1
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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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Navarrete-Miguel M, Giussani A, Rubio M, Boggio-Pasqua M, Borin AC, Roca-Sanjuán D. Quantum-Chemistry Study of the Photophysical Properties of 4-Thiouracil and Comparisons with 2-Thiouracil. J Phys Chem A 2024; 128:2273-2285. [PMID: 38504122 PMCID: PMC10982997 DOI: 10.1021/acs.jpca.3c06310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 02/16/2024] [Accepted: 03/03/2024] [Indexed: 03/21/2024]
Abstract
DNA in living beings is constantly damaged by exogenous and endogenous agents. However, in some cases, DNA photodamage can have interesting applications, as it happens in photodynamic therapy. In this work, the current knowledge on the photophysics of 4-thiouracil has been extended by further quantum-chemistry studies to improve the agreement between theory and experiments, to better understand the differences with 2-thiouracil, and, last but not least, to verify its usefulness as a photosensitizer for photodynamic therapy. This study has been carried out by determining the most favorable deactivation paths of UV-vis photoexcited 4-thiouracil by means of the photochemical reaction path approach and an efficient combination of the complete-active-space second-order perturbation theory//complete-active-space self-consistent field (CASPT2//CASSCF), (CASPT2//CASPT2), time-dependent density functional theory (TDDFT), and spin-flip TDDFT (SF-TDDFT) methodologies. By comparing the data computed herein for both 4-thiouracil and 2-thiouracil, a rationale is provided on the relatively higher yields of intersystem crossing, triplet lifetime and singlet oxygen production of 4-thiouracil, and the relatively higher yield of phosphorescence of 2-thiouracil.
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Affiliation(s)
- Miriam Navarrete-Miguel
- Instituto
de Ciencia Molecular, Universitat de València, P.O. Box 22085, ES-46071 Valencia, Spain
| | - Angelo Giussani
- Instituto
de Ciencia Molecular, Universitat de València, P.O. Box 22085, ES-46071 Valencia, Spain
| | - Mercedes Rubio
- Departament
de Química Física, Universitat
de València, 46100 Burjassot, Spain
| | - Martial Boggio-Pasqua
- Laboratoire
de Chimie et Physique Quantiques, IRSAMC,
CNRS et Université Toulouse 3, 118 route de Narbonne, 31062 Toulouse, France
| | - Antonio Carlos Borin
- Department
of Fundamental Chemistry, Institute of Chemistry,
University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo CEP 05508-000, Brazil
| | - Daniel Roca-Sanjuán
- Instituto
de Ciencia Molecular, Universitat de València, P.O. Box 22085, ES-46071 Valencia, Spain
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3
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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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4
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Günsel A, Yıldırım A, Taslimi P, Erden Y, Taskin-Tok T, Pişkin H, Bilgiçli AT, Gülçin İ, Nilüfer Yarasir M. Cytotoxicity effects and biochemical investigation of novel tetrakis-phthalocyanines bearing 2-thiocytosine moieties with molecular docking studies. INORG CHEM COMMUN 2022. [DOI: 10.1016/j.inoche.2022.109263] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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5
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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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6
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Xu T, Hu Z, Lv M, Zhou Z, Xu J, Sun Z, Sun H, Chen J. Hydrogen atom and water complex determine the excited state dynamics of 8-azaguanine. Chem Phys 2021. [DOI: 10.1016/j.chemphys.2021.111118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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7
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Vos E, Scott TR, González-Vázquez J, Corral I, Truhlar DG, Gagliardi L. Intrastrand Photolesion Formation in Thio-Substituted DNA: A Case Study Including Single-Reference and Multireference Methods. J Phys Chem A 2020; 124:10422-10433. [PMID: 33284609 DOI: 10.1021/acs.jpca.0c06814] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The substitution of canonical nucleobases by thiated analogues in natural DNA has been exploited in pharmacology, photochemotherapy, and structural biology. Thionucleobases react with adjacent thymines leading to 6-4 pyrimidine-pyrimidone photoproducts (6-4PPs), which are a major source of DNA photodamage, in particular intrastrand cross-linked photolesions. Here, we study the mechanism responsible for the formation of 6-4PPs in thionucleobases by employing quantum-mechanical calculations. We use multiconfiguration pair-density functional theory, complete active space second-order perturbation theory, and Kohn-Sham density functional theory. Scrutinizing the photochemistry of thionucleobases can elucidate the reaction mechanism of these prodrugs and identify the role that triplet excited states play in the generation of photolesions in the natural biopolymer. Three different possible mechanisms to generate the 6-4PPs are presented, and we conclude that the use of multireference approaches is indispensable to capture important features of the potential energy surface.
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Affiliation(s)
- Eva Vos
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Thais R Scott
- Department of Chemistry, Pritzker School of Molecular Engineering, James Franck Institute, Chicago Center for Theoretical Chemistry, The University of Chicago, 5735 S Ellis Ave., Chicago, Illinois 60637, United States
| | - Jesús González-Vázquez
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.,Institute of Advanced Chemical Sciences (IadChem), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Inés Corral
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.,Institute of Advanced Chemical Sciences (IadChem), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States
| | - Laura Gagliardi
- Department of Chemistry, Pritzker School of Molecular Engineering, James Franck Institute, Chicago Center for Theoretical Chemistry, The University of Chicago, 5735 S Ellis Ave., Chicago, Illinois 60637, United States
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8
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Ortiz-Rodríguez LA, Crespo-Hernández CE. Thionated organic compounds as emerging heavy-atom-free photodynamic therapy agents. Chem Sci 2020; 11:11113-11123. [PMID: 34094354 PMCID: PMC8162790 DOI: 10.1039/d0sc04747c] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 09/15/2020] [Indexed: 12/13/2022] Open
Abstract
This minireview focuses on recent progress in developing heavy-atom-free photosensitizers based on the thionation of nucleic acid derivatives and other biocompatible organic compounds for prospective applications in photodynamic therapy. Particular attention is given to the use of thionated nucleobase derivatives as "one-two punch" photodynamic agents. These versatile photosensitizers can act as "Trojan horses" upon metabolization into DNA and exposure to activating light. Their incorporation into cellular DNA increases their selectivity and photodynamic efficacy against highly proliferating skin cancer tumor cells, while simultaneously enabling the use of low irradiation doses both in the presence and in the absence of molecular oxygen. Also reviewed are their primary photochemical reactions, modes of action, and photosensitization mechanisms. New developments of emerging thionated organic photosensitizers absorbing visible and near-infrared radiation are highlighted. Future research directions, as well as, other prospective applications of heavy-atom-free, thionated photosensitizers are discussed.
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9
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Excited State Lifetimes of Sulfur-Substituted DNA and RNA Monomers Probed Using the Femtosecond Fluorescence Up-Conversion Technique. Molecules 2020; 25:molecules25030584. [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] [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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10
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Skotnicki K, Taras-Goslinska K, Janik I, Bobrowski K. Radiation Induced One-Electron Oxidation of 2-Thiouracil in Aqueous Solutions. Molecules 2019; 24:E4402. [PMID: 31810289 PMCID: PMC6930642 DOI: 10.3390/molecules24234402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 11/27/2019] [Accepted: 11/27/2019] [Indexed: 11/17/2022] Open
Abstract
Oxidative damage to 2-thiouracil (2-TU) by hydroxyl (•OH) and azide (●N3) radicals produces various primary reactive intermediates. Their optical absorption spectra and kinetic characteristics were studied by pulse radiolysis with UV-vis spectrophotometric and conductivity detection and by time-dependent density functional theory (TD-DFT) method. The transient absorption spectra recorded in the reactions of •OH with 2-TU depend on the concentration of 2-TU, however, only slightly on pH. At low concentrations, they are characterized by a broad absorption band with a weakly pronounced maxima located at λ = 325, 340 and 385 nm, whereas for high concentrations, they are dominated by an absorption band with λmax ≈ 425 nm. Based on calculations using TD-DFT method, the transient absorption spectra at low concentration of 2-TU were assigned to the ●OH-adducts to the double bond at C5 and C6 carbon atoms (3●, 4●) and 2c-3e bonded ●OH adduct to sulfur atom (1…●OH) and at high concentration of 2-TU also to the dimeric 2c-3e S-S-bonded radical in neutral form (2●). The dimeric radical (2●) is formed in the reaction of thiyl-type radical (6●) with 2-TU and both radicals are in an equilibrium with Keq = 4.2 × 103 M-1. Similar equilibrium (with Keq = 4.3 × 103 M-1) was found for pH above the pKa of 2-TU which involves admittedly the same radical (6●) but with the dimeric 2c-3e S-S bonded radical in anionic form (2●-). In turn, ●N3-induced oxidation of 2-TU occurs via radical cation with maximum spin location on the sulfur atom which subsequently undergoes deprotonation at N1 atom leading again to thiyl-type radical (6●). This radical is a direct precursor of dimeric radical (2●).
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Affiliation(s)
- Konrad Skotnicki
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland;
| | | | - Ireneusz Janik
- Notre Dame Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Krzysztof Bobrowski
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland;
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11
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Li XD, Gao YT, Sun YJ, Jin XY, Wang D, Liu L, Cheng L. A NaI/H2O2-Mediated Sulfenylation and Selenylation of Unprotected Uracil and Its Derivatives. Org Lett 2019; 21:6643-6647. [DOI: 10.1021/acs.orglett.9b02183] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xue-Dong Li
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Yu-Ting Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ying-Jie Sun
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiao-Yang Jin
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dong Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Li Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liang Cheng
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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12
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Rizzi V, Cosma P, Abbattista R, Fini P, Agostiano A, Cataldi TRI, Losito I. Reactivity of 4-thiothymidine with Fenton reagent investigated by UV-visible spectroscopy and electrospray ionization mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2019; 54:389-401. [PMID: 30769378 DOI: 10.1002/jms.4343] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 02/03/2019] [Accepted: 02/11/2019] [Indexed: 06/09/2023]
Abstract
The reactivity of the sulfur-containing nucleoside 4-thio-(2'-deoxy)-thymidine usually abbreviated as 4-thio-thymidine, (S4 -TdR) under Fenton conditions, ie, in the presence of H2 O2 and catalytic amounts of Fe(II), was investigated by UV-vis spectroscopy and electrospray ionization single and tandem mass spectrometry (ESI-MS and MS/MS). S4 -TdR hydroxylated on the S atom was found to be a key reaction intermediate, ultimately leading to (2'-deoxy)-thymidine usually abbreviated as thymidine, (TdR) as the main reaction product. This finding was in accordance with the outcome of the reaction between S4 -TdR and H2 O2 , previously investigated in our laboratory. On the other hand, the additional presence of •OH radicals, induced by the Fe(II)/H2 O2 combination, led to the increased generation of another interesting S4 -TdR product, already observed after its reaction with H2 O2 alone, ie, the covalent dimer including a SS bridge between two S4 -TdR molecules. More importantly, multihydroxylated derivatives of S4 -TdR and TdR were detected as peculiar products obtained under Fenton conditions. Among them, a product bearing an OH group both on the methyl group linked to the thymine ring and on the C5 atom of the ring was found to prevail. The results obtained during this study, integrated by those found previously in our laboratory, indicate 4-thiothymidine as a promising molecular probe for the recognition, through a careful characterization of its reaction products, of the prevailing species among reactive oxygen species (ROS) corresponding to singlet-state oxygen, hydrogen peroxide, and hydroxylic radical.
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Affiliation(s)
- Vito Rizzi
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Pinalysa Cosma
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
- Consiglio Nazionale delle Ricerche CNR-IPCF, UOS Bari, Bari, Italy
| | - Ramona Abbattista
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Paola Fini
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
- Consiglio Nazionale delle Ricerche CNR-IPCF, UOS Bari, Bari, Italy
| | - Angela Agostiano
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
- Consiglio Nazionale delle Ricerche CNR-IPCF, UOS Bari, Bari, Italy
| | - Tommaso R I Cataldi
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
- Centro Interdipartimentale SMART, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Ilario Losito
- Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", Bari, Italy
- Centro Interdipartimentale SMART, Università degli Studi di Bari "Aldo Moro", Bari, Italy
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13
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Zhou Z, Hu Z, Zhang X, Jia M, Wang X, Su H, Sun H, Chen J, Xu J. pH Controlled Intersystem Crossing and Singlet Oxygen Generation of 8-Azaadenine in Aqueous Solution. Chemphyschem 2019; 20:757-765. [PMID: 30702794 DOI: 10.1002/cphc.201800969] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/30/2019] [Indexed: 01/01/2023]
Abstract
Azabases are intriguing DNA and RNA analogues and have been used as effective antiviral and anticancer medicines. However, photosensitivity of these drugs has also been reported. Here, pH-controlled intersystem crossing (ISC) process of 9H 8-azaadenine (8-AA) in aqueous solution is reported. Broadband transient absorption measurements reveal that the hydrogen atom at N9 position can greatly affect ISC of 8-AA and ISC is more favorable when 8-AA is in its neutral form in aqueous solution. The initial excited ππ* (S2 ) state evolves through ultrafast internal conversion (IC) (4.2 ps) to the lower-lying nπ* state (S1 ), which further stands as a door way state for ISC with a time constant of 160 ps. The triplet state has a lifetime of 6.1 μs. On the other hand, deprotonation at N9 position promotes the IC from the ππ* (S2 ) state to the ground state (S0 ) and the lifetime of the S2 state is determined to be 10 ps. The experimental results are further supported by time-dependent density functional theory (TDDFT) calculations. Singlet oxygen generation yield is measured to be 13.8 % for the neutral 8-AA while the deprotonated one exhibit much lower yield (<2 %), implying that this compound could be a potential pH-sensitized photodynamic therapy agent.
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Affiliation(s)
- Zhongneng Zhou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Zhubin Hu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Xianwang Zhang
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Menghui Jia
- Shanghai Institute of Optics and Fine Mechanics, Shanghai, 201800, China
| | - Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Haitao Sun
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China
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14
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Zou X, Sun Z, Zhao H, Zhang CY. Mechanistic insight into photocrosslinking reaction between triplet state 4-thiopyrimidine and thymine. Phys Chem Chem Phys 2019; 21:21305-21316. [DOI: 10.1039/c9cp04089g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Multiple nonadiabatic pathways greatly facilitate the proceeding of photocrosslinking reactions between 4-thiopyrimidine and thymine.
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Affiliation(s)
- Xiaoran Zou
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Zhonghua Sun
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Hongmei Zhao
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science
- Beijing
- P. R. China
| | - Chun-yang Zhang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
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15
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Mai S, Mohamadzade A, Marquetand P, González L, Ullrich S. Simulated and Experimental Time-Resolved Photoelectron Spectra of the Intersystem Crossing Dynamics in 2-Thiouracil. Molecules 2018; 23:E2836. [PMID: 30388739 PMCID: PMC6278540 DOI: 10.3390/molecules23112836] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 10/25/2018] [Accepted: 10/26/2018] [Indexed: 11/16/2022] Open
Abstract
We report time-dependent photoelectron spectra recorded with a single-photon ionization setup and extensive simulations of the same spectra for the excited-state dynamics of 2-thiouracil (2TU) in the gas phase. We find that single-photon ionization produces very similar results as two-photon ionization, showing that the probe process does not have a strong influence on the measured dynamics. The good agreement between the single-photon ionization experiments and the simulations shows that the norms of Dyson orbitals allow for qualitatively describing the ionization probabilities of 2TU. This reasonable performance of Dyson norms is attributed to the particular electronic structure of 2TU, where all important neutral and ionic states involve similar orbital transitions and thus the shape of the Dyson orbitals do not strongly depend on the initial neutral and final ionic state. We argue that similar situations should also occur in other biologically relevant thio-nucleobases, and that the time-resolved photoelectron spectra of these bases could therefore be adequately modeled with the techniques employed here.
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Affiliation(s)
- Sebastian Mai
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria.
| | - Abed Mohamadzade
- Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA.
| | - Philipp Marquetand
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria.
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria.
| | - Susanne Ullrich
- Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA.
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16
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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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17
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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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18
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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: 66] [Impact Index Per Article: 11.0] [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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19
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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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20
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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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21
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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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22
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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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23
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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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24
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Brem R, Guven M, Karran P. Oxidatively-generated damage to DNA and proteins mediated by photosensitized UVA. Free Radic Biol Med 2017; 107:101-109. [PMID: 27989755 PMCID: PMC5462485 DOI: 10.1016/j.freeradbiomed.2016.10.488] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/19/2016] [Accepted: 10/21/2016] [Indexed: 11/19/2022]
Abstract
UVA accounts for about 95% of the solar ultraviolet (UV) radiation that reaches Earth and most likely contributes to human skin cancer risk. In contrast to UVB, which comprises the remaining 5% and is absorbed by DNA nucleobases to cause direct photodamage, UVA damages DNA indirectly. It does this largely through its interactions with cellular chromophores that act as photosensitisers to generate reactive oxygen species. Exogenously supplied chemicals, including some widely-prescribed medicines, may also act as photosensitisers and these drugs are associated with an increased risk of sun-related cancer. Because they amplify the effects of UVA on cells, they provide a means to investigate the mechanisms and effects of UVA-induced photodamage. Here, we describe some of the major lesions induced by two groups of UVA photosensitisers, the DNA thionucleotides and the fluoroquinolone antibiotics. In thionucleotides, replacement of the oxygen atoms of canonical nucleobases by sulfur converts them into strong UVA chromophores that can be incorporated into DNA. The fluoroquinolones are also UVA chromophores. They are not incorporated into DNA and induce a different range of DNA damages. We also draw attention to the potentially important contribution of photochemical protein damage to the cellular effects of photosensitised UVA. Proteins targeted for oxidation damage include DNA repair factors and we suggest that UVA-mediated protein damage may contribute to sunlight-induced cancer risk.
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Affiliation(s)
- Reto Brem
- The Francis Crick Institute, 1, Midland Road, London NW1 1AT, UK
| | - Melisa Guven
- The Francis Crick Institute, 1, Midland Road, London NW1 1AT, UK
| | - Peter Karran
- The Francis Crick Institute, 1, Midland Road, London NW1 1AT, UK.
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25
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Mai S, Ashwood B, Marquetand P, Crespo-Hernández CE, González L. Solvatochromic Effects on the Absorption Spectrum of 2-Thiocytosine. J Phys Chem B 2017; 121:5187-5196. [PMID: 28452483 PMCID: PMC5447245 DOI: 10.1021/acs.jpcb.7b02715] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
![]()
The
solvatochromic effects of six different solvents on the UV
absorption spectrum of 2-thiocytosine have been studied by a combination
of experimental and theoretical techniques. The steady-state absorption
spectra show significant shifts of the absorption bands, where in
more polar solvents the first absorption maximum shifts to higher
transition energies and the second maximum to lower energies. The
observed solvatochromic shifts have been rationalized using three
popular solvatochromic scales and with high-level multireference quantum
chemistry calculations including implicit and explicit solvent effects.
It has been found that the dipole moments of the excited states account
for some general shifts in the excitation energies, whereas the explicit
solvent interactions explain the differences in the spectra recorded
in the different solvents.
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Affiliation(s)
- Sebastian Mai
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Strasse 17, 1090 Vienna, Austria
| | - Brennan Ashwood
- Center for Chemical Dynamics and Department of Chemistry, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Philipp Marquetand
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Strasse 17, 1090 Vienna, Austria
| | - Carlos E Crespo-Hernández
- Center for Chemical Dynamics and Department of Chemistry, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Strasse 17, 1090 Vienna, Austria
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26
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Bai S, Barbatti M. On the decay of the triplet state of thionucleobases. Phys Chem Chem Phys 2017; 19:12674-12682. [DOI: 10.1039/c7cp02050c] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
The double-well triplet state of thionucleobases allows for a two-step mechanistic control of their triplet decay lifetime.
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27
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Martinez-Fernandez L, Fahleson T, Norman P, Santoro F, Coriani S, Improta R. Optical absorption and magnetic circular dichroism spectra of thiouracils: a quantum mechanical study in solution. Photochem Photobiol Sci 2017; 16:1415-1423. [DOI: 10.1039/c7pp00105c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The excited electronic states of thiouracils, the analogues of uracil where the carbonyl oxygens are substituted by sulphur atoms, have been investigated by computing the magnetic circular dichroism (MCD) and one-photon absorption (OPA) spectra at the TD-DFT level of theory.
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Affiliation(s)
| | - T. Fahleson
- KTH Royal Institute of Technology
- SE-10044 Stockholm
- Sweden
| | - P. Norman
- KTH Royal Institute of Technology
- SE-10044 Stockholm
- Sweden
| | - F. Santoro
- Istituto di Chimica dei Composti Organometallici (ICCOM-CNR)
- Area della Ricerca del CNR
- I-56124 Pisa
- Italy
| | - S. Coriani
- Department of Chemistry
- Technical University of Denmark
- Denmark
| | - R. Improta
- Istituto di Biostrutture e Bioimmagini-CNR
- I-80134 Napoli
- Italy
- LIDYL
- CEA
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28
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Stepchenko VA, Miroshnikov AI, Seela F, Mikhailopulo IA. Enzymatic synthesis and phosphorolysis of 4(2)-thioxo- and 6(5)-azapyrimidine nucleosides by E. coli nucleoside phosphorylases. Beilstein J Org Chem 2016; 12:2588-2601. [PMID: 28144328 PMCID: PMC5238616 DOI: 10.3762/bjoc.12.254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/17/2016] [Indexed: 11/23/2022] Open
Abstract
The trans-2-deoxyribosylation of 4-thiouracil (4SUra) and 2-thiouracil (2SUra), as well as 6-azauracil, 6-azathymine and 6-aza-2-thiothymine was studied using dG and E. coli purine nucleoside phosphorylase (PNP) for the in situ generation of 2-deoxy-α-D-ribofuranose-1-phosphate (dRib-1P) followed by its coupling with the bases catalyzed by either E. coli thymidine (TP) or uridine (UP) phosphorylases. 4SUra revealed satisfactory substrate activity for UP and, unexpectedly, complete inertness for TP; no formation of 2'-deoxy-2-thiouridine (2SUd) was observed under analogous reaction conditions in the presence of UP and TP. On the contrary, 2SU, 2SUd, 4STd and 2STd are good substrates for both UP and TP; moreover, 2SU, 4STd and 2'-deoxy-5-azacytidine (Decitabine) are substrates for PNP and the phosphorolysis of the latter is reversible. Condensation of 2SUra and 5-azacytosine with dRib-1P (Ba salt) catalyzed by the accordant UP and PNP in Tris∙HCl buffer gave 2SUd and 2'-deoxy-5-azacytidine in 27% and 15% yields, respectively. 6-Azauracil and 6-azathymine showed good substrate properties for both TP and UP, whereas only TP recognizes 2-thio-6-azathymine as a substrate. 5-Phenyl and 5-tert-butyl derivatives of 6-azauracil and its 2-thioxo derivative were tested as substrates for UP and TP, and only 5-phenyl- and 5-tert-butyl-6-azauracils displayed very low substrate activity. The role of structural peculiarities and electronic properties in the substrate recognition by E. coli nucleoside phosphorylases is discussed.
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Affiliation(s)
- Vladimir A Stepchenko
- Institute of Bioorganic Chemistry, National Academy of Sciences, Acad. Kuprevicha 5/2, 220141 Minsk, Belarus
| | - Anatoly I Miroshnikov
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, 117997 GSP, Moscow B-437, Russia
| | - Frank Seela
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstraße 11, D-48149 Münster, Germany
| | - Igor A Mikhailopulo
- Institute of Bioorganic Chemistry, National Academy of Sciences, Acad. Kuprevicha 5/2, 220141 Minsk, Belarus
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29
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Zhang XH, Xu YZ. NMR studies on 4-thio-5-furan-modified and 4-thio-5-thiophene-modified nucleosides. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2016; 54:887-892. [PMID: 27529164 DOI: 10.1002/mrc.4501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 08/03/2016] [Accepted: 08/12/2016] [Indexed: 06/06/2023]
Abstract
Systematic NMR characterization of 4-thio-5-furan-pyrimidine nucleosides or 4-thio-5-thiophene-pyrimidine nucleosides (ribonucleosides and 2'-deoxynucleosides) was performed. All proton and carbon signals of 4-thio-5-thiophene-ribouridine and related analogues were unambiguously assigned. The orientations of the base (4-thiouridine or its deoxy analogue) relative to the ring (furan or thiophene) are explored by a NMR approach and further supported by X-ray crystallographic studies. The procedures presented here would be applicable to other modified nucleosides and nucleotides. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Xiao-Hui Zhang
- College of Environment and Chemical Engineering, Dalian University, Dalian, 116622, China.
| | - Yao-Zhong Xu
- Department of Life, Health and Chemical Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
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30
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Mai S, Pollum M, Martínez-Fernández L, Dunn N, Marquetand P, Corral I, Crespo-Hernández CE, González L. The origin of efficient triplet state population in sulfur-substituted nucleobases. Nat Commun 2016; 7:13077. [PMID: 27703148 PMCID: PMC5059480 DOI: 10.1038/ncomms13077] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 09/01/2016] [Indexed: 12/19/2022] Open
Abstract
Elucidating the photophysical mechanisms in sulfur-substituted nucleobases (thiobases) is essential for designing prospective drugs for photo- and chemotherapeutic applications. Although it has long been established that the phototherapeutic activity of thiobases is intimately linked to efficient intersystem crossing into reactive triplet states, the molecular factors underlying this efficiency are poorly understood. Herein we combine femtosecond transient absorption experiments with quantum chemistry and nonadiabatic dynamics simulations to investigate 2-thiocytosine as a necessary step to unravel the electronic and structural elements that lead to ultrafast and near-unity triplet-state population in thiobases in general. We show that different parts of the potential energy surfaces are stabilized to different extents via thionation, quenching the intrinsic photostability of canonical DNA and RNA nucleobases. These findings satisfactorily explain why thiobases exhibit the fastest intersystem crossing lifetimes measured to date among bio-organic molecules and have near-unity triplet yields, whereas the triplet yields of canonical nucleobases are nearly zero.
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Affiliation(s)
- Sebastian Mai
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, Vienna 1090, Austria
| | - Marvin Pollum
- Center for Chemical Dynamics and Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA
| | | | - Nicholas Dunn
- Center for Chemical Dynamics and Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA
| | - Philipp Marquetand
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, Vienna 1090, Austria
| | - Inés Corral
- Universidad Autónoma de Madrid, Departamento de Química, Cantoblanco, Madrid 28049, Spain
| | - Carlos E. Crespo-Hernández
- Center for Chemical Dynamics and Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, Vienna 1090, Austria
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31
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Pollum M, Jockusch S, Crespo-Hernández CE. Increase in the photoreactivity of uracil derivatives by doubling thionation. Phys Chem Chem Phys 2016; 17:27851-61. [PMID: 26439833 DOI: 10.1039/c5cp04822b] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ability of 4-thiouracil to strongly absorb UVA radiation and to populate a reactive triplet state in high yield has enabled its use as a versatile photocrosslinker for nearly 50 years. In this contribution, we present a detailed spectroscopic and photochemical investigation of the 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil series in an effort to further advance this chemistry and to scrutinize the photoreactivity of 2,4-dithiouracil. Our results reveal that excitation of 2,4-dithiouracil leads to intersystem crossing to the triplet manifold in 220 ± 40 fs, which enables the population of the reactive triplet state with near unity yield (ΦT = 0.90 ± 0.15) and ultimately leads to a ca. 50% singlet oxygen generation (ΦΔ = 0.49 ± 0.02)-one of the highest singlet oxygen yields reported to date for a photoexcited thiobase. In addition, the long-lived triplet state of 2,4-dithiouracil reacts efficiently with the nucleic acid base adenine 5'-monophosphate through a direct, oxygen-independent photocycloaddition mechanism and at a rate that is at least 3-fold faster than that of 4-thiouracil under equal conditions. The new physico-chemical insights reported for these RNA-thiobase derivatives are compared to those of the DNA and RNA bases and the DNA-thiobase derivatives. Furthermore, the strong near-visible absorption and increased photoreactivity measured for 2,4-dithiouracil lays a solid foundation for developing RNA-targeted photocrosslinking and phototherapeutic agents that are more effective than those currently available.
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Affiliation(s)
- M Pollum
- Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, OH 44106, USA.
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Mai S, Marquetand P, González L. Intersystem Crossing Pathways in the Noncanonical Nucleobase 2-Thiouracil: A Time-Dependent Picture. J Phys Chem Lett 2016; 7:1978-83. [PMID: 27167106 PMCID: PMC4893732 DOI: 10.1021/acs.jpclett.6b00616] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The deactivation mechanism after ultraviolet irradiation of 2-thiouracil has been investigated using nonadiabatic dynamics simulations at the MS-CASPT2 level of theory. It is found that after excitation the S2 quickly relaxes to S1, and from there intersystem crossing takes place to both T2 and T1 with a time constant of 400 fs and a triplet yield above 80%, in very good agreement with recent femtosecond experiments in solution. Both indirect S1 → T2 → T1 and direct S1 → T1 pathways contribute to intersystem crossing, with the former being predominant. The results contribute to the understanding of how some noncanonical nucleobases respond to harmful ultraviolet light, which could be relevant for prospective photochemotherapeutic applications.
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Brem R, Zhang X, Xu YZ, Karran P. UVA photoactivation of DNA containing halogenated thiopyrimidines induces cytotoxic DNA lesions. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2015; 145:1-10. [PMID: 25747491 PMCID: PMC4376468 DOI: 10.1016/j.jphotobiol.2015.02.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 02/10/2015] [Accepted: 02/12/2015] [Indexed: 11/20/2022]
Abstract
Growing cells incorporate thio-iodo-deoxyuridine and thio-bromo-deoxyuridine into DNA. They are non-toxic but act as powerful UVA photosensitisers. UVA lesions include DNA-protein and DNA–DNA crosslinks. Singlet oxygen is involved in the formation of this potentially lethal damage. Thio-halo-deoxynucleosides offer a potential selective therapeutic option.
Photochemotherapy, the combination of a photosensitiser and ultraviolet (UV) or visible light, is an effective treatment for skin conditions including cancer. The high mutagenicity and non-selectivity of photochemotherapy regimes warrants the development of alternative approaches. We demonstrate that the thiopyrimidine nucleosides 5-bromo-4-thiodeoxyuridine (SBrdU) and 5-iodo-4-thiodeoxyuridine (SIdU) are incorporated into the DNA of cultured human and mouse cells where they synergistically sensitise killing by low doses of UVA radiation. The DNA halothiopyrimidine/UVA combinations induce DNA interstrand crosslinks, DNA-protein crosslinks, DNA strand breaks, nucleobase damage and lesions that resemble UV-induced pyrimidine(6-4)pyrimidone photoproducts. These are potentially lethal DNA lesions and cells defective in their repair are hypersensitive to killing by SBrdU/UVA and SIdU/UVA. DNA SIdU and SBrdU generate lethal DNA photodamage by partially distinct mechanisms that reflect the different photolabilities of their C–I and C–Br bonds. Although singlet oxygen is involved in photolesion formation, DNA SBrdU and SIdU photoactivation does not detectably increase DNA 8-oxoguanine levels. The absence of significant collateral damage to normal guanine suggests that UVA activation of DNA SIdU or SBrdU might offer a strategy to target hyperproliferative skin conditions that avoids the extensive formation of a known mutagenic DNA lesion.
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Affiliation(s)
- Reto Brem
- Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, Herts. EN6 3LD, UK.
| | - Xiaohui Zhang
- College of Environment and Chemical Engineering, Dalian University, Dalian 116622, China
| | - Yao-Zhong Xu
- Department of Life, Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
| | - Peter Karran
- Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, Herts. EN6 3LD, UK
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Zhang XH, Yin HY, Trigiante G, Brem R, Karran P, Pitak MB, Coles SJ, Xu YZ. 5-Iodo-4-thio-2′-deoxyuridine: Synthesis, Structure, and Cytotoxic Activity. CHEM LETT 2015. [DOI: 10.1246/cl.140965] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Xiao-Hui Zhang
- College of Environment and Chemical Engineering, Dalian University
| | - Hong-Yan Yin
- College of Environment and Chemical Engineering, Dalian University
| | | | - Reto Brem
- Cancer Research UK London Research Institute, Clare Hall Laboratories
| | - Peter Karran
- Cancer Research UK London Research Institute, Clare Hall Laboratories
| | - Mateusz B. Pitak
- UK National Crystallography Service, Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton
| | - Simon J. Coles
- UK National Crystallography Service, Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton
| | - Yao-Zhong Xu
- Department of Life, Health and Chemical Sciences, the Open University
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Zhang X, Gao R, Li D, Yin H, Zhang J, Cao H, Zheng X. Study on Interaction between 5-Bromo-4-thio-2'-deoxyuridine and human serum albumin by spectroscopy and molecular docking. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 136 Pt C:1775-1781. [PMID: 25467669 DOI: 10.1016/j.saa.2014.10.081] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Revised: 10/18/2014] [Accepted: 10/23/2014] [Indexed: 06/04/2023]
Abstract
The interaction between 5-Bromo-4-thio-2'-deoxyuridine (4-SBrdU) and human serum albumin (HSA) was investigated by the methods of UV-vis absorbance, fluorescence and circular dichroism (CD) spectroscopy and molecular docking under simulative physiological conditions. The results showed that the quenching mechanism of HAS by 4-SBrdU was dynamic fluorescence quenching, hydrophobic interaction was the main intermolecular force based on thermodynamic data, the fluorescence experimental results were in agreement with results obtained by the molecular docking study.
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Affiliation(s)
- Xiaohui Zhang
- College of Environment and Chemical Engineering, Dalian University, Dalian, Liaoning 116622, China.
| | - Ruiqi Gao
- College of Environment and Chemical Engineering, Dalian University, Dalian, Liaoning 116622, China
| | - Depeng Li
- College of Environment and Chemical Engineering, Dalian University, Dalian, Liaoning 116622, China
| | - Hongyan Yin
- College of Environment and Chemical Engineering, Dalian University, Dalian, Liaoning 116622, China
| | - Juling Zhang
- MOE Key laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, Guangdong 510631, China
| | - Hongyu Cao
- College of Bioengineering, Dalian University, Dalian, Liaoning 116622, China
| | - Xuefang Zheng
- College of Bioengineering, Dalian University, Dalian, Liaoning 116622, China
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Pollum M, Jockusch S, Crespo-Hernández CE. 2,4-Dithiothymine as a Potent UVA Chemotherapeutic Agent. J Am Chem Soc 2014; 136:17930-3. [DOI: 10.1021/ja510611j] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marvin Pollum
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Steffen Jockusch
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Carlos E. Crespo-Hernández
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, Ohio 44106, United States
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Photochemistry of Nucleic Acid Bases and Their Thio- and Aza-Analogues in Solution. Top Curr Chem (Cham) 2014; 355:245-327. [DOI: 10.1007/128_2014_554] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Exploring the binding of 4-thiothymidine with human serum albumin by spectroscopy, atomic force microscopy, and molecular modeling methods. Carbohydr Res 2014; 384:102-11. [DOI: 10.1016/j.carres.2013.11.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 11/21/2013] [Accepted: 11/27/2013] [Indexed: 11/15/2022]
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Reelfs O, Karran P, Young AR. 4-Thiothymidine sensitization of DNA to UVA offers potential for a novel photochemotherapy. Photochem Photobiol Sci 2012; 11:148-54. [PMID: 22044942 DOI: 10.1039/c1pp05188a] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 09/23/2011] [Indexed: 02/11/2024]
Abstract
Photochemotherapy, in which ultraviolet radiation (UVR: 280-400 nm) or visible light is combined with a photosensitizing drug to produce a therapeutic effect that neither drug or radiation can achieve alone, is a proven therapeutic strategy for a number of non-malignant hyperproliferative skin conditions and various cancers. Examples are psoralen plus UVA (320-400 nm) radiation (PUVA) and photodynamic therapy (PDT). All existing photochemotherapies have drawbacks - for example the association of PUVA with the development of skin cancer, and pain that is often associated with PDT treatment of skin lesions. There is a clear need to develop alternative approaches that involve lower radiation doses and/or improved selectivity for target cells. In this review, we explore the possibility to address this need by exploiting thionucleoside-mediated DNA photosensitisation to low, non toxic doses of UVA radiation.
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Affiliation(s)
- Olivier Reelfs
- King's College London, King's College London School of Medicine, Division of Genetics and Molecular Medicine, St John's Institute of Dermatology, London, UK SE19RT.
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Reelfs O, Macpherson P, Ren X, Xu YZ, Karran P, Young AR. Identification of potentially cytotoxic lesions induced by UVA photoactivation of DNA 4-thiothymidine in human cells. Nucleic Acids Res 2011; 39:9620-32. [PMID: 21890905 PMCID: PMC3239200 DOI: 10.1093/nar/gkr674] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2011] [Revised: 07/28/2011] [Accepted: 07/31/2011] [Indexed: 11/24/2022] Open
Abstract
Photochemotherapy-in which a photosensitizing drug is combined with ultraviolet or visible radiation-has proven therapeutic effectiveness. Existing approaches have drawbacks, however, and there is a clinical need to develop alternatives offering improved target cell selectivity. DNA substitution by 4-thiothymidine (S(4)TdR) sensitizes cells to killing by ultraviolet A (UVA) radiation. Here, we demonstrate that UVA photoactivation of DNA S(4)TdR does not generate reactive oxygen or cause direct DNA breakage and is only minimally mutagenic. In an organotypic human skin model, UVA penetration is sufficiently robust to kill S(4)TdR-photosensitized epidermal cells. We have investigated the DNA lesions responsible for toxicity. Although thymidine is the predominant UVA photoproduct of S(4)TdR in dilute solution, more complex lesions are formed when S(4)TdR-containing oligonucleotides are irradiated. One of these, a thietane/S(5)-(6-4)T:T, is structurally related to the (6-4) pyrimidine:pyrimidone [(6-4) Py:Py] photoproducts induced by UVB/C radiation. These lesions are detectable in DNA from S(4)TdR/UVA-treated cells and are excised from DNA more efficiently by keratinocytes than by leukaemia cells. UVA irradiation also induces DNA interstrand crosslinking of S(4)TdR-containing duplex oligonucleotides. Cells defective in repairing (6-4) Py:Py DNA adducts or processing DNA crosslinks are extremely sensitive to S(4)TdR/UVA indicating that these lesions contribute significantly to S(4)TdR/UVA cytotoxicity.
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Affiliation(s)
- Olivier Reelfs
- King's College London, School of Medicine, Division of Genetics and Molecular Medicine, St John's Institute of Dermatology, London, SE1 9RT, UK.
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