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Affiliation(s)
- Hans‐Achim Wagenknecht
- Institute of Organic ChemistryKarlsruhe Institute of Technology (KIT)Fritz-Haber-Weg 676131KarlsruheGermany
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Lu C, Gutierrez-Bayona NE, Taylor JS. The effect of flanking bases on direct and triplet sensitized cyclobutane pyrimidine dimer formation in DNA depends on the dipyrimidine, wavelength and the photosensitizer. Nucleic Acids Res 2021; 49:4266-4280. [PMID: 33849058 PMCID: PMC8096240 DOI: 10.1093/nar/gkab214] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 03/15/2021] [Accepted: 04/08/2021] [Indexed: 12/11/2022] Open
Abstract
Cyclobutane pyrimidine dimers (CPDs) are the major products of DNA produced by direct absorption of UV light, and result in C to T mutations linked to human skin cancers. Most recently a new pathway to CPDs in melanocytes has been discovered that has been proposed to arise from a chemisensitized pathway involving a triplet sensitizer that increases mutagenesis by increasing the percentage of C-containing CPDs. To investigate how triplet sensitization may differ from direct UV irradiation, CPD formation was quantified in a 129-mer DNA designed to contain all 64 possible NYYN sequences. CPD formation with UVB light varied about 2-fold between dipyrimidines and 12-fold with flanking sequence and was most frequent at YYYR and least frequent for GYYN sites in accord with a charge transfer quenching mechanism. In contrast, photosensitized CPD formation greatly favored TT over C-containing sites, more so for norfloxacin (NFX) than acetone, in accord with their differing triplet energies. While the sequence dependence for photosensitized TT CPD formation was similar to UVB light, there were significant differences, especially between NFX and acetone that could be largely explained by the ability of NFX to intercalate into DNA.
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Affiliation(s)
- Chen Lu
- Department of Chemistry, Washington University, One Brookings Dr., St. Louis, MO 63130, USA
| | | | - John-Stephen Taylor
- Department of Chemistry, Washington University, One Brookings Dr., St. Louis, MO 63130, USA
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Lee W, Matsika S. Stabilization of the Triplet Biradical Intermediate of 5-Methylcytosine Enhances Cyclobutane Pyrimidine Dimer (CPD) Formation in DNA. Chemistry 2020; 26:14181-14186. [PMID: 32809239 DOI: 10.1002/chem.202002834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/01/2020] [Indexed: 11/08/2022]
Abstract
Cyclobutane pyrimidine dimer (CPD) is a photoproduct formed by two stacked pyrimidine bases through a cycloaddition reaction upon irradiation. Owing to its close association with skin cancer, the mechanism of CPD formation has been studied thoroughly. Among many aspects of CPD, its formation involving 5-methylcytosine (5mC) has been of special interest because the CPD yield is known to increase with C5-methylation of cytosine. In this work, high-level quantum mechanics/molecular mechanics (QM/MM) calculations are used to examine a previously experimentally detected pathway for CPD formation in hetero (thymine-cytosine and thymine-5mC) dipyrimidines, which is facilitated through intersystem crossing in thymine and formation of a triplet biradical intermediate. A DNA duplex model system containing a core sequence TmCG or TCG is used. The stabilization of a radical center in the biradical intermediate by the methyl group of 5mC can lead to increased CPD yield in TmCG compared with its non-methylated counterpart, TCG, thereby suggesting the existence of a new pathway of CPD formation enhanced by 5mC.
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Affiliation(s)
- Wook Lee
- Department of Biochemistry, Kangwon National University, Chuncheon, 24341, South Korea
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, Philadelphia, PA, 19122, USA
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Gontcharov J, Liu L, Pilles BM, Carell T, Schreier WJ, Zinth W. Triplet-Induced Lesion Formation at CpT and TpC Sites in DNA. Chemistry 2019; 25:15164-15172. [PMID: 31538684 PMCID: PMC6899856 DOI: 10.1002/chem.201903573] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Indexed: 12/22/2022]
Abstract
UV irradiation induces DNA lesions particularly at dipyrimidine sites. Using time-resolved UV pump (250 nm) and mid-IR probe spectroscopy the triplet pathway of cyclobutane pyrimidine dimer (CPD) formation within TpC and CpT sequences was studied. The triplet state is initially localized at the thymine base but decays with 30 ns under formation of a biradical state extending over both bases of the dipyrimidine. Subsequently this state either decays back to the electronic ground state on the 100 ns time scale or forms a cyclobutane pyrimidine dimer lesion (CPD). Stationary IR spectroscopy and triplet sensitization via 2'-methoxyacetophenone (2-M) in the UVA range shows that the lesions are formed with an efficiency of approximately 1.5 %. Deamination converts the cytosine moiety of the CPD lesions on the time scale of 10 hours into uracil which gives CPD(UpT) and CPD(TpU) lesions in which the coding potential of the initial cytosine base is vanished.
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Affiliation(s)
- Julia Gontcharov
- Lehrstuhl für BioMolekulare OptikFakultät für Physik and Center for Integrated Protein Science Munich CIPSMLudwig-Maximilians-Universität MünchenOettingenstr. 6780538MünchenGermany
| | - Lizhe Liu
- Lehrstuhl für BioMolekulare OptikFakultät für Physik and Center for Integrated Protein Science Munich CIPSMLudwig-Maximilians-Universität MünchenOettingenstr. 6780538MünchenGermany
| | - Bert M. Pilles
- Lehrstuhl für BioMolekulare OptikFakultät für Physik and Center for Integrated Protein Science Munich CIPSMLudwig-Maximilians-Universität MünchenOettingenstr. 6780538MünchenGermany
| | - Thomas Carell
- Center for Integrated Protein Science am Department ChemistryLudwig-Maximilians-Universität MünchenButenandtstraße 5–1381377MünchenGermany
| | - Wolfgang J. Schreier
- Lehrstuhl für BioMolekulare OptikFakultät für Physik and Center for Integrated Protein Science Munich CIPSMLudwig-Maximilians-Universität MünchenOettingenstr. 6780538MünchenGermany
| | - Wolfgang Zinth
- Lehrstuhl für BioMolekulare OptikFakultät für Physik and Center for Integrated Protein Science Munich CIPSMLudwig-Maximilians-Universität MünchenOettingenstr. 6780538MünchenGermany
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