1
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Gómez S, Cappelli C. When Tautomers Matter: UV-Vis Absorption Spectra of Hypoxanthine in Aqueous Solution from Fully Atomistic Simulations. Chemphyschem 2024; 25:e202400107. [PMID: 38747323 DOI: 10.1002/cphc.202400107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 05/13/2024] [Indexed: 07/03/2024]
Abstract
The UV-Vis spectrum of the solvated purine derivative Hypoxanthine (HYX) is investigated using the Quantum Mechanics/Fluctuating Charges (QM/FQ) multiscale approach combined with a sampling of configurations through atomistic Molecular Dynamics (MD) simulations. Keto 1H7H and 1H9H tautomeric forms of HYX are the most stable in aqueous solution and form different stable complexes with the surrounding water molecules, ultimately affecting the electronic absorption spectra. The final simulated spectrum resulting from the combination of the individual spectra of tautomers agrees very well with most of the characteristics in the measured spectrum. The importance of considering the effect of the solute tautomers and, in parallel, the contribution of the different solvent arrangements around the solute when modeling spectral properties, is highlighted. In addition, the high quality of the computed spectra leads to suggesting an alternative way for acquiring tautomeric populations from combined computational/experimental spectra.
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Affiliation(s)
- Sara Gómez
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, 56126, Pisa, Italy
| | - Chiara Cappelli
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, 56126, Pisa, Italy
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2
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Wada S, Tsutsumi T, Saita K, Taketsugu T. Ab initio molecular dynamics study of intersystem crossing dynamics for MH 2 (M = Si, Ge, Sn, Pb) on spin-pure and spin-mixed potential energy surfaces. J Comput Chem 2024; 45:552-562. [PMID: 38009451 DOI: 10.1002/jcc.27271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/18/2023] [Accepted: 11/14/2023] [Indexed: 11/28/2023]
Abstract
Recently, surface-hopping ab initio molecular dynamics (SH-AIMD) simulations have come to be used to discuss the mechanisms and dynamics of excited-state chemical reactions, including internal conversion and intersystem crossing. In dynamics simulations involving intersystem crossing, there are two potential energy surfaces (PESs) governing the motion of nuclei: PES in a spin-pure state and PES in a spin-mixed state. The former gives wrong results for molecular systems with large spin-orbit coupling (SOC), while the latter requires a potential gradient that includes a change in SOC at each point, making the computational cost very high. In this study, we systematically investigate the extent to which the magnitude of SOC affects the results of the spin-pure state-based dynamics simulations for the hydride MH2 (M = Si, Ge, Sn, Pb) by performing SH-AIMD simulations based on spin-pure and spin-mixed states. It is clearly shown that spin-mixed state PESs are indispensable for the dynamics simulation of intersystem crossing in systems containing elements Sn and Pb from the fifth period onward. Furthermore, in addition to the widely used Tully's fewest switches (TFS) algorithm, the Zhu-Nakamura (ZN) global switching algorithm, which is computationally less expensive, is applied to SH for comparison. The results from TFS- and ZN-SH-AIMD methods are in qualitative agreement, suggesting that the less expensive ZN-SH-AIMD can be successfully utilized to investigate the dynamics of photochemical reactions based on quantum chemical calculations.
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Affiliation(s)
- Satoi Wada
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Japan
| | - Takuro Tsutsumi
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Kenichiro Saita
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Tetsuya Taketsugu
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan
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3
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Ortiz-Rodríguez LA, Caldero-Rodríguez NE, Seth SK, Díaz-González K, Crespo-Hernández CE. Electronic relaxation mechanism of 9-methyl-2,6-diaminopurine and 2,6-diaminopurine-2'-deoxyribose in solution. Photochem Photobiol 2024; 100:393-403. [PMID: 38018292 DOI: 10.1111/php.13887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/16/2023] [Accepted: 11/05/2023] [Indexed: 11/30/2023]
Abstract
Prolonged ultraviolet exposure results in the formation of cyclobutane pyrimidine dimers (CPDs) in RNA. Consequently, prebiotic photolesion repair mechanisms should have played an important role in the maintenance of the structural integrity of primitive nucleic acids. 2,6-Diaminopurine is a prebiotic nucleobase that repairs CPDs with high efficiency when incorporated into polymers. We investigate the electronic deactivation pathways of 2,6-diaminopurine-2'-deoxyribose and 9-methyl-2,6-diaminopurine in acetonitrile and aqueous solution to shed light on the photophysical and excited state properties of the 2,6-diaminopurine chromophore. Evidence is presented that both are photostable compounds exhibiting similar deactivation mechanisms upon the population of the S1 (ππ* La ) state at 290 nm. The mechanism involves deactivation through the C2- and C6-reaction coordinates and >99% of the excited state population decays through nonradiative pathways involving two conical intersections with the ground state. The radiative and nonradiative lifetimes are longer in aqueous solution compared to acetonitrile. While τ1 is similar in both derivatives, τ2 is ca. 1.5-fold longer in 2,6-diaminopurine-2'-deoxyribose due to a more efficient trapping in the S1 (ππ* La ) minimum. Therefore, 2,6-diaminopurine could have accumulated in significant quantities during prebiotic times to be incorporated into non-canonical RNA and play a significant role in its photoprotection.
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Affiliation(s)
| | | | - Sourav Kanti Seth
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio, USA
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4
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Gate G, Williams A, Boldissar S, Šponer J, Szabla R, de Vries M. The tautomer-specific excited state dynamics of 2,6-diaminopurine using resonance-enhanced multiphoton ionization and quantum chemical calculations. Photochem Photobiol 2024; 100:404-418. [PMID: 38124372 DOI: 10.1111/php.13897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 10/25/2023] [Accepted: 11/14/2023] [Indexed: 12/23/2023]
Abstract
2,6-Diaminopurine (2,6-dAP) is an alternative nucleobase that potentially played a role in prebiotic chemistry. We studied its excited state dynamics in the gas phase by REMPI, IR-UV hole burning, and ps pump-probe spectroscopy and performed quantum chemical calculations at the SCS-ADC(2) level of theory to interpret the experimental results. We found the 9H tautomer to have a small barrier to ultrafast relaxation via puckering of its 6-membered ring. The 7H tautomer has a larger barrier to reach a conical intersection and also has a sizable triplet yield. These results are discussed relative to other purines, for which 9H tautomerization appears to be more photostable than 7H and homosubstituted purines appear to be less photostable than heterosubstituted or singly substituted purines.
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Affiliation(s)
- Gregory Gate
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Ann Williams
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Samuel Boldissar
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Jiří Šponer
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacky University Olomouc, Olomouc-Holice, Czech Republic
| | - Rafal Szabla
- Institute of Advanced Materials, Faculty of Chemistry, Wrocław University of Science and Technology, Wrocław, Poland
| | - Mattanjah de Vries
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
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5
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Zhou Q, Hao Y, Jie J, Wang S, Xia Y, Yang C, Liu L, Fang WH, Su H. Dual Functionality of 6-Methylthioguanine: Synergistic Effects Enhancing the Photolability of DNA Nucleobases. JACS AU 2024; 4:441-453. [PMID: 38425924 PMCID: PMC10900203 DOI: 10.1021/jacsau.3c00575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 01/05/2024] [Accepted: 01/05/2024] [Indexed: 03/02/2024]
Abstract
A small chemical modification of the nucleobase structure can significantly enhance the photoactivity of DNA, which may incur DNA damage, thus holding promising applications in photochemotherapy treatment of cancers or pathogens. However, single substitution confers only limited phototoxicity to DNA. Herein, we combine femtosecond and nanosecond time-resolved spectroscopy with high-level ab initio calculations to disentangle the excited-state dynamics of 6-methylthioguanine (me6-TG) under variable wavelength UVA excitation (310-330 nm). We find that double substitution of nucleobases (thionation and methylation) boosts the photoactivity by introducing more reactive channels. Intriguingly, 1nNπ*, rather than 1nSπ*, acts as the doorway state engendering the formation of the long-lived reactive triplet state in me6-TG. The 1nNπ* induces a low spin-orbit coupling of 8.3 cm-1, which increases the intersystem crossing (ISC) time (2.91 ± 0.14 ns). Despite the slowed ISC, the triplet quantum yield (ΦT) still accounts for a large fraction (0.6 ± 0.1), consistent with the potential energy surface that favors excited-state bifurcation to 1nNπ*min (3.36 ± 0.15 ps) rather than 1ππ*min (5.05 ± 0.26 ps), such that the subsequent ISC to triplet via 1nNπ*min constitutes the main relaxation pathway in me6-TG. Although this ΦT is inferior to its single-substituted predecessor 6-thioguanine (6-TG, 0.8 ± 0.2), the effect of thionation in synergy with methylation opens a unique C-S bond cleavage pathway through crossing to a repulsive 1πσ* state, generating thiyl radicals as highly reactive intermediates that may invoke biological damage. This photodissociation channel is extremely difficult for conventional nucleobases. These findings demonstrate the synergistic effects of double functionality substitution in modulating excited-state dynamics and enhancing the photolabile character of DNA nucleobases, providing inspirations for the rational design of advanced photodynamic and photochemotherapy approaches.
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Affiliation(s)
| | | | - Jialong Jie
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Shuo Wang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ye Xia
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Chunfan Yang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Lihong Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Wei-Hai Fang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, China
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6
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Reza MM, Durán-Hernández J, González-Cano B, Jara-Cortés J, López-Arteaga R, Cadena-Caicedo A, Muñoz-Rugeles L, Hernández-Trujillo J, Peon J. Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms. J Phys Chem B 2023; 127:8432-8445. [PMID: 37733881 DOI: 10.1021/acs.jpcb.3c03246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
Abstract
Nicotinamide adenine dinucleotide (NADH) is an important enzyme cofactor with emissive properties that allow it to be used in fluorescence microscopies to study cell metabolism. Its oxidized form NAD+, on the other hand, is considered to produce negligible fluorescence. In this contribution, we describe the photophysics of the isolated nicotinamidic system in both its reduced and oxidized states. This was achieved through the study of model molecules that do not carry the adenine nucleotide since its absorbance would overlap with the absorption spectrum of the nicotinamidic chromophores. We studied three model molecules: nicotinamide (niacinamide, an oxidized form without nitrogen substitution), the oxidized chromophore 1-benzyl-3-carbamoyl-pyridinium bromide (NBzOx), and its reduced form 1-benzyl-1,4-dihydronicotinamide (NBz). For a full understanding of the dynamics, we performed both femtosecond-resolved emission and transient absorption experiments. The oxidized systems, nicotinamide and NBzOx, have similar photophysics, where the originally excited bright state decays on an ultrafast timescale of less than 400 fs. The depopulation of this state is followed by excited-state positive absorption signals, which evolve in two timescales: the first one is from 1 to a few picoseconds and is followed by a second decaying component of 480 ps for nicotinamide in water and of 80-90 ps for nicotinamide in methanol and NBzOx in aqueous solution. The long decay times are assigned as the S1 lifetimes populated from the original higher-lying bright singlet, where this state is nonemissive but can be detected by transient absorption. While for NBzOx in aqueous solution and for nicotinamide in methanol, the S1 signal decays to the solvent-only level, for the aqueous solutions of nicotinamide, a small transient absorption signal remains after the 480 ps decay. This residual signal was assigned to a small population of triplet states formed during the slower S1 decay for nicotinamide in water. The experimental results were complemented by XMS-CASPT2 calculations, which reveal that in the oxidized forms, the rapid evolution of the initial π-π* state is due to a direct crossing with lower-energy dark n-π* singlet states. This coincides with the experimental observation of long-lived nonemissive states (80 to 480 ps depending on the system). On the other hand, the reduced model compound NBz has a long-lived emissive π-π* S1 state, which decays with a 510 ps time constant, similarly to the parent compound NADH. This is consistent with the XMS-CASPT2 calculations, which show that for the reduced chromophore, the dark states lie at higher energies than the bright π-π* S1 state.
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Affiliation(s)
- Mariana M Reza
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Durán-Hernández
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Beatriz González-Cano
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Jara-Cortés
- Unidad Académica de Ciencias Básicas e Ingenierías, Universidad Autónoma de Nayarit, Tepic 63155, México
| | - Rafael López-Arteaga
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Andrea Cadena-Caicedo
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Leonardo Muñoz-Rugeles
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Hernández-Trujillo
- Departamento de Física y Química Teórica, Facultad de Química, UNAM, Ciudad de México 04510, México
| | - Jorge Peon
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
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7
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Alfonso Hernandez L, Freixas VM, Rodriguez-Hernandez B, Tretiak S, Fernandez-Alberti S, Oldani N. Exciton-vibrational dynamics induces efficient self-trapping in a substituted nanoring. Phys Chem Chem Phys 2022; 24:24095-24104. [PMID: 36178044 DOI: 10.1039/d2cp03162k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cycloparaphenylenes, being the smallest segments of carbon nanotubes, have emerged as prototypes of the simplest carbon nanohoops. Their unique structure-dynamics-optical properties relationships have motivated a wide variety of synthesis of new related nanohoop species. Studies of how chemical changes, introduced in these new materials, lead to systems with new structural, dynamics and optical properties, expand their functionalities for optoelectronics applications. Herein, we study the effect that conjugation extension of a cycloparaphenylene through the introduction of a satellite tetraphenyl substitution has on its structural and dynamical properties. Our non-adiabatic excited state molecular dynamics simulations suggest that this substitution accelerates the electronic relaxation from the high-energy band to the lowest excited state. This is partially due to efficient conjugation achieved between specific phenyl units as introduced by the tetraphenyl substitution. We observe a particular exciton redistribution during relaxation, in which the tetraphenyl substitution plays a significant role. As a result, an efficient inter-band energy transfer takes place. Besides, the observed phonon-exciton interplay induces a significant exciton self-trapping. Our results encourage and guide the future studies of new phenyl substitutions in carbon nanorings with desired optoelectronic properties.
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Affiliation(s)
- Laura Alfonso Hernandez
- Departamento de Ciencia Tecnologia, Universidad Nacional de Quilmes/CONICET, B1876BXD Bernal, Argentina.
| | - Victor M Freixas
- Departamento de Ciencia Tecnologia, Universidad Nacional de Quilmes/CONICET, B1876BXD Bernal, Argentina.
| | | | - Sergei Tretiak
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | | | - Nicolas Oldani
- Departamento de Ciencia Tecnologia, Universidad Nacional de Quilmes/CONICET, B1876BXD Bernal, Argentina.
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8
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Mandal S, Srinivasan V. Rationalizing the Unexpected Sensitivity in Excited State Lifetimes of Adenine to Tautomerization by Nonadiabatic Molecular Dynamics. J Phys Chem B 2022; 126:7077-7087. [PMID: 36083211 DOI: 10.1021/acs.jpcb.2c03178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The remarkable photostability of canonical nucleobases makes them ideal building blocks for DNA and RNA. Even minor structural changes are expected to lead to drastic alteration of their subpicosecond excited state lifetimes. However, it is interesting to note that while the 9H- and 7H-amino tautomers of adenine possess drastically different lifetimes, 9H- and 7H-keto guanine possess similar excited state lifetimes. With an aim to explain this unexpected difference in sensitivity of lifetimes to tautomerization, we have investigated the excited state relaxation mechanism of UV-excited adenine and guanine tautomers using surface hopping based nonadiabatic molecular dynamics. We find that internal conversion in both guanine tautomers is almost barrierless while both adenine tautomers encounter significant barriers before they can deactivate. Moreover, the major deactivation channel (C2-puckering) in 9H-amino adenine is overall more efficient than the one (C6-puckering) in the 7H-amino form. We trace this difference to the frequent rotation of the amino group which disrupts its conjugation with the heterocyclic ring thereby reducing the strength of nonadiabatic coupling and, hence, delaying internal conversion.
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Affiliation(s)
- Satyajit Mandal
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal 462 066, India
| | - Varadharajan Srinivasan
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal 462 066, India
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9
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Caldero-Rodríguez NE, Crespo-Hernández CE. Excited state dynamics of 2'-deoxyisoguanosine and isoguanosine in aqueous solution. Phys Chem Chem Phys 2022; 24:6769-6781. [PMID: 35244114 DOI: 10.1039/d1cp05795b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photostability is thought to be an inherent property of nucleobases required to survive the extreme ultraviolet radiation conditions of the prebiotic era. Previous studies have shown that absorption of ultraviolet radiation by the canonical nucleosides results in ultrafast internal conversion to the ground state, demonstrating that these nucleosides efficiently dissipate the excess electronic energy to the environment. In recent years, studies on the photophysical and photochemical properties of nucleobase derivatives have revealed that chemical substitution influences the electronic relaxation pathways of purine and pyrimidine nucleobases. It has been suggested that amino or carbonyl substitution at the C6 position could increase the photostability of the purine derivatives more than the substitution at the C2 position. This investigation aims to elucidate the excited state dynamics of 2'-deoxyisoguanosine (dIsoGuo) and isoguanosine (IsoGuo) in aqueous solution at pH 7.4 and 1.4, which contain an amino group at the C6 position and a carbonyl group at the C2 position of the purine chromophore. The study of these derivatives is performed using absorption and emission spectroscopies, broadband transient absorption spectroscopy, and density functional and time-dependent density functional levels of theory. It is shown that the primary relaxation mechanism of dIsoGuo and IsoGuo involves nonradiative decay pathways, where the population decays from the S1(ππ*) state through internal conversion to the ground state via two relaxation pathways with lifetimes of hundreds of femtoseconds and less than 2 ps, making these purine nucleosides photostable in aqueous solution.
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10
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Vos E, Hoehn SJ, Krul SE, Crespo-Hernández CE, González-Vázquez J, Corral I. Disclosing the Role of C4-Oxo Substitution in the Photochemistry of DNA and RNA Pyrimidine Monomers: Formation of Photoproducts from the Vibrationally Excited Ground State. J Phys Chem Lett 2022; 13:2000-2006. [PMID: 35191712 PMCID: PMC8900130 DOI: 10.1021/acs.jpclett.2c00052] [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: 01/08/2022] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Oxo and amino substituted purines and pyrimidines have been suggested as protonucleobases participating in ancient pre-RNA forms. Considering electromagnetic radiation as a key environmental selection pressure on early Earth, the investigation of the photophysics of modified nucleobases is crucial to determine their viability as nucleobases' ancestors and to understand the factors that rule the photostability of natural nucleobases. In this Letter, we combine femtosecond transient absorption spectroscopy and quantum mechanical simulations to reveal the photochemistry of 4-pyrimidinone, a close relative of uracil. Irradiation of 4-pyrimidinone with ultraviolet radiation populates the S1(ππ*) state, which decays to the vibrationally excited ground state in a few hundred femtoseconds. Analysis of the postirradiated sample in water reveals the formation of a 6-hydroxy-5H-photohydrate and 3-(N-(iminomethyl)imino)propanoic acid as the primary photoproducts. 3-(N-(Iminomethyl)imino)propanoic acid originates from the hydrolysis of an unstable ketene species generated from the C4-N3 photofragmentation of the pyrimidine core.
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Affiliation(s)
- Eva Vos
- Departamento
de Química, Módulo 13, Universidad
Autónoma de Madrid, 28049 Madrid, Spain
| | - Sean J. Hoehn
- Department
of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Sarah E. Krul
- 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
| | - Jesús González-Vázquez
- Departamento
de Química, Módulo 13, Universidad
Autónoma de Madrid, 28049 Madrid, Spain
- Institute
for Advanced Research in Chemistry (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Inés Corral
- Departamento
de Química, Módulo 13, Universidad
Autónoma de Madrid, 28049 Madrid, Spain
- Institute
for Advanced Research in Chemistry (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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11
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Caldero-Rodríguez NE, Ortiz-Rodríguez LA, Gonzalez AA, Crespo-Hernández CE. Photostability of 2,6-diaminopurine and its 2'-deoxyriboside investigated by femtosecond transient absorption spectroscopy. Phys Chem Chem Phys 2022; 24:4204-4211. [PMID: 35119441 DOI: 10.1039/d1cp05269a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultraviolet radiation (UVR) from the sun is essential for the prebiotic syntheses of nucleotides, but it can also induce photolesions such as the cyclobutane pyrimidine dimers (CPDs) to RNA or DNA oligonucleotide in prebiotic Earth. 2,6-Diaminopurine (26DAP) has been proposed to repair CPDs in high yield under prebiotic conditions and be a key component in enhancing the photostability of higher-order prebiotic DNA structures. However, its electronic relaxation pathways have not been studied, which is necessary to know whether 26DAP could have survived the intense UV fluxes of the prebiotic Earth. We investigate the electronic relaxation mechanism of both 26DAP and its 2'-deoxyribonucleoside (26DAP-d) in aqueous solution using steady-state and femtosecond transient absorption measurements that are complemented with electronic-structure calculations. The results demonstrate that both purine derivatives are significantly photostable to UVR. It is shown that upon excitation at 287 nm, the lowest energy 1ππ* state is initially populated. The population then branches following two relaxation coordinates in the 1ππ* potential energy surface, which are identified as the C2- and C6-relaxation coordinates. The population following the C6-coordinate internally converts to the ground state nonradiatively through a nearly barrierless conical intersection within 0.7 ps in 26DAP or within 1.1 ps in 26DAP-d. The population that follows the C2-relaxation coordinate decays back to the ground state by a combination of nonradiative internal conversion via a conical intersection and fluorescence emission from the 1ππ* minimum in 43 ps and 1.8 ns for the N9 and N7 tautomers of 26DAP, respectively, or in 70 ps for 26DAP-d. Fluorescence quantum yields of 0.037 and 0.008 are determined for 26DAP and 26DAP-d, respectively. Collectively, it is demonstrated that most of the excited state population in 26DAP and 26DAP-d decays back to the ground state via both nonradiative and radiative relaxation pathways. This result lends support to the idea that 26DAP could have accumulated in large enough quantities during the prebiotic era to participate in the formation of prebiotic RNA or DNA oligomers and act as a key component in the protection of the prebiotic genetic alphabet.
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Affiliation(s)
| | | | - Andres A Gonzalez
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
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12
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Sebris A, Novosjolova I, Traskovskis K, Kokars V, Tetervenoka N, Vembris A, Turks M. Photophysical and Electrical Properties of Highly Luminescent 2/6-Triazolyl-Substituted Push-Pull Purines. ACS OMEGA 2022; 7:5242-5253. [PMID: 35187339 PMCID: PMC8851656 DOI: 10.1021/acsomega.1c06359] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 01/13/2022] [Indexed: 06/14/2023]
Abstract
New push-pull N(9)-alkylated 6-piperidino-2-triazolylpurine and 2-piperidino-6-triazolylpurine derivatives are synthesized, and their optical and optoelectronic properties are comprehensively characterized with experimental and computational methods. The compounds possess intense violet or blue fluorescence with fluorescence quantum yields of up to 91% in solution and 40% in host-free films. Depending on their structural composition, the compounds have ionization energy in the range of 5.25-6.04 eV, electron affinity of 2.18-3.15 eV, and triplet energy of 2.52-2.95 eV. Due to the presence of hole-transporting purine and electron-transporting triazole fragments, compounds exhibit bipolar charge-transportation ability. Despite the favorable emissive properties of the studied push-pull purines, their electroluminescence in thin films is quenched owing to large current densities that are present even at a moderate driving voltage. This marks application directions related to a predominantly charge-transportation functionality as the most suitable for this compound class.
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Affiliation(s)
- Armands Sebris
- Faculty
of Materials Science and Applied Chemistry, Riga Technical University, P. Valdena Str. 3, LV-1048 Riga, Latvia
| | - Irina Novosjolova
- Faculty
of Materials Science and Applied Chemistry, Riga Technical University, P. Valdena Str. 3, LV-1048 Riga, Latvia
| | - Kaspars Traskovskis
- Faculty
of Materials Science and Applied Chemistry, Riga Technical University, P. Valdena Str. 3, LV-1048 Riga, Latvia
| | - Valdis Kokars
- Faculty
of Materials Science and Applied Chemistry, Riga Technical University, P. Valdena Str. 3, LV-1048 Riga, Latvia
| | - Natalija Tetervenoka
- Institute
of Solid State Physics, University of Latvia, Kengaraga Str. 8, LV-1063 Riga, Latvia
| | - Aivars Vembris
- Institute
of Solid State Physics, University of Latvia, Kengaraga Str. 8, LV-1063 Riga, Latvia
| | - Ma̅ris Turks
- Faculty
of Materials Science and Applied Chemistry, Riga Technical University, P. Valdena Str. 3, LV-1048 Riga, Latvia
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13
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Romeo-Gella F, Arpa EM, Corral I. A molecular insight into the photophysics of barbituric acid, a candidate for canonical nucleobases' ancestor. Phys Chem Chem Phys 2022; 24:1405-1414. [PMID: 34982082 DOI: 10.1039/d1cp04987a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
This work investigates the photophysics of barbituric acid at different pH conditions using ab initio methods. Our calculations ascribe the most intense bands at ca. 260 nm at neutral pH and 210 nm at acidic pH conditions in the absorption spectra of this chromophore to the lowest lying ππ* transitions. Consistently with the ultrashort excited state lifetimes experimentally registered, the potential energy landscapes of both the neutral and deprotonated forms of barbituric acid combined with the interpretation of their transient absorption spectra suggest the deactivation of these systems along the singlet manifold. Compared to uracil, its closest natural nucleobase, barbituric acid presents a red shifted absorption spectrum, due to the lowering by more than 0.5 eV of the lowest-energy ππ* excited state, and a much more complex topography of the S1 potential energy surface, with several energetically accessible local minima. This fact, however, does not affect the excited state lifetimes, which for barbituric acid were experimentally registered in the sub-ps time scale.
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Affiliation(s)
- Fernando Romeo-Gella
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049, Madrid, Spain.
| | - Enrique M Arpa
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049, Madrid, Spain.
| | - Inés Corral
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049, Madrid, Spain. .,Institute for Advanced Research in Chemistry (IAdChem), Universidad Autónoma de Madrid, 28049, Madrid, Spain
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14
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Kim J, Woo KC, Kim KK, Kang M, Kim SK. Tunneling dynamics dictated by the multidimensional conical intersection seam in the πσ*‐mediated photochemistry of heteroaromatic molecules. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Junggil Kim
- Department of Chemistry, KAIST Daejeon Republic of Korea
| | - Kyung Chul Woo
- Department of Chemistry, KAIST Daejeon Republic of Korea
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences Nanyang Technological University Singapore Singapore
| | - Kuk Ki Kim
- Department of Chemistry, KAIST Daejeon Republic of Korea
| | - Minseok Kang
- Department of Chemistry, KAIST Daejeon Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST Daejeon Republic of Korea
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15
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Jara-Cortés J, Leal-Sánchez E, Francisco E, Pérez-Pimienta JA, Martín Pendás Á, Hernández-Trujillo J. Implementation of the interacting quantum atom energy decomposition using the CASPT2 method. Phys Chem Chem Phys 2021; 23:27508-27519. [PMID: 34874377 DOI: 10.1039/d1cp02837e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We present an implementation of the interacting quantum atom (IQA) energy decomposition scheme using the complete active space second-order perturbation theory (CASPT2). This combination yields a real-space interpretation tool with a proper account of the static and dynamic correlation that is particularly relevant for the description of processes in electronic excited states. The IQA/CASPT2 approach allows determination of the energy redistribution that takes place along a photophysical/photochemical deactivation path in terms of self- and interatomic contributions. The applicability of the method is illustrated by the description of representative processes spanning different bonding regimes: noble gas excimer and exciplex formation, the reaction of ozone with a chlorine atom, and the photodissociations of formaldehyde and cyclobutane. These examples show the versatility of using CASPT2 with the significant information provided by the IQA partition to describe chemical processes with a large multiconfigurational character.
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Affiliation(s)
- Jesús Jara-Cortés
- Unidad Académica de Ciencias Básicas e Ingenierías, Universidad Autónoma de Nayarit, Tepic 63155, Mexico.
| | - Edith Leal-Sánchez
- Departamento de Física y Química Teórica, Facultad de Química, UNAM, México City 04510, Mexico
| | - Evelio Francisco
- Departamento de Química Física y Analítica, Faculta de Química, Universidad de Oviedo, Oviedo 33006, Spain
| | - José A Pérez-Pimienta
- Unidad Académica de Ciencias Básicas e Ingenierías, Universidad Autónoma de Nayarit, Tepic 63155, Mexico.
| | - Ángel Martín Pendás
- Departamento de Química Física y Analítica, Faculta de Química, Universidad de Oviedo, Oviedo 33006, Spain
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16
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Krul SE, Hoehn SJ, Feierabend KJ, Crespo-Hernández CE. Excited state dynamics of 7-deazaguanosine and guanosine 5'-monophosphate. J Chem Phys 2021; 154:075103. [PMID: 33607894 DOI: 10.1063/5.0038123] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Minor structural modifications to the DNA and RNA nucleobases have a significant effect on their excited state dynamics and electronic relaxation pathways. In this study, the excited state dynamics of 7-deazaguanosine and guanosine 5'-monophosphate are investigated in aqueous solution and in a mixture of methanol and water using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient spectra are collected using photon densities that ensure no parasitic multiphoton-induced signal from solvated electrons. The data can be fit satisfactorily using a two- or three-component kinetic model. By analyzing the results from steady-state, time-resolved, computational calculations, and the methanol-water mixture, the following general relaxation mechanism is proposed for both molecules, Lb → La → 1πσ*(ICT) → S0, where the 1πσ*(ICT) stands for an intramolecular charge transfer excited singlet state with significant πσ* character. In general, longer lifetimes for internal conversion are obtained for 7-deazaguanosine compared to guanosine 5'-monophosphate. Internal conversion of the 1πσ*(ICT) state to the ground state occurs on a similar time scale of a few picoseconds in both molecules. Collectively, the results demonstrate that substitution of a single nitrogen atom for a methine (C-H) group at position seven of the guanine moiety stabilizes the 1ππ* Lb and La states and alters the topology of their potential energy surfaces in such a way that the relaxation dynamics in 7-deazaguanosine are slowed down compared to those in guanosine 5'-monophosphate but not for the internal conversion of 1πσ*(ICT) state to the ground state.
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Affiliation(s)
- Sarah E Krul
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Sean J Hoehn
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Karl J Feierabend
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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17
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Dziuba D, Didier P, Ciaco S, Barth A, Seidel CAM, Mély Y. Fundamental photophysics of isomorphic and expanded fluorescent nucleoside analogues. Chem Soc Rev 2021; 50:7062-7107. [PMID: 33956014 DOI: 10.1039/d1cs00194a] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fluorescent nucleoside analogues (FNAs) are structurally diverse mimics of the natural essentially non-fluorescent nucleosides which have found numerous applications in probing the structure and dynamics of nucleic acids as well as their interactions with various biomolecules. In order to minimize disturbance in the labelled nucleic acid sequences, the FNA chromophoric groups should resemble the natural nucleobases in size and hydrogen-bonding patterns. Isomorphic and expanded FNAs are the two groups that best meet the criteria of non-perturbing fluorescent labels for DNA and RNA. Significant progress has been made over the past decades in understanding the fundamental photophysics that governs the spectroscopic and environmentally sensitive properties of these FNAs. Herein, we review recent advances in the spectroscopic and computational studies of selected isomorphic and expanded FNAs. We also show how this information can be used as a rational basis to design new FNAs, select appropriate sequences for optimal spectroscopic response and interpret fluorescence data in FNA applications.
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Affiliation(s)
- Dmytro Dziuba
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
| | - Pascal Didier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
| | - Stefano Ciaco
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France. and Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via Aldo Moro 2, 53100 Siena, Italy
| | - Anders Barth
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Claus A M Seidel
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Yves Mély
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
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18
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Abstract
In this article, we review nonadiabatic molecular dynamics (NAMD) methods for modeling spin-crossover transitions. First, we discuss different representations of electronic states employed in the grid-based and direct NAMD simulations. The nature of interstate couplings in different representations is highlighted, with the main focus on nonadiabatic and spin-orbit couplings. Second, we describe three NAMD methods that have been used to simulate spin-crossover dynamics, including trajectory surface hopping, ab initio multiple spawning, and multiconfiguration time-dependent Hartree. Some aspects of employing different electronic structure methods to obtain information about potential energy surfaces and interstate couplings for NAMD simulations are also discussed. Third, representative applications of NAMD to spin crossovers in molecular systems of different sizes and complexities are highlighted. Finally, we pose several fundamental questions related to spin-dependent processes. These questions should be possible to address with future methodological developments in NAMD.
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Affiliation(s)
- Saikat Mukherjee
- Institut de Chimie Radicalaire, CNRS 7273, Aix-Marseille University, 13013 Marseille, France;
| | - Dmitry A Fedorov
- Oak Ridge Associated Universities, Oak Ridge, Tennessee 37830, USA;
| | - Sergey A Varganov
- Department of Chemistry, University of Nevada, Reno, Nevada 89557-0216, USA;
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19
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Shahrokh L, Omidyan R, Azimi G. Theoretical insights on the excited-state-deactivation mechanisms of protonated thymine and cytosine. Phys Chem Chem Phys 2021; 23:8916-8925. [PMID: 33876051 DOI: 10.1039/d0cp06673g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ab initio and surface-hopping nonadiabatic dynamics simulation methods were employed to investigate relaxation mechanisms in protonated thymine (TH+) and cytosine (CH+). A few conical intersections were located between 1ππ* and S0 states for each system with the CASSCF (8,8) theoretical model and relevant contributions to the deactivation mechanism of titled systems were addressed by the determination of potential energy profiles at the CASPT2 (12,10) theoretical level. It was revealed that the relaxation of the 1ππ* state of the most stable conformer of both systems to the ground state is mostly governed by the accessible S1/S0 conical intersection resulting from the barrier-free out-of-plane deformation. Interestingly, it was exhibited that the ring puckering coordinate driven from the C6 position of the heterocycle ring in TH+ and CH+ plays the most prominent role in the deactivation mechanism of considered systems. Our ab initio results are also supported by excited-state nonadiabatic dynamics simulations based on ADC(2), describing the ultrashort S1 lifetime of TH+/CH+ by analyzing trajectories leading excited systems to the ground. It was confirmed that the excited-state population mostly relaxes to the ground via the ring puckering coordinate from the C6 moiety. Overall, the theoretical results of this study shed light on the deactivation mechanism of protonated DNA bases.
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Affiliation(s)
- Leila Shahrokh
- Department of Chemistry, University of Isfahan, 81746-73441, Isfahan, Iran.
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20
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Zhang K, Wang F, Jiang Y, Wang X, Pan H, Sun Z, Sun H, Xu J, Chen J. New Insights about the Photostability of DNA/RNA Bases: Triplet nπ* State Leads to Effective Intersystem Crossing in Pyrimidinones. J Phys Chem B 2021; 125:2042-2049. [PMID: 33600186 DOI: 10.1021/acs.jpcb.0c10611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The high photostability of DNA/RNA nucleobases is attributed to the effective internal conversions of their bright 1ππ* states to the ground state through conical intersections. Intersystem crossing (ISC) from singlet to triplet excited states is a minor decay pathway in nucleobases and it is observed with ∼1-2% quantum yields (QYs) in pyrimidine bases. Presumably, ISC in pyrimidines takes place from the dark singlet 1nπ* state to the lowest triplet 3ππ* state. However, recent studies showed that ISC from the initial populated bright 1ππ* state to higher energy triplet 3nπ* states indeed occurs in the subpicosecond timescale. Such a mechanism is still poorly understood since direct observation of this pathway is challenging. Herein, excited state dynamics of three pyrimidinones, which share the same skeleton with pyrimidine bases, is investigated in different solvents. Compared to canonical pyrimidine bases, removing the oxygen atom at the C4 position revokes the low-lying dark 1nπ* state in pyrimidinones, resulting in direct ISC from the S1 (1ππ*) state to triplet T3 (3nπ*) state with much higher QYs. Meanwhile, hydrogen bonding between the carbonyl group in pyrimidinones and protic solvents can accelerate vibrational cooling of the hot S1 (1ππ*) state, leading to higher fluorescence QYs and smaller ISC rate constants. These results not only evidence the hypothesis of the direct 1ππ* → 3nπ* ISC mechanism, but also contribute to a better understanding of triplet formation in pyrimidines.
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Affiliation(s)
- Kun Zhang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Fufang Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Yanrong Jiang
- 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
| | - Zhenrong Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Haitao Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Jianhua Xu
- 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
| | - 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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21
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Mukazhanova A, Malone W, Negrin-Yuvero H, Fernandez-Alberti S, Tretiak S, Sharifzadeh S. Photoexcitation dynamics in perylene diimide dimers. J Chem Phys 2020; 153:244117. [PMID: 33380092 DOI: 10.1063/5.0031485] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We utilize first-principles theory to investigate photo-induced excited-state dynamics of functionalized perylene diimide. This class of materials is highly suitable for solar energy conversion because of the strong optical absorbance, efficient energy transfer, and chemical tunability. We couple time-dependent density functional theory to a recently developed time-resolved non-adiabatic dynamics approach based on a semi-empirical description. By studying the monomer and dimer, we focus on the role stacking plays on the time-scales associated with excited-state non-radiative relaxation from a high excitonic state to the lowest energy exciton. We predict that the time-scale for energy conversion in the dimer is significantly faster than that in the monomer when equivalent excited states are accounted for. Additionally, for the dimer, the decay from the second to the nearly degenerate lowest energy excited-state involves two time-scales: a rapid decay on the order of ∼10 fs followed by a slower decay of ∼100 fs. Analysis of the spatial localization of the electronic transition density during the internal conversion process points out the existence of localized states on individual monomers, indicating that the strength of thermal fluctuations exceeds electronic couplings between the states such that the exciton hops between localized states throughout the simulation.
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Affiliation(s)
- Aliya Mukazhanova
- Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215, USA
| | - Walter Malone
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Hassiel Negrin-Yuvero
- Universidad Nacional de Quilmes/CONICET, Roque Saenz Peña 352, B1876BXD Bernal, Argentina
| | | | - Sergei Tretiak
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Sahar Sharifzadeh
- Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215, USA
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22
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Arpa EM, Brister MM, Hoehn SJ, Crespo-Hernández CE, Corral I. On the Origin of the Photostability of DNA and RNA Monomers: Excited State Relaxation Mechanism of the Pyrimidine Chromophore. J Phys Chem Lett 2020; 11:5156-5161. [PMID: 32501702 DOI: 10.1021/acs.jpclett.0c00935] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Today's genetic composition is the result of continual refinement processes on primordial heterocycles present in prebiotic Earth and at least partially regulated by ultraviolet radiation. Femtosecond transient absorption spectroscopy and state-of-the-art ab initio calculations are combined to unravel the electronic relaxation mechanism of pyrimidine, the common chromophore of the nucleobases. The excitation of pyrimidine at 268 nm populates the S1(nπ*) state directly. A fraction of the population intersystem crosses to the triplet manifold within 7.8 ps, partially decaying within 1.5 ns, while another fraction recovers the ground state in >3 ns. The pyrimidine chromophore is not responsible for the photostability of the nucleobases. Instead, C2 and C4 amino and/or carbonyl functionalization is essential for shaping the topography of pyrimidine's potential energy surfaces and results in accessible conical intersections between the initially populated electronic excited state and the ground state.
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Affiliation(s)
| | - Matthew M Brister
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Sean J Hoehn
- 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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23
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Inamori M, Ikabata Y, Yoshikawa T, Nakai H. Unveiling controlling factors of the S0/S1 minimum energy conical intersection (2): Application to penalty function method. J Chem Phys 2020; 152:144108. [DOI: 10.1063/1.5142592] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- Mayu Inamori
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Yasuhiro Ikabata
- Waseda Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Takeshi Yoshikawa
- Waseda Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Hiromi Nakai
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
- Waseda Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520, Japan
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24
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Skotnicki K, Taras-Goslinska K, Janik I, Bobrowski K. Radiation Induced One-Electron Oxidation of 2-Thiouracil in Aqueous Solutions. Molecules 2019; 24:E4402. [PMID: 31810289 PMCID: PMC6930642 DOI: 10.3390/molecules24234402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 11/27/2019] [Accepted: 11/27/2019] [Indexed: 11/17/2022] Open
Abstract
Oxidative damage to 2-thiouracil (2-TU) by hydroxyl (•OH) and azide (●N3) radicals produces various primary reactive intermediates. Their optical absorption spectra and kinetic characteristics were studied by pulse radiolysis with UV-vis spectrophotometric and conductivity detection and by time-dependent density functional theory (TD-DFT) method. The transient absorption spectra recorded in the reactions of •OH with 2-TU depend on the concentration of 2-TU, however, only slightly on pH. At low concentrations, they are characterized by a broad absorption band with a weakly pronounced maxima located at λ = 325, 340 and 385 nm, whereas for high concentrations, they are dominated by an absorption band with λmax ≈ 425 nm. Based on calculations using TD-DFT method, the transient absorption spectra at low concentration of 2-TU were assigned to the ●OH-adducts to the double bond at C5 and C6 carbon atoms (3●, 4●) and 2c-3e bonded ●OH adduct to sulfur atom (1…●OH) and at high concentration of 2-TU also to the dimeric 2c-3e S-S-bonded radical in neutral form (2●). The dimeric radical (2●) is formed in the reaction of thiyl-type radical (6●) with 2-TU and both radicals are in an equilibrium with Keq = 4.2 × 103 M-1. Similar equilibrium (with Keq = 4.3 × 103 M-1) was found for pH above the pKa of 2-TU which involves admittedly the same radical (6●) but with the dimeric 2c-3e S-S bonded radical in anionic form (2●-). In turn, ●N3-induced oxidation of 2-TU occurs via radical cation with maximum spin location on the sulfur atom which subsequently undergoes deprotonation at N1 atom leading again to thiyl-type radical (6●). This radical is a direct precursor of dimeric radical (2●).
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Affiliation(s)
- Konrad Skotnicki
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland;
| | | | - Ireneusz Janik
- Notre Dame Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Krzysztof Bobrowski
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland;
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25
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Sapunar M, Domcke W, Došlić N. UV absorption spectra of DNA bases in the 350-190 nm range: assignment and state specific analysis of solvation effects. Phys Chem Chem Phys 2019; 21:22782-22793. [PMID: 31595896 DOI: 10.1039/c9cp04662c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The theoretical assignment of electronic spectra of polyatomic molecules is a challenging problem that requires the specification of the character of a large number of electronic states. We propose a procedure for automatically determining the character of electronic transitions and apply it to the study of UV spectra of DNA bases in the gas phase and in the aqueous environment. The procedure is based on the computation of electronic wave function overlaps and accounts for an extensive sampling of nuclear geometries. Novelties of this work are the theoretical assignment of the electronic spectra of DNA bases up to 190 nm and a state specific analysis of solvation effects. By accounting for different effects contributing to the total solvent shift we obtained a good agreement between the computed and experimental spectra. Effects of vibrational averaging, temperature and solvent-induced structural changes shift excitation energies to lower values. Solvent-solute electrostatic interactions are state specific and strongly destabilize nRyd states, and to lesser extent nπ* and πRyd states. Altogether, this results in the stabilization of ππ* states and destabilization of nπ*, πRyd and nRyd states in solution.
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Affiliation(s)
- Marin Sapunar
- Department of Physical Chemistry, Ruder Bošković Institute, 10000 Zagreb, Croatia.
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26
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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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27
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Zhou Z, Hu Z, Zhang X, Jia M, Wang X, Su H, Sun H, Chen J, Xu J. pH Controlled Intersystem Crossing and Singlet Oxygen Generation of 8-Azaadenine in Aqueous Solution. Chemphyschem 2019; 20:757-765. [PMID: 30702794 DOI: 10.1002/cphc.201800969] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/30/2019] [Indexed: 01/01/2023]
Abstract
Azabases are intriguing DNA and RNA analogues and have been used as effective antiviral and anticancer medicines. However, photosensitivity of these drugs has also been reported. Here, pH-controlled intersystem crossing (ISC) process of 9H 8-azaadenine (8-AA) in aqueous solution is reported. Broadband transient absorption measurements reveal that the hydrogen atom at N9 position can greatly affect ISC of 8-AA and ISC is more favorable when 8-AA is in its neutral form in aqueous solution. The initial excited ππ* (S2 ) state evolves through ultrafast internal conversion (IC) (4.2 ps) to the lower-lying nπ* state (S1 ), which further stands as a door way state for ISC with a time constant of 160 ps. The triplet state has a lifetime of 6.1 μs. On the other hand, deprotonation at N9 position promotes the IC from the ππ* (S2 ) state to the ground state (S0 ) and the lifetime of the S2 state is determined to be 10 ps. The experimental results are further supported by time-dependent density functional theory (TDDFT) calculations. Singlet oxygen generation yield is measured to be 13.8 % for the neutral 8-AA while the deprotonated one exhibit much lower yield (<2 %), implying that this compound could be a potential pH-sensitized photodynamic therapy agent.
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Affiliation(s)
- Zhongneng Zhou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Zhubin Hu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Xianwang Zhang
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Menghui Jia
- Shanghai Institute of Optics and Fine Mechanics, Shanghai, 201800, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Haitao Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China
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28
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Martínez-Fernández L, Arslancan S, Ivashchenko D, Crespo-Hernández CE, Corral I. Tracking the origin of photostability in purine nucleobases: the photophysics of 2-oxopurine. Phys Chem Chem Phys 2019; 21:13467-13473. [DOI: 10.1039/c9cp00879a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Molding purine PES through functionalization: whilst purine C2-substitution maintains the features of the spectroscopic PES of the heterocycle, C6-functionalization reshapes its topography leading to photostable systems.
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Affiliation(s)
| | - Serra Arslancan
- Departamento de Química
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
| | - Dmytro Ivashchenko
- Departamento de Química
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
- Departamento de Química e Bioquímica
| | | | - Inés Corral
- Departamento de Química
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
- IADCHEM
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29
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Zhou P, Zhao L. How Does the O6-Methylation Regulate the Excited-State Decay of Guanine Monomers. J Phys Chem B 2018; 123:201-206. [DOI: 10.1021/acs.jpcb.8b08606] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Panwang Zhou
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, Liaoning, China
| | - Li Zhao
- School of Science, China University of Petroleum, Qingdao 266580, Shandong, China
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30
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Mai S, Marquetand P, González L. Nonadiabatic dynamics: The SHARC approach. WILEY INTERDISCIPLINARY REVIEWS. COMPUTATIONAL MOLECULAR SCIENCE 2018; 8:e1370. [PMID: 30450129 PMCID: PMC6220962 DOI: 10.1002/wcms.1370] [Citation(s) in RCA: 224] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/05/2018] [Accepted: 04/06/2018] [Indexed: 12/12/2022]
Abstract
We review the Surface Hopping including ARbitrary Couplings (SHARC) approach for excited-state nonadiabatic dynamics simulations. As a generalization of the popular surface hopping method, SHARC allows simulating the full-dimensional dynamics of molecules including any type of coupling terms beyond nonadiabatic couplings. Examples of these arbitrary couplings include spin-orbit couplings or dipole moment-laser field couplings, such that SHARC can describe ultrafast internal conversion, intersystem crossing, and radiative processes. The key step of the SHARC approach consists of a diagonalization of the Hamiltonian including these couplings, such that the nuclear dynamics is carried out on potential energy surfaces including the effects of the couplings-this is critical in any applications considering, for example, transition metal complexes or strong laser fields. We also give an overview over the new SHARC2.0 dynamics software package, released under the GNU General Public License, which implements the SHARC approach and several analysis tools. The review closes with a brief survey of applications where SHARC was employed to study the nonadiabatic dynamics of a wide range of molecular systems. This article is categorized under: Theoretical and Physical Chemistry > Reaction Dynamics and KineticsSoftware > Simulation MethodsSoftware > Quantum Chemistry.
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Affiliation(s)
- Sebastian Mai
- Institute of Theoretical Chemistry, Faculty of Chemistry University of Vienna Vienna Austria
| | - Philipp Marquetand
- Institute of Theoretical Chemistry, Faculty of Chemistry University of Vienna Vienna Austria
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry University of Vienna Vienna Austria
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31
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Nakai H, Inamori M, Ikabata Y, Wang Q. Unveiling Controlling Factors of the S0/S1 Minimum Energy Conical Intersection: A Theoretical Study. J Phys Chem A 2018; 122:8905-8910. [DOI: 10.1021/acs.jpca.8b07864] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hiromi Nakai
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
- Waseda Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520, Japan
| | - Mayu Inamori
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Yasuhiro Ikabata
- Waseda Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Qi Wang
- Waseda Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
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32
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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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33
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Affiliation(s)
- Juan J. Nogueira
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, A-1090 Wien, Austria;,
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, A-1090 Wien, Austria;,
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34
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Ashwood B, Ortiz-Rodríguez LA, Crespo-Hernández CE. Photochemical relaxation pathways of S 6-methylthioinosine and O 6-methylguanosine in solution. Faraday Discuss 2018; 207:351-374. [PMID: 29372193 DOI: 10.1039/c7fd00193b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
S6-Methylthioinosine and O6-methylguanosine are byproducts resulting from the enzymatic reactions of sulfur-substituted prodrugs in cells and from the interaction of alkylating agents with cellular DNA, respectively. Their photochemistry has not been investigated, and it is currently unknown whether light absorption by these byproducts may pose any threat to the cell. In this contribution, their photoinduced processes upon absorption of UVB radiation are reported using broadband transient absorption spectroscopy. Plausible electronic relaxation mechanisms are proposed for both biological molecules, which are supported by steady-state absorption and emission measurements, and by singlet and triplet vertical excitation energies performed on a large subset of ground-state optimized conformational isomers in solution. The results are compared to the body of knowledge gathered in the scientific literature about the light-induced processes in the sulfur-substituted and canonical purine monomers. In particular, it is shown that S6-methylation decreases the rate to populate the lowest-energy triplet state and blueshifts the ground-state absorption spectrum compared to those for the sulfur-substituted prodrugs and for the 6-thioguanosine metabolite. Similarly, O6-methylation decreases the rate of internal conversion to the ground state observed in the guanine monomers by more than 10-fold in acetonitrile and 40-fold in aqueous solution, while it redshifts the ground-state absorption spectrum. Collectively, this investigation provides relevant new insights about the relationship between structural modifications of the purine chromophore and the electronic relaxation mechanisms in this important group of biological molecules.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry, Center for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA.
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35
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Penfold TJ, Gindensperger E, Daniel C, Marian CM. Spin-Vibronic Mechanism for Intersystem Crossing. Chem Rev 2018; 118:6975-7025. [DOI: 10.1021/acs.chemrev.7b00617] [Citation(s) in RCA: 401] [Impact Index Per Article: 66.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Thomas J. Penfold
- Chemistry - School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon-Tyne NE1 7RU, United Kingdom
| | - Etienne Gindensperger
- Laboratoire de Chimie Quantique, Institut de Chimie UMR-7177, CNRS - Université de Strasbourg, 1 Rue Blaise Pascal 67008 Strasbourg, France
| | - Chantal Daniel
- Laboratoire de Chimie Quantique, Institut de Chimie UMR-7177, CNRS - Université de Strasbourg, 1 Rue Blaise Pascal 67008 Strasbourg, France
| | - Christel M. Marian
- Institut für Theoretische Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
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36
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Schneider KRA, Traber P, Reichardt C, Weiss H, Kupfer S, Görls H, Gräfe S, Weigand W, Dietzek B. Unusually Short-Lived Solvent-Dependent Excited State in a Half-Sandwich Ru(II) Complex Induced by Low-Lying 3MC States. J Phys Chem A 2018; 122:1550-1559. [PMID: 29369626 DOI: 10.1021/acs.jpca.7b11470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A ruthenium complex with a half-sandwich geometry ([(p-cymene)Ru(Cl)(curcuminoid)]) was synthesized, characterized, and investigated regarding its ultrafast photophysics. These photophysical investigations of the complex revealed a weak and short-lived emission from the initially populated 1MLCT state and solvent-dependent photoinduced dynamics, where the secondarily populated 3MC state is stabilized by nonpolar solvents. Overall the decay of the 3dd-MC state to the ground state is completed within picoseconds. This short excited-state lifetime is in stark contrast to the typically observed long-lived 3MLCT states with lifetimes of nanoseconds or microseconds in unstrained, octahedral ruthenium complexes but is in good agreement with the findings for distorted octahedral complexes. This is pointing to the half-sandwich geometry as a new and easy approach to study these otherwise often concealed dd states.
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Affiliation(s)
- Kilian R A Schneider
- Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT) e. V. , Albert-Einstein-Straße 9, 07745 Jena, Germany
| | | | - Christian Reichardt
- Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT) e. V. , Albert-Einstein-Straße 9, 07745 Jena, Germany
| | | | | | | | | | | | - Benjamin Dietzek
- Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT) e. V. , Albert-Einstein-Straße 9, 07745 Jena, Germany
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37
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Böhnke H, Röttger K, Ingle RA, Marroux HJB, Bohnsack M, Orr-Ewing AJ, Temps F. Efficient intersystem crossing in 2-aminopurine riboside probed by femtosecond time-resolved transient vibrational absorption spectroscopy. Phys Chem Chem Phys 2018; 20:20033-20042. [DOI: 10.1039/c8cp02664e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The photophysical dynamics of 2-aminopurine, a fluorescent analogue of the canonical nucleobase adenine, has been studied by femtosecond transient vibrational absorption spectroscopy.
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Affiliation(s)
- Hendrik Böhnke
- Institute of Physical Chemistry
- Christian-Albrechts-University Kiel
- 24098 Kiel
- Germany
| | - Katharina Röttger
- Institute of Physical Chemistry
- Christian-Albrechts-University Kiel
- 24098 Kiel
- Germany
- School of Chemistry
| | | | | | - Mats Bohnsack
- Institute of Physical Chemistry
- Christian-Albrechts-University Kiel
- 24098 Kiel
- Germany
| | | | - Friedrich Temps
- Institute of Physical Chemistry
- Christian-Albrechts-University Kiel
- 24098 Kiel
- Germany
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38
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Freixas VM, Fernandez-Alberti S, Makhov DV, Tretiak S, Shalashilin D. An ab initio multiple cloning approach for the simulation of photoinduced dynamics in conjugated molecules. Phys Chem Chem Phys 2018; 20:17762-17772. [DOI: 10.1039/c8cp02321b] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Multidimensional wave function: a superposition of Gaussian coherent states guided by Ehrenfest trajectories suited to clone and swap their electronic amplitudes.
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Affiliation(s)
| | | | - Dmitry V. Makhov
- School of Chemistry
- University of Leeds
- Leeds LS2 9JT
- UK
- School of Mathematics
| | - Sergei Tretiak
- Center for Nonlinear Studies (CNLS), and Center for Integrated Nanotechnologies (CINT)
- Los Alamos National Laboratory
- Los Alamos
- USA
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39
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Berenbeim JA, Boldissar S, Siouri FM, Gate G, Haggmark MR, Aboulache B, Cohen T, de Vries MS. Excited-State Dynamics of Isocytosine: A Hybrid Case of Canonical Nucleobase Photodynamics. J Phys Chem Lett 2017; 8:5184-5189. [PMID: 28985073 DOI: 10.1021/acs.jpclett.7b02032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present resonant two-photon ionization (R2PI) spectra of isocytosine (isoC) and pump-probe results on two of its tautomers. IsoC is one of a handful of alternative bases that have been proposed in scenarios of prebiotic chemistry. It is structurally similar to both cytosine (C) and guanine (G). We compare the excited-state dynamics with the Watson-Crick (WC) C and G tautomeric forms. These results suggest that the excited-state dynamics of WC form of G may primarily depend on the heterocyclic substructure of the pyrimidine moiety, which is chemically identical to isoC. For WC isoC we find a single excited-state decay with a rate of ∼1010 s-1, while the enol form has multiple decay rates, the fastest of which is 7 times slower than for WC isoC. The excited-state dynamics of isoC exhibits striking similarities with that of G, more so than with the photodynamics of C.
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Affiliation(s)
- Jacob A Berenbeim
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Samuel Boldissar
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Faady M Siouri
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Gregory Gate
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Michael R Haggmark
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Briana Aboulache
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Trevor Cohen
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
| | - Mattanjah S de Vries
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States
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40
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Ashwood B, Ortiz-Rodríguez LA, Crespo-Hernández CE. Excited-State Dynamics in O 6-Methylguanosine: Impact of O 6-Methylation on the Relaxation Mechanism of Guanine Monomers. J Phys Chem Lett 2017; 8:4380-4385. [PMID: 28850232 DOI: 10.1021/acs.jpclett.7b02090] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Absorption of ultraviolet radiation by DNA bases results in ultrafast internal conversion to the ground state, which minimizes photodamage. However, exogenous and endogenous alkylating agents present in the cellular environment can methylate the nucleobases in DNA. In particular, methylation of guanosine at the O6 position in DNA leads to the formation of the O6-methylguanosine adduct, which may alter the photostability of DNA. This contribution demonstrates that O6-methylation of guanosine red shifts its ground-state absorption spectrum and slows down the rate of internal conversion to the ground state by ∼40-fold in aqueous solution. The 40-fold decrease in the rate of excited-state decay increases the probability of photodamage within cellular DNA. It is proposed that the longer decay lifetime corresponds to relaxation of the excited-state population in O6-methylguanosine along a C6-puckered reaction coordinate in the 1ππ*(La) potential energy surface that runs parallel to an ultrafast internal conversion pathway along a C2-puckered coordinate.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Luis A Ortiz-Rodríguez
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University , Cleveland, Ohio 44106, United States
| | - Carlos E Crespo-Hernández
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University , Cleveland, Ohio 44106, United States
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41
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Atkins AJ, González L. Trajectory Surface-Hopping Dynamics Including Intersystem Crossing in [Ru(bpy) 3] 2. J Phys Chem Lett 2017; 8:3840-3845. [PMID: 28766339 DOI: 10.1021/acs.jpclett.7b01479] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Surface-hopping dynamics coupled to linear response TDDFT and explicit nonadiabatic and spin-orbit couplings have been used to model the ultrafast intersystem crossing (ISC) dynamics in [Ru(bpy)3]2+. Simulations using an ensemble of trajectories starting from the singlet metal-to-ligand charge transfer (1MLCT) band show that the manifold of 3MLCT triplet states is first populated from high-lying singlet states within 26 ± 3 fs. ISC competes with an intricate internal conversion relaxation process within the singlet manifold to the lowest singlet state. Normal-mode analysis and principal component analysis, combined with further dynamical simulations where the nuclei are frozen, unequivocally demonstrate that it is not only the high density of states and the large spin-orbit couplings of the system that promote ISC. Instead, geometrical relaxation involving the nitrogen atoms is required to allow for state mixing and efficient triplet population transfer.
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Affiliation(s)
- Andrew J Atkins
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Straße 17, A-1090 Vienna, Austria
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Straße 17, A-1090 Vienna, Austria
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42
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Mondal S, Puranik M. Sub-50 fs excited state dynamics of 6-chloroguanine upon deep ultraviolet excitation. Phys Chem Chem Phys 2017; 18:13874-87. [PMID: 27146198 DOI: 10.1039/c6cp01746k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The photophysical properties of natural nucleobases and their respective nucleotides are ascribed to the sub-picosecond lifetime of their first singlet states in the UV-B region (260-350 nm). Electronic transitions of the ππ* type, which are stronger than those in the UV-B region, lie at the red edge of the UV-C range (100-260 nm) in all isolated nucleobases. The lowest energetic excited states in the UV-B region of nucleobases have been investigated using a plethora of experimental and theoretical methods in gas and solution phases. The sub-picosecond lifetime of these molecules is not a general attribute of all nucleobases but specific to the five primary nucleobases and a few xanthine and methylated derivatives. To determine the overall UV photostability, we aim to understand the effect of more energetic photons lying in the UV-C region on nucleobases. To determine the UV-C initiated photophysics of a nucleobase system, we chose a halogen substituted purine, 6-chloroguanine (6-ClG), that we had investigated previously using resonance Raman spectroscopy. We have performed quantitative measurements of the resonance Raman cross-section across the Bb absorption band (210-230 nm) and constructed the Raman excitation profiles. We modeled the excitation profiles using Lee and Heller's time-dependent theory of resonance Raman intensities to extract the initial excited state dynamics of 6-ClG within 30-50 fs after photoexcitation. We found that imidazole and pyrimidine rings of 6-ClG undergo expansion and contraction, respectively, following photoexcitation to the Bb state. The amount of distortions of the excited state structure from that of the ground state structure is reflected by the total internal reorganization energy that is determined at 112 cm(-1). The contribution of the inertial component of the solvent response towards the total reorganization energy was obtained at 1220 cm(-1). In addition, our simulation also yields an instantaneous response of the first solvation shell within an ultrafast timescale of less than 30 fs following photoexcitation.
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Affiliation(s)
- Sayan Mondal
- Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411008, India.
| | - Mrinalini Puranik
- Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411008, India.
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43
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Abstract
Here we present the excited state dynamics of jet-cooled 6-thioguanine (6-TG), using resonance-enhanced multiphoton ionization (REMPI), IR-UV double resonance spectroscopy, and pump-probe spectroscopy in the nanosecond and picosecond time domains. We report data on two thiol tautomers, which appear to have different excited state dynamics. These decay to a dark state, possibly a triplet state, with rates depending on tautomer form and on excitation wavelength, with the fastest rate on the order of 1010 s-1. We also compare 6-TG with 9-enolguanine, for which we observed decay to a dark state with a 2 orders of magnitude smaller rate. At increased excitation energy (∼+500 cm-1) an additional pathway appears for the predominant thiol tautomer. Moreover, the excited state dynamics for 6-TG thiols is different from that recently predicted for thiones.
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Affiliation(s)
- Faady M Siouri
- Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93016-9510, United States
| | - Samuel Boldissar
- Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93016-9510, United States
| | - Jacob A Berenbeim
- Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93016-9510, United States
| | - Mattanjah S de Vries
- Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93016-9510, United States
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44
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Stephansen AB, Sølling TI. Distortion dependent intersystem crossing: A femtosecond time-resolved photoelectron spectroscopy study of benzene, toluene, and p-xylene. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:044008. [PMID: 28345010 PMCID: PMC5336472 DOI: 10.1063/1.4977735] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 02/16/2017] [Indexed: 05/05/2023]
Abstract
The competition between ultrafast intersystem crossing and internal conversion in benzene, toluene, and p-xylene is investigated with time-resolved photoelectron spectroscopy and quantum chemical calculations. By exciting to S2 out-of-plane symmetry breaking, distortions are activated at early times whereupon spin-forbidden intersystem crossing becomes (partly) allowed. Natural bond orbital analysis suggests that the pinnacle carbon atoms distorting from the aromatic plane change hybridization between the planar Franck-Condon geometry and the deformed (boat-shaped) S2 equilibrium geometry. The effect is observed to increase in the presence of methyl-groups on the pinnacle carbon-atoms, where largest extents of σ and π orbital-mixing are observed. This is fully consistent with the time-resolved spectroscopy data: Toluene and p-xylene show evidence for ultrafast triplet formation competing with internal conversion, while benzene appears to only decay via internal conversion within the singlet manifold. For toluene and p-xylene, internal conversion to S1 and intersystem crossing to T3 occur within the time-resolution of our instrument. The receiver triplet state (T3) is found to undergo internal conversion in the triplet manifold within ≈100-150 fs (toluene) or ≈180-200 fs (p-xylene) as demonstrated by matching rise and decay components of upper and lower triplet states. Overall, the effect of methylation is found to both increase the intersystem crossing probability and direct the molecular axis of the excited state dynamics.
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Affiliation(s)
- Anne B Stephansen
- Department of Chemistry, University of Copenhagen , Universitetsparken 5, DK-2100 København Ø, Denmark
| | - Theis I Sølling
- Department of Chemistry, University of Copenhagen , Universitetsparken 5, DK-2100 København Ø, Denmark
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45
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Arslancan S, Martínez-Fernández L, Corral I. Photophysics and Photochemistry of Canonical Nucleobases’ Thioanalogs: From Quantum Mechanical Studies to Time Resolved Experiments. Molecules 2017. [PMCID: PMC6152766 DOI: 10.3390/molecules22060998] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Interest in understanding the photophysics and photochemistry of thiated nucleobases has been awakened because of their possible involvement in primordial RNA or their potential use as photosensitizers in medicinal chemistry. The interpretation of the photodynamics of these systems, conditioned by their intricate potential energy surfaces, requires the powerful interplay between experimental measurements and state of the art molecular simulations. In this review, we provide an overview on the photophysics of natural nucleobases’ thioanalogs, which covers the last 30 years and both experimental and computational contributions. For all the canonical nucleobase’s thioanalogs, we have compiled the main steady state absorption and emission features and their interpretation in terms of theoretical calculations. Then, we revise the main topographical features, including stationary points and interstate crossings, of their potential energy surfaces based on quantum mechanical calculations and we conclude, by combining the outcome of different spectroscopic techniques and molecular dynamics simulations, with the mechanism by which these nucleobase analogs populate their triplet excited states, which are at the origin of their photosensitizing properties.
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Affiliation(s)
- Serra Arslancan
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Madrid 28049, Spain;
| | - Lara Martínez-Fernández
- Istituto Biostrutture e Bioimmagini-Consiglio Nazionale delle Ricerche, Via Mezzocannone 16, Napoli I-80134, Italy
- Correspondence: (L.M.-F.); (I.C.); Tel.: +34-91-497-8471 (I.C.)
| | - Inés Corral
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Madrid 28049, Spain;
- Institute for Advanced Research in Chemical Sciences (IADCHEM), Universidad Autónoma de Madrid, Madrid 28049, Spain
- Correspondence: (L.M.-F.); (I.C.); Tel.: +34-91-497-8471 (I.C.)
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46
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Rovira AR, Fin A, Tor Y. Expanding a fluorescent RNA alphabet: synthesis, photophysics and utility of isothiazole-derived purine nucleoside surrogates. Chem Sci 2017; 8:2983-2993. [PMID: 28451365 PMCID: PMC5380116 DOI: 10.1039/c6sc05354h] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 01/26/2017] [Indexed: 01/09/2023] Open
Abstract
A series of emissive ribonucleoside purine mimics, all comprised of an isothiazolo[4,3-d]pyrimidine core, was prepared using a divergent pathway involving a key Thorpe-Ziegler cyclization. In addition to an adenosine and a guanosine mimic, analogues of the noncanonical xanthosine, isoguanosine, and 2-aminoadenosine were also synthesized and found to be emissive. Isothiazolo 2-aminoadenosine, an adenosine surrogate, was found to be particularly emissive and effectively deaminated by adenosine deaminase. Competitive studies with adenosine deaminase with each analogue in combination with native adenosine showed preference for the native substrate while still deaminating the isothiazolo analogues.
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Affiliation(s)
- Alexander R Rovira
- Department of Chemistry and Biochemistry , University of California , San Diego , La Jolla , California 92093-0358 , USA .
| | - Andrea Fin
- Department of Chemistry and Biochemistry , University of California , San Diego , La Jolla , California 92093-0358 , USA .
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry , University of California , San Diego , La Jolla , California 92093-0358 , USA .
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47
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Ultrafast Electronic Deactivation Dynamics of Xanthosine Monophosphate. Molecules 2017; 22:molecules22010160. [PMID: 28106804 PMCID: PMC6155666 DOI: 10.3390/molecules22010160] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 01/12/2017] [Accepted: 01/13/2017] [Indexed: 11/30/2022] Open
Abstract
Ultrafast energy dissipation is a crucial factor for the photostability of DNA and RNA, but even some of the key electronic deactivation pathways in monomeric nucleic acid building stones are still controversial. Here, we report on the excited-state dynamics of the rare nucleotide xanthosine monophosphate as a function of deprotonation state (XMP vs. XMP−) and excitation wavelength (λpump= 278–243 nm) by femtosecond time-resolved fluorescence and absorption spectroscopy. We show that the predominating relaxation channel leads to a return of the photo-excited molecules to the electronic ground state in τ∼1 ps. The mechanism likely involves an out-of-plane deformation of the five-membered ring, different from the main electronic deactivation pathways in the canonical purine bases adenine and guanine. The results are discussed in terms of the structural and electronic differences of XMP compared to the canonical nucleotides.
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48
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Carlos Borin A, Mai S, Marquetand P, González L. Ab initio molecular dynamics relaxation and intersystem crossing mechanisms of 5-azacytosine. Phys Chem Chem Phys 2017; 19:5888-5894. [DOI: 10.1039/c6cp07919a] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Nonadiabatic SHARC dynamics simulations reveal the molecular deformations involved in the photodeactivation pathways of 5-azacytosine.
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Affiliation(s)
- Antonio Carlos Borin
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- NAP-PhotoTech the USP Consortium for Photochemical Technology
- São Paulo
| | - Sebastian Mai
- Institute of Theoretical Chemistry
- Faculty of Chemistry
- University of Vienna
- 1090 Vienna
- Austria
| | - Philipp Marquetand
- Institute of Theoretical Chemistry
- Faculty of Chemistry
- University of Vienna
- 1090 Vienna
- Austria
| | - Leticia González
- Institute of Theoretical Chemistry
- Faculty of Chemistry
- University of Vienna
- 1090 Vienna
- Austria
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49
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Mondal S, Puranik M. Ultrafast structural dynamics of photoexcited adenine. Phys Chem Chem Phys 2017; 19:20224-20240. [DOI: 10.1039/c7cp03092d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ultraviolet Resonance Raman (UVRR) spectroscopy derives distinct electronic properties of adenine in the La (260 nm) and Bb (210 nm) excited states.
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Affiliation(s)
- Sayan Mondal
- Indian Institute of Science Education and Research
- Pune – 411008
- India
| | - Mrinalini Puranik
- Indian Institute of Science Education and Research
- Pune – 411008
- India
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50
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DiScipio RM, Santiago RY, Taylor D, Crespo-Hernández CE. Electronic relaxation pathways of the biologically relevant pterin chromophore. Phys Chem Chem Phys 2017; 19:12720-12729. [DOI: 10.1039/c7cp01574g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Femtosecond-to-microsecond transient absorption spectroscopy is used to report the ultrafast relaxation mechanism of 2-amino-1H-pteridin-4-one (pterin) for the first time.
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Affiliation(s)
- R. M. DiScipio
- Department of Chemistry and Center for Chemical Dynamics
- Case Western Reserve University
- Cleveland
- USA
| | - R. Y. Santiago
- Department of Chemistry and Center for Chemical Dynamics
- Case Western Reserve University
- Cleveland
- USA
| | - D. Taylor
- Department of Chemistry and Center for Chemical Dynamics
- Case Western Reserve University
- Cleveland
- USA
| | - C. E. Crespo-Hernández
- Department of Chemistry and Center for Chemical Dynamics
- Case Western Reserve University
- Cleveland
- USA
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