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Cui X, Fan J, Lyu Y, Zhou X, Meng Q, Zhang C. Quasi-intrinsic thiobase derivatives as potential targeted photosensitizers in two-photon photodynamic therapy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 316:124311. [PMID: 38663131 DOI: 10.1016/j.saa.2024.124311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 04/08/2024] [Accepted: 04/17/2024] [Indexed: 05/15/2024]
Abstract
In this study, a set of potential quasi-intrinsic photosensitizers for two-photon photodynamic therapy (PDT) are proposed based on the unnatural 2-amino-8-(1'-β-ᴅ-2'-deoxyribofuranosyl)-imidazo[1,2-ɑ]-1,3,5-triazin-4(8H)-one (P), which is paired with the 6-amino-5-nitro-3-(1'-β-ᴅ-2'-deoxyribofuranosyl)-2(1H)-pyridone (Z) and can specifically recognize breast and liver cancer cells. Herein, the effects of sulfur substitution and electron-donating/electron-withdrawing groups on the photophysical properties in aqueous solution are systematically investigated. The one- and two-photon absorption spectra evidence that the modifications could result in red-shifted absorption wavelength and large two-photon absorption cross-section, which contributes to selective excitation and provides effective PDT for deep-seated tissues. To ensure the efficient triplet state population, the singlet-triplet energy gaps and spin-orbit coupling constants were examined, which is responsible for a rapid intersystem crossing rate. Furthermore, these thiobase derivatives are characterized by the long-lived T1 state and the large energy gap for radiationless transition to ensure the generation of cytotoxic singlet oxygen.
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Affiliation(s)
- Xixi Cui
- School of Physics and Electronics, Shandong Normal University, Jinan 250358, PR China
| | - Jianzhong Fan
- School of Physics and Electronics, Shandong Normal University, Jinan 250358, PR China
| | - Yongkang Lyu
- School of Physics and Electronics, Shandong Normal University, Jinan 250358, PR China
| | - Xucong Zhou
- School of Basic Medical Sciences, Shandong Second Medical University, Weifang 261053, PR China
| | - Qingtian Meng
- School of Physics and Electronics, Shandong Normal University, Jinan 250358, PR China.
| | - Changzhe Zhang
- School of Physics and Electronics, Shandong Normal University, Jinan 250358, PR China.
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2
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Vinod K, Jadhav SD, Hariharan M. Room Temperature Phosphorescence in Crystalline Iodinated Eumelanin Monomer. Chemistry 2024; 30:e202400499. [PMID: 38502668 DOI: 10.1002/chem.202400499] [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: 02/03/2024] [Revised: 03/01/2024] [Accepted: 03/19/2024] [Indexed: 03/21/2024]
Abstract
We report the room temperature phosphorescence upon iodination on a crystalline eumelanin monomer with shielded hydroxyl moieties, ethyl 5,6-dimethoxyindole-2-carboxylate (DMICE). Ultrafast intersystem crossing (ISC) is observed in the iodinated (IDMICE) as well as brominated (BDMICE) analogues of the eumelanin monomer derivative in solution. The triplet quantum yields (φT) and intersystem crossing rates (kISC) of the halogenated eumelanin derivatives areφ T B D M I C E ${{\phi{} }_{T}^{BDMICE}}$ =25.4±1.1 %;k I S C B D M I C E ${{k}_{ISC}^{BDMICE}}$ =1.95×109 s-1 andφ T I D M I C E ${{\phi{} }_{T}^{IDMICE}}$ =59.1±1.6 %;k I S C I D M I C E = ${{k}_{ISC}^{IDMICE}=}$ 1.36×1010 s-1, as monitored using transient absorption spectroscopy. Theoretical calculations based on nuclear ensemble method reveal that computed kISC and spin-orbit coupling matrix elements for eumelanin derivatives are larger for IDMICE relative to BDMICE. The halogen and π-π interactions, with distinct excitonic coupling and higher ISC rate promote phosphorescence in IDMICE molecular crystals. Accessing triplet excited states and resultant photoluminescence through structural modification of eumelanin scaffolds paves way for exploring the versatility of eumelanin-inspired molecules as bio-functional materials.
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Affiliation(s)
- Kavya Vinod
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram, 695551, Kerala, India
| | - Sohan D Jadhav
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram, 695551, Kerala, India
| | - Mahesh Hariharan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram, 695551, Kerala, India
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3
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Pal AK, Datta A. First-principles design of heavy-atom-free singlet oxygen photosensitizers for photodynamic therapy. J Chem Phys 2024; 160:164720. [PMID: 38682739 DOI: 10.1063/5.0196557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 04/10/2024] [Indexed: 05/01/2024] Open
Abstract
In photodynamic therapy (PDT) treatment, heavy-atom-free photosensitizers (PSs) are a great source of singlet oxygen photosensitizer. Reactive oxygen species (ROS) are produced by an energy transfer from the lowest energy triplet excited state to the molecular oxygen of cancer cells. To clarify the photophysical characteristics in the excited states of a few experimentally identified thionated (>C=S) molecules and their oxygenated congeners (>C=O), a quantum chemical study is conducted. This study illustrates the properties of the excited states in oxygen congeners that render them unsuitable for PDT treatment. Concurrently, a hierarchy is presented based on the utility of the lowest-energy triplet excitons of thionated compounds. Their non-radiative decay rates are calculated for reverse-ISC and inter-system crossover (ISC) processes. In addition, the vibronic importance of C=O and C=S bonds is clarified by the computation of the Huang-Rhys factor, effective vibrational mode, and reorganization energy inside the Marcus-Levich-Jörtner system. ROS generation in thionated PSs exceeds their oxygen congeners as kf ≪ kISC, where radiative decay rate is designated as kf. As a result, the current work offers a calculated strategy for analyzing the effectiveness of thionated photosensitizers in PDT.
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Affiliation(s)
- Arun K Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, West Bengal, India
| | - Ayan Datta
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, West Bengal, India
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4
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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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5
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Abdelgawwad AMA, Roca-Sanjuán D, Francés-Monerris A. Electronic spectroscopy of gemcitabine and derivatives for possible dual-action photodynamic therapy applications. J Chem Phys 2023; 159:224106. [PMID: 38078522 DOI: 10.1063/5.0170949] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Accepted: 11/12/2023] [Indexed: 12/18/2023] Open
Abstract
In this paper, we explore the molecular basis of combining photodynamic therapy (PDT), a light-triggered targeted anticancer therapy, with the traditional chemotherapeutic properties of the well-known cytotoxic agent gemcitabine. A photosensitizer prerequisite is significant absorption of biocompatible light in the visible/near IR range, ideally between 600 and 1000 nm. We use highly accurate multiconfigurational CASSCF/MS-CASPT2/MM and TD-DFT methodologies to determine the absorption properties of a series of gemcitabine derivatives with the goal of red-shifting the UV absorption band toward the visible region and facilitating triplet state population. The choice of the substitutions and, thus, the rational design is based on important biochemical criteria and on derivatives whose synthesis is reported in the literature. The modifications tackled in this paper consist of: (i) substitution of the oxygen atom at O2 position with heavier atoms (O → S and O → Se) to red shift the absorption band and increase the spin-orbit coupling, (ii) addition of a lipophilic chain at the N7 position to enhance transport into cancer cells and slow down gemcitabine metabolism, and (iii) attachment of aromatic systems at C5 position to enhance red shift further. Results indicate that the combination of these three chemical modifications markedly shifts the absorption spectrum toward the 500 nm region and beyond and drastically increases spin-orbit coupling values, two key PDT requirements. The obtained theoretical predictions encourage biological studies to further develop this anticancer approach.
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Affiliation(s)
| | - Daniel Roca-Sanjuán
- Institut de Ciència Molecular, Universitat de València, 46071 València, Spain
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6
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McGarry LF, El-Zubir O, Waddell PG, Cucinotta F, Houlton A, Horrocks BR. Vesicles, fibres, films and crystals: A low-molecular-weight-gelator [Au(6-thioguanosine) 2]Cl which exhibits a co-operative anion-induced transition from vesicles to a fibrous metallo-hydrogel. SOFT MATTER 2023; 19:8386-8402. [PMID: 37873806 PMCID: PMC10630954 DOI: 10.1039/d3sm01006f] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 10/19/2023] [Indexed: 10/25/2023]
Abstract
We describe a simple coordination compound of Au(I) and 6-thioguanosine, [Au(6-tGH)2]Cl, that has a rich self-assembly chemistry. In aqueous solution, the discrete complex assembles into a supramolecular fibre and forms a luminescent hydrogel at concentrations above about 1 mM. Below this concentration, the macromolecular structure is a vesicle. Through appropriate control of the solvent polarity, the gel can be turned into a lamellar film or crystallised. The molecular structure of [Au(6-tGH)2]Cl was determined using single crystal X-ray diffraction, which showed bis-6-thioguanosine linearly coordinated through the thione moiety to a central Au(I) ion. In the vesicles, the photoluminescence spectrum shows a broad, weak band at 550 nm owing to aurophilic interactions. Co-operative self-assembly from vesicle to fibre is made possible through halogen hydrogen bonding interactions and the aurophilic interactions are lost, resulting in a strong photoluminescence band at 490 nm with vibronic structure typical of an intraligand transition. The vesicle-fibre transition is also revealed by a large increase of ellipticity in the circular dichroism spectrum with a prominent peak near 390 nm owing to the helical structure of the fibres. Atomic force microscopy shows that at the same time as fibres form, the sample gels. Imaging near the vesicle-fibre transition shows that the fibres form between vesicles and a mechanism for the transition based on vesicle collisions is proposed.
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Affiliation(s)
- Liam F McGarry
- Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Osama El-Zubir
- Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Paul G Waddell
- Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Fabio Cucinotta
- Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Andrew Houlton
- Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Benjamin R Horrocks
- Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
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7
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Xie M, Ren SX, Hu D, Zhong JM, Luo J, Tan Y, Li YP, Si LP, Cao J. The impact of the chalcogen-substitution element and initial spectroscopic state on excited-state relaxation pathways in nucleobase photosensitizers: a combination of static and dynamic studies. Phys Chem Chem Phys 2023; 25:27756-27765. [PMID: 37814579 DOI: 10.1039/d3cp03730d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023]
Abstract
The substitution of oxygen with chalcogen in carbonyl group(s) of canonical nucleobases gives an impressive triplet generation, enabling their promising applications in medicine and other emerging techniques. The excited-state relaxation S2(ππ*) → S1(nπ*) → T1(ππ*) has been considered the preferred path for triplet generation in these nucleobase derivatives. Here, we demonstrate enhanced quantum efficiency of direct intersystem crossing from S2 to triplet manifold upon substitution with heavier chalcogen elements. The excited-state relaxation dynamics of sulfur/selenium substituted guanines in a vacuum is investigated using a combination of static quantum chemical calculations and on-the-fly excited-state molecular dynamics simulations. We find that in sulfur-substitution the S2 state predominantly decays to the S1 state, while upon selenium-substitution the S2 state deactivation leads to simultaneous population of the S1 and T2,3 states in the same time scale and multi-state quasi-degeneracy region S2/S1/T2,3. Interestingly, the ultrafast deactivation of the spectroscopic S3 state of both studied molecules to the S1 state occurs through a successive S3 → S2 → S1 path involving a multi-state quasi-degeneracy S3/S2/S1. The populated S1 and T2 states will cross the lowest triplet state, and the S1 → T intersystem crossing happens in a multi-state quasi-degeneracy region S1/T2,3/T1 and is accelerated by selenium-substitution. The present study reveals the influence of both the chalcogen substitution element and initial spectroscopic state on the excited-state relaxation mechanism of nucleobase photosensitizers and also highlights the important role of multi-state quasi-degeneracy in mediating the complex relaxation process. These theoretical results provide additional insights into the intrinsic photophysics of nucleobase-based photosensitizers and are helpful for designing novel photo-sensitizers for real applications.
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Affiliation(s)
- Min Xie
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Shuang-Xiao Ren
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Die Hu
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Ji-Meng Zhong
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Jie Luo
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Yin Tan
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Yan-Ping Li
- School of Medicine, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Li-Ping Si
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
| | - Jun Cao
- School of Materials Science and Hydrogen Energy & Guangdong Key Laboratory for Hydrogen Energy Technologies, Foshan University, Foshan, Guangdong, 528000, P. R. China
- Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang, Guizhou, 550018, P. R. China.
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8
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Ortiz-Rodríguez LA, Fang YG, Niogret G, Hadidi K, Hoehn SJ, Folkwein HJ, Jockusch S, Tor Y, Cui G, Levi L, Crespo-Hernández CE. Thieno[3,4- d]pyrimidin-4(3 H)-thione: an effective, oxygenation independent, heavy-atom-free photosensitizer for cancer cells. Chem Sci 2023; 14:8831-8841. [PMID: 37621444 PMCID: PMC10445467 DOI: 10.1039/d3sc02592f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/24/2023] [Indexed: 08/26/2023] Open
Abstract
All-organic, heavy-atom-free photosensitizers based on thionation of nucleobases are receiving increased attention because they are easy to make, noncytotoxic, work both in the presence and absence of molecular oxygen, and can be readily incorporated into DNA and RNA. In this contribution, the DNA and RNA fluorescent probe, thieno[3,4-d]pyrimidin-4(1H)-one, has been thionated to develop thieno[3,4-d]pyrimidin-4(3H)-thione, which is nonfluorescent and absorbs near-visible radiation with about 60% higher efficiency. Steady-state absorption and emission spectra are combined with transient absorption spectroscopy and CASPT2 calculations to delineate the electronic relaxation mechanisms of both pyrimidine derivatives in aqueous and acetonitrile solutions. It is demonstrated that thieno[3,4-d]pyrimidin-4(3H)-thione efficiently populates the long-lived and reactive triplet state generating singlet oxygen with a quantum yield of about 80% independent of solvent. It is further shown that thieno[3,4-d]pyrimidin-4(3H)-thione exhibits high photodynamic efficacy against monolayer melanoma cells and cervical cancer cells both under normoxic and hypoxic conditions. Our combined spectroscopic, computational, and in vitro data demonstrate the excellent potential of thieno[3,4-d]pyrimidin-4(1H)-thione as a heavy-atom-free PDT agent and paves the way for further development of photosensitizers based on the thionation of thieno[3,4-d]pyrimidine derivatives. Collectively, the experimental and computational results demonstrate that thieno[3,4-d]pyrimidine-4(3H)-thione stands out as the most promising thiobase photosensitizer developed to this date.
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Affiliation(s)
| | - Ye-Guang Fang
- Key Lab of Theoretical and Computational Photochemistry, Ministry of Education, Chemistry College, Beijing Normal University Beijing 100875 China
| | - Germain Niogret
- Department of Chemistry and Biochemistry, University of California San Diego La Jolla CA 92093 USA
| | - Kaivin Hadidi
- Department of Chemistry and Biochemistry, University of California San Diego La Jolla CA 92093 USA
| | - Sean J Hoehn
- Department of Chemistry, Case Western Reserve University Cleveland OH 44106 USA
| | - Heather J Folkwein
- Department of Chemistry, Case Western Reserve University Cleveland OH 44106 USA
| | - Steffen Jockusch
- Center for Photochemical Sciences, Bowling Green State University Bowling Green Ohio 43403 USA
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California San Diego La Jolla CA 92093 USA
| | - Ganglong Cui
- Key Lab of Theoretical and Computational Photochemistry, Ministry of Education, Chemistry College, Beijing Normal University Beijing 100875 China
| | - Liraz Levi
- Celloram Inc Cleveland OH 44106 USA
- Department of Pediatrics, Case Western Reserve University School of Medicine Cleveland Ohio 44106 USA
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9
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Valverde D, Mai S, Canuto S, Borin AC, González L. Ultrafast Intersystem Crossing Dynamics of 6-Selenoguanine in Water. JACS AU 2022; 2:1699-1711. [PMID: 35911449 PMCID: PMC9327080 DOI: 10.1021/jacsau.2c00250] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Rationalizing the photochemistry of nucleobases where an oxygen is replaced by a heavier atom is essential for applications that exploit near-unity triplet quantum yields. Herein, we report on the ultrafast excited-state deactivation mechanism of 6-selenoguanine (6SeGua) in water by combining nonadiabatic trajectory surface-hopping dynamics with an electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) scheme. We find that the predominant relaxation mechanism after irradiation starts on the bright singlet S2 state that converts internally to the dark S1 state, from which the population is transferred to the triplet T2 state via intersystem crossing and finally to the lowest T1 state. This S2 → S1 → T2 → T1 deactivation pathway is similar to that observed for the lighter 6-thioguanine (6tGua) analogue, but counterintuitively, the T1 lifetime of the heavier 6SeGua is shorter than that of 6tGua. This fact is explained by the smaller activation barrier to reach the T1/S0 crossing point and the larger spin-orbit couplings of 6SeGua compared to 6tGua. From the dynamical simulations, we also calculate transient absorption spectra (TAS), which provide two time constants (τ1 = 131 fs and τ2 = 191 fs) that are in excellent agreement with the experimentally reported value (τexp = 130 ± 50 fs) (Farrel et al. J. Am. Chem. Soc. 2018, 140, 11214). Intersystem crossing itself is calculated to occur with a time scale of 452 ± 38 fs, highlighting that the TAS is the result of a complex average of signals coming from different nonradiative processes and not intersystem crossing alone.
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Affiliation(s)
- Danillo Valverde
- Department
of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Avenida Professor Lineu Prestes, 748, São Paulo, São Paulo CEP 05508-000, Brazil
- Institute
of Physics, University of São Paulo, Rua do Matão 1371, São Paulo, São Paulo CEP 05508-090, Brazil
| | - Sebastian Mai
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, Vienna 1090, Austria
| | - Sylvio Canuto
- Institute
of Physics, University of São Paulo, Rua do Matão 1371, São Paulo, São Paulo CEP 05508-090, Brazil
| | - Antonio Carlos Borin
- Department
of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Avenida Professor Lineu Prestes, 748, São Paulo, São Paulo CEP 05508-000, Brazil
| | - Leticia González
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, Vienna 1090, Austria
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10
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Nam Y, Montorsi F, Keefer D, Cavaletto SM, Lee JY, Nenov A, Garavelli M, Mukamel S. Time-Resolved Optical Pump-Resonant X-ray Probe Spectroscopy of 4-Thiouracil: A Simulation Study. J Chem Theory Comput 2022; 18:3075-3088. [PMID: 35476905 DOI: 10.1021/acs.jctc.2c00064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We theoretically monitor the photoinduced ππ* → nπ* internal conversion process in 4-thiouracil (4TU), triggered by an optical pump. The element-sensitive spectroscopic signatures are recorded by a resonant X-ray probe tuned to the sulfur, oxygen, or nitrogen K-edge. We employ high-level electronic structure methods optimized for core-excited electronic structure calculation combined with quantum nuclear wavepacket dynamics computed on two relevant nuclear modes, fully accounting for their quantum nature of nuclear motions. We critically discuss the capabilities and limitations of the resonant technique. For sulfur and nitrogen, we document a pre-edge spectral window free from ground-state background and rich with ππ* and nπ* absorption features. The lowest sulfur K-edge shows strong absorption for both ππ* and nπ*. In the lowest nitrogen K-edge window, we resolve a state-specific fingerprint of the ππ* and an approximate timing of the conical intersection via its depletion. A spectral signature of the nπ* transition, not accessible by UV-vis spectroscopy, is identified. The oxygen K-edge is not sensitive to molecular deformations and gives steady transient absorption features without spectral dynamics. The ππ*/nπ* coherence information is masked by more intense contributions from populations. Altogether, element-specific time-resolved resonant X-ray spectroscopy provides a detailed picture of the electronic excited-state dynamics and therefore a sensitive window into the photophysics of thiobases.
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Affiliation(s)
- Yeonsig Nam
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States.,Convergence Research Center for Energy and Environmental Sciences, Sungkyunkwan University, Suwon 16419, Korea
| | - Francesco Montorsi
- Dipartimento di Chimica Industriale "Toso Montanari", Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Daniel Keefer
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Stefano M Cavaletto
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Jin Yong Lee
- Convergence Research Center for Energy and Environmental Sciences, Sungkyunkwan University, Suwon 16419, Korea.,Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea
| | - Artur Nenov
- Dipartimento di Chimica Industriale "Toso Montanari", Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale "Toso Montanari", Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Shaul Mukamel
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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11
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Teles-Ferreira DC, Manzoni C, Martínez-Fernández L, Cerullo G, de Paula AM, Borrego-Varillas R. Ultrafast Excited-State Decay Mechanisms of 6-Thioguanine Followed by Sub-20 fs UV Transient Absorption Spectroscopy. Molecules 2022; 27:molecules27041200. [PMID: 35208987 PMCID: PMC8878119 DOI: 10.3390/molecules27041200] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/01/2022] [Accepted: 02/02/2022] [Indexed: 11/23/2022] Open
Abstract
Understanding the primary steps following UV photoexcitation in sulphur-substituted DNA bases (thiobases) is fundamental for developing new phototherapeutic drugs. However, the investigation of the excited-state dynamics in sub-100 fs time scales has been elusive until now due to technical challenges. Here, we track the ultrafast decay mechanisms that lead to the electron trapping in the triplet manifold for 6-thioguanine in an aqueous solution, using broadband transient absorption spectroscopy with a sub-20 fs temporal resolution. We obtain experimental evidence of the fast internal conversion from the S2(ππ*) to the S1(nπ*) states, which takes place in about 80 fs and demonstrates that the S1(nπ*) state acts as a doorway to the triplet population in 522 fs. Our results are supported by MS-CASPT2 calculations, predicting a planar S2(ππ*) pseudo-minimum in agreement with the stimulated emission signal observed in the experiment.
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Affiliation(s)
| | - Cristian Manzoni
- Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci 32, I-20133 Milano, Italy; (C.M.); (G.C.)
| | - Lara Martínez-Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemistry (IADCHEM), Campus de Excelencia UAM-CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain;
| | - Giulio Cerullo
- Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci 32, I-20133 Milano, Italy; (C.M.); (G.C.)
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Ana Maria de Paula
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, MG, Brazil;
| | - Rocío Borrego-Varillas
- Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci 32, I-20133 Milano, Italy; (C.M.); (G.C.)
- Correspondence:
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12
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Teles-Ferreira DC, van Stokkum IH, Conti I, Ganzer L, Manzoni C, Garavelli M, Cerullo G, Nenov A, Borrego Varillas R, de Paula AM. Coherent vibrational modes promote the ultrafast internal conversion and intersystem crossing in thiobases. Phys Chem Chem Phys 2022; 24:21750-21758. [DOI: 10.1039/d2cp02073d] [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
Thionated nucleobases are obtained by replacing oxygen with sulphur atoms in the canonical nucleobases. They absorb light efficiently in the near-ultraviolet, populating singlet states which undergo intersystem crossing to the...
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13
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Nam Y, Keefer D, Nenov A, Conti I, Aleotti F, Segatta F, Lee JY, Garavelli M, Mukamel S. Conical Intersection Passages of Molecules Probed by X-ray Diffraction and Stimulated Raman Spectroscopy. J Phys Chem Lett 2021; 12:12300-12309. [PMID: 34931839 DOI: 10.1021/acs.jpclett.1c03814] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Conical intersections (CoIns) play an important role in ultrafast relaxation channels. Their monitoring remains a formidable experimental challenge. We theoretically compare the probing of the S2 → S1 CoIn passage in 4-thiouracil by monitoring its vibronic coherences, using off-resonant X-ray-stimulated Raman spectroscopy (TRUECARS) and time-resolved X-ray diffraction (TRXD). The quantum nuclear wavepacket (WP) dynamics provides an accurate picture of the photoinduced dynamics. Upon photoexcitation, the WP oscillates among the Franck-Condon point, the S2 minimum, and the CoIn with a 70 fs period. A vibronic coherence first emerges at 20 fs and can be observed until the S2 state is fully depopulated. The distribution of the vibronic frequencies involved in the coherence is recorded by the TRUECARS spectrogram. The TRXD signal provides spatial images of electron densities associated with the CoIn. In combination, the two signals provide a complementary picture of the nonadiabatic passage, which helps in the study of the underlying photophysics in thiobases.
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Affiliation(s)
- Yeonsig Nam
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
- Convergence Research Center for Energy and Environmental Sciences, Sungkyunkwan University, Suwon 16419, Korea
| | - Daniel Keefer
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Artur Nenov
- Dipartimento di Chimica Industriale "Toso Montanari," Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Irene Conti
- Dipartimento di Chimica Industriale "Toso Montanari," Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Flavia Aleotti
- Dipartimento di Chimica Industriale "Toso Montanari," Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Francesco Segatta
- Dipartimento di Chimica Industriale "Toso Montanari," Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Jin Yong Lee
- Convergence Research Center for Energy and Environmental Sciences, Sungkyunkwan University, Suwon 16419, Korea
- Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea
| | - Marco Garavelli
- Dipartimento di Chimica Industriale "Toso Montanari," Universita' degli Studi di Bologna, I-40136 Bologna, Italy
| | - Shaul Mukamel
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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14
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Dong J, Huang C, Guo S, Xia Y, Hou Y, Yang C, Zhang X, Jie J, Zhu BZ, Su H. Free-Radical-Mediated Photoinduced Electron Transfer between 6-Thioguanine and Tryptophan Leading to DNA-Protein-Like Cross-Link. J Phys Chem B 2021; 126:14-22. [PMID: 34951313 DOI: 10.1021/acs.jpcb.1c03380] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nucleobase analog 6-thioguanine (6-TG) has emerged as important immunosuppressant, anti-inflammatory, and anticancer drug in the past few decades, but its unique photosensitivity of absorbing strongly ultraviolet UVA light elicits photochemical hazards in many ways. The particularly intriguing yet unresolved question is whether the direct photoreaction of 6-TG can promote DNA-protein cross-links (DPCs) formation, which are large DNA adducts blocking DNA replication and physically impede DNA-related processes. Herein, by real-time observation of radical intermediates using time-resolved UV-vis absorption spectroscopy in conjunction with product analysis by HPLC-MS, we discover that UVA excitation of 6-TG triggers direct covalent cross-linking with tryptophan (TrpH) via an exquisite radical mechanism of electron transfer. The photoexcitation prepares the redox-active triplet 36-TG*, which initiates electron transfer with TrpH, creating TrpH•+ and 6-TG•- in the first step. The deprotonated Trp• undergoes radical-recombination with its geminate partner 6-TG•- and eliminates a H2S, leading to the cross-linking product 6-TG-Trp. The photoadduct structures (two chiral isomers and one constitutional isomer) are identified unambiguously, validating further the mechanism. These findings pinpoint the exact amino acid that is vulnerable to photo-cross-linking with 6-TG and establish a mechanistic framework for understanding mutagenic DPCs formation and developing photoprobes based on this new type of photo-cross-linking.
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Affiliation(s)
- Junjie Dong
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Chunhua Huang
- State Key Lab of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, P. R. China
| | - Shaoshi Guo
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ye Xia
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Yue Hou
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Chunfan Yang
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Xianwang Zhang
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Jialong Jie
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ben-Zhan Zhu
- State Key Lab of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, P. R. China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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15
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Xie BB, Tang XF, Liu XY, Chang XP, Cui G. Mechanistic photophysics and photochemistry of unnatural bases and sunscreen molecules: insights from electronic structure calculations. Phys Chem Chem Phys 2021; 23:27124-27149. [PMID: 34849517 DOI: 10.1039/d1cp03994f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photophysics and photochemistry are basic subjects in the study of light-matter interactions and are ubiquitous in diverse fields such as biology, energy, materials, and environment. A full understanding of mechanistic photophysics and photochemistry underpins many recent advances and applications. This contribution first provides a short discussion on the theoretical calculation methods we have used in relevant studies, then we introduce our latest progress on the mechanistic photophysics and photochemistry of two classes of molecular systems, namely unnatural bases and sunscreens. For unnatural bases, we disclose the intrinsic driving forces for the ultrafast population to reactive triplet states, impacts of the position and degree of chalcogen substitutions, and the effects of complex environments. For sunscreen molecules, we reveal the photoprotection mechanisms that dissipate excess photon energy to the surroundings by ultrafast internal conversion to the ground state. Finally, relevant theoretical challenges and outlooks are discussed.
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Affiliation(s)
- Bin-Bin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
| | - Xiu-Fang Tang
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
| | - Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, Sichuan, 610068, China
| | - Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
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16
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Ortiz-Rodríguez LA, Hoehn SJ, Acquah C, Abbass N, Waidmann L, Crespo-Hernández CE. Femtosecond intersystem crossing to the reactive triplet state of the 2,6-dithiopurine skin cancer photosensitizer. Phys Chem Chem Phys 2021; 23:25048-25055. [PMID: 34730146 DOI: 10.1039/d1cp04415j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Site-selected sulfur-substituted nucleobases are a class of all organic, heavy-atom-free photosensitizers for photodynamic therapy applications that exhibit excellent photophysical properties such as strong absorption in the ultraviolet-A region of the electromagnetic spectrum, near-unity triplet yields, and a high yield of singlet oxygen generation. Recent investigations on doubly thionated nucleobases, 2,4-dithiothymine, 2,4-dithiouracil, and 2,6-dithiopurine, demonstrated that these set of dithionated nucleobases outperform the photodynamic efficacy exhibit by 4-thiothymidine-the most widely studied singly substituted thiobase to date. Out of the three dithionated nucleobases, 2,6-dithiopurine was shown to be the most effective, exhibiting inhibition of cell proliferation of up to 63% when combined with a low UVA dose of 5 J cm-2. In this study, we elucidated the electronic relaxation pathways leading to the population of the reactive triplet state of 2,6-dithiopurine. 2,6-Dithiopurine populates the triplet manifold in less than 150 fs, reaching the nπ* triplet state minimum within a lifetime of 280 ± 50 fs. Subsequently, the population in the nπ* triplet state minimum internally converts to the long-lived ππ* triplet state within a lifetime of 3 ± 1 ps. The relatively slow internal conversion lifetime is associated with major conformational relaxation in going from the nπ* to ππ* triplet state minimum. A unity triplet yield of 1.0 ± 0.1 is measured.
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Affiliation(s)
| | - Sean J Hoehn
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Chris Acquah
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Nadia Abbass
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Lidia Waidmann
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
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17
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Ortiz-Rodríguez LA, Ortiz-Zayas G, Pollum M, Hoehn SJ, Jockusch S, Crespo-Hernández CE. Intramolecular Charge Transfer in the Azathioprine Prodrug Quenches Intersystem Crossing to the Reactive Triplet State in 6-Mercaptopurine †. Photochem Photobiol 2021; 98:617-632. [PMID: 34480764 DOI: 10.1111/php.13513] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 08/30/2021] [Indexed: 11/26/2022]
Abstract
The thiopurine prodrugs 6-mercaptopurine and azathioprine are among the world's essential medications for acute lymphoblastic leukemia, immunosuppression and several autoimmune conditions. Thiopurine prodrugs are efficient UVA absorbers and singlet oxygen generators and the long-term treatment with these prodrugs correlates with a high incidence of sunlight-induced skin cancer in patients. In this contribution, we show that the electronic relaxation mechanisms and photochemical properties of azathioprine are remarkably different from those of 6-mercaptopurine upon absorption of UVA radiation. UVA excitation of 6-mercaptopurine results in nearly 100% triplet yield and up to 30% singlet oxygen generation, whereas excitation of azathioprine with UVA leads to triplet yields of 15-3% depending on pH of the aqueous solution and <1% singlet oxygen generation. While photoexcitation of 6-mercaptopurine and other thiopurine prodrugs can facilitate oxidatively generated cell damage, azathioprine's poor photosensitization ability reveals the use of interchromophoric charge-transfer interactions for the molecular design of photostable prodrugs exhibiting a remarkable reduction in photocytotoxic side effects before drug metabolization.
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Affiliation(s)
| | | | - Marvin Pollum
- Department of Chemistry, Case Western Reserve University, Cleveland, OH, USA
| | - Sean J Hoehn
- Department of Chemistry, Case Western Reserve University, Cleveland, OH, USA
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18
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Saigusa H, Oyama A, Kitamura S, Asami H. Structural Characterization of 6-Thioguanosine and Its Monohydrate in the Gas Phase. J Phys Chem A 2021; 125:7217-7225. [PMID: 34433270 DOI: 10.1021/acs.jpca.1c05219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Detailed structural analysis of 6-thioguanosine (6TGs) in relation to its tautomerization and sugar conformation is performed in the gas phase using UV and IR spectroscopy combined with ab initio calculations. We have observed a thiol tautomer of 6TGs with its sugar moiety in the syn conformation that is stabilized by a strong intramolecular H-bonding between O5'H of the sugar and N3 atom of the guanine moiety. This observation is consistent with previous results for guanosine (Gs) in which the corresponding enol form is solely detected. We have also identified a monohydrate of 6TGs consisting of a thiol tautomer with the water linking guanine moiety and sugar OH group. It is demonstrated that hydration behavior of 6TGs is significantly different from that of Gs as a result of a weaker H-bonding ability of the thiol group.
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Affiliation(s)
- Hiroyuki Saigusa
- Graduate School for Bio- and Nanosystem Sciences, Yokohama City University, Yokohama 236-0027, Japan
| | - Ayumi Oyama
- Graduate School for Bio- and Nanosystem Sciences, Yokohama City University, Yokohama 236-0027, Japan
| | - Saki Kitamura
- Graduate School for Bio- and Nanosystem Sciences, Yokohama City University, Yokohama 236-0027, Japan
| | - Hiroya Asami
- Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
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19
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Zhu YH, Zhang TS, Tang XF, Xie BB, Cui G. MS-CASPT2 studies on the mechanistic photophysics of tellurium-substituted guanine and cytosine. Phys Chem Chem Phys 2021; 23:12421-12430. [PMID: 34028476 DOI: 10.1039/d1cp01142a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sulfur-substituted nucleobases are highly promising photosensitizers that are widely used in photodynamic therapy, and there are numerous studies exploring their unique photophysical behaviors. However, relevant photophysical investigations on selenium and tellurium substitutions are still rare. Herein, the high-level multistate complete-active-space second-order perturbation (MS-CASPT2) method was performed for the first time to explore the excited-state relaxation processes of tellurium-substituted guanine (TeG) and cytosine (TeC). Based on the electronic state properties in the Franck-Condon (FC) region, we found that the lowest five (S0, S1, S2, T1, and T2) and six (S0, S1, S2, T1, T2 and T3) states will participate in the nonadiabatic transition processes of TeG and TeC systems, respectively. In these electronic states, two kinds of minimum and intersection structures (i.e., planar and twisted structures) were obtained for both TeG and TeC systems. The linearly interpolated internal coordinate (LIIC) paths and spin-orbit coupling (SOC) constants revealed several possible planar and twisted excited-state decay channels, which could lead the systems to the lowest reactive triplet state of T1. Small energy barriers in the T1 state will trap the TeG and TeC systems for a while before they finally populate to the ground state. Although tellurium substitution would further redshift the absorption wavelength and enhance the intersystem crossing (ISC) rate to the T1 state compared with sulfur and selenium substitutions, the rapid ISC process of T1 → S0 may make it a less effective photosensitizer to sensitize the molecular oxygen. We believe our present work will provide important mechanistic insights into the photophysics of tellurium-substituted nucleobases.
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Affiliation(s)
- Yun-Hua Zhu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
| | - Teng-Shuo Zhang
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, P. R. China
| | - Xiu-Fang Tang
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
| | - Bin-Bin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
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20
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Euceda N, Jahnke J, Espinal A, Louis MF, Bashkin E, Roccanova P, Espaillat A, Fuentes GV, Nieto F, Gao R. Thioguanine restoration through type I photosensitization-superoxide oxidation-glutathione reduction cycles. Phys Chem Chem Phys 2021; 23:5069-5073. [PMID: 33655288 DOI: 10.1039/d1cp00101a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
UVA-induced deleterious effect of thiopurine prodrugs including azathioprine, 6-mercaptopurine and 6-thioguanine (6-TG) increases the risk of cancer development due to the incorporation of 6-TG in patients' DNA. The catalytic mechanism by which thiobases act as a sustained oxidant producer has yet to be explored, especially through the Type I electron transfer pathway that produces superoxide radicals (O2˙-). Under Fenton-like conditions O2˙- radicals convert to extremely reactive hydroxyl radicals (˙OH), thus carrying even higher risk of biological damage than that induced by the well-studied type II reaction. By monitoring 6-TG/UVA-induced photochemistry in mass spectra and superoxide radicals (O2˙-) via nitro blue tetrazolium (NBT) reduction, this work provides two new findings: (1) in the presence of reduced glutathione (GSH), the production of O2˙-via the type I reaction is enhanced 10-fold. 6-TG thiyl radicals are identified as the primary intermediate formed in the reaction of 6-TG with O2˙-. The restoration of 6-TG and concurrent generation of O2˙- occur via a 3-step-cycle: 6-TG type I photosensitization, O2˙- oxidation and GSH reduction. (2) In the absence of GSH, 6-TG thiyl radicals undergo oxygen addition and sulfur dioxide removal to form carbon radicals (C6) which further convert to thioether by reacting with 6-TG molecules. These findings help explain not only thiol-regulation in a biological system but chemoprevention of cancer.
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Affiliation(s)
- Nelson Euceda
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - Joyce Jahnke
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - Aileen Espinal
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - Monique F Louis
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - Edan Bashkin
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - Patricia Roccanova
- Biological Sciences Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA
| | - Abraham Espaillat
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - German V Fuentes
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
| | - Fernando Nieto
- Biological Sciences Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA
| | - Ruomei Gao
- Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568, USA.
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21
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Fang YG, Valverde D, Mai S, Canuto S, Borin AC, Cui G, González L. Excited-State Properties and Relaxation Pathways of Selenium-Substituted Guanine Nucleobase in Aqueous Solution and DNA Duplex. J Phys Chem B 2021; 125:1778-1789. [PMID: 33570942 PMCID: PMC8023715 DOI: 10.1021/acs.jpcb.0c10855] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The excited-state properties and relaxation mechanisms after light irradiation of 6-selenoguanine (6SeG) in water and in DNA have been investigated using a quantum mechanics/molecular mechanics (QM/MM) approach with the multistate complete active space second-order perturbation theory (MS-CASPT2) method. In both environments, the S1 1(nSeπ5*) and S2 1(πSeπ5*) states are predicted to be the spectroscopically dark and bright states, respectively. Two triplet states, T1 3(πSeπ5*) and T2 3(nSeπ5*), are found energetically below the S2 state. Extending the QM region to include the 6SeG-Cyt base pair slightly stabilizes the S2 state and destabilizes the S1, due to hydrogen-bonding interactions, but it does not affect the order of the states. The optimized minima, conical intersections, and singlet-triplet crossings are very similar in water and in DNA, so that the same general mechanism is found. Additionally, for each excited state geometry optimization in DNA, three kind of structures ("up", "down", and "central") are optimized which differ from each other by the orientation of the C═Se group with respect to the surrounding guanine and thymine nucleobases. After irradiation to the S2 state, 6SeG evolves to the S2 minimum, near to a S2/S1 conical intersection that allows for internal conversion to the S1 state. Linear interpolation in internal coordinates indicate that the "central" orientation is less favorable since extra energy is needed to surmount the high barrier in order to reach the S2/S1 conical intersection. From the S1 state, 6SeG can further decay to the T1 3(πSeπ5*) state via intersystem crossing, where it will be trapped due to the existence of a sizable energy barrier between the T1 minimum and the T1/S0 crossing point. Although this general S2 → T1 mechanism takes place in both media, the presence of DNA induces a steeper S2 potential energy surface, that it is expected to accelerate the S2 → S1 internal conversion.
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Affiliation(s)
- Ye-Guang Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Danillo Valverde
- Institute of Physics, University of São Paulo, Rua do Matão 1371, São Paulo, SP 05508-090, Brazil
| | - Sebastian Mai
- Photonics Institute, Vienna University of Technology, Gußhausstraße 27-29, 1040 Vienna, Austria.,Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria
| | - Sylvio Canuto
- Institute of Physics, University of São Paulo, Rua do Matão 1371, São Paulo, SP 05508-090, Brazil
| | - Antonio Carlos Borin
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000. São Paulo, SP Brazil
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria
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22
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Ortiz-Rodríguez LA, Hoehn SJ, Loredo A, Wang L, Xiao H, Crespo-Hernández CE. Electronic Relaxation Pathways in Heavy-Atom-Free Photosensitizers Absorbing Near-Infrared Radiation and Exhibiting High Yields of Singlet Oxygen Generation. J Am Chem Soc 2021; 143:2676-2681. [PMID: 33587618 PMCID: PMC7985834 DOI: 10.1021/jacs.0c13203] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heavy-atom-free photosensitizers (HAF-PSs) based on thionation of carbonyl groups of readily accessible organic compounds are rapidly emerging as a versatile class of molecules. However, their photochemical properties and electronic relaxation mechanisms are currently unknown. Investigating the excited-state dynamics is essential to understand their benefits and limitations and to develop photosensitizers with improved photochemical properties. Herein, the photochemical and electronic-structure properties of two of the most promising HAF-PSs developed to date are revealed. It is shown that excitation of thio-4-(dimethylamino)naphthalamide and thionated Nile Red with near-infrared radiation leads to the efficient population of the triplet manifold through multiple relaxation pathways in hundreds of femtoseconds. The strong singlet-triplet couplings in this family of photosensitizers should enable a broad range of applications, including in photodynamic therapy, photocatalysis, photovoltaics, organic LEDs, and photon up-conversion.
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Affiliation(s)
- Luis A. Ortiz-Rodríguez
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Sean J. Hoehn
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Axel Loredo
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Lushun Wang
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Han Xiao
- Department of Chemistry, Department of Biosciences, and Department of Bioengineering, Rice University, Houston, Texas 77005, United States
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23
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Peng Q, Zhu YH, Zhang TS, Liu XY, Fang WH, Cui G. Selenium substitution effects on excited-state properties and photophysics of uracil: a MS-CASPT2 study. Phys Chem Chem Phys 2020; 22:12120-12128. [PMID: 32440669 DOI: 10.1039/d0cp01369b] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The photophysics of selenium-substituted nucleobases has attracted recent experimental attention because they could serve as potential photosensitizers in photodynamic therapy. Herein, we present a comprehensive MS-CASPT2 study on the spectroscopic and excited-state properties, and photophysics of 2-selenouracil (2SeU), 4-selenouracil (4SeU), and 2,4-selenouracil (24SeU). Relevant minima, conical intersections, crossing points, and excited-state relaxation paths in the lowest five electronic states (i.e., S0, S1, S2, T2, and T1) are explored. On the basis of these results, their photophysical mechanisms are proposed. Upon photoirradiation to the bright S2 state, 2SeU quickly relaxes to its S2 minimum and then moves in an essentially barrierless way to a nearby S2/S1 conical intersection near which the S1 state is populated. Next, the S1 system arrives at an S1/T2/T1 intersection where a large S1/T1 spin-orbit coupling of 430.8 cm-1 makes the T1 state populated. In this state, a barrier of 6.8 kcal mol-1 will trap 2SeU for a while. In parallel, for 4SeU or 24SeU, the system first relaxes to the S2 minimum and then overcomes a small barrier to approach an S2/S1 conical intersection. Once hopping to the S1 state, there exists an extended region with very close S1, T2, and T1 energies. Similarly, a large S1/T1 spin-orbit coupling of 426.8 cm-1 drives the S1→ T1 intersystem crossing process thereby making the T1 state populated. Similarly, an energy barrier heavily suppresses electronic transition to the S0 state. The present work manifests that different selenium substitutions on uracil can lead to a certain extent of different vertical and adiabatic excitation energies, excited-state properties, and relaxation pathways. These insights could help understand the photophysics of selenium-substituted nucleobases.
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Affiliation(s)
- Qin Peng
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
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24
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Norell J, Odelius M, Vacher M. Ultrafast dynamics of photo-excited 2-thiopyridone: Theoretical insights into triplet state population and proton transfer pathways. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:024101. [PMID: 32206689 PMCID: PMC7078009 DOI: 10.1063/1.5143228] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 02/29/2020] [Indexed: 06/10/2023]
Abstract
Ultrafast non-adiabatic dynamics of the small heteroaromatic compound 2-thiopyridone has been studied with surface hopping simulations based on multi-configurational quantum chemistry. Initial excitation of the bright S 2 ( π , π * ) state is found to promptly relax to S 1 ( n , π * ) through in-plane motion. The subsequent dynamics are oppositely driven by out-of-plane motion, which results in both complex population transfers among all the available states and intersystem crossing predominantly through the "El-Sayed forbidden" S 1 ( n , π * ) to T 2 ( n , π * ) channel, through significant mixing of electronic excitation characters. Despite this complexity, the femto- to picosecond triplet population, expected from several spectroscopic measurements, is well described as a simple exponential decay of the singlet state manifold. No proton transfer is found in the reported trajectories, but two mechanisms for its possible mediation in previously reported experiments are proposed based on the observed structural dynamics: (i) ultrafast intra-molecular transfer driven by the initially coherent in-plane motion and (ii) inter-molecular solvent-mediated transfer driven by the out-of-plane modes that dominate the later motion.
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Affiliation(s)
- Jesper Norell
- Department of Physics, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Michael Odelius
- Department of Physics, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden
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25
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Brister MM, Gustavsson T, Crespo-Hernández CE. Excited State Lifetimes of Sulfur-Substituted DNA and RNA Monomers Probed Using the Femtosecond Fluorescence Up-Conversion Technique. Molecules 2020; 25:E584. [PMID: 32013184 PMCID: PMC7037914 DOI: 10.3390/molecules25030584] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 01/23/2020] [Accepted: 01/26/2020] [Indexed: 11/16/2022] Open
Abstract
Sulfur-substituted DNA and RNA nucleobase derivatives (a.k.a., thiobases) are an important family of biomolecules. They are used as prodrugs and as chemotherapeutic agents in medical settings, and as photocrosslinker molecules in structural-biology applications. Remarkably, excitation of thiobases with ultraviolet to near-visible light results in the population of long-lived and reactive triplet states on a time scale of hundreds of femtoseconds and with near-unity yields. This efficient nonradiative decay pathway explains the vanishingly small fluorescence yields reported for the thiobases and the scarcity of fluorescence lifetimes in the literature. In this study, we report fluorescence lifetimes for twelve thiobase derivatives, both in aqueous solution at physiological pH and in acetonitrile. Excitation is performed at 267 and 362 nm, while fluorescence emission is detected at 380, 425, 450, 525, or 532 nm. All the investigated thiobases reveal fluorescence lifetimes that decay in a few hundreds of femtoseconds and with magnitudes that depend and are sensitive to the position and degree of sulfur-atom substitution and on the solvent environment. Interestingly, however, three thiopyrimidine derivatives (i.e., 2-thiocytidine, 2-thiouridine, and 4-thiothymidine) also exhibit a small amplitude fluorescence component of a few picoseconds in aqueous solution. Furthermore, the N-glycosylation of thiobases to form DNA or RNA nucleoside analogues is demonstrated as affecting their fluorescence lifetimes. In aqueous solution, the fluorescence decay signals exciting at 267 nm are equal or slower than those collected exciting at 362 nm. In acetonitrile, however, the fluorescence decay signals recorded upon 267 nm excitation are, in all cases, faster than those measured exciting at 362 nm. A comparison to the literature values show that, while both the DNA and RNA nucleobase and thiobase derivatives exhibit sub-picosecond fluorescence lifetimes, the 1ππ* excited-state population in the nucleobase monomers primarily decay back to the ground state, whereas it predominantly populates long-lived and reactive triplet states in thiobase monomers.
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Affiliation(s)
- Matthew M. Brister
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106, USA;
| | - Thomas Gustavsson
- LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
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26
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Teles‐Ferreira DC, Conti I, Borrego‐Varillas R, Nenov A, Van Stokkum IHM, Ganzer L, Manzoni C, Paula AM, Cerullo G, Garavelli M. A Unified Experimental/Theoretical Description of the Ultrafast Photophysics of Single and Double Thionated Uracils. Chemistry 2019; 26:336-343. [DOI: 10.1002/chem.201904541] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Indexed: 12/28/2022]
Affiliation(s)
- Danielle Cristina Teles‐Ferreira
- Departamento de Física Universidade Federal de Minas Gerais 31270-901 Belo Horizonte MG Brazil
- Electrical Engineering Department Federal Institute of Minas Gerais Formiga MG Brazil
| | - Irene Conti
- Dipartimento di Chimica Industriale Università degli Studi di Bologna Viale del Risorgimento 4 40136 Bologna Italy
| | - Rocío Borrego‐Varillas
- IFN-CNR Department of Physics Politecnico di Milano P.za L. da Vinci 32 20133 Milano Italy
| | - Artur Nenov
- Dipartimento di Chimica Industriale Università degli Studi di Bologna Viale del Risorgimento 4 40136 Bologna Italy
| | - Ivo H. M. Van Stokkum
- Department of Physics and Astronomy Faculty of Sciences Vrije Universiteit Amsterdam De Boelelaan 1081 1081HV Amsterdam The Netherlands
| | - Lucia Ganzer
- IFN-CNR Department of Physics Politecnico di Milano P.za L. da Vinci 32 20133 Milano Italy
| | - Cristian Manzoni
- IFN-CNR Department of Physics Politecnico di Milano P.za L. da Vinci 32 20133 Milano Italy
| | - Ana Maria Paula
- Departamento de Física Universidade Federal de Minas Gerais 31270-901 Belo Horizonte MG Brazil
| | - Giulio Cerullo
- IFN-CNR Department of Physics Politecnico di Milano P.za L. da Vinci 32 20133 Milano Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale Università degli Studi di Bologna Viale del Risorgimento 4 40136 Bologna Italy
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27
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Norell J, Ljungdahl A, Odelius M. Interdependent Electronic Structure, Protonation, and Solvatization of Aqueous 2-Thiopyridone. J Phys Chem B 2019; 123:5555-5567. [PMID: 31244103 DOI: 10.1021/acs.jpcb.9b03084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
2-Thiopyridone (2-TP), a common model system for excited-state proton transfer, has been simulated in aqueous solution with ab initio molecular dynamics. The interplay of electronic structure, protonation, and solvatization is investigated by comparison of three differently protonated molecular forms and between the lowest singlet and triplet electronic states. An interdependence clearly manifests in the mixed-character T1 state for the 2-TP form, systematic structural distortions of the 2-mercaptopyridine (2-MP) form, and photobase protolysis of the 2-TP- form, in the aqueous phase. In comparison, simplified continuum models for the solvatization are found to be significantly inaccurate for several of the species. To facilitate future computational studies, we therefore present a minimal representative solvatization complex for each stable form and electronic state. Our findings demonstrate the importance of explicit solvatization of the compound and sets the stage for including it also in future studies.
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Affiliation(s)
- Jesper Norell
- Department of Physics, AlbaNova University Center , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Anton Ljungdahl
- Department of Physics, AlbaNova University Center , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Michael Odelius
- Department of Physics, AlbaNova University Center , Stockholm University , SE-106 91 Stockholm , Sweden
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28
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Fang YG, Peng Q, Fang Q, Fang W, Cui G. MS-CASPT2 Studies on the Photophysics of Selenium-Substituted Guanine Nucleobase. ACS OMEGA 2019; 4:9769-9777. [PMID: 31460068 PMCID: PMC6649137 DOI: 10.1021/acsomega.9b01276] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 05/23/2019] [Indexed: 05/30/2023]
Abstract
The MS-CASPT2 method has been employed to optimize minimum-energy structures of 6-selenoguanine (6SeGua) and related two- and three-state intersection structures in and between the lowest five electronic states, i.e., S2(1ππ*), S1(1 nπ*), T2(3 nπ*), T1(3ππ*), and S0. In combination with MS-CASPT2 calculated linearly interpolated internal coordinate paths, the photophysical mechanism of 6SeGua has been proposed. The initially populated S2(1ππ*) state decays to either S1(1 nπ*) or T2(3 nπ*) states through a three-state S2/S1/T2 intersection point. The large S2/T2 spin-orbit coupling of 435 cm-1, according to the classical El-Sayed rule, benefits the S2 → T2 intersystem crossing process. The S1(1 nπ*) state that stems from the S2 → S1 internal conversion process at the S2/S1/T2 intersection point can further jump to the T2(3 nπ*) state through the S1 → T2 intersystem crossing process. This process does not comply with the El-Sayed rule, but it is still related to a comparatively large spin-orbit coupling of 39 cm-1 and is expected to occur relatively fast. Finally, the T2(3 nπ*) state, which is populated from the above S2 → T2 and S1 → T2 intersystem crossing processes, decays to the T1(3ππ*) state via an internal conversion process. Because there is merely a small energy barrier of 0.11 eV separating the T1(3ππ*) minimum and an energetically allowed two-state T1/S0 intersection point, the T1(3ππ*) state still can decay to the S0 state quickly, which is also enhanced by a large T1/S0 spin-orbit coupling of 252 cm-1. Our proposed mechanism explains experimentally observed ultrafast intersystem crossing processes in 6SeGua and its 835-fold acceleration of the T1 state decay to the S0 state compared with 6tGua. Finally, we have found that the ground-state electronic structure of 6SeGua has more apparent multireference character.
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29
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Liu ZY, Hu JW, Huang CH, Huang TH, Chen DG, Ho SY, Chen KY, Li EY, Chou PT. Sulfur-Based Intramolecular Hydrogen-Bond: Excited-State Hydrogen-Bond On/Off Switch with Dual Room-Temperature Phosphorescence. J Am Chem Soc 2019; 141:9885-9894. [DOI: 10.1021/jacs.9b02765] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Zong-Ying Liu
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, Republic of China
| | - Jiun-Wei Hu
- Department of Chemical Engineering, Feng Chia University, Taichung, 40724 Taiwan, Republic of China
| | - Chun-Hao Huang
- Department of Chemistry, National Taiwan Normal University, Taipei, 11677 Taiwan, Republic of China
| | - Teng-Hsing Huang
- Department of Chemical Engineering, Feng Chia University, Taichung, 40724 Taiwan, Republic of China
| | - Deng-Gao Chen
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, Republic of China
| | - Ssu-Yu Ho
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, Republic of China
| | - Kew-Yu Chen
- Department of Chemical Engineering, Feng Chia University, Taichung, 40724 Taiwan, Republic of China
| | - Elise Y. Li
- Department of Chemistry, National Taiwan Normal University, Taipei, 11677 Taiwan, Republic of China
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, Republic of China
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30
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Di Mascio P, Martinez GR, Miyamoto S, Ronsein GE, Medeiros MHG, Cadet J. Singlet Molecular Oxygen Reactions with Nucleic Acids, Lipids, and Proteins. Chem Rev 2019; 119:2043-2086. [DOI: 10.1021/acs.chemrev.8b00554] [Citation(s) in RCA: 253] [Impact Index Per Article: 50.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Paolo Di Mascio
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05508-000, São Paulo, SP Brazil
| | - Glaucia R. Martinez
- Departamento de Bioquímica e Biologia Molecular, Setor de Ciências Biológicas, Universidade Federal do Paraná, 81531-990 Curitiba, PR, Brazil
| | - Sayuri Miyamoto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05508-000, São Paulo, SP Brazil
| | - Graziella E. Ronsein
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05508-000, São Paulo, SP Brazil
| | - Marisa H. G. Medeiros
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05508-000, São Paulo, SP Brazil
| | - Jean Cadet
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, J1H 5N4 Québec, Canada
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31
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Xia Y, Wang F, Wang RN, Liu KH, Su HM. Reaction kinetics between thiobases and singlet oxygen studied by direct detection of the 1O2 luminescence decay. CHINESE J CHEM PHYS 2019. [DOI: 10.1063/1674-0068/cjcp1811268] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Ye Xia
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Fei Wang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ren-nian Wang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Kun-hui Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Hong-mei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, China
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32
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Xie BB, Cui CX. Theoretical studies on photo-induced cycloaddition and (6-4) reactions of the thymidine:4-thiothymidine dimer in a DNA duplex. Phys Chem Chem Phys 2019; 21:2006-2016. [DOI: 10.1039/c8cp07063f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Photo-induced cycloaddition and (6-4) reactions of the thymidine:4-thiothymidine dimer in a DNA duplex.
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Affiliation(s)
- Bin-Bin Xie
- Hangzhou Institute of Advanced Studies
- Zhejiang Normal University
- Hangzhou 311231
- P. R. China
- Key Laboratory of Theoretical and Computational Photochemistry
| | - Cheng-Xing Cui
- School of Chemistry and Chemical Engineering
- Henan Institute of Science and Technology
- Xinxiang 453003
- P. R. China
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33
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Janicki MJ, Szabla R, Šponer J, Góra RW. Solvation effects alter the photochemistry of 2-thiocytosine. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.06.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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34
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Nenov A, Conti I, Borrego-Varillas R, Cerullo G, Garavelli M. Linear absorption spectra of solvated thiouracils resolved at the hybrid RASPT2/MM level. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.07.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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35
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Borrego-Varillas R, Teles-Ferreira DC, Nenov A, Conti I, Ganzer L, Manzoni C, Garavelli M, Maria de Paula A, Cerullo G. Observation of the Sub-100 Femtosecond Population of a Dark State in a Thiobase Mediating Intersystem Crossing. J Am Chem Soc 2018; 140:16087-16093. [DOI: 10.1021/jacs.8b07057] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Rocío Borrego-Varillas
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | | | - Artur Nenov
- Dipartimento di Chimica Industriale, Università degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Irene Conti
- Dipartimento di Chimica Industriale, Università degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Lucia Ganzer
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Cristian Manzoni
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale, Università degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy
| | - Ana Maria de Paula
- Departamento de Física, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte-MG, Brazil
| | - Giulio Cerullo
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
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36
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Miyata S, Tanabe S, Isozaki T, Xu YZ, Suzuki T. Characteristics of the excited triplet states of thiolated guanosine derivatives and singlet oxygen generation. Photochem Photobiol Sci 2018; 17:1469-1476. [PMID: 30280174 DOI: 10.1039/c8pp00240a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Thioguanine is sensitive to UVA light and generates singlet molecular oxygen (1O2*) when exposed to UVA. Three thioguanosine derivatives, 2',3',5'-tri-O-acetyl-6-thioguanosine (ta6TGuo), 2',3',5'-tri-O-acetyl-8-thioguanosine (ta8TGuo), and 2',3',5'-tri-O-acetyl-6,8-dithioguanosine (taDTGuo) were explored photophysically and photochemically. Nanosecond transient absorption and time-resolved near-infrared emission measurements were carried out to investigate the characteristics of their excited triplet states in acetonitrile solution. The quantum yield of intersystem crossing (ΦISC), the intrinsic decay rate constant (k0), the quenching rate constant by 3O2 (kq) and the self-quenching rate constant (kSQ) of their triplet states were all determined. From the precise analysis of the quantum yield of 1O2* generation (ΦΔ) against the concentration of dissolved molecular oxygen, the fraction of the triplet states quenched by dissolved oxygen which gives rise to 1O2* formation (SΔ) was successfully obtained with high accuracy. The ΦΔ values at low oxygen concentrations reveal that these thioguanosines, particularly taDTGuo, can still effectively generate 1O2* at low molecular oxygen concentrations like carcinomatous microenvironments. These findings indicate that taDTGuo would perform well as a potential agent for photo-induced cancer therapies.
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Affiliation(s)
- Shoma Miyata
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan.
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37
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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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38
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Farrell KM, Brister MM, Pittelkow M, Sølling TI, Crespo-Hernández CE. Heavy-Atom-Substituted Nucleobases in Photodynamic Applications: Substitution of Sulfur with Selenium in 6-Thioguanine Induces a Remarkable Increase in the Rate of Triplet Decay in 6-Selenoguanine. J Am Chem Soc 2018; 140:11214-11218. [DOI: 10.1021/jacs.8b07665] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Kieran M. Farrell
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Matthew M. Brister
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Michael Pittelkow
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Theis I. Sølling
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Carlos E. Crespo-Hernández
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
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39
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Liu XY, Li ZW, Fang WH, Cui G. Nonadiabatic dynamics simulations on internal conversion and intersystem crossing processes in gold(i) compounds. J Chem Phys 2018; 149:044301. [PMID: 30068207 DOI: 10.1063/1.5029991] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The position at which the second gold(i)-phosphine group is attached was experimentally found to play a noticeable role in intersystem crossing rates of gold(i) naphthalene derivatives. However, the physical origin is ambiguous. Herein we have employed generalized trajectory-based surface-hopping dynamics simulations to simulate the excited-state relaxation dynamics of these gold(i) naphthalene compounds including both the intersystem crossing process from the initially populated first excited singlet states S1 to triplet manifolds and internal conversion processes within these triplet states. Our predicted intersystem crossing rates are consistent with experiments very well. On the basis of the present results, we have found that (1) ultrafast and subpicosecond intersystem crossing processes are mainly caused by small energy gaps and large spin-orbit couplings between S1 and Tn; (2) adding the second gold(i)-phosphine group does not increase spin-orbit couplings between S1 and Tn but decrease their values remarkably, which implies that heavy-atom effects are state-specific, not state-universal; (3) the position at which the second gold(i)-phosphine group is attached has a remarkable influence on the electronic structures of S1 and Tn and their relative energies, which affect energy gaps and spin-orbit couplings between S1 and Tn and eventually modulate intersystem crossing rates from S1 to Tn. These new insights are very useful for the design of gold-containing compounds with excellent photoluminescence properties. Finally, this work also exemplifies that different isomers of a compound could have distinct excited-state relaxation dynamics.
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Affiliation(s)
- Xiang-Yang Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Zi-Wen Li
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
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Introduction to State-of-the-Art Multidimensional Time-Resolved Spectroscopy Methods. Top Curr Chem (Cham) 2018; 376:28. [DOI: 10.1007/s41061-018-0206-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 06/13/2018] [Indexed: 10/28/2022]
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41
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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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Pollum M, Lam M, Jockusch S, Crespo‐Hernández CE. Dithionated Nucleobases as Effective Photodynamic Agents against Human Epidermoid Carcinoma Cells. ChemMedChem 2018. [DOI: 10.1002/cmdc.201800148] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Marvin Pollum
- Department of Chemistry Case Western Reserve University Cleveland OH 44106 USA
| | - Minh Lam
- Department of Medicine Case Western Reserve University School of Medicine Cleveland OH 44106 USA
| | - Steffen Jockusch
- Department of Chemistry Columbia University New York NY 10027 USA
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Miyata S, Yamada T, Isozaki T, Sugimura H, Xu YZ, Suzuki T. Absorption Characteristics and Quantum Yields of Singlet Oxygen Generation of Thioguanosine Derivatives. Photochem Photobiol 2018; 94:677-684. [DOI: 10.1111/php.12900] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 01/17/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Shoma Miyata
- Department of Chemistry and Biological Science; Aoyama Gakuin University; Sagamihara Kanagawa Japan
| | - Takeshi Yamada
- Department of Chemistry and Biological Science; Aoyama Gakuin University; Sagamihara Kanagawa Japan
| | - Tasuku Isozaki
- Department of Chemistry and Biological Science; Aoyama Gakuin University; Sagamihara Kanagawa Japan
| | - Hideyuki Sugimura
- Department of Chemistry and Biological Science; Aoyama Gakuin University; Sagamihara Kanagawa Japan
| | - Yao-Zhong Xu
- School of Life, Health and Chemical Sciences; the Open University; Milton Keynes UK
| | - Tadashi Suzuki
- Department of Chemistry and Biological Science; Aoyama Gakuin University; Sagamihara Kanagawa Japan
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Miyata S, Hoshino M, Isozaki T, Yamada T, Sugimura H, Xu YZ, Suzuki T. Acid Dissociation Equilibrium and Singlet Molecular Oxygen Quantum Yield of Acetylated 6,8-Dithioguanosine in Aqueous Buffer Solution. J Phys Chem B 2018; 122:2912-2921. [DOI: 10.1021/acs.jpcb.8b00517] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Shoma Miyata
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Mina Hoshino
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Tasuku Isozaki
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Takeshi Yamada
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Hideyuki Sugimura
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Yao-Zhong Xu
- School of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, U.K
| | - Tadashi Suzuki
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
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Bai S, Barbatti M. Mechanism of enhanced triplet decay of thionucleobase by glycosylation and rate-modulating strategies. Phys Chem Chem Phys 2018; 20:16428-16436. [DOI: 10.1039/c8cp02306a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Functionalization of the sugar group can be used to control the triplet decay rate of thionucleosides.
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Koyama D, Milner MJ, Orr-Ewing AJ. Evidence for a Double Well in the First Triplet Excited State of 2-Thiouracil. J Phys Chem B 2017; 121:9274-9280. [PMID: 28895733 DOI: 10.1021/acs.jpcb.7b06917] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The computationally predicted presence of two structurally distinct minima in the first triplet excited (T1) state of 2-thiouracil (2TU) is substantiated by sub-picosecond transient vibrational absorption spectroscopy (TVAS) in deuterated acetonitrile solution. Following 300 nm ultraviolet excitation to the second singlet excited state of 2TU, a transient infrared absorption band centered at 1643 cm-1 is observed within our minimum time resolution of 0.3 ps. It is assigned either to 2TU molecules in the S1 state or to vibrationally hot T1-state molecules, with the latter assignment more consistent with recent computational and experimental studies. The 1643 cm-1 band decays with a time constant of 7.2 ± 0.8 ps, and there is corresponding growth of several further bands centered at 1234, 1410, 1424, 1443, 1511, 1626, and 1660 cm-1 which show no decline in intensity over the 1 ns time limit of our measurements. These spectral features are assigned to two different conformations of 2TU, corresponding to separate energy minima on the T1-state potential energy surface, on the basis of their extended lifetimes, computed infrared frequencies, and the observed quenching of the bands by addition of styrene. Corresponding measurements for the 4-thiouracil (4TU) isomer show sub-picosecond population of the T1 state, which vibrationally cools with a time constant of 5.2 ± 0.6 ps. However, TVAS measurements in the carbonyl stretching region do not distinguish the two computed T1-state conformers of 4TU because of the similarity of their vibrational frequencies.
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Affiliation(s)
- Daisuke Koyama
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Matthew J Milner
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
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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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Bhattacharyya K, Datta A. Visible-Light-Mediated Excited State Relaxation in Semi-Synthetic Genetic Alphabet: d5SICS and dNaM. Chemistry 2017; 23:11494-11498. [PMID: 28675549 DOI: 10.1002/chem.201702583] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Indexed: 12/17/2022]
Abstract
The excited state dynamics of an unnatural base pair (UBP) d5SICS/dNaM were investigated by accurate ab-initio calculations. Time-dependent density functional and high-level multireference calculations (MS-CASPT2) were performed to elucidate the excitation of this UBP and its excited state relaxation mechanism. After excitation to the bright state S2 (ππ*), it decays to the S1 state and then undergoes efficient intersystem crossing to the triplet manifold. The presence of sulfur atom in d5SICS leads to strong spin-orbit coupling (SOC) and a small energy gap that facilitates intersystem crossing from S1 (ns π*) to T2 (ππ*) followed by internal conversion to T1 state. Similarly in dNaM, the deactivation pathway follows analogous trends. CASPT2 calculations suggest that the S1 (ππ*) state is a dark state below the accessible S2 (ππ*) bright state. During the ultrafast deactivation, it exhibits bond length inversion. From S1 state, significant SOC leads the population transfer to T3 due to a smaller energy gap. Henceforth, fast internal conversion occurs from T3 to T2 followed by T1 . From time-dependent trajectory surface hopping dynamics, it is found that excited state relaxation occurs on a sub-picosecond timescale in d5SICS and dNaM. Our findings strongly suggest that there is enough energy available in triplet state of UBP to generate reactive oxygen species and induce phototoxicity with respect to cellular DNA.
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Affiliation(s)
- Kalishankar Bhattacharyya
- Department of Spectroscopy, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, 700032, Kolkata, West Bengal, India
| | - Ayan Datta
- Department of Spectroscopy, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, 700032, Kolkata, West Bengal, India
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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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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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