1
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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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2
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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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3
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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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4
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Martínez-Fernández L, Kohl FR, Zhang Y, Ghosh S, Saks AJ, Kohler B. Triplet Excimer Formation in a DNA Duplex with Silver Ion-Mediated Base Pairs. J Am Chem Soc 2024; 146:1914-1925. [PMID: 38215466 DOI: 10.1021/jacs.3c08793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2024]
Abstract
The dynamics of excited electronic states in self-assembled structures formed between silver(I) ions and cytosine-containing DNA strands or monomeric cytosine derivatives were investigated by time-resolved infrared (TRIR) spectroscopy and quantum mechanical calculations. The steady-state and time-resolved spectra depend sensitively on the underlying structures, which change with pH and the nucleobase and silver ion concentrations. At pH ∼ 4 and low dC20 strand concentration, an intramolecularly folded i-motif is observed, in which protons, and not silver ions, mediate C-C base pairing. However, at the higher strand concentrations used in the TRIR measurements, dC20 strands associate pairwise to yield duplex structures containing C-Ag+-C base pairs with a high degree of propeller twisting. UV excitation of the silver ion-mediated duplex produces a long-lived excited state, which we assign to a triplet excimer state localized on a pair of stacked cytosines. The computational results indicate that the propeller-twisted motifs induced by metal-ion binding are responsible for the enhanced intersystem crossing that populates the triplet state and not a generic heavy atom effect. Although triplet excimer states have been discussed frequently as intermediates in the formation of cyclobutane pyrimidine dimers, we find neither computational nor experimental evidence for cytosine-cytosine photoproduct formation in the systems studied. These findings provide a rare demonstration of a long-lived triplet excited state that is formed in a significant yield in a DNA duplex, demonstrating that supramolecular structural changes induced by metal ion binding profoundly affect DNA photophysics.
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Affiliation(s)
- Lara Martínez-Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemical Science (IADCHEM), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Forrest R Kohl
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Yuyuan Zhang
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Supriya Ghosh
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Andrew J Saks
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
| | - Bern Kohler
- Department of Chemistry and Biochemistry, 100 West 18th Avenue, Columbus, 43210 Ohio, United States
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5
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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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6
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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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7
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Nicolaidou E, Parker AW, Sazanovich IV, Towrie M, Hayes SC. Unraveling Excited State Dynamics of a Single-Stranded DNA-Assembled Conjugated Polyelectrolyte. J Phys Chem Lett 2023; 14:9794-9803. [PMID: 37883808 PMCID: PMC10641883 DOI: 10.1021/acs.jpclett.3c01803] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 10/21/2023] [Accepted: 10/23/2023] [Indexed: 10/28/2023]
Abstract
Conformational templating of conjugated polyelectrolytes with single-stranded DNAs (ssDNAs) has the prospect of tailoring excited state dynamics for specific optoelectronic applications. We use ultrafast time-resolved infrared spectroscopy to study the photophysics of a cationic polythiophene assembled with different ssDNAs, inducing distinct conformations (flexible disordered structures vs more rigid complexes with increased backbone planarity). Intrachain polarons are always produced upon selective excitation of the polymer, the extent being dependent on backbone torsional order. Polaron formation and decay were monitored through evolution of IR-active vibrational modes that interfere with mid-IR polaron electronic absorption giving rise to Fano-antiresonances. Selective UV excitation of ssDNAs revealed that stacking interactions between thiophene rings and nucleic acid bases can promote the formation of an intermolecular charge transfer complex. The findings inform designers of functional conjugated polymers by identifying that involvement of the scaffold in the photophysics needs to be considered when developing such structures for optoelectronic applications.
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Affiliation(s)
- Eliana Nicolaidou
- Department
of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Anthony W. Parker
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Igor V. Sazanovich
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Michael Towrie
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Sophia C. Hayes
- Department
of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
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8
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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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9
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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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10
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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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11
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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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12
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Bull GD, Thompson KC. The oxidation of guanine by photoionized 2-aminopurine. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2021. [DOI: 10.1016/j.jpap.2021.100025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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13
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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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14
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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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15
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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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16
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Reveguk ZV, Khoroshilov EV, Sharkov AV, Pomogaev VA, Buglak AA, Tarnovsky AN, Kononov AI. Exciton Absorption and Luminescence in i-Motif DNA. Sci Rep 2019; 9:15988. [PMID: 31690734 PMCID: PMC6831829 DOI: 10.1038/s41598-019-52242-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/17/2019] [Indexed: 11/08/2022] Open
Abstract
We have studied the excited-state dynamics for the i-motif form of cytosine chains (dC)10, using the ultrafast fluorescence up-conversion technique. We have also calculated vertical electronic transition energies and determined the nature of the corresponding excited states in a model tetramer i-motif structure. Quantum chemical calculations of the excitation spectrum of a tetramer i-motif structure predict a significant (0.3 eV) red shift of the lowest-energy transition in the i-motif form relative to its absorption maximum, which agrees with the experimental absorption spectrum. The lowest excitonic state in i-(dC)10 is responsible for a 2 ps red-shifted emission at 370 nm observed in the decay-associated spectra obtained on the femtosecond time-scale. This delocalized (excitonic) excited state is likely a precursor to a long-lived excimer state observed in previous studies. Another fast 310 fs component at 330 nm is assigned to a monomer-like locally excited state. Both emissive states form within less than the available time resolution of the instrument (100 fs). This work contributes to the understanding of excited-state dynamics of DNA within the first few picoseconds, which is the most interesting time range with respect to unraveling the photodamage mechanism, including the formation of the most dangerous DNA lesions such as cyclobutane pyrimidine dimers.
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Affiliation(s)
- Zakhar V Reveguk
- Department of Molecular Biophysics and Polymer Physics, Saint-Petersburg State University, 199034, St. Petersburg, Russia
| | - Evgeny V Khoroshilov
- P.N. Lebedev Physical Institute, Russian Academy of Sciences, 53 Leninsky Pr., 119991, Moscow, Russia
| | - Andrey V Sharkov
- P.N. Lebedev Physical Institute, Russian Academy of Sciences, 53 Leninsky Pr., 119991, Moscow, Russia
| | - Vladimir A Pomogaev
- Department of Physics, Tomsk State University, Tomsk, 634050, Russia
- Department of Chemistry and Green-Nano Materials Research Center, College of Natural Sciences, Kyungpook National University 1370 Sankyuk-dong, Buk-gu, Daegu, 702-701, Republic of Korea
| | - Andrey A Buglak
- Department of Molecular Biophysics and Polymer Physics, Saint-Petersburg State University, 199034, St. Petersburg, Russia
| | - Alexander N Tarnovsky
- Department of Chemistry and the Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH, USA
| | - Alexei I Kononov
- Department of Molecular Biophysics and Polymer Physics, Saint-Petersburg State University, 199034, St. Petersburg, Russia.
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17
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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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18
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Segarra-Martí J, Tran T, Bearpark MJ. Ultrafast and radiationless electronic excited state decay of uracil and thymine cations: computing the effects of dynamic electron correlation. Phys Chem Chem Phys 2019; 21:14322-14330. [PMID: 30698175 DOI: 10.1039/c8cp07189f] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In this article we characterise the radiationless decay of the first few electronic excited states of the cations of DNA/RNA nucleobases uracil and thymine, including the effects of dynamic electron correlation on energies and geometries (optimised with XMS-CASPT2). In both systems, we find that one state of 2n and another two of 2π+ character can be populated following photoionisation, and their different minima and interstate crossings are located. We find strong similarities between uracil and thymine cations: with accessible conical intersections suggesting that depopulation of their electronic excited states takes place on ultrafast timescales in both systems, suggesting that they are photostable in agreement with previous theoretical (uracil+) evidence. We find that dynamic electron correlation separates the energy levels of the "3-state" conical intersection (D2/D1/D0)CI previously located with CASSCF for uracil+, which will therefore have a different geometry and higher energy. Simulating the electronic and vibrational absorptions allows us to characterise spectral fingerprints that could be used to monitor these cation photo-processes experimentally.
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Affiliation(s)
- Javier Segarra-Martí
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, W12 0BZ, London, UK.
| | - Thierry Tran
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, W12 0BZ, London, UK.
| | - Michael J Bearpark
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, W12 0BZ, London, UK.
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19
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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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20
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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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21
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Ashwood B, Pollum M, Crespo-Hernández CE. Photochemical and Photodynamical Properties of Sulfur-Substituted Nucleic Acid Bases. Photochem Photobiol 2018; 95:33-58. [PMID: 29978490 DOI: 10.1111/php.12975] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Accepted: 06/28/2018] [Indexed: 12/25/2022]
Abstract
Sulfur-substituted nucleobases (a.k.a., thiobases) are among the world's leading prescriptions for chemotherapy and immunosuppression. Long-term treatment with azathioprine, 6-mercaptopurine and 6-thioguanine has been correlated with the photoinduced formation of carcinomas. Establishing an in-depth understanding of the photochemical properties of these prodrugs may provide a route to overcoming these carcinogenic side effects, or, alternatively, a basis for developing effective compounds for targeted phototherapy. In this review, a broad examination is undertaken, surveying the basic photochemical properties and excited-state dynamics of sulfur-substituted analogs of the canonical DNA and RNA nucleobases. A molecular-level understanding of how sulfur substitution so remarkably perturbs the photochemical properties of the nucleobases is presented by combining experimental results with quantum-chemical calculations. Structure-property relationships demonstrate the impact of site-specific sulfur substitution on the photochemical properties, particularly on the population of the reactive triplet state. The value of fundamental photochemical investigations for driving the development of ultraviolet-A chemotherapeutics is showcased. The most promising photodynamic agents identified thus far have been investigated in various carcinoma cell lines and shown to decrease cell proliferation upon exposure to ultraviolet-A radiation. Overarching principles have been elucidated for the impact that sulfur substitution of the carbonyl oxygen has on the photochemical properties of the nucleobases.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry, Case Western Reserve University, Cleveland, OH
| | - Marvin Pollum
- Department of Chemistry, Case Western Reserve University, Cleveland, OH
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22
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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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23
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Keane PM, Kelly JM. Transient absorption and time-resolved vibrational studies of photophysical and photochemical processes in DNA-intercalating polypyridyl metal complexes or cationic porphyrins. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.02.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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24
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Pilles BM, Maerz B, Chen J, Bucher DB, Gilch P, Kohler B, Zinth W, Fingerhut BP, Schreier WJ. Decay Pathways of Thymine Revisited. J Phys Chem A 2018; 122:4819-4828. [PMID: 29747505 DOI: 10.1021/acs.jpca.8b02050] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The decay of electronically excited states of thymine (Thy) and thymidine 5'-monophosphate (TMP) was studied by time-resolved UV/vis and IR spectroscopy. In addition to the well-established ultrafast internal conversion to the ground state, a so far unidentified UV-induced species is observed. In D2O, this species decays with a time constant of 300 ps for thymine and of 1 ns for TMP. The species coexists with the lowest triplet state and is formed with a comparably high quantum yield of about 10% independent of the solvent. The experimentally determined spectral signatures are discussed in the light of quantum chemical calculations of the singlet and triplet excited states of thymine.
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Affiliation(s)
- Bert M Pilles
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM , Ludwig-Maximilians-Universität München , Oettingenstrasse 67 , München 80538 , Germany
| | - Benjamin Maerz
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM , Ludwig-Maximilians-Universität München , Oettingenstrasse 67 , München 80538 , Germany
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy , East China Normal University , 3663 North Zhongshan Road , Shanghai 200062 , China
| | - Dominik B Bucher
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM , Ludwig-Maximilians-Universität München , Oettingenstrasse 67 , München 80538 , Germany
| | - Peter Gilch
- Institut für Physikalische Chemie , Heinrich-Heine-Universität Düsseldorf , Universitätsstrasse 1 , Düsseldorf 40225 , Germany
| | - Bern Kohler
- Department of Chemistry and Biochemistry , The Ohio State University , 100 West 18th Avenue , Columbus , Ohio 43210 , United States
| | - Wolfgang Zinth
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM , Ludwig-Maximilians-Universität München , Oettingenstrasse 67 , München 80538 , Germany
| | - Benjamin P Fingerhut
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie , Max-Born-Strasse 2A , Berlin D-12489 , Germany
| | - Wolfgang J Schreier
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM , Ludwig-Maximilians-Universität München , Oettingenstrasse 67 , München 80538 , Germany
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25
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Dereka B, Vauthey E. Solute-Solvent Interactions and Excited-State Symmetry Breaking: Beyond the Dipole-Dipole and the Hydrogen-Bond Interactions. J Phys Chem Lett 2017; 8:3927-3932. [PMID: 28786689 DOI: 10.1021/acs.jpclett.7b01821] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Symmetry breaking of the excited state of a linear quadrupolar acceptor-donor-acceptor molecule was investigated using time-resolved infrared spectroscopy in 55 solvents allowing the influence of several solute-solvent interactions to be examined separately. No symmetry breaking was found in nonpolar solvents irrespective of their refractive index, indicating that differences in dispersion interactions between the two arms of the molecule do not suffice to induce an asymmetric distribution of the excitation. However, symmetry breaking was observed in nondipolar but quadrupolar solvents like benzene to an extent that can be as large as that found in medium dipolar solvents like THF. Whereas larger symmetry breaking occurs in the most dipolar solvents, the strongest are observed in protic solvents due to hydrogen bonding. Strong evidence of the formation of halogen bonds in the excited state is also presented, confirming the idea of symmetry-breaking-induced asymmetrical photochemistry.
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Affiliation(s)
- Bogdan Dereka
- Department of Physical Chemistry, University of Geneva , 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva , 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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26
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Martínez-Fernández L, Pepino AJ, Segarra-Martí J, Jovaišaitė J, Vaya I, Nenov A, Markovitsi D, Gustavsson T, Banyasz A, Garavelli M, Improta R. Photophysics of Deoxycytidine and 5-Methyldeoxycytidine in Solution: A Comprehensive Picture by Quantum Mechanical Calculations and Femtosecond Fluorescence Spectroscopy. J Am Chem Soc 2017; 139:7780-7791. [DOI: 10.1021/jacs.7b01145] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- L. Martínez-Fernández
- Istituto di Biostrutture e Bioimmagini,
CNR, Via Mezzocannone 16, I-80134 Napoli, Italy
| | - A. J. Pepino
- Dipartimento di Chimica Industriale “T. Montanari”, Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
| | - J. Segarra-Martí
- Laboratoire de Chimie UMR 5182, Univ Lyon, ENS de Lyon, CNRS, Université Lyon 1, F-69342 Lyon, France
| | - J. Jovaišaitė
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
| | - I. Vaya
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
| | - A. Nenov
- Dipartimento di Chimica Industriale “T. Montanari”, Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
| | - D. Markovitsi
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
| | - T. Gustavsson
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
| | - A. Banyasz
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
| | - M. Garavelli
- Dipartimento di Chimica Industriale “T. Montanari”, Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
| | - R. Improta
- Istituto di Biostrutture e Bioimmagini,
CNR, Via Mezzocannone 16, I-80134 Napoli, Italy
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
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27
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Szabla R, Kruse H, Šponer J, Góra RW. Water–chromophore electron transfer determines the photochemistry of cytosine and cytidine. Phys Chem Chem Phys 2017; 19:17531-17537. [DOI: 10.1039/c7cp02635h] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Irradiation of aqueous cytidine may result in a water–chromophore electron transfer process which explains numerous experimental observations, including photodamage.
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Affiliation(s)
- Rafał Szabla
- Institute of Physics
- Polish Academy of Sciences
- PL-02668 Warsaw
- Poland
- Institute of Biophysics
| | - Holger Kruse
- Institute of Biophysics
- Academy of Sciences of the Czech Republic
- 61265, Brno
- Czech Republic
| | - Jiří Šponer
- Institute of Biophysics
- Academy of Sciences of the Czech Republic
- 61265, Brno
- Czech Republic
| | - Robert W. Góra
- Department of Physical and Quantum Chemistry
- Wroclaw University of Science and Technology
- 50-370 Wrocław
- Poland
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28
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Effects of ionization on stability of 1-methylcytosine - DFT and PCM studies. J Mol Model 2016; 22:146. [PMID: 27259531 PMCID: PMC4893064 DOI: 10.1007/s00894-016-3020-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/26/2016] [Indexed: 01/01/2023]
Abstract
Consequences of ionization were studied by quantum-chemical methods (DFT and PCM) for 1-methylcytosine (MC)—a model of the nucleobase cytosine (C) connected with sugar in DNA. For calculations, three prototropic tautomers (one amino and two imino forms) and two imino zwitterions were considered, including conformational or configurational isomerism of exo heterogroups. Ionization and interactions between neighboring groups affect intramolecular proton-transfers, geometric and thermodynamic parameters, and electron delocalization for individual isomers. We discovered that an imino isomer is present in the isomeric mixture in the highest amount for positively ionized MC. Its contribution in neutral and negatively ionized MC is considerably smaller. Acid-base parameters for selected radical ions were estimated in the gas phase and compared to those of neutral MC. Gas-phase acidity of radical cations is close to that of the conjugate acid of MC, and gas-phase basicity of radical anions is close to that of the conjugate base of MC. Various routes of amino-imino conversion between neutral and ionized isomers were considered. Energetic-barrier for intramolecular proton-transfer in MC is close to that in the parent system—formamidine.
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29
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Ma C, Cheng CCW, Chan CTL, Chan RCT, Kwok WM. Remarkable effects of solvent and substitution on the photo-dynamics of cytosine: a femtosecond broadband time-resolved fluorescence and transient absorption study. Phys Chem Chem Phys 2016; 17:19045-57. [PMID: 26126728 DOI: 10.1039/c5cp02624e] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytosine (Cyt) among all the nucleic acid bases features the most complex and least understood nonradiative deactivation, a process that is crucially important for its photostability. Herein, the excited state dynamics of Cyt and a series of its N1- and C5-derivatives, including the full set of Cyt nucleosides and nucleotides in DNA and RNA and the nucleosides of 5-methyl cytosine, 5-methylcytidine and 2'-deoxy-5-methylcytidine, have been investigated in water and in methanol employing femtosecond broadband time-resolved fluorescence coupled with fs transient absorption spectroscopy. The results reveal remarkable state-specific effects of the substitution and solvent in tuning distinctively the timescales and pathways of the nonradiative decays. For Cyt and the N1-derivatives, the nonradiative deactivations occur in a common two-state process through three channels, two from the light-absorbing ππ* state with respectively the sub-picosecond (∼0.2 ps) and the picosecond (∼1.5 ps) time constant, and the third is due to an optically dark nπ* state with the lifetime ranging from several to hundreds of picoseconds depending on solvents and substitutions. Compared to Cyt, the presence of the ribose or deoxyribose moiety at the N1 position of N1-derivatives facilitates the formation of the nπ* at the sub-picosecond timescale and at the same time increases its lifetime by ∼4-6 times in both water and methanol. In sharp contrast, the existence of the methyl group at the C5 position of the C5-derivatives eliminates completely the sub-picosecond ππ* channel and the channel due to the nπ*, but on the other hand slows down the decay of the ππ* state which after relaxation exhibits a single time constant of ∼4.1 to ∼7.6 ps depending on solvents. Varying the solvent from water to methanol accelerates only slightly the decay of the ππ* state in all the compounds; while for Cyt and its N1-derivatives, this change of solvent also retards strongly the nπ* channel, prolongs its lifetime from such as ∼7.7 ps in water to ∼52 ps in methanol for Cyt and from ∼30 ps in water to ∼186 ps in methanol for deoxycytidine. The spectral signatures we obtained for the ππ* and the nπ* states allow unambiguous evidence for clarifying uncertainties in the excited states of Cyt and the derivatives. The results provide a unifying experimental characterization at an improved level of detail about the photophysics of Cyt and its analogues under biologically relevant conditions and may help in understanding the photostability as well as photo-damages of the bases and related DNAs.
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Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzheng, Guangdong, P. R. China
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30
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Dereka B, Rosspeintner A, Li Z, Liska R, Vauthey E. Direct Visualization of Excited-State Symmetry Breaking Using Ultrafast Time-Resolved Infrared Spectroscopy. J Am Chem Soc 2016; 138:4643-9. [PMID: 26986957 DOI: 10.1021/jacs.6b01362] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Most symmetric quadrupolar molecules designed for two-photon absorption behave as dipolar molecules in the S1 electronic excited state. This is usually explained by a breakup of the symmetry in the excited state. However, the origin of this process and its dynamics are still not fully understood. Here, excited-state symmetry breaking in a quadrupolar molecule with a D-π-A-π-D motif, where D and A are electron donating and accepting units, is observed in real time using ultrafast transient infrared absorption spectroscopy. The nature of the relaxed S1 state was found to strongly depend on the solvent polarity: (1) in nonpolar solvents, it is symmetric and quadrupolar; (2) in weakly polar media, the quadrupolar state observed directly after excitation transforms to a symmetry broken S1 state with one arm bearing more excitation than the other; and (3) in highly polar solvents, the excited state evolves further to a purely dipolar S1 state with the excitation localized entirely on one arm. The time scales associated with the transitions between these states coincide with those of solvation dynamics, indicating that symmetry breaking is governed by solvent fluctuations.
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Affiliation(s)
- Bogdan Dereka
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Zhiquan Li
- Institute of Applied Synthetic Chemistry, Vienna University of Technology , Getreidemarkt 9/163/MC, 1060 Vienna, Austria
| | - Robert Liska
- Institute of Applied Synthetic Chemistry, Vienna University of Technology , Getreidemarkt 9/163/MC, 1060 Vienna, Austria
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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31
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Keane PM, Baptista FR, Gurung SP, Devereux SJ, Sazanovich IV, Towrie M, Brazier JA, Cardin CJ, Kelly JM, Quinn SJ. Long-Lived Excited-State Dynamics of i-Motif Structures Probed by Time-Resolved Infrared Spectroscopy. Chemphyschem 2016; 17:1281-7. [PMID: 26879336 DOI: 10.1002/cphc.201501183] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Indexed: 01/22/2023]
Abstract
UV-generated excited states of cytosine (C) nucleobases are precursors to mutagenic photoproduct formation. The i-motif formed from C-rich sequences is known to exhibit high yields of long-lived excited states following UV absorption. Here the excited states of several i-motif structures have been characterized following 267 nm laser excitation using time-resolved infrared spectroscopy (TRIR). All structures possess a long-lived excited state of ∼300 ps and notably in some cases decays greater than 1 ns are observed. These unusually long-lived lifetimes are attributed to the interdigitated DNA structure which prevents direct base stacking overlap.
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Affiliation(s)
- Páraic M Keane
- Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK.
| | | | - Sarah P Gurung
- Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK
- Diamond Light Source, Harwell Science and Innovation campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Stephen J Devereux
- School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
| | - Igor V Sazanovich
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Michael Towrie
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - John A Brazier
- Department of Pharmacy, University of Reading, Whiteknights, Reading, RG6 6AD, UK
| | - Christine J Cardin
- Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK
| | - John M Kelly
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland
| | - Susan J Quinn
- School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland.
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32
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Crespo-Hernández CE, Martínez-Fernández L, Rauer C, Reichardt C, Mai S, Pollum M, Marquetand P, González L, Corral I. Electronic and structural elements that regulate the excited-state dynamics in purine nucleobase derivatives. J Am Chem Soc 2015; 137:4368-81. [PMID: 25763596 PMCID: PMC4410903 DOI: 10.1021/ja512536c] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Indexed: 12/20/2022]
Abstract
The excited-state dynamics of the purine free base and 9-methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally excited (1)nπ* state. Following vibrational and conformational relaxation, the (1)nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments show an almost 2-fold increase in the intersystem crossing rate on going from polar aprotic to nonpolar solvents, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface-hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demonstrate that the accessibility of the nπ* states and the topology of the potential energy surfaces in the vicinity of conical intersections are key elements in controlling the excited-state dynamics of the purine derivatives. From a structural perspective, it is shown that the purine chromophore is not responsible for the ultrafast internal conversion in the adenine and guanine monomers. Instead, C6 functionalization plays an important role in regulating the rates of radiative and nonradiative relaxation. C6 functionalization inhibits access to the (1)nπ* state while simultaneously facilitating access to the (1)ππ*(La)/S0 conical intersection, such that population of the (1)nπ* state cannot compete with the relaxation pathways to the ground state involving ring puckering at the C2 position.
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Affiliation(s)
- Carlos E. Crespo-Hernández
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United
States
| | - Lara Martínez-Fernández
- Departamento
de Química, Facultad de Ciencias, Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Módulo 13, Cantoblanco, 28049 Madrid, Spain
| | - Clemens Rauer
- Institute
of Theoretical Chemistry, University of
Vienna, Währinger
Str. 17, 1090 Vienna, Austria
| | - Christian Reichardt
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United
States
| | - Sebastian Mai
- Institute
of Theoretical Chemistry, University of
Vienna, Währinger
Str. 17, 1090 Vienna, Austria
| | - Marvin Pollum
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United
States
| | - Philipp Marquetand
- Institute
of Theoretical Chemistry, University of
Vienna, Währinger
Str. 17, 1090 Vienna, Austria
| | - Leticia González
- Institute
of Theoretical Chemistry, University of
Vienna, Währinger
Str. 17, 1090 Vienna, Austria
| | - Inés Corral
- Departamento
de Química, Facultad de Ciencias, Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Módulo 13, Cantoblanco, 28049 Madrid, Spain
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33
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Szabla R, Campos J, Šponer JE, Šponer J, Góra RW, Sutherland JD. Excited-state hydrogen atom abstraction initiates the photochemistry of β-2'-deoxycytidine. Chem Sci 2015; 6:2035-2043. [PMID: 27182431 PMCID: PMC4866440 DOI: 10.1039/c4sc03761h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 01/07/2015] [Indexed: 11/21/2022] Open
Abstract
Understanding the effects of ultraviolet radiation on nucleotides in solution is an important step towards a comprehensive description of the photochemistry of nucleic acids and their constituents. Apart from having implications for mutagenesis and DNA photoprotection mechanisms, the photochemistry of cytidines is a central element in UV-assisted syntheses of pyrimidine nucleotides under prebiotically plausible conditions. In this contribution, we present UV-irradiation experiments of β-2'-deoxycytidine in aqueous solution involving H-D exchange followed by NMR spectroscopic analysis of the photoproducts. We further elucidate the outcome of these experiments by means of high-level quantum chemical calculations. In particular, we show that prolonged UV-irradiation of cytidine may lead to H-C1' hydrogen atom abstraction by the carbonyl oxygen atom of cytosine. This process may enable photoanomerisation and nucleobase loss, two previously unexplained photoreactions observed in pyrimidine nucleotides.
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Affiliation(s)
- Rafał Szabla
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic.
| | - Jesús Campos
- School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK; Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Judit E Šponer
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic. ; CEITEC - Central European Institute of Technology, Masaryk University, Campus Bohunice, Kamenice 5, CZ-62500 Brno, Czech Republic
| | - Jiřĺ Šponer
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic. ; CEITEC - Central European Institute of Technology, Masaryk University, Campus Bohunice, Kamenice 5, CZ-62500 Brno, Czech Republic
| | - Robert W Góra
- Theoretical Chemistry Group, Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland.
| | - John D Sutherland
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 0QH, UK.
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34
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Nakayama A, Yamazaki S, Taketsugu T. Quantum Chemical Investigations on the Nonradiative Deactivation Pathways of Cytosine Derivatives. J Phys Chem A 2014; 118:9429-37. [DOI: 10.1021/jp506740r] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Akira Nakayama
- Catalysis
Research Center, Hokkaido University, Sapporo 001-0021, Japan
| | - Shohei Yamazaki
- Department
of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, Hirosaki 036-8561, Japan
| | - Tetsuya Taketsugu
- Department
of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
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35
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Zou X, Dai X, Liu K, Zhao H, Song D, Su H. Photophysical and Photochemical Properties of 4-Thiouracil: Time-Resolved IR Spectroscopy and DFT Studies. J Phys Chem B 2014; 118:5864-72. [DOI: 10.1021/jp501658a] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiaoran Zou
- State Key Laboratory of Molecular
Reaction Dynamics, Beijing National Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaojuan Dai
- State Key Laboratory of Molecular
Reaction Dynamics, Beijing National Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Kunhui Liu
- State Key Laboratory of Molecular
Reaction Dynamics, Beijing National Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongmei Zhao
- State Key Laboratory of Molecular
Reaction Dynamics, Beijing National Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Di Song
- State Key Laboratory of Molecular
Reaction Dynamics, Beijing National Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongmei Su
- State Key Laboratory of Molecular
Reaction Dynamics, Beijing National Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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36
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Cheng CCW, Ma C, Chan CTL, Ho KYF, Kwok WM. The solvent effect and identification of a weakly emissive state in nonradiative dynamics of guanine nucleosides and nucleotides--a combined femtosecond broadband time-resolved fluorescence and transient absorption study. Photochem Photobiol Sci 2014; 12:1351-65. [PMID: 23538894 DOI: 10.1039/c3pp25450j] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combined method of femtosecond broadband time-resolved fluorescence (fs-TRF) and transient absorption (fs-TA) was employed to investigate the excited state dynamics of 2'-deoxyguanosine (dG) and 2'-deoxyguanosine 5'-monophosphate (dGMP). Comparative fs-TRF and fs-TA measurements were conducted on dG and dGMP in neutral water, deuterated water, and methanol with excitation wavelengths of 245, 267 and 285 nm. Very similar results were observed with dG and dGMP. The data provide compelling evidence for the co-existence of two nonradiative pathways. One is the generally recognized Laππ* mediated channel, the other involves an unprecedented weakly emissive state which plays a significant role in the overall deactivation processes. The Laππ* channel features biphasic dynamics with time constants (τ1/τ2) of ~0.2/0.8 ps in water and ~0.25/1.0 ps in methanol. The biphasic decay arises due to a partial transfer with τ1 of the Laππ* population to the newly identified state followed by conversion in τ2 of the remaining Laππ* molecules into the electronic ground state. The channel mediated by the weakly emissive species shows solvent-dependent dynamics with time constants (τ3) of ~2.0 ps in water, ~2.3 ps in deuterated water, and ~4.1 ps in methanol. The species features absorption at UV wavelengths (~300-400 nm) and exhibits deeply red-shifted fluorescence (λmax ~ 520 nm) with polarization direction varied markedly from that of the Laππ* but close to the Lbππ*. This species acts as an effective quenching state to the radiative decay of the brightly emissive Laππ* and Lbππ*. It sets in promptly (<~50 fs) after the photoexcitation and is further populated through nonadiabatic coupling with the Laππ*. The overall involvement of this state is facilitated with excitation at high energy and is favoured in methanol over water. According to the spectral character and the solvent effect in particular the kinetic isotope effect, the species is tentatively associated to the πσ* state with charge transfer (CT) character which is considered to be preferentially stabilized by hydrogen-bonding between the guanine amino and surrounding solvent molecules. The result of this study leads to a dramatically different picture of guanine deactivation. It demonstrates a crucial role of the solvent in shaping the nonradiative dynamics of guanine nucleosides and nucleotides. The data presented are important for understanding the detailed photophysics of not only the monomeric guanine but also DNA assemblies that contain guanine in base pairs or have a guanine tetrad as the structural motif.
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Affiliation(s)
- Chopen Chan-Wut Cheng
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
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37
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Bucher DB, Pilles BM, Pfaffeneder T, Carell T, Zinth W. Fingerprinting DNA oxidation processes: IR characterization of the 5-methyl-2'-deoxycytidine radical cation. Chemphyschem 2014; 15:420-3. [PMID: 24382745 DOI: 10.1002/cphc.201300954] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Indexed: 11/08/2022]
Abstract
Methylated cytidine plays an important role as an epigenetic signal in gene regulation. Its oxidation products are assumed to be involved in active demethylation processes but also in damaging DNA. Here, we report the photochemical production of the 5-methyl-2'-deoxycytidine radical cation via a two-photon ionization process. The radical cation is detected by time-resolved IR spectroscopy and identified by band assignment using density functional theory calculations. Two final oxidation products are characterized with liquid chromatography coupled to mass spectrometry.
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Affiliation(s)
- Dominik B Bucher
- BioMolecular Optics and Center for Integrated Protein Science, Ludwig-Maximilians-Universität, Oettingenstr. 67, 80538 München (Germany), Fax: (+49) 89-2180-9202; Center for Integrated Protein Science, Department für Chemie, Ludwig-Maximilians-Universität, Butenandtstr. 5-13, 81377 München (Germany)
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38
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Photochemistry of Nucleic Acid Bases and Their Thio- and Aza-Analogues in Solution. Top Curr Chem (Cham) 2014; 355:245-327. [DOI: 10.1007/128_2014_554] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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39
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Keane PM, Wojdyla M, Doorley GW, Kelly JM, Parker AW, Clark IP, Greetham GM, Towrie M, Magno LM, Quinn SJ. Long-lived excited states in i-motif DNA studied by picosecond time-resolved IR spectroscopy. Chem Commun (Camb) 2014; 50:2990-2. [DOI: 10.1039/c3cc46594b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Dorfman KE, Fingerhut BP, Mukamel S. Broadband infrared and Raman probes of excited-state vibrational molecular dynamics: simulation protocols based on loop diagrams. Phys Chem Chem Phys 2013; 15:12348-59. [PMID: 23783120 PMCID: PMC3744248 DOI: 10.1039/c3cp51117k] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Vibrational motions in electronically excited states can be observed either by time and frequency resolved infrared absorption or by off resonant stimulated Raman techniques. Multipoint correlation function expressions are derived for both signals. Three representations which suggest different simulation protocols for the signals are developed. These are based on the forward and the backward propagation of the wavefunction, sum over state expansion using an effective vibrational Hamiltonian or a semiclassical treatment of a bath. We show that the effective temporal (Δt) and spectral (Δω) resolution of the techniques is not controlled solely by experimental knobs but also depends on the system dynamics being probed. The Fourier uncertainty ΔωΔt > 1 is never violated.
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Affiliation(s)
- Konstantin E Dorfman
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
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Koch M, Rosspeintner A, Adamczyk K, Lang B, Dreyer J, Nibbering ETJ, Vauthey E. Real-Time Observation of the Formation of Excited Radical Ions in Bimolecular Photoinduced Charge Separation: Absence of the Marcus Inverted Region Explained. J Am Chem Soc 2013; 135:9843-8. [DOI: 10.1021/ja403481v] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Marius Koch
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
| | - Katrin Adamczyk
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - Bernhard Lang
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
| | - Jens Dreyer
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - Erik T. J. Nibbering
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
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Nielsen JB, Thøgersen J, Jensen SK, Keiding SR. Photo protection of RNA building blocks: Adenosine 5′-monophosphate, cytidine 5′-monophosphate and cytosine. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Nakayama A, Harabuchi Y, Yamazaki S, Taketsugu T. Photophysics of cytosine tautomers: new insights into the nonradiative decay mechanisms from MS-CASPT2 potential energy calculations and excited-state molecular dynamics simulations. Phys Chem Chem Phys 2013; 15:12322-39. [DOI: 10.1039/c3cp51617b] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Keane PM, Wojdyla M, Doorley GW, Kelly JM, Clark IP, Parker AW, Greetham GM, Towrie M, Magno LM, Quinn SJ. Ultrafast IR spectroscopy of polymeric cytosine nucleic acids reveal the long-lived species is due to a localised state. Phys Chem Chem Phys 2012; 14:6307-11. [PMID: 22358255 DOI: 10.1039/c2cp23774a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The decay pathways of UV-excited cytosine polymers are investigated using picosecond time-resolved infrared spectroscopy. Similar yields of a non-emissive (1)nπ* state are found in the single-stranded dC(30) polymer as in the dCMP monomer, but with a longer lifetime in the polymer (80 ps vs. 39 ps). A longer lifetime is also found in the d(CpC) dinucleotide. No evidence of excimer states is observed, suggesting that localised (1)nπ* excited states are the most significant intermediates present on the picosecond timescale.
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Affiliation(s)
- Páraic M Keane
- School of Chemistry and Centre for Synthesis and Chemical Biology, Trinity College, Dublin 2, Ireland
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