1
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Xu P, Wang D, Li D, Long J, Zhang S, Zhang B. UV wavelength-dependent photoionization quantum yields for the dark 1nπ* state of aqueous thymidine. Phys Chem Chem Phys 2024. [PMID: 39229763 DOI: 10.1039/d4cp02594f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
Despite the important role of the dark 1nπ* state in the photostability of thymidine in aqueous solution, no detailed ultraviolet (UV) wavelength-dependent investigation of the 1nπ* quantum yield (QY) in aqueous thymidine has been experimentally performed. Here, we investigate the wavelength-dependent photoemission spectra of aqueous thymidine from 266.7 to 240 nm using liquid-microjet photoelectron spectroscopy. Two observed ionization channels are assigned to resonant ionizations from 1ππ* to the cationic ground state D0 (π-1) and 1nπ* to the cationic excited state D1 (n-1). The weak 1nπ* → D1 ionization channel appears due to ultrafast 1ππ* → 1nπ* internal conversion within the pulse duration of ∼180 fs. The obtained 1nπ* quantum yields exhibit a strong wavelength dependence, ranging from 0 to 0.27 ± 0.01, suggesting a hitherto uncharacterized 1nπ* feature. The corresponding vertical ionization energies (VIEs) of D0 and D1 of aqueous thymidine are experimentally determined to be 8.47 ± 0.12 eV and 9.22 ± 0.29 eV, respectively. Our UV wavelength-dependent QYs might indicate that different structural critical points to connect the multidimensional 1ππ*/1nπ* conical intersection seam onto the multidimensional potential energy surface of the 1ππ* state might exist and determine the relaxation processes of aqueous thymidine upon UV excitation.
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Affiliation(s)
- Piao Xu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dongdong Wang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Duoduo Li
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jinyou Long
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Song Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bing Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
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2
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Chen Z, Wang X, Jia M, He X, Pan H, Chen J. Ribose and Deoxyribose Group Alter Excited-State Dynamics of 5-Azacytosine in Solution. Photochem Photobiol 2024; 100:291-297. [PMID: 35993879 DOI: 10.1111/php.13696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/16/2022] [Indexed: 10/15/2022]
Abstract
5-Azacytosine (5-AC) is one of the best interesting noncanonical nucleobases due to its functionalization and structural imitation of natural bases. 5-AC can be used as the scaffold of two important chemotherapeutic medicines, 5-azacytidine and 2'-deoxy-5-azacytidine. Furthermore, increased sensitivity to UV leads to the photochemical effects of 5-AC also attracted attention. Yet, no study has been reported to explore the effect of glycosyl groups on the photophysical and photochemical properties of 5-AC, which can help to reveal the photostability of related actual clinic drugs. In this study, the excited-state dynamics of 5-azacytidine and 2'-deoxy-5-azacytidine are studied by femtosecond transient absorption and quantum-chemical calculations while revisiting that of 5-AC with a wider probe spectral range. It is shown that glycosyl substitution on the N1 position leads to ultrafast excited-state relaxation within several picoseconds in both nucleosides, which is distinct compared with the 17 ps lifetime seen in 5-AC. It is proposed that these changes are due to altering the energy level of the dark nπ* state. Moreover, our results suggest that it should be cautioned to simply replace sugar groups with methyl groups when doing a theoretical calculation study on nucleobases and their derivatives.
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Affiliation(s)
- Ziwei Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
| | - Menghui Jia
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
| | - Xiaoxiao He
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
| | - Haifeng Pan
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China
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3
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Ma C, Xiong Q, Lin J, Wong AKW, Wang M, Kwok WM. Ultrafast excited state dynamics of isocytosine unveiled by femtosecond broadband time-resolved spectroscopy combined with density functional theoretical study. Photochem Photobiol 2024; 100:355-367. [PMID: 37688287 DOI: 10.1111/php.13849] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 08/12/2023] [Accepted: 08/14/2023] [Indexed: 09/10/2023]
Abstract
Isocytosine, having important applications in antivirus and drug development, is among the building blocks of Hachimoji nucleic acids. In this report, we present an investigation of the excited state dynamics of isocytosine in both protic and aprotic solvents, which was conducted by a combination of methods including steady-state spectroscopy, femtosecond broadband time-resolved fluorescence, and transient absorption. These methods were coupled with density functional and time-dependent density functional theory calculations. The results of our study provide the first direct evidence for a highly efficient nonradiative mechanism achieved through internal conversion from the ππ* state of the isocytosine keto-N(3)H form occurring within subpicoseconds and picoseconds following photo-excitation. Our study also unveils a crucial role of solvent, particularly solute-solvent hydrogen bonding, in determining the tautomeric composition and regulating the pathways and dynamics of the deactivation processes. The deactivation processes of isocytosine in the solvents examined are found to be distinct from those of cytosine and the case known for isocytosine in the gas phase mainly due to different tautomeric forms involved. Overall, our findings demonstrate the high photo-stability of isocytosine in the solution and showcase the remarkable effect of covalent modification in altering the spectral character and excited state dynamics of nucleobases.
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Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, China
| | - Qingwu Xiong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China
| | - Jingdong Lin
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, China
| | - Allen Ka-Wa Wong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China
| | - Mingliang Wang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, China
| | - Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China
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4
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Martinez-Fernandez L, Improta R. The photophysics of protonated cytidine and hemiprotonated cytidine base pair: A computational study. Photochem Photobiol 2024; 100:314-322. [PMID: 37409732 DOI: 10.1111/php.13832] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 05/25/2023] [Accepted: 06/19/2023] [Indexed: 07/07/2023]
Abstract
We here study the effect that a lowering of the pH has on the excited state processes of cytidine and a cytidine/cytidine pair in solution, by integrating time-dependent density functional theory and CASSCF/CASPT2 calculations, and including solvent by a mixed discrete/continuum model. Our calculations reproduce the effect of protonation at N3 on the steady-state infrared and absorption spectra of a protonated cytidine (CH+ ), and predict that an easily accessible non-radiative deactivation route exists for the spectroscopic state, explaining its sub-ps lifetime. Indeed, an extremely small energy barrier separates the minimum of the lowest energy bright state from a crossing region with the ground electronic state, reached by out-of-plane motion of the hydrogen substituents of the CC double bond, the so-called ethylenic conical intersection typical of cytidine and other pyrimidine bases. This deactivation route is operative for the two bases forming an hemiprotonated cytidine base pair, [CH·C]+ , the building blocks of I-motif secondary structures, whereas interbase processes play a minor role. N3 protonation disfavors instead the nπ* transitions, associated with the long-living components of cytidine photoactivated dynamics.
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Affiliation(s)
- Lara Martinez-Fernandez
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemical Sciences (IADCHEM), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Madrid, Spain
| | - Roberto Improta
- Consiglio Nazionale delle Ricerche, Istituto di Biostrutture e Bioimmagini (IBB-CNR), Naples, Italy
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5
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Zhou Q, Hao Y, Jie J, Wang S, Xia Y, Yang C, Liu L, Fang WH, Su H. Dual Functionality of 6-Methylthioguanine: Synergistic Effects Enhancing the Photolability of DNA Nucleobases. JACS AU 2024; 4:441-453. [PMID: 38425924 PMCID: PMC10900203 DOI: 10.1021/jacsau.3c00575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 01/05/2024] [Accepted: 01/05/2024] [Indexed: 03/02/2024]
Abstract
A small chemical modification of the nucleobase structure can significantly enhance the photoactivity of DNA, which may incur DNA damage, thus holding promising applications in photochemotherapy treatment of cancers or pathogens. However, single substitution confers only limited phototoxicity to DNA. Herein, we combine femtosecond and nanosecond time-resolved spectroscopy with high-level ab initio calculations to disentangle the excited-state dynamics of 6-methylthioguanine (me6-TG) under variable wavelength UVA excitation (310-330 nm). We find that double substitution of nucleobases (thionation and methylation) boosts the photoactivity by introducing more reactive channels. Intriguingly, 1nNπ*, rather than 1nSπ*, acts as the doorway state engendering the formation of the long-lived reactive triplet state in me6-TG. The 1nNπ* induces a low spin-orbit coupling of 8.3 cm-1, which increases the intersystem crossing (ISC) time (2.91 ± 0.14 ns). Despite the slowed ISC, the triplet quantum yield (ΦT) still accounts for a large fraction (0.6 ± 0.1), consistent with the potential energy surface that favors excited-state bifurcation to 1nNπ*min (3.36 ± 0.15 ps) rather than 1ππ*min (5.05 ± 0.26 ps), such that the subsequent ISC to triplet via 1nNπ*min constitutes the main relaxation pathway in me6-TG. Although this ΦT is inferior to its single-substituted predecessor 6-thioguanine (6-TG, 0.8 ± 0.2), the effect of thionation in synergy with methylation opens a unique C-S bond cleavage pathway through crossing to a repulsive 1πσ* state, generating thiyl radicals as highly reactive intermediates that may invoke biological damage. This photodissociation channel is extremely difficult for conventional nucleobases. These findings demonstrate the synergistic effects of double functionality substitution in modulating excited-state dynamics and enhancing the photolabile character of DNA nucleobases, providing inspirations for the rational design of advanced photodynamic and photochemotherapy approaches.
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Affiliation(s)
| | | | - Jialong Jie
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Shuo Wang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ye Xia
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Chunfan Yang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Lihong Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Wei-Hai Fang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, China
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6
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Ma C, Xiong Q, Lin J, Zeng X, Wang M, Kwok WM. Is 1-methylcytosine a faithful model compound for ultrafast deactivation dynamics of cytosine nucleosides in solution? Phys Chem Chem Phys 2024; 26:2963-2972. [PMID: 38214513 DOI: 10.1039/d3cp05509d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
1-Methylcytosine (1mCyt) is the base for nucleoside N1-methylpseudodeoxycytidine of Hachimoji nucleic acids and a frequently used model compound for theoretical studies on excited states of cytosine nucleosides. However, there is little experimental characterization of spectra and photo-dynamic properties of 1mCyt. Herein, we report a comprehensive investigation into excited state dynamics and effects of solvents on fluorescence dynamics of 1mCyt in both water and acetonitrile. The study employed femtosecond broadband time-resolved fluorescence, transient absorption, and steady-state spectroscopy, along with density functional theory and time-dependent density functional theory calculations. The results obtained provide the first experimental evidence for identifying a dark-natured ∼5.7 ps lifetime nπ* state in the ultrafast non-radiative deactivation with 1mCyt in aqueous solution. This study also demonstrates a significant effect of the solvent on 1mCyt's fluorescence emission, which highlights the crucial role of solute-solvent hydrogen bonding in altering structures and reshaping the radiative as well as nonradiative dynamics of the 1mCyt's ππ* state in the aprotic solvent compared to the protic solvent. The solvent effect exhibited by 1mCyt is distinctive from that known for deoxycytidine, indicating the need for caution in using 1mCyt for modelling the ultrafast dynamics of Cyt nucleosides in solvents with varying properties. Overall, our study unveils a deactivation mechanism that confers a high degree of photo-stability for 1mCyt in solution, shedding light on the molecular basis for solvent-induced effects on the excited state dynamics of nucleobases and derivatives.
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Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, P. R. China.
| | - Qingwu Xiong
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, P. R. China.
- College of Physics and optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, P. R. China
| | - Jingdong Lin
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, P. R. China.
| | - Xiaoyan Zeng
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, P. R. China.
| | - Mingliang Wang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, P. R. China.
| | - Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, 999077, P. R. China.
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7
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Hoehn SJ, Krul SE, Pogharian MM, Mao E, Crespo-Hernández CE. Photochemical Stability of 5-Methylcytidine Relative to Cytidine: Photophysical Insight for mRNA Therapeutic Applications. J Phys Chem Lett 2023; 14:10856-10862. [PMID: 38032072 DOI: 10.1021/acs.jpclett.3c01606] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
5-Methylcytidine (5mCyd) has recently been investigated with renewed interest in its utilization in mRNA therapeutics. However, its photostability following exposure to electromagnetic radiation has been overlooked. This Letter compares the photostability and excited-state dynamics of 5mCyd with those of the canonical RNA nucleoside, cytidine (Cyd), using steady-state and femtosecond transient absorption spectroscopy under physiologic conditions. 5mCyd is shown to have a 5-fold higher fluorescence yield and a 5-fold longer 1ππ* excited-state decay lifetime. Importantly, however, the excited-state population in 5mCyd decays primarily by internal conversion, with a photodegradation rate 3 times smaller than that in Cyd. In Cyd, the population of a 1nπ* state with a lifetime of ca. 45 ps is implicated in the formation 6-hydroxycytidine and other photoproducts.
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Affiliation(s)
- Sean J Hoehn
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Sarah E Krul
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Michael M Pogharian
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Erqian Mao
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
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8
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Zhao L, Geng X, Han G, Guo Y, Liu R, Chen J. Revealing the excited-state dynamics of cytidine and the role of excited-state proton transfer process. Phys Chem Chem Phys 2023; 25:32002-32009. [PMID: 37975722 DOI: 10.1039/d3cp03683a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
The high photostability of DNAs and RNAs is inextricably related to the photochemical and photophysical properties of their building blocks, nucleobases and nucleosides, which can dissipate the absorbed UV light energy in a harmless manner. The deactivation mechanism of the nucleosides, especially the decay pathways of cytidine (Cyd), has been a matter of intense debate. In the current study, we employ high-level electronic structure calculations combined with excited state non-adiabatic dynamic simulations to provide a clear picture of the excited state deactivation of Cyd in both gas phase and aqueous solution. In both environments, a barrierless decay path driven by the ring-puckering motion and a relaxation channel with a small energy barrier driven by the elongation motion of CO bond are assigned to <200 fs and sub-picosecond decay time component, respectively. The presence of ribose group has a subtle effect on the dynamic behavior of Cyd in gas phase as the ribose-to-base hydrogen/proton transfer process is energetically inaccessible with a sizable energy barrier of about 1.4 eV. However, this energy barrier is significantly reduced in water, especially when an explicit water molecule is present. Therefore, we argue that the long-lived decay channel found in aqueous solution could be assigned to the Cyd-water intermolecular hydrogen/proton transfer process. The present study postulates a novel scenario toward deep understanding the intrinsic photostability of DNAs and RNAs and provides solid evidence to disclose the long history debate of cytidine excited-state decay mechanism, especially for the assignment of experimentally observed time components.
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Affiliation(s)
- Li Zhao
- College of Science, China University of Petroleum (East China), Qingdao 266580, Shandong, China.
| | - Xuehui Geng
- College of Science, China University of Petroleum (East China), Qingdao 266580, Shandong, China.
| | - Guoxia Han
- College of Science, China University of Petroleum (East China), Qingdao 266580, Shandong, China.
| | - Yahui Guo
- College of Science, China University of Petroleum (East China), Qingdao 266580, Shandong, China.
| | - Runze Liu
- Institute of Molecular Sciences and Engineering, Shandong University, Qingdao 266235, P. R. China
| | - Junsheng Chen
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 KøbenhavnØ, Denmark.
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9
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Cuéllar-Zuquin J, Pepino AJ, Fdez. Galván I, Rivalta I, Aquilante F, Garavelli M, Lindh R, Segarra-Martí J. Characterizing Conical Intersections in DNA/RNA Nucleobases with Multiconfigurational Wave Functions of Varying Active Space Size. J Chem Theory Comput 2023; 19:8258-8272. [PMID: 37882796 PMCID: PMC10851440 DOI: 10.1021/acs.jctc.3c00577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 10/13/2023] [Accepted: 10/13/2023] [Indexed: 10/27/2023]
Abstract
We characterize the photochemically relevant conical intersections between the lowest-lying accessible electronic excited states of the different DNA/RNA nucleobases using Cholesky decomposition-based complete active space self-consistent field (CASSCF) algorithms. We benchmark two different basis set contractions and several active spaces for each nucleobase and conical intersection type, measuring for the first time how active space size affects conical intersection topographies in these systems and the potential implications these may have toward their description of photoinduced phenomena. Our results show that conical intersection topographies are highly sensitive to the electron correlation included in the model: by changing the amount (and type) of correlated orbitals, conical intersection topographies vastly change, and the changes observed do not follow any converging pattern toward the topographies obtained with the largest and most correlated active spaces. Comparison across systems shows analogous topographies for almost all intersections mediating population transfer to the dark 1nO/Nπ* states, while no similarities are observed for the "ethylene-like" conical intersection ascribed to mediate the ultrafast decay component to the ground state in all DNA/RNA nucleobases. Basis set size seems to have a minor effect, appearing to be relevant only for purine-based derivatives. We rule out structural changes as a key factor in classifying the different conical intersections, which display almost identical geometries across active space and basis set change, and we highlight instead the importance of correctly describing the electronic states involved at these crossing points. Our work shows that careful active space selection is essential to accurately describe conical intersection topographies and therefore to adequately account for their active role in molecular photochemistry.
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Affiliation(s)
- Juliana Cuéllar-Zuquin
- Instituto
de Ciencia Molecular, Universitat de Valencia, P.O. Box 22085, ES-46071 Valencia, Spain
| | - Ana Julieta Pepino
- Dipartimento
di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Ignacio Fdez. Galván
- Department
of Chemistry − BMC, Uppsala University, P.O. Box 576, SE-75123 Uppsala, Sweden
| | - Ivan Rivalta
- Dipartimento
di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
- ENSL,
CNRS, Laboratoire de Chimie UMR 5182, 46 Allée d’Italie, 69364 Lyon, France
| | - Francesco Aquilante
- Theory
and Simulation of Materials (THEOS), and National Centre for Computational
Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Marco Garavelli
- Dipartimento
di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Roland Lindh
- Department
of Chemistry − BMC, Uppsala University, P.O. Box 576, SE-75123 Uppsala, Sweden
| | - Javier Segarra-Martí
- Instituto
de Ciencia Molecular, Universitat de Valencia, P.O. Box 22085, ES-46071 Valencia, Spain
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10
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Reza MM, Durán-Hernández J, González-Cano B, Jara-Cortés J, López-Arteaga R, Cadena-Caicedo A, Muñoz-Rugeles L, Hernández-Trujillo J, Peon J. Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms. J Phys Chem B 2023; 127:8432-8445. [PMID: 37733881 DOI: 10.1021/acs.jpcb.3c03246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
Abstract
Nicotinamide adenine dinucleotide (NADH) is an important enzyme cofactor with emissive properties that allow it to be used in fluorescence microscopies to study cell metabolism. Its oxidized form NAD+, on the other hand, is considered to produce negligible fluorescence. In this contribution, we describe the photophysics of the isolated nicotinamidic system in both its reduced and oxidized states. This was achieved through the study of model molecules that do not carry the adenine nucleotide since its absorbance would overlap with the absorption spectrum of the nicotinamidic chromophores. We studied three model molecules: nicotinamide (niacinamide, an oxidized form without nitrogen substitution), the oxidized chromophore 1-benzyl-3-carbamoyl-pyridinium bromide (NBzOx), and its reduced form 1-benzyl-1,4-dihydronicotinamide (NBz). For a full understanding of the dynamics, we performed both femtosecond-resolved emission and transient absorption experiments. The oxidized systems, nicotinamide and NBzOx, have similar photophysics, where the originally excited bright state decays on an ultrafast timescale of less than 400 fs. The depopulation of this state is followed by excited-state positive absorption signals, which evolve in two timescales: the first one is from 1 to a few picoseconds and is followed by a second decaying component of 480 ps for nicotinamide in water and of 80-90 ps for nicotinamide in methanol and NBzOx in aqueous solution. The long decay times are assigned as the S1 lifetimes populated from the original higher-lying bright singlet, where this state is nonemissive but can be detected by transient absorption. While for NBzOx in aqueous solution and for nicotinamide in methanol, the S1 signal decays to the solvent-only level, for the aqueous solutions of nicotinamide, a small transient absorption signal remains after the 480 ps decay. This residual signal was assigned to a small population of triplet states formed during the slower S1 decay for nicotinamide in water. The experimental results were complemented by XMS-CASPT2 calculations, which reveal that in the oxidized forms, the rapid evolution of the initial π-π* state is due to a direct crossing with lower-energy dark n-π* singlet states. This coincides with the experimental observation of long-lived nonemissive states (80 to 480 ps depending on the system). On the other hand, the reduced model compound NBz has a long-lived emissive π-π* S1 state, which decays with a 510 ps time constant, similarly to the parent compound NADH. This is consistent with the XMS-CASPT2 calculations, which show that for the reduced chromophore, the dark states lie at higher energies than the bright π-π* S1 state.
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Affiliation(s)
- Mariana M Reza
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Durán-Hernández
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Beatriz González-Cano
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Jara-Cortés
- Unidad Académica de Ciencias Básicas e Ingenierías, Universidad Autónoma de Nayarit, Tepic 63155, México
| | - Rafael López-Arteaga
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Andrea Cadena-Caicedo
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Leonardo Muñoz-Rugeles
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Hernández-Trujillo
- Departamento de Física y Química Teórica, Facultad de Química, UNAM, Ciudad de México 04510, México
| | - Jorge Peon
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
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11
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Chang XP, Fan FR, Zhang TS, Xie BB. Quantum mechanics/molecular mechanics studies on the excited-state decay mechanisms of cytidine aza-analogues: 5-azacytidine and 2'-deoxy-5-azacytidine in aqueous solution. Phys Chem Chem Phys 2023; 25:26258-26269. [PMID: 37743787 DOI: 10.1039/d3cp03628f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The excited state properties and deactivation pathways of two DNA methylation inhibitors, i.e., 5-azacytidine (5ACyd) and 2'-deoxy-5-azacytidine (5AdCyd) in aqueous solution, are comprehensively explored with the QM(CASPT2//CASSCF)/MM protocol. We systematically map the feasible decay mechanisms based on the obtained excited-state decay paths involving all the identified minimum-energy structures, conical intersections, and crossing points driving the different internal conversion (IC) and intersystem crossing (ISC) routes in and between the 1ππ*, 1nπ*, 3ππ*, 3nπ*, and S0 states. Unlike the 1nπ* state below the 1ππ* state in 5ACyd, deoxyribose group substitution at the N1 position leads to the 1ππ* state becoming the S1 state in 5AdCyd. In 5ACyd and 5AdCyd, the initially populated 1ππ* state mainly deactivates to the S0 state through the direct 1ππ* → S0 IC or mediated by the 1nπ* state. The former nearly barrierless IC channel of 1ππ* → S0 occurs ultrafast via the nearby low-lying 1ππ*/S0 conical intersection. In the latter IC channel of 1ππ* → 1nπ* → S0, the initially photoexcited 1ππ* state first approaches the nearby S2/S1 conical section 1ππ*/1nπ* and then undergoes efficient IC to the 1nπ* state, followed by the further IC to the initial S0 state via the S1/S0 conical intersection 1nπ*/S0. The 1nπ*/S0 conical intersection is estimated to be located 6.0 and 4.9 kcal mol-1 above the 1nπ* state minimum in 5ACyd and 5AdCyd, respectively, at the QM(CASPT2)/MM level. In addition to the efficient singlet-mediated IC channels, the minor ISC routes would populate 1ππ* to T1(ππ*) through 1ππ* → T1 or 1ππ* → 1nπ* → T1. Relatively, the 1ππ* → 1nπ* → T1 route benefits from the spin-orbit coupling (SOC) of 1nπ*/3ππ* of 8.7 cm-1 in 5ACyd and 10.2 cm-1 in 5AdCyd, respectively. Subsequently, the T1 system will approach the nearby T1/S0 crossing point 3ππ*/S0 driving it back to the S0 state. Given the 3ππ*/S0 crossing point located above the T1 minimum and the small T1/S0 SOC, i.e., 8.4 kcal mol-1 and 2.1 cm-1 in 5ACyd and 6.8 kcal mol-1 and 1.9 cm-1 in 5AdCyd, respectively, the slow T1 → S0 would trap the system in the T1 state for a while. The present work could contribute to understanding the mechanistic photophysics and photochemistry of similar aza-nucleosides and their derivatives.
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Affiliation(s)
- Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, China.
| | - Feng-Ran Fan
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, China.
| | - Teng-Shuo Zhang
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China
| | - Bin-Bin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, Hangzhou 311231, China
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12
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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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13
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Tichý O, Pederzoli M, Pittner J, Burda JV. Vertical Excitation Energies and Lifetimes of the Two Lowest Singlet Excited States of Cytosine, 5-Aza-cytosine, and the Triazine Family: Quantum Mechanics-Molecular Mechanics Studies. J Chem Theory Comput 2023; 19:1976-1985. [PMID: 36961980 PMCID: PMC10100535 DOI: 10.1021/acs.jctc.2c01262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2023]
Abstract
A swarm of semi-classical quantum mechanics/molecular mechanics molecular-dynamics simulations where OM2/MNDO is combined with the Gromacs program for consideration of explicit water is performed, solving the time-dependent Schrödinger equation in each step of the trajectories together with the Tully's fewest switches algorithm. Within this stochastic treatment, time dependent probabilities of the three lowest electronic states are determined. The fact that nucleobases are quickly deactivated is confirmed in the cytosine case where our best lifetime estimation is τ1=0.82 ps for the model with 100 water molecules with the SPCE force field and a time step of 0.1 fs. Lifetimes of the remaining molecules are visibly longer: 5-azacytosine, 2,4-diamino-1,3,5-triazine (DT), and 2,4,6-triamino-1,3,5-triazine (TT) molecules have an S1 → S0 de-excitation time of slightly above 10 ps. The lifetimes of the triazine family increases with the increasing number of exocyclic amino groups, that is, s-triazine < 2-amino-1,3,5-triazine < DT < TT. This can be explained by a higher mobility of the carbon-bonded hydrogen atoms in comparison with heavier amino groups since their movement is slowed down due to a substantially higher mass than hydrogen atoms, which can easier reach the out-of-plane positions required in the conical intersection structures. Moreover, bulkier NH2 ligands suffer due to greater friction caused by the surrounding water environment. These mechanical aspects caused a change in the explored lifetime dependences in comparison with our previous gas-phase study.
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Affiliation(s)
- Ondřej Tichý
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - Marek Pederzoli
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences, Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Jiří Pittner
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences, Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Jaroslav V Burda
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
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14
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Orimo N, Yamamoto YI, Karashima S, Boyer A, Suzuki T. Ultrafast Electronic Relaxation in 6-Methyluracil and 5-Fluorouracil in Isolated and Aqueous Conditions: Substituent and Solvent Effects. J Phys Chem Lett 2023; 14:2758-2763. [PMID: 36897645 DOI: 10.1021/acs.jpclett.3c00195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
We report ultrafast extreme ultraviolet photoelectron spectroscopy of 6-methyluracil (6mUra) and 5-fluorouracil (5FUra) in the gas phase and 6mUra and 5-fluorouridine in an aqueous environment. In the gas phase, internal conversion (IC) occurs from 1ππ* to 1nπ* states in tens of femtoseconds, followed by intersystem crossing to the 3ππ* state in several picoseconds. In an aqueous solution, 6mUra undergoes IC almost exclusively to the ground state (S0) in about 100 fs, which is essentially the same process as that for unsubstituted uracil, but much faster than that for thymine (5-methyluracil). The different dynamics for C5 and C6 methylation suggest that IC from 1ππ* to S0 is facilitated by out-of-plane (OOP) motion of the C5 substituent. The slow IC for C5-substituted molecules in an aqueous environment is ascribed to the solvent reorganization that is required for this OOP motion to occur. The slow rate for 5FUrd may arise in part from an increased barrier height due to C5 fluorination.
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Affiliation(s)
- Natsumi Orimo
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - Yo-Ichi Yamamoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - Shutaro Karashima
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - Alexie Boyer
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - Toshinori Suzuki
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
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15
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Miura Y, Yamamoto YI, Karashima S, Orimo N, Hara A, Fukuoka K, Ishiyama T, Suzuki T. Formation of Long-Lived Dark States during Electronic Relaxation of Pyrimidine Nucleobases Studied Using Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy. J Am Chem Soc 2023; 145:3369-3381. [PMID: 36724068 DOI: 10.1021/jacs.2c09803] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Ultrafast electronic relaxation of nucleobases from 1ππ* states to the ground state (S0) is considered essential for the photostability of DNA. However, transient absorption spectroscopy (TAS) has indicated that some nucleobases in aqueous solutions create long-lived 1nπ*/3ππ* dark states from the 1ππ* states with a high quantum yield of 0.4-0.5. We investigated electronic relaxation in pyrimidine nucleobases in both aqueous solutions and the gas phase using extreme ultraviolet (EUV) time-resolved photoelectron spectroscopy. Femtosecond EUV probe pulses cause ionization from all electronic states involved in the relaxation process, providing a clear overview of the electronic dynamics. The 1nπ* quantum yields for aqueous cytidine and uracil (Ura) derivatives were found to be considerably lower (<0.07) than previous estimates reported by TAS. On the other hand, aqueous thymine (Thy) and thymidine exhibited a longer 1ππ* lifetime and a higher quantum yield (0.12-0.22) for the 1nπ* state. A similar trend was found for isolated Thy and Ura in the gas phase: the 1ππ* lifetimes are 39 and 17 fs and the quantum yield for 1nπ* are 1.0 and 0.45 for Thy and Ura, respectively. The result indicates that single methylation to the C5 position hinders the out-of-plane deformation that drives the system to the conical intersection region between 1ππ* and S0, providing a large impact on the photophysics/photochemistry of a pyrimidine nucleobase. The significant reduction of 1nπ* yield in aqueous solution is ascribed to the destabilization of the 1nπ* state induced by hydrogen bonding.
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Affiliation(s)
- Yuta Miura
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Yo-Ichi Yamamoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Shutaro Karashima
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Natsumi Orimo
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Ayano Hara
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Kanae Fukuoka
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Tatsuya Ishiyama
- Department of Applied Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama930-8555, Japan
| | - Toshinori Suzuki
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
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16
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Dong T, Yu P, Zhao J, Wang J. Probing the local structure and dynamics of nucleotides using vibrationally enhanced alkynyl stretching. Phys Chem Chem Phys 2022; 24:29988-29998. [PMID: 36472165 DOI: 10.1039/d2cp03920f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Monitoring the site-specific local structure and dynamics of polynucleotides and DNA is important for understanding their biological functions. However, structurally characterizing these biomolecules with high time resolution has been known to be experimentally challenging. In this work, several 5-silylethynyl-2'-deoxynucleosides and 5-substituted phenylethynyl-2'-deoxynucleosides on the basis of deoxycytidine (dC) and deoxythymidine (dT) were synthesized, in which the alkynyl group shows intensified CC stretching vibration with infrared transition dipole moment magnitude close to that of typical CO stretching, and exhibits structural sensitivities in both vibrational frequency and spectral width. In particular, 5-trimethylsilylethynyl-2'-dC (TMSEdC, molecule 1a) was examined in detail using femtosecond nonlinear IR spectroscopy. The solvent dependent CC stretching frequency of 1a can be reasonably interpreted mainly as the hydrogen-bonding effect between the solvent and cytosine base ring structure. Transient 2D IR and pump-probe IR measurements of 1a carried out comparatively in two aprotic solvents (DMSO and THF) and one protic solvent (MeOH) further reveal solvent dependent ultrafast vibrational properties, including diagonal anharmonicity, spectral diffusion, vibrational relaxation and anisotropy dynamics. These observed sensitivities are rooted in an extended π-conjugation of the base ring structure in which the CC group is actively involved. Our results show that the intensified CC stretching vibration can potentially provide a site-specific IR probe for monitoring the equilibrium and ultrafast structural dynamics of polynucleotides.
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Affiliation(s)
- Tiantian Dong
- Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Pengyun Yu
- Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Juan Zhao
- Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jianping Wang
- Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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17
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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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18
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Cherneva TD, Todorova MM, Bakalska RI, Horkel E, Delchev VB. Non-radiative deactivation of excited cytosine: probing of different DFT functionals and basis sets in solvents with different polarity. J Mol Model 2022; 28:306. [PMID: 36085333 DOI: 10.1007/s00894-022-05313-6] [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: 06/17/2022] [Accepted: 08/30/2022] [Indexed: 11/28/2022]
Abstract
The vertical excitation and emission energies of the cytosine oxo-amino form were calculated at the TD DFT level of theory with several functionals, basis sets, and solvents with different polarity (PCM). They were compared with the experimental UV absorption and fluorescence maxima, revealing that the minimal deviation of the vertical excitation energies from the of UV absorption maxima can be achieved when the hybrid functional B3LYP is applied within the calculations. Regular correlations like curves with saturation between the vertical excitation/emission energies and the dielectric constants were registered. The relaxation of the 1ππ* excited state through an ethylene-like conical intersection S0/S1 should occur through decrease of the decay rate (commented qualitatively here) with the rise of the solvent polarity.
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Affiliation(s)
- T D Cherneva
- Faculty of Chemistry, University of Plovdiv, Tzar Assen 24 Str, Plovdiv, Bulgaria
| | - M M Todorova
- Faculty of Chemistry, University of Plovdiv, Tzar Assen 24 Str, Plovdiv, Bulgaria
| | - R I Bakalska
- Faculty of Chemistry, University of Plovdiv, Tzar Assen 24 Str, Plovdiv, Bulgaria
| | - E Horkel
- Inst. Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060, Vienna, Austria
| | - V B Delchev
- Faculty of Chemistry, University of Plovdiv, Tzar Assen 24 Str, Plovdiv, Bulgaria.
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19
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Krul SE, Costa GJ, Hoehn SJ, Valverde D, Oliveira LMF, Borin AC, Crespo-Hernández CE. Resolving Ultrafast Photoinitiated Dynamics of the Hachimoji 5-Aza-7-Deazaguanine Nucleobase: Impact of Synthetically Expanding the Genetic Alphabet. Photochem Photobiol 2022; 99:693-705. [PMID: 35938218 DOI: 10.1111/php.13688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 08/05/2022] [Indexed: 11/29/2022]
Abstract
The guanine derivative, 5-aza-7-deazaguanine (5N7C G) has recently been proposed as one of four unnatural bases, termed Hachimoji (8-letter) to expand the genetic code. We apply steady-state and time-resolved spectroscopy to investigate its electronic relaxation mechanism and probe the effect of atom substitution on the relaxation mechanism in polar protic and polar aprotic solvents. Mapping of the excited state potential energy surfaces is performed, from which the critical points are optimized by using the state-of-art Extended Multi-State Complete Active Space Second-Order Perturbation Theory. It is demonstrated that excitation to the lowest energy 1 ππ* state of 5N7C G results in complex dynamics leading to ca. 10 to 30-fold slower relaxation (depending on solvent) compared to guanine. A significant conformational change occurs at the S1 minimum, resulting in a 10-fold greater fluorescence quantum yield compared to guanine. The fluorescence quantum yield and S1 decay lifetime increase going from water to acetonitrile to propanol. The solvent-dependent results are supported by the quantum chemical calculations showing an increase in the energy barrier between the S1 minimum and the S1 /S0 conical intersection going from water to propanol. The longer lifetimes might make 5N7C G more photochemical active to adjacent nucleobases than guanine or other nucleobases within DNA.
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Affiliation(s)
- Sarah E Krul
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Ave, Cleveland, Ohio, 44106, United States
| | - Gustavo J Costa
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000. São Paulo, SP, Brazil
| | - Sean J Hoehn
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Ave, Cleveland, Ohio, 44106, United States
| | - Danillo Valverde
- Unité de Chimie Physique Theorique et Structurale, Namur Institute of Structured Matter, Université de Namur, B-5000, Namur, Belgium
| | - Leonardo M F Oliveira
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000. São Paulo, SP, Brazil
| | - Antonio Carlos Borin
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000. São Paulo, SP, Brazil
| | - Carlos E Crespo-Hernández
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Ave, Cleveland, Ohio, 44106, United States
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20
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Martínez Fernández L, Santoro F, Improta R. Nucleic Acids as a Playground for the Computational Study of the Photophysics and Photochemistry of Multichromophore Assemblies. Acc Chem Res 2022; 55:2077-2087. [PMID: 35833758 DOI: 10.1021/acs.accounts.2c00256] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
ConspectusThe interaction between light and multichromophoric assemblies (MCAs) is the primary event of many fundamental processes, from photosynthesis to organic photovoltaics, and it triggers dynamical processes that share remarkable similarities at the molecular scale: light absorption, energy and charge transfer, internal conversions, emission, and so on. Those events often involve many chromophores and different excited electronic states that are coupled on an ultrafast time scale. This Account aims to discuss some of the chemical physical effects ruling these processes, a fundamental step toward their control, based on our experience on nucleic acids.In the last 15 years, we have, indeed, studied the photophysics and photochemistry of DNA and its components. By combining different quantum mechanical methods, we investigated the molecular processes responsible for the damage of the genetic code or, on the contrary, those preventing it by dissipating the excess energy deposited in the system by UV absorption. Independently of its fundamental biological role, DNA, with its fluctuating closely stacked bases stabilized by weak nonbonding interactions, can be considered a prototypical MCA. Therefore, it allows one to tackle within a single system many of the conceptual and methodological challenges involved in the study of photoinduced processes in MCA.In this Account, by using the outcome of our studies on oligonucleotides as a guideline, we thus highlight the most critical modellistic issues to be faced when studying, either experimentally or computationally, the interaction between UV light and DNA and, at the same time, bring out their general relevance for the study of MCAs.We first discuss the rich photoactivated dynamics of nucleobases (the chromophores), highlighting the main effects modulating the interplay between their excited states and how the latter can affect the photoactivated dynamics of the polynucleotides, either providing effective monomer-like nonradiative decay routes or triggering reactive processes (e.g., triplet generation).We then tackle the reaction paths involving multiple bases, showing that in the DNA duplex the most important ones involve two stacked bases, forming a neutral excimer or a charge transfer (CT) state, which exhibit different spectral signatures and photochemical reactivity. In particular, we analyze the factors affecting the dynamic equilibrium between the excimer and CT, such as the fluctuations of the backbone or the rearrangement of the solvent.Next, we highlight the importance of the effects not directly connected to the chromophores, such as the flexibility of the backbone or the solvent effect. The former, affecting the stacking geometry of the bases, can determine the preference between different deactivation paths. The latter is particularly influential for CT states, making very important an accurate treatment of dynamical solvation effects, involving both the solvent bulk and specific solute-solvent interactions.In the last section, we describe the main methodological challenges related to the study of polynucleotide excited states and stress the benefits derived by the integration of complementary approaches, both computational and experimental. Only exploiting different point of views, in our opinion, it is possible to shed light on the complex phenomena triggered by light absorption in DNA, as in every MCA.
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Affiliation(s)
- Lara Martínez Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemistry (IADCHEM), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, 28049 Madrid, Spain
| | - Fabrizio Santoro
- Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area della Ricerca del CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Roberto Improta
- Istituto di Biostrutture e Bioimmagini-CNR (IBB-CNR), Via De Amicis 95, I-80145 Napoli, Italy
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21
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Lizondo-Aranda P, Martínez-Fernández L, Miranda MA, Improta R, Gustavsson T, Lhiaubet-Vallet V. The Excited State Dynamics of a Mutagenic Cytidine Etheno Adduct Investigated by Combining Time-Resolved Spectroscopy and Quantum Mechanical Calculations. J Phys Chem Lett 2022; 13:251-257. [PMID: 34968067 PMCID: PMC9135321 DOI: 10.1021/acs.jpclett.1c03534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/10/2021] [Indexed: 06/14/2023]
Abstract
Joint femtosecond fluorescence upconversion experiments and theoretical calculations provide a hitherto unattained degree of characterization and understanding of the mutagenic etheno adduct 3,N4-etheno-2'-deoxycytidine (εdC) excited state relaxation. This endogenously formed lesion is attracting great interest because of its ubiquity in human tissues and its highly mutagenic properties. The εdC fluorescence is modified with respect to that of the canonical base dC, with a 3-fold increased lifetime and quantum yield at neutral pH. This behavior is amplified upon protonation of the etheno ring (εdCH+). Quantum mechanical calculations show that the lowest energy state ππ*1 is responsible for the fluorescence and that the main nonradiative decay pathway to the ground state goes through an ethene-like conical intersection, involving the out-of-plane motion of the C5 and C6 substituents. This conical intersection is lower in energy than the ππ* state (ππ*1) minimum, but a sizable energy barrier explains the increase of εdC and εdCH+ fluorescence lifetimes with respect to that of dC.
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Affiliation(s)
- Paloma Lizondo-Aranda
- Instituto
Universitario Mixto de Tecnología Química (UPV-CSIC), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas, Avda de los Naranjos s/n, 46022 Valencia, Spain
| | - Lara Martínez-Fernández
- Departamento
de Química, Facultad de Ciencias and IADCHEM (Institute for
Advanced Research in Chemistry) Universidad
Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Miguel A. Miranda
- Instituto
Universitario Mixto de Tecnología Química (UPV-CSIC), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas, Avda de los Naranjos s/n, 46022 Valencia, Spain
| | - Roberto Improta
- Istituto
di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Napoli, Italy
| | - Thomas Gustavsson
- Université
Paris-Saclay, CEA, CNRS, LIDYL, 91191 Gif-sur-Yvette, France
| | - Virginie Lhiaubet-Vallet
- Instituto
Universitario Mixto de Tecnología Química (UPV-CSIC), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas, Avda de los Naranjos s/n, 46022 Valencia, Spain
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22
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Ventura E, Andrade do Monte S, T. do Casal M, Pinheiro M, Toldo JM, Barbatti M. Modeling the heating and cooling of a chromophore after photoexcitation. Phys Chem Chem Phys 2022; 24:9403-9410. [PMID: 35385568 PMCID: PMC9020442 DOI: 10.1039/d2cp00686c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The heating of a chromophore due to internal conversion and its cooling down due to energy dissipation to the solvent are crucial phenomena to characterize molecular photoprocesses. In this work, we simulated the ab initio nonadiabatic dynamics of cytosine, a prototypical chromophore undergoing ultrafast internal conversion, in three solvents—argon matrix, benzene, and water—spanning an extensive range of interactions. We implemented an analytical energy-transfer model to analyze these data and extract heating and cooling times. The model accounts for nonadiabatic effects, and excited- and ground-state energy transfer, and can analyze data from any dataset containing kinetic energy as a function of time. Cytosine heats up in the subpicosecond scale and cools down within 25, 4, and 1.3 ps in argon, benzene, and water, respectively. The time constants reveal that a significant fraction of the benzene and water heating occurs while cytosine is still electronically excited. An analytical energy-transfer model is implemented to obtain a chromophore's heating and cooling times in a given solvent by using quantities available in nonadiabatic dynamics simulations.![]()
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Affiliation(s)
- Elizete Ventura
- Universidade Federal da Paraíba, 58059-900, João Pessoa-PB, Brazil
| | | | | | - Max Pinheiro
- Aix Marseille University, CNRS, ICR, Marseille, France
| | | | - Mario Barbatti
- Aix Marseille University, CNRS, ICR, Marseille, France
- Institut Universitaire de France, 75231 Paris, France
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23
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Kabaciński P, Romanelli M, Ponkkonen E, Jaiswal VK, Carell T, Garavelli M, Cerullo G, Conti I. Unified Description of Ultrafast Excited State Decay Processes in Epigenetic Deoxycytidine Derivatives. J Phys Chem Lett 2021; 12:11070-11077. [PMID: 34748341 PMCID: PMC8607503 DOI: 10.1021/acs.jpclett.1c02909] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 11/01/2021] [Indexed: 06/13/2023]
Abstract
Epigenetic DNA modifications play a fundamental role in modulating gene expression and regulating cellular and developmental biological processes, thereby forming a second layer of information in DNA. The epigenetic 2'-deoxycytidine modification 5-methyl-2'-deoxycytidine, together with its enzymatic oxidation products (5-hydroxymethyl-2'-deoxycytidine, 5-formyl-2'-deoxycytidine, and 5-carboxyl-2'-deoxycytidine), are closely related to deactivation and reactivation of DNA transcription. Here, we combine sub-30-fs transient absorption spectroscopy with high-level correlated multiconfigurational CASPT2/MM computational methods, explicitly including the solvent, to obtain a unified picture of the photophysics of deoxycytidine-derived epigenetic DNA nucleosides. We assign all the observed time constants and identify the excited state relaxation pathways, including the competition of intersystem crossing and internal conversion for 5-formyl-2'-deoxycytidine and ballistic decay to the ground state for 5-carboxy-2'-deoxycytidine. Our work contributes to shed light on the role of epigenetic derivatives in DNA photodamage as well as on their possible therapeutic use.
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Affiliation(s)
- Piotr Kabaciński
- IFN-CNR,
Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Marco Romanelli
- Dipartimento
di Chimica Industriale, Università
degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Eveliina Ponkkonen
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, Munich 81377, Germany
| | - Vishal Kumar Jaiswal
- Dipartimento
di Chimica Industriale, Università
degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Thomas Carell
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, Munich 81377, Germany
| | - Marco Garavelli
- Dipartimento
di Chimica Industriale, Università
degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Giulio Cerullo
- IFN-CNR,
Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Irene Conti
- Dipartimento
di Chimica Industriale, Università
degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
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24
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Ho J, Cheng P. Ultrafast excited‐state dynamics of gas‐phase 5‐methylcytosine tautomers. J CHIN CHEM SOC-TAIP 2021. [DOI: 10.1002/jccs.202100254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jr‐Wei Ho
- Department of Chemistry National Tsing Hua University Hsinchu Taiwan
| | - Po‐Yuan Cheng
- Department of Chemistry National Tsing Hua University Hsinchu Taiwan
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25
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Wang X, Martínez-Fernández L, Zhang Y, Zhang K, Improta R, Kohler B, Xu J, Chen J. Solvent-Dependent Stabilization of a Charge Transfer State is the Key to Ultrafast Triplet State Formation in an Epigenetic DNA Nucleoside. Chemistry 2021; 27:10932-10940. [PMID: 33860588 DOI: 10.1002/chem.202100787] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Indexed: 11/10/2022]
Abstract
2'-Deoxy-5-formylcytidine (5fdCyd), a naturally occurring nucleoside found in mammalian DNA and mitochondrial RNA, exhibits important epigenetic functionality in biological processes. Because it efficiently generates triplet excited states, it is an endogenous photosensitizer capable of damaging DNA, but the intersystem crossing (ISC) mechanism responsible for ultrafast triplet state generation is poorly understood. In this study, time-resolved mid-IR spectroscopy and quantum mechanical calculations reveal the distinct ultrafast ISC mechanisms of 5fdCyd in water versus acetonitrile. Our experiment indicates that in water, ISC to triplet states occurs within 1 ps after 285 nm excitation. PCM-TD-DFT computations suggest that this ultrafast ISC is mediated by a singlet state with significant cytosine-to-formyl charge-transfer (CT) character. In contrast, ISC in acetonitrile proceeds via a dark 1 nπ* state with a lifetime of ∼3 ps. CT-induced ISC is not favored in acetonitrile because reaching the minimum of the gateway CT state is hampered by intramolecular hydrogen bonding, which enforces planarity between the aldehyde group and the aromatic group. Our study provides a comprehensive picture of the non-radiative decay of 5fdCyd in solution and new insights into the factors governing ISC in biomolecules. We propose that the intramolecular CT state observed here is a key to the excited-state dynamics of epigenetic nucleosides with modified exocyclic functional groups, paving the way to study their effects in DNA strands.
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Affiliation(s)
- Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200241, P. R. China
| | - Lara Martínez-Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemistry (IADCHEM), Universidad Autónoma de Madrid Campus de Excelencia UAM-CSIC Cantoblanco, 28049, Madrid, Spain
| | - Yuyuan Zhang
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, USA
| | - Kun Zhang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200241, P. R. China
| | - Roberto Improta
- Istituto di Biostrutture e Bioimmagini CNR, Via Mezzocannone 16, 80134, Napoli, Italy
| | - Bern Kohler
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, USA
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200241, P. R. China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, P. R. China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200241, P. R. China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, P. R. China
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26
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Kohl FR, Zhang Y, Charnay AP, Martínez-Fernández L, Kohler B. Ultrafast excited state dynamics of silver ion-mediated cytosine-cytosine base pairs in metallo-DNA. J Chem Phys 2021; 153:105104. [PMID: 32933288 DOI: 10.1063/5.0020463] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
To better understand the nexus between structure and photophysics in metallo-DNA assemblies, the parallel-stranded duplex formed by the all-cytosine oligonucleotide, dC20, and silver nitrate was studied by circular dichroism (CD), femtosecond transient absorption spectroscopy, and time-dependent-density functional theory calculations. Silver(I) ions mediate Cytosine-Cytosine (CC) base pairs by coordinating to the N3 atoms of two cytosines. Although these silver(I) mediated CC base pairs resemble the proton-mediated CC base pairs found in i-motif DNA at first glance, a comparison of experimental and calculated CD spectra reveals that silver ion-mediated i-motif structures do not form. Instead, the parallel-stranded duplex formed between dC20 and silver ions is proposed to contain consecutive silver-mediated base pairs with high propeller twist-like ones seen in a recent crystal structure of an emissive, DNA-templated silver cluster. Femtosecond transient absorption measurements with broadband probing from the near UV to the near IR reveal an unusually long-lived (>10 ns) excited state in the dC20 silver ion complex that is not seen in dC20 in single-stranded or i-motif forms. This state is also absent in a concentrated solution of cytosine-silver ion complexes that are thought to assemble into planar ribbons or sheets that lack stacked silver(I) mediated CC base pairs. The large propeller twist angle present in metal-mediated base pairs may promote the formation of long-lived charged separated or triplet states in this metallo-DNA.
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Affiliation(s)
- Forrest R Kohl
- Department of Chemistry and Biochemistry, 100 W. 18th Ave., Columbus, Ohio 43210, USA
| | - Yuyuan Zhang
- Department of Chemistry and Biochemistry, 100 W. 18th Ave., Columbus, Ohio 43210, USA
| | - Aaron P Charnay
- Department of Chemistry and Biochemistry, 100 W. 18th Ave., Columbus, Ohio 43210, USA
| | - Lara Martínez-Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemistry (IADCHEM), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Bern Kohler
- Department of Chemistry and Biochemistry, 100 W. 18th Ave., Columbus, Ohio 43210, USA
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27
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Chan RCT, Chan CTL, Ma C, Gu KY, Xie HX, Wong AKW, Xiong QW, Wang ML, Kwok WM. Long living excited state of protonated adenosine unveiled by ultrafast fluorescence spectroscopy and density functional theoretical study. Phys Chem Chem Phys 2021; 23:6472-6480. [PMID: 33729247 DOI: 10.1039/d0cp06439d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Adenosine (Ado) possesses ultrafast nonradiative dynamics accounting for its remarkably high photostability. The deactivation dynamics of Ado after protonation in an aqueous solution remains an elusive issue. Herein we report an investigation of the excited state dynamics of protonated Ado (AdoH+) performed using ultrafast time-resolved fluorescence spectroscopy combined with density functional theoretical calculation. The result obtained from comparison of conformers with protonation at different sites revealed that the syn-conformer with protonation occurring at the N3 position (syn-N3) is the predominant form of AdoH+ in the ground state, similar to that of Ado. In contrast, the fluorescence of AdoH+ with maximum intensity at 385 nm, significantly red-shifted from that of Ado, displaying decay dynamics composed of an ultrafast component with the lifetime of ∼0.5 ps and a slower one of ∼2.9 ns. The former is because of the decay of the syn-N3 conformer, similar to that reported for AdoH+ under the gas phase condition. The latter is due to the syn-N1 conformer formed via ultrafast proton transfer of the syn-N3. The excited state of syn-N1 has a peculiar nonplanar conformation over the purine molecule, which is responsible for the substantial Stokes shift showed in the fluorescence spectrum and correlates with a large energy barrier for nonradiative decay likely involving a reversed proton transfer. This study demonstrates the importance of protonation and solvent environment in altering dramatically the excited states of Ado, providing insight for better understanding nonradiative dynamics of both the monomeric bases and the oligomeric or polymeric DNAs.
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Affiliation(s)
- Ruth Chau-Ting Chan
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, P. R. China.
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28
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Yaghoubi Jouybari M, Liu Y, Improta R, Santoro F. Quantum dynamics of the ππ*/nπ* decay of the epigenetic nucleobase 1,5-dimethyl-cytosine in the gas phase. Phys Chem Chem Phys 2020; 22:26525-26535. [PMID: 33188675 DOI: 10.1039/d0cp04123h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We study the ultrafast dynamics of 1,5-dimethyl-cytosine, a model for 5-methyl-cytidine, after photoexcitation to the first two bright ππ* states, focusing on the possible population transfer to dark nπ* states. To that end we propagate the initial wave packets on the coupled potential energy surfaces of the seven lowest energy excited states modelled with a diabatic linear vibronic coupling (LVC) model, considering all the vibrational coordinates. Time-evolution is computed by the multilayer version of the multiconfigurational time dependent Hartree (ML-MCTDH) method. The LVC Hamiltonian is parametrized with time-dependent density functional theory (TD-DFT) calculations adopting PBE0 and CAM-B3LYP functionals, which provide a different energy gap between the lowest energy nπ* states and the spectroscopic ππ* state. Population of the lowest ππ* flows to a dark nπ* state which involves a lone pair (LP) of the carbonyl oxygen (nOπ*), but the extent of such transfer is much larger according to PBE0 than to CAM-B3LYP. Photoexcitation to the second bright state gives rise to much richer dynamics with an ultrafast (50 fs) complete decay to the lowest ππ*, to nOπ* and to another nπ* in which the excited electron comes from the LP of the ring nitrogen. We perform a detailed analysis of the vibronic dynamics both in terms of normal modes and valence coordinates (bond lengths and angles). The comparison with the analogous dynamics in 1-methyl-cytosine, a model for cytidine, provides insights into the effect of methylation at carbon 5 on the electronic and nuclear dynamics.
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Affiliation(s)
- Martha Yaghoubi Jouybari
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), SS di Pisa, Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa, Italy.
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29
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Yaghoubi Jouybari M, Liu Y, Improta R, Santoro F. Ultrafast Dynamics of the Two Lowest Bright Excited States of Cytosine and 1-Methylcytosine: A Quantum Dynamical Study. J Chem Theory Comput 2020; 16:5792-5808. [PMID: 32687360 DOI: 10.1021/acs.jctc.0c00455] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The nonadiabatic quantum dynamics (QD) of cytosine and 1-methylcytosine in the gas phase is simulated for 250 fs after a photoexcitation to one of the first two bright states. The nuclear wavepacket is propagated on the coupled diabatic potential energy surfaces of the lowest seven excited states, including ππ*, nπ*, and Rydberg states along all the vibrational degrees of freedom. We focus in particular on the interplay between the bright and the dark nπ* states, not considering the decay to the ground electronic state. To run these simulations, we implemented an automatic general procedure to parametrize linear vibronic coupling (LVC) models with time-dependent density functional theory (DFT) computations and interfaced it with Gaussian package. The wavepacket was propagated with the multilayer version of the multiconfigurational time dependent Hartree method. Two different density functionals, PBE0 and CAM-B3LYP, which provide a different description of the relative stability of the lowest energy dark states, were used to parametrize the LVC Hamiltonian. Part of the photoexcited population on lowest HOMO-LUMO transition (πHπL*) decays within less than 100 fs to a nπ* state which mainly involves a promotion of an electron from the oxygen lone pair to the LUMO (nOπL*). The population of the second ππ* state decays almost completely, in <100 fs, not only to πHπL* and to nOπL* states but also to another nπL* state involving the nitrogen lone pair. The efficiency of the adopted protocol allowed us to check the accuracy of the predictions by repeating the QD simulations with different LVC Hamiltonians parametrized either at the ground-state minimum or at stationary structures of different relevant excited states.
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Affiliation(s)
- Martha Yaghoubi Jouybari
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), SS di Pisa, Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa, Italy
| | - Yanli Liu
- School of Physics and Optoelectronics Engineering, Ludong University, 264025 Yantai, Shandong, PR China
| | - Roberto Improta
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Biostrutture e Bioimmagini (IBB-CNR), via Mezzocannone 16, I-80136 Napoli, Italy
| | - Fabrizio Santoro
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), SS di Pisa, Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa, Italy
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30
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Trachsel MA, Blaser S, Lobsiger S, Siffert L, Frey HM, Blancafort L, Leutwyler S. Locating Cytosine Conical Intersections by Laser Experiments and Ab Initio Calculations. J Phys Chem Lett 2020; 11:3203-3210. [PMID: 32251591 DOI: 10.1021/acs.jpclett.0c00779] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The decay mechanism of S0 → S1 excited cytosine (Cyt) and the effect of substitution are studied combining jet-cooled spectroscopy (nanosecond resonant two-photon ionization (R2PI) and picosecond lifetime measurements) with CASPT2//CASSCF computations for eight derivatives. For Cyt and five derivatives substituted at N1, C5, and C6, rapid internal conversion sets in at 250-1200 cm-1 above the 000 bands. The break-off in the spectra correlates with the calculated barriers toward the "C5-C6 twist" conical intersection, which unambiguously establishes the decay mechanism at low S1 state vibrational energies. The barriers increase with substituents that stabilize the charge shifts at C4, C5, and C6 following (1ππ*) excitation. The R2PI spectra of the clamped derivatives 5,6-trimethyleneCyt (TMCyt) and 1-methyl-TMCyt (1M-TMCyt), which decay along an N3 out-of-plane coordinate, extend up to +3500 and +4500 cm-1.
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Affiliation(s)
- Maria A Trachsel
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Susan Blaser
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Simon Lobsiger
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Luca Siffert
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Hans-Martin Frey
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Lluís Blancafort
- Institut de Quı́mica Computacional i Catàlisi and Departament de Quı́mica, Universitat de Girona, C/M.A. Capmany 69, 17003 Girona, Spain
| | - Samuel Leutwyler
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
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31
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Xu R, Hu Z, Wang X, Liu Y, Zhou Z, Xu J, Sun Z, Sun H, Chen J. Intramolecular Charge Transfer in 5-Halogen Cytidines Revealed by Femtosecond Time-Resolved Spectroscopy. J Phys Chem B 2020; 124:2560-2567. [DOI: 10.1021/acs.jpcb.0c00455] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Rui Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Zhubin Hu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Yufeng Liu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Zhongneng Zhou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Zhenrong Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Haitao Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, 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 200062, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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32
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Jaiswal VK, Segarra-Martí J, Marazzi M, Zvereva E, Assfeld X, Monari A, Garavelli M, Rivalta I. First-principles characterization of the singlet excited state manifold in DNA/RNA nucleobases. Phys Chem Chem Phys 2020; 22:15496-15508. [DOI: 10.1039/d0cp01823f] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
TD-DFT characterization of the high-energy singlet excited state manifold of the canonical DNA/RNA nucleobasesin vacuumis assessed against RASPT2 reference computations for reliable simulations of linear and non-linear electronic spectra.
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Affiliation(s)
- Vishal K. Jaiswal
- Dipartimento di Chimica Industriale “Toso Montanari”
- Università di Bologna
- Viale del Risorgimento 4
- I-40136 Bologna
- Italy
| | - Javier Segarra-Martí
- Univ Lyon, Ens de Lyon, CNRS
- Université Lyon 1
- Laboratoire de Chimie UMR 5182
- Lyon
- France
| | - Marco Marazzi
- Université de Lorraine and CNRS
- LPCT UMR 7019
- F-54000 Nancy
- France
- CNRS, Laboratoire de Physique et Chimie Théoriques
| | - Elena Zvereva
- Université de Lorraine and CNRS
- LPCT UMR 7019
- F-54000 Nancy
- France
- CNRS, Laboratoire de Physique et Chimie Théoriques
| | - Xavier Assfeld
- Université de Lorraine and CNRS
- LPCT UMR 7019
- F-54000 Nancy
- France
- CNRS, Laboratoire de Physique et Chimie Théoriques
| | - Antonio Monari
- Université de Lorraine and CNRS
- LPCT UMR 7019
- F-54000 Nancy
- France
- CNRS, Laboratoire de Physique et Chimie Théoriques
| | - Marco Garavelli
- Dipartimento di Chimica Industriale “Toso Montanari”
- Università di Bologna
- Viale del Risorgimento 4
- I-40136 Bologna
- Italy
| | - Ivan Rivalta
- Dipartimento di Chimica Industriale “Toso Montanari”
- Università di Bologna
- Viale del Risorgimento 4
- I-40136 Bologna
- Italy
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33
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Szkaradek KE, Stadlbauer P, Šponer J, Góra RW, Szabla R. UV-induced hydrogen transfer in DNA base pairs promoted by dark nπ* states. Chem Commun (Camb) 2020; 56:201-204. [DOI: 10.1039/c9cc06180k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Formation of an excited-state complex enables ultrafast photorelaxation of dark nπ* states in GC and HC base pairs.
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Affiliation(s)
- Kinga E. Szkaradek
- Department of Physical and Quantum Chemistry
- Wroclaw University of Science and Technology
- Faculty of Chemistry
- Wrocław
- Poland
| | - Petr Stadlbauer
- Regional Centre of Advanced Technologies and Materials
- Faculty of Science
- Palacky University
- 771 46 Olomouc
- Czech Republic
| | - Jiří Šponer
- Regional Centre of Advanced Technologies and Materials
- Faculty of Science
- Palacky University
- 771 46 Olomouc
- Czech Republic
| | - Robert W. Góra
- Department of Physical and Quantum Chemistry
- Wroclaw University of Science and Technology
- Faculty of Chemistry
- Wrocław
- Poland
| | - Rafał Szabla
- Institute of Biophysics of the Czech Academy of Sciences
- 61265 Brno
- Czech Republic
- Institute of Physics
- Polish Academy of Sciences
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34
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Valadan M, Pomarico E, Della Ventura B, Gesuele F, Velotta R, Amoresano A, Pinto G, Chergui M, Improta R, Altucci C. A multi-scale time-resolved study of photoactivated dynamics in 5-benzyl uracil, a model for DNA/protein interactions. Phys Chem Chem Phys 2019; 21:26301-26310. [PMID: 31686060 DOI: 10.1039/c9cp03839f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We combine fluorescence up-conversion and time correlated single photon counting experiments to investigate the 5-benzyl uracil excited state dynamics in methanol from 100 fs up to several ns. This molecule has been proposed as a model for DNA/protein interactions. Our results show emission bands at about 310 and 350 nm that exhibit bi-exponential sub-ps decays. Calculations, including solvent effects by a mixed discrete-continuum model, indicate that the Franck Condon region is characterized by significant coupling between the excited states of the benzyl and the uracil moieties, mirrored by the short-lived emission at 310 nm. Two main ground state recovery pathways are identified, both contributing to the 350 nm emission. The first 'photophysical' decay path involves a ππ* excited state localized on the uracil and is connected to the ground electronic state by an easily accessible crossing with S0, accounting for the short lifetime component. Simulations indicate that a possible second pathway is characterized by exciplex formation, with partial benzene → uracil charge transfer character, that may lead instead to photocyclization. The relevance of our results is discussed in view of the photoactivated dynamics of DNA/protein complexes, with implications on their interaction mechanisms.
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Affiliation(s)
- Mohammadhassan Valadan
- Department of Physics "Ettore Pancini", University of Naples "Federico II", Naples, 80126, Italy.
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35
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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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36
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Wang X, Yu Y, Zhou Z, Liu Y, Yang Y, Xu J, Chen J. Ultrafast Intersystem Crossing in Epigenetic DNA Nucleoside 2′-Deoxy-5-formylcytidine. J Phys Chem B 2019; 123:5782-5790. [DOI: 10.1021/acs.jpcb.9b04361] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Yang Yu
- Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Zhongneng Zhou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Yangyi Liu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Youjun Yang
- Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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37
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Brister MM, Crespo-Hernández CE. Excited-State Dynamics in the RNA Nucleotide Uridine 5'-Monophosphate Investigated Using Femtosecond Broadband Transient Absorption Spectroscopy. J Phys Chem Lett 2019; 10:2156-2161. [PMID: 30995048 DOI: 10.1021/acs.jpclett.9b00492] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Damage to RNA from ultraviolet radiation induces chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential; however, investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5'-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally excited ground state, a long-lived 1nπ* state, and a receiver triplet state within 200 fs. The receiver state internally converts to the long-lived 3ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.
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Affiliation(s)
- Matthew M Brister
- Department of Chemistry , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Carlos E Crespo-Hernández
- Department of Chemistry , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
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38
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Zhou Z, Hu Z, Zhang X, Jia M, Wang X, Su H, Sun H, Chen J, Xu J. pH Controlled Intersystem Crossing and Singlet Oxygen Generation of 8-Azaadenine in Aqueous Solution. Chemphyschem 2019; 20:757-765. [PMID: 30702794 DOI: 10.1002/cphc.201800969] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/30/2019] [Indexed: 01/01/2023]
Abstract
Azabases are intriguing DNA and RNA analogues and have been used as effective antiviral and anticancer medicines. However, photosensitivity of these drugs has also been reported. Here, pH-controlled intersystem crossing (ISC) process of 9H 8-azaadenine (8-AA) in aqueous solution is reported. Broadband transient absorption measurements reveal that the hydrogen atom at N9 position can greatly affect ISC of 8-AA and ISC is more favorable when 8-AA is in its neutral form in aqueous solution. The initial excited ππ* (S2 ) state evolves through ultrafast internal conversion (IC) (4.2 ps) to the lower-lying nπ* state (S1 ), which further stands as a door way state for ISC with a time constant of 160 ps. The triplet state has a lifetime of 6.1 μs. On the other hand, deprotonation at N9 position promotes the IC from the ππ* (S2 ) state to the ground state (S0 ) and the lifetime of the S2 state is determined to be 10 ps. The experimental results are further supported by time-dependent density functional theory (TDDFT) calculations. Singlet oxygen generation yield is measured to be 13.8 % for the neutral 8-AA while the deprotonated one exhibit much lower yield (<2 %), implying that this compound could be a potential pH-sensitized photodynamic therapy agent.
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Affiliation(s)
- Zhongneng Zhou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Zhubin Hu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Xianwang Zhang
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Menghui Jia
- Shanghai Institute of Optics and Fine Mechanics, Shanghai, 201800, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Haitao Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China
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39
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Sarap CS, Partovi-Azar P, Fyta M. Enhancing the optical detection of mutants from healthy DNA with diamondoids. J Mater Chem B 2019. [DOI: 10.1039/c9tb00122k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A polarized laser pulse can distinguish between healthy and mutated DNA nucleotides hydrogen bonded to small diamond cages.
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Affiliation(s)
| | - Pouya Partovi-Azar
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- 06120 Halle (Saale)
- Germany
| | - Maria Fyta
- Institute for Computational Physics
- Universität Stuttgart
- 70569 Stuttgart
- Germany
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40
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Pepino AJ, Segarra-Martí J, Nenov A, Rivalta I, Improta R, Garavelli M. UV-induced long-lived decays in solvated pyrimidine nucleosides resolved at the MS-CASPT2/MM level. Phys Chem Chem Phys 2018; 20:6877-6890. [PMID: 29459916 DOI: 10.1039/c7cp08235e] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The most relevant 'dark' electronic excited states in DNA/RNA pyrimidine nucleosides are mapped in water employing hybrid MS-CASPT2/MM optimisations with explicit solvation and including the sugar. Conical intersections (CIs) between initially accessed bright 1ππ* and the lowest energy dark 1nπ* excited states, involving the lone pair localised on the oxygen and/or nitrogen atoms are characterised. They are found in the vicinities of the Franck-Condon (FC) region and are shown to facilitate non-adiabatic population transfer. The excited state population of the 1nOπ* state, localised in the carbonyl moiety on all pyrimidine nucleosides, is predicted to rapidly evolve to its minimum, displaying non-negligible potential energy barriers along its non-radiative decay, and accounting for the ps signal registered in pump-probe experiments as well as for an efficient population of the triplet state. Cytidine displays an additional 1nNπ* state localised in the N3 atom and that leads to its excited state minimum displaying large potential energy barriers in the pathway connecting to the CI with the ground state. Sugar-to-base hydrogen/proton transfer processes are assessed in solution for the first time, displaying a sizable barrier along its decay and thus being competitive with other slow decay channels in the ps and ns timescales. A unified deactivation scheme for the long-lived channels of pyrimidine nucleosides is delivered, where the 1nOπ* state is found to mediate the long-lived decay in the singlet manifold and act as the doorway for triplet population and thus accounting for the recorded phosphorescence and, more generally, for the transient/photoelectron spectral signals registered up to the ns timescale.
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Affiliation(s)
- Ana Julieta Pepino
- Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy.
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41
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Wei SC, Ho JW, Yen HC, Shi HQ, Cheng LH, Weng CN, Chou WK, Chiu CC, Cheng PY. Ultrafast Excited-State Dynamics of Hydrogen-Bonded Cytosine Microsolvated Clusters with Protic and Aprotic Polar Solvents. J Phys Chem A 2018; 122:9412-9425. [PMID: 30452255 DOI: 10.1021/acs.jpca.8b09526] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Microsolvation effects on the ultrafast excited-state deactivation dynamics of cytosine (Cy) were studied in hydrogen-bonded Cy clusters with protic and aprotic solvents using mass-resolved femtosecond pump-probe ionization spectroscopy. Two protic solvents, water (H2O) and methanol (MeOH), and one aprotic solvent, tetrahydrofuran (THF), were investigated, and transients of Cy·(H2O)1-6, Cy·(MeOH)1-3, and Cy·THF microsolvated clusters produced in supersonic expansions were measured. With the aid of electronic structure calculations, we assigned the observed dynamics to the low-energy isomers of various Cy clusters and discussed the microsolvation effect on the excited-state deactivation dynamics. With the protic solvents only the microsolvated clusters of Cy keto tautomer were observed. The observed decay time constants of Cy·(H2O) n are 0.5 ps for n = 1 and ∼0.2-0.25 ps for n = 2-6. For Cy·(MeOH) n clusters, the decay time constant for n = 1 cluster is similar to that of the Cy monohydrate, but for n = 2 and 3 the decays are about a factor of 2 slower than the corresponding microhydrates. With the aprotic solvent, THF, hydrogen-bonded complexes of both keto and enol tautomers are present in the beam. The keto-Cy·THF shows a decay similar to that of the keto-Cy monomer, whereas the enol-Cy·THF exhibits a 2-fold slower decay than the enol-Cy monomer, suggesting an increase in the barrier to excited-state deactivation upon binding of one THF molecule to the enol form of Cy.
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Affiliation(s)
- Shih-Chun Wei
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Jr-Wei Ho
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Hung-Chien Yen
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Hui-Qi Shi
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Li-Hao Cheng
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Chih-Nan Weng
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Wei-Kuang Chou
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Chih-Chung Chiu
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
| | - Po-Yuan Cheng
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan 30043 , Republic of China
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42
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Zhou P, Zhao L. How Does the O6-Methylation Regulate the Excited-State Decay of Guanine Monomers. J Phys Chem B 2018; 123:201-206. [DOI: 10.1021/acs.jpcb.8b08606] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Panwang Zhou
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, Liaoning, China
| | - Li Zhao
- School of Science, China University of Petroleum, Qingdao 266580, Shandong, China
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43
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Ma C, Chan RCT, Chan CTL, Wong AKW, Chung BPY, Kwok WM. Fluorescence and Ultrafast Fluorescence Unveil the Formation, Folding Molecularity, and Excitation Dynamics of Homo-Oligomeric and Human Telomeric i-Motifs at Acidic and Neutral pH. Chem Asian J 2018; 13:3706-3717. [PMID: 30230251 DOI: 10.1002/asia.201801117] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 08/28/2018] [Indexed: 01/07/2023]
Abstract
i-Motifs are tetraplex DNAs known to be stable at acidic pH. The structure of i-motifs is important in DNA nanotechnology; i-motif-forming sequences with consecutive cytosine (C) molecules are abundant throughout the human genome. There is, however, little information on the structure of C-rich DNAs under physiologically relevant neutral conditions. The electron dynamics of i-motifs, crucial to both biology and materials applications, also remains largely unexplored. In this work, we report a combined femtosecond and nanosecond broadband time-resolved fluorescence (TRF) and steady-state fluorescence investigation on homo-oligomer dC20 , a human telomeric sequence (HTS) 5'-dC3 (TA2 C3 )3 , and its analogue performed with different excitation at both acidic and neutral pH. Our study provides direct observation of intrinsic fluorescence and the first full probe of the real-time dynamics of the intrinsic fluorescence from i-motifs formed from varied sequences and pH conditions. The results obtained demonstrate concrete evidence for the existence at neutral pH of i-motifs from both dC20 and the HTS. It also identifies that, under neutral conditions, the i-motif from dC20 adopting the bimolecular folding structure is significantly more stable than the HTS i-motif featuring the unimolecular topology. Our femtosecond and nanosecond TRF study unveils excitation dynamics distinctive of the interdigitated architecture of i-motifs with the excited states involved exhibiting deactivation over a remarkably broad timescale through multiple channels involving proton-coupled electron transfer lasting tens of picoseconds, as signified by the solvent kinetic isotope effect, and structure-dependent charge recombination in the hundreds of picoseconds to tens of nanoseconds time regime.
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Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, P. R. China
| | - Ruth Chau-Ting Chan
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
| | - Chris Tsz-Leung Chan
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, P. R. China
| | - Allen Ka-Wa Wong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
| | - Bowie Po-Yee Chung
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
| | - Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
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44
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Ai Y, Xing J, Zhang A, Zhao C, Liu Y, Xie B, Chen W, Cui G, Lu Z, Wang X. Computational Study on the Excited-State Decay of 5-Methylcytosine and 5-Hydroxymethylcytosine: The Common Form of DNA Methylation and Its Oxidation Product. J Phys Chem B 2018; 122:10424-10434. [DOI: 10.1021/acs.jpcb.8b07830] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | | | | | | | | | - Binbin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China
| | | | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | | | - Xiangke Wang
- NAAM Research Group, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
- Collaborative Innovation Centre of Radiation Medicine of Jiangsu Higher Education Institutions, School for Radiological and Interdisciplinary Sciences, Soochow University, Suzhou 215123, P. R. China
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45
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Röttger K, Marroux HJB, Böhnke H, Morris DTJ, Voice AT, Temps F, Roberts GM, Orr-Ewing AJ. Probing the excited state relaxation dynamics of pyrimidine nucleosides in chloroform solution. Faraday Discuss 2018; 194:683-708. [PMID: 27711889 DOI: 10.1039/c6fd00068a] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Ultrafast transient electronic and vibrational absorption spectroscopy (TEAS and TVAS) of 2'-deoxy-cytidine (dC) and 2'-deoxy-thymidine (dT) dissolved in chloroform examines their excited-state dynamics and the recovery of ground electronic state molecules following absorption of ultraviolet light. The chloroform serves as a weakly interacting solvent, allowing comparisons to be drawn with prior experimental studies of the photodynamics of these nucleosides in the gas phase and in polar solvents such as water. The pyrimidine base nucleosides have some propensity to dimerize in aprotic solvents, but the monomer photochemistry can be resolved clearly and is the focus of this study. UV absorption at a wavelength of 260 nm excites a 1ππ* ← S0 transition, but prompt crossing of a significant fraction (50% in dC, 17% in dT) of the 1ππ* population into a nearby 1nπ* state is too fast for the experiments to resolve. The remaining flux on the 1ππ* state leaves the vertical Franck-Condon region and encounters a conical intersection with the ground electronic state of ethylenic twist character. In dC, the 1ππ* state decays to the ground state with a time constant of 1.1 ± 0.1 ps. The lifetime of the 1nπ* state is much longer in the canonical forms of both molecules: recovery of the ground state population from these states occurs with time constants of 18.6 ± 1.1 ps in amino-oxo dC and ∼114 ps in dT, indicating potential energy barriers to the 1nπ*/S0 conical intersections. The small fraction of the imino-oxo tautomer of dC present in solution has a longer-lived 1nπ* state with a lifetime for ground state recovery of 193 ± 55 ps. No evidence is found for photo-induced tautomerization of amino-oxo dC to the imino-oxo form, or for population of low lying triplet states of this nucleoside. In contrast, ∼8% of the UV-excited dT molecules access the long-lived T1 (3ππ*) state through the 1nπ* state. The primary influence of the solvent appears to be the degree to which it destabilizes the states of 1nπ* character, with consequences for the lifetimes of these states as well as the triplet state yields.
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Affiliation(s)
- Katharina Röttger
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK. and Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - Hugo J B Marroux
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Hendrik Böhnke
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - David T J Morris
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Angus T Voice
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Friedrich Temps
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - Gareth M Roberts
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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46
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Wang X, Zhou Z, Tang Y, Chen J, Zhong D, Jianhua Xu. Excited State Decay Pathways of 2'-Deoxy-5-methylcytidine and Deoxycytidine Revisited in Solution: A Comprehensive Kinetic Study by Femtosecond Transient Absorption. J Phys Chem B 2018; 122:7027-7037. [PMID: 29939745 DOI: 10.1021/acs.jpcb.8b00927] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methylated cytosine is proved to have an important role as an epigenetic signal in gene regulation and is often referred to "the fifth base of DNA". A comprehensive understanding of the electronic excited state relaxation in cytosine and its methylated derivatives is crucial for revealing UV-induced photodamage to the biological genome. Because of the existence of multiple closely lying "bright" and "dark" excited states, the decay pathways in these DNA nucleosides are the most complex and the least understood so far. In this study, femtosecond transient absorption with different excitation wavelengths (240-296 nm) was used to study the relaxation of excited electronic states of 5-methylcytosine (5mC) and 2'-deoxy-5-methylcytidine (5mdCyd) in phosphate buffered aqueous solution and in acetonitrile solution. Two distinct nonradiative decay channels were directly observed. The first one is a several picosecond internal conversion channel that involves two bright ππ* states (ππ*2 and ππ*1) when ππ*2 state is initially populated. The second channel contains the lower energy ππ*1 state and a so far experimental unidentified long-lived state which exhibits a several nanosecond lifetime. The long-lived state can only be accessed by the initially excited ππ*1 state. Inspired by this new discovery in 5mC and 5mdCyd, we revisited the decay of excited state of 2'-deoxycytidine (dCyd), revealing very similar decay pathways. Additionally, a well-known dark nOπ* state (carbonyl lone pair) with ∼30 ps lifetime is present in both decay channels in dCyd. With our detailed experimental results, we successfully reconcile the long history debate of cytosine excited state relaxation mechanism by pointing out that the reason for the complex dynamics under traditional 266 nm excitation is mixed signals from the above-mentioned two distinct decay pathways. Our findings lead to a dramatically different and new picture of electronic energy relaxation in 5mdCyd/dCyd and could help to understand photostability as well as UV-induced photodamage of these nucleotides and related DNAs.
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Affiliation(s)
- Xueli Wang
- State Key Laboratory of Precision Spectroscopy , East China Normal University , Shanghai , 200062 China
| | - Zhongneng Zhou
- State Key Laboratory of Precision Spectroscopy , East China Normal University , Shanghai , 200062 China
| | - Yuankai Tang
- State Key Laboratory of Precision Spectroscopy , East China Normal University , Shanghai , 200062 China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy , East China Normal University , Shanghai , 200062 China.,Collaborative Innovation Center of Extreme Optics , Shanxi University , Taiyuan , Shanxi 030006 , China
| | - Dongping Zhong
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy , East China Normal University , Shanghai , 200062 China.,Collaborative Innovation Center of Extreme Optics , Shanxi University , Taiyuan , Shanxi 030006 , China
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47
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Conti I, Garavelli M. Evolution of the Excitonic State of DNA Stacked Thymines: Intrabase ππ* → S 0 Decay Paths Account for Ultrafast (Subpicosecond) and Longer (>100 ps) Deactivations. J Phys Chem Lett 2018; 9:2373-2379. [PMID: 29668287 DOI: 10.1021/acs.jpclett.8b00698] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Monomer-like ring puckering decay paths for two stacked quantum mechanical thymines inside a solvated DNA duplex described at the molecular mechanics level are mapped using a hybrid CASPT2//CASSCF/MM protocol that accounts for steric, electronic and electrostatic interactions within the nucleobases native environment. Asymmetric stacking between nucleobases open ups different intrabase ππ* decay paths accounting for distinctive excited state lifetimes, spanning the subps to subns time window.
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Affiliation(s)
- Irene Conti
- Dipartimento di Chimica Industriale "Toso Montanari" , Università di Bologna , Viale del Risorgimento 4 , I-40136 Bologna , Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale "Toso Montanari" , Università di Bologna , Viale del Risorgimento 4 , I-40136 Bologna , Italy
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48
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Ma C, Ou YQ, Chan CTL, Wong AKW, Chan RCT, Chung BPY, Jiang C, Wang ML, Kwok WM. Nonradiative dynamics determined by charge transfer induced hydrogen bonding: a combined femtosecond time-resolved fluorescence and density functional theoretical study of methyl dimethylaminobenzoate in water. Phys Chem Chem Phys 2018; 20:1240-1251. [DOI: 10.1039/c7cp05140a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen bonding with water alters nonradiative pathway of a twisted charge transfer state in methyl dimethylaminobenzoate.
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Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen
- P. R. China
| | - Yue-Qun Ou
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen
- P. R. China
| | - Chris Tsz-Leung Chan
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen
- P. R. China
| | - Allen Ka-Wa Wong
- Department of Applied Biology and Chemical Technology
- The Hong Kong Polytechnic University
- Kowloon
- P. R. China
| | - Ruth Chau-Ting Chan
- Department of Applied Biology and Chemical Technology
- The Hong Kong Polytechnic University
- Kowloon
- P. R. China
| | - Bowie Po-Yee Chung
- Department of Applied Biology and Chemical Technology
- The Hong Kong Polytechnic University
- Kowloon
- P. R. China
| | - Chao Jiang
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen
- P. R. China
| | - Ming-Liang Wang
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen
- P. R. China
| | - Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology
- The Hong Kong Polytechnic University
- Kowloon
- P. R. China
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49
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Martinez-Fernandez L, Improta R. Photoactivated proton coupled electron transfer in DNA: insights from quantum mechanical calculations. Faraday Discuss 2018; 207:199-216. [DOI: 10.1039/c7fd00195a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The energetics of the two main proton coupled electron transfer processes that could occur in DNA are determined by means of time dependent-DFT calculations, using the M052X functional and the polarizable continuum model to include solvent effect.
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Affiliation(s)
| | - Roberto Improta
- Consiglio Nazionale delle Ricerche
- Istituto di Biostrutture e Bioimmagini
- 80136 Naples
- Italy
- LIDYL
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50
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Ashwood B, Ortiz-Rodríguez LA, Crespo-Hernández CE. Excited-State Dynamics in O 6-Methylguanosine: Impact of O 6-Methylation on the Relaxation Mechanism of Guanine Monomers. J Phys Chem Lett 2017; 8:4380-4385. [PMID: 28850232 DOI: 10.1021/acs.jpclett.7b02090] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Absorption of ultraviolet radiation by DNA bases results in ultrafast internal conversion to the ground state, which minimizes photodamage. However, exogenous and endogenous alkylating agents present in the cellular environment can methylate the nucleobases in DNA. In particular, methylation of guanosine at the O6 position in DNA leads to the formation of the O6-methylguanosine adduct, which may alter the photostability of DNA. This contribution demonstrates that O6-methylation of guanosine red shifts its ground-state absorption spectrum and slows down the rate of internal conversion to the ground state by ∼40-fold in aqueous solution. The 40-fold decrease in the rate of excited-state decay increases the probability of photodamage within cellular DNA. It is proposed that the longer decay lifetime corresponds to relaxation of the excited-state population in O6-methylguanosine along a C6-puckered reaction coordinate in the 1ππ*(La) potential energy surface that runs parallel to an ultrafast internal conversion pathway along a C2-puckered coordinate.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Luis A Ortiz-Rodríguez
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Carlos E Crespo-Hernández
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University , Cleveland, Ohio 44106, United States
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