1
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Oliveira LMF, Valverde D, Costa GJ, Borin AC. The copious photochemistry of 2,6-diaminopurine: Luminescence, triplet population, and ground state recovery. Photochem Photobiol 2024; 100:323-338. [PMID: 37403286 DOI: 10.1111/php.13833] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/15/2023] [Accepted: 06/19/2023] [Indexed: 07/06/2023]
Abstract
9H- and 7H-2,6-Diaminopurine (26DAP) photoinduced events in vacuum were studied at the MS-CASPT2/cc-pVDZ level of theory. The S1 1 (ππ* La ) state is initially populated evolving barrierless towards its minimum energy structure, from where two photochemical events can take place in both tautomers. The first is the return of the electronic population to the ground state via the C6 conical intersection (CI-C6). The second involves an internal conversion to the ground through the C2 conical intersection (CI-C2). According to our geodesic interpolated paths connecting the critical structures, the second route is less favorable in both tautomers, due to the presence of high energy barriers. Our calculations suggest a competition between fluorescence and ultrafast relaxation to the electronic ground state via internal conversion process. Based on our calculated potential energy surfaces and experimental excited state lifetimes from the literature, we can infer that the 7H- must have a greater fluorescence yield than the 9H-tautomer. We also explored the triplet state population mechanisms on the 7H-26DAP to understand their long-lived components observed experimentally.
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Affiliation(s)
- Leonardo M F Oliveira
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Danillo Valverde
- Unité de Chimie Physique Théorique et Structurale, Namur Institute of Structured Matter, Université de Namur, Namur, Belgium
| | - Gustavo J Costa
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Antonio Carlos Borin
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
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2
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Gate G, Williams A, Boldissar S, Šponer J, Szabla R, de Vries M. The tautomer-specific excited state dynamics of 2,6-diaminopurine using resonance-enhanced multiphoton ionization and quantum chemical calculations. Photochem Photobiol 2024; 100:404-418. [PMID: 38124372 DOI: 10.1111/php.13897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 10/25/2023] [Accepted: 11/14/2023] [Indexed: 12/23/2023]
Abstract
2,6-Diaminopurine (2,6-dAP) is an alternative nucleobase that potentially played a role in prebiotic chemistry. We studied its excited state dynamics in the gas phase by REMPI, IR-UV hole burning, and ps pump-probe spectroscopy and performed quantum chemical calculations at the SCS-ADC(2) level of theory to interpret the experimental results. We found the 9H tautomer to have a small barrier to ultrafast relaxation via puckering of its 6-membered ring. The 7H tautomer has a larger barrier to reach a conical intersection and also has a sizable triplet yield. These results are discussed relative to other purines, for which 9H tautomerization appears to be more photostable than 7H and homosubstituted purines appear to be less photostable than heterosubstituted or singly substituted purines.
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Affiliation(s)
- Gregory Gate
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Ann Williams
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Samuel Boldissar
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Jiří Šponer
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacky University Olomouc, Olomouc-Holice, Czech Republic
| | - Rafal Szabla
- Institute of Advanced Materials, Faculty of Chemistry, Wrocław University of Science and Technology, Wrocław, Poland
| | - Mattanjah de Vries
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
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3
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Bezabih MS, Kaliakin DS, Blanco-González A, Barneschi L, Tarnovsky AN, Olivucci M. Comparative Study of Uracil Excited-State Photophysics in Water and Acetonitrile via RMS-CASPT2-Driven Quantum-Classical Trajectories. J Phys Chem B 2023; 127:10871-10879. [PMID: 38055701 DOI: 10.1021/acs.jpcb.3c06433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
We present a nonadiabatic molecular dynamics study of the ultrafast processes occurring in uracil upon UV light absorption, leading to electronic excitation and subsequent nonradiative decay. Previous studies have indicated that the mechanistic details of this process are drastically different depending on whether the process takes place in the gas phase, acetonitrile, or water. However, such results have been produced using quantum chemical methods that did not incorporate both static and dynamic electron correlation. In order to assess the previously proposed mechanisms, we simulate the photodynamics of uracil in the three environments mentioned above using quantum-classical trajectories and, for solvated uracil, hybrid quantum mechanics/molecular mechanics (QM/MM) models driven by the rotated multistate complete active space second-order perturbation (RMS-CASPT2) method. To do so, we exploit the gradient recently made available in OpenMolcas and compare the results to those obtained using the complete active space self-consistent field (CASSCF) method only accounting for static electron correlation. We show that RMS-CASPT2 produces, in general, a mechanistic picture different from the one obtained at the CASSCF level but confirms the hypothesis advanced on the basis of previous ROKS and TDDFT studies thus highlighting the importance of incorporating dynamic electron correlation in the investigation of ultrafast electronic deactivation processes.
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Affiliation(s)
- Meseret Simachew Bezabih
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Danil S Kaliakin
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | | | - Leonardo Barneschi
- Dipartimento di Biotechnologie, Chimica e Farmacia, Università di Siena, I-53100 Siena, Italy
| | - Alexander N Tarnovsky
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Massimo Olivucci
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
- Dipartimento di Biotechnologie, Chimica e Farmacia, Università di Siena, I-53100 Siena, Italy
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4
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Chang XP, Fan FR, Zhang TS, Xie BB. Quantum mechanics/molecular mechanics studies on the excited-state decay mechanisms of cytidine aza-analogues: 5-azacytidine and 2'-deoxy-5-azacytidine in aqueous solution. Phys Chem Chem Phys 2023; 25:26258-26269. [PMID: 37743787 DOI: 10.1039/d3cp03628f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The excited state properties and deactivation pathways of two DNA methylation inhibitors, i.e., 5-azacytidine (5ACyd) and 2'-deoxy-5-azacytidine (5AdCyd) in aqueous solution, are comprehensively explored with the QM(CASPT2//CASSCF)/MM protocol. We systematically map the feasible decay mechanisms based on the obtained excited-state decay paths involving all the identified minimum-energy structures, conical intersections, and crossing points driving the different internal conversion (IC) and intersystem crossing (ISC) routes in and between the 1ππ*, 1nπ*, 3ππ*, 3nπ*, and S0 states. Unlike the 1nπ* state below the 1ππ* state in 5ACyd, deoxyribose group substitution at the N1 position leads to the 1ππ* state becoming the S1 state in 5AdCyd. In 5ACyd and 5AdCyd, the initially populated 1ππ* state mainly deactivates to the S0 state through the direct 1ππ* → S0 IC or mediated by the 1nπ* state. The former nearly barrierless IC channel of 1ππ* → S0 occurs ultrafast via the nearby low-lying 1ππ*/S0 conical intersection. In the latter IC channel of 1ππ* → 1nπ* → S0, the initially photoexcited 1ππ* state first approaches the nearby S2/S1 conical section 1ππ*/1nπ* and then undergoes efficient IC to the 1nπ* state, followed by the further IC to the initial S0 state via the S1/S0 conical intersection 1nπ*/S0. The 1nπ*/S0 conical intersection is estimated to be located 6.0 and 4.9 kcal mol-1 above the 1nπ* state minimum in 5ACyd and 5AdCyd, respectively, at the QM(CASPT2)/MM level. In addition to the efficient singlet-mediated IC channels, the minor ISC routes would populate 1ππ* to T1(ππ*) through 1ππ* → T1 or 1ππ* → 1nπ* → T1. Relatively, the 1ππ* → 1nπ* → T1 route benefits from the spin-orbit coupling (SOC) of 1nπ*/3ππ* of 8.7 cm-1 in 5ACyd and 10.2 cm-1 in 5AdCyd, respectively. Subsequently, the T1 system will approach the nearby T1/S0 crossing point 3ππ*/S0 driving it back to the S0 state. Given the 3ππ*/S0 crossing point located above the T1 minimum and the small T1/S0 SOC, i.e., 8.4 kcal mol-1 and 2.1 cm-1 in 5ACyd and 6.8 kcal mol-1 and 1.9 cm-1 in 5AdCyd, respectively, the slow T1 → S0 would trap the system in the T1 state for a while. The present work could contribute to understanding the mechanistic photophysics and photochemistry of similar aza-nucleosides and their derivatives.
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Affiliation(s)
- Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, China.
| | - Feng-Ran Fan
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, China.
| | - Teng-Shuo Zhang
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China
| | - Bin-Bin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, Hangzhou 311231, China
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5
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Chang XP, Zhao G, Zhang TS, Xie BB. Quantum mechanics/molecular mechanics studies on mechanistic photophysics of cytosine aza-analogues: 2,4-diamino-1,3,5-triazine and 2-amino-1,3,5-triazine in aqueous solution. Phys Chem Chem Phys 2023; 25:7669-7680. [PMID: 36857660 DOI: 10.1039/d2cp05639a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The excited-state properties and photophysics of cytosine aza-analogues, i.e., 2,4-diamino-1,3,5-triazine (2,4-DT) and 2-amino-1,3,5-triazine (2-AT) in solution have been systematically explored using the QM(MS-CASPT2//CASSCF)/MM approach. The excited-state nonradiative relaxation mechanisms for the initially photoexcited S1(ππ*) state decay back to the S0 state are proposed in terms of the present computed minima, surface crossings (conical intersections and singlet-triplet crossings), and excited-state decay paths in the S1, S2, T1, T2, and S0 states. Upon photoexcitation to the bright S1(ππ*) state, 2,4-DT quickly relaxes to its S1 minimum and then overcomes a small energy barrier of 5.1 kcal mol-1 to approach a S1/S0 conical intersection, where the S1 system hops to the S0 state through S1 → S0 internal conversion (IC). In addition, at the S1 minimum, the system could partially undergo intersystem crossing (ISC) to the T1 state, followed by further ISC to the S0 state via the T1/S0 crossing point. In the T1 state, an energy barrier of 7.9 kcal mol-1 will trap 2,4-DT for a while. In parallel, for 2-AT, the system first relaxes to the S1 minimum and then S1 → S0 IC or S1 → T1 → S0 ISCs take place to the S0 state by surmounting a large barrier of 15.3 kcal mol-1 or 11.9 kcal mol-1, respectively, which heavily suppress electronic transition to the S0 state. Different from 2,4-DT, upon photoexcitation in the Franck-Condon region, 2-AT can quickly evolve in an essentially barrierless manner to nearby S2/S1 conical intersection, where the S2 and T1 states can be populated. Once it hops to the S2 state, the system will overcome a relatively small barrier (6.6 kcal mol-1vs. 15.3 kcal mol-1) through IC to the S0 state. Similarly, an energy barrier of 11.9 kcal mol-1 heavily suppresses the T1 state transformation to the S0 state. The present work manifests that the amination/deamination of the triazine rings can affect some degree of different vertical and adiabatic excitation energies and nonradiative decay pathways in solution. It not only rationalizes excited-state decay dynamics of 2,4-DT and 2-AT in aqueous solution but could also provide insights into the understanding of the photophysics of aza-nucleobases.
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Affiliation(s)
- Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, China.
| | - Geng Zhao
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, China.
| | - Teng-Shuo Zhang
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China
| | - Bin-Bin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, Hangzhou 311231, China
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6
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Camiruaga A, Usabiaga I, Calabrese C, Lamas I, Basterretxea FJ, Fernández JA. Exploring the Influence of Intermolecular Interactions in Prebiotic Chemistry Using Laser Spectroscopy and Calculations. Chemistry 2022; 28:e202103636. [PMID: 34854511 PMCID: PMC9299682 DOI: 10.1002/chem.202103636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Indexed: 11/09/2022]
Abstract
One of the most fascinating questions in chemistry is why nature chose CGAT as the alphabet of life. Very likely, such selection was the result of multiple factors and a long period of refinement. Here, we explore how the intermolecular interactions influenced such process, by characterizing the formation of dimers between adenine, theobromine and 4-aminopyrimidine. Using a combination of mass-resolved excitation spectroscopy and DFT calculations, we determined the structure of adenine-theobromine and 4-aminopyrimidine-theobromine dimers. The binding energy of these dimers is very close to the canonical adenine-thymine nucleobases. Likewise, the dimers are able to adopt Watson-Crick conformations. These findings seem to indicate that there were many options available to build the first versions of the informational polymers, which also had to compete with other molecules, such as 4-aminopyrimidine, which does not have a valid attaching point for a saccharide. For some reason, nature did not select the most strongly-bonded partners or if it did, such proto-bases were later replaced by the nowadays canonical CGAT.
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Affiliation(s)
- Ander Camiruaga
- Department of Physical ChemistryFaculty of Science and TechnologyUniversity of the Basque Country (UPV/EHU)Barrio Sarriena, S/N, Leioa48940Spain
| | - Imanol Usabiaga
- Department of Physical ChemistryFaculty of Science and TechnologyUniversity of the Basque Country (UPV/EHU)Barrio Sarriena, S/N, Leioa48940Spain
| | - Camilla Calabrese
- Department of Physical ChemistryFaculty of Science and TechnologyUniversity of the Basque Country (UPV/EHU)Barrio Sarriena, S/N, Leioa48940Spain
- Instituto Biofisika (UPV/EHU-CSIC)University of the Basque Country (UPV/EHU)Barrio Sarriena S/N, Leioa48940Spain
| | - Iker Lamas
- Department of Physical ChemistryFaculty of Science and TechnologyUniversity of the Basque Country (UPV/EHU)Barrio Sarriena, S/N, Leioa48940Spain
| | - Francisco J. Basterretxea
- Department of Physical ChemistryFaculty of Science and TechnologyUniversity of the Basque Country (UPV/EHU)Barrio Sarriena, S/N, Leioa48940Spain
| | - José A. Fernández
- Department of Physical ChemistryFaculty of Science and TechnologyUniversity of the Basque Country (UPV/EHU)Barrio Sarriena, S/N, Leioa48940Spain
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7
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Gate G, Szabla R, Haggmark MR, Šponer J, Sobolewski AL, de Vries MS. Photodynamics of alternative DNA base isoguanine. Phys Chem Chem Phys 2019; 21:13474-13485. [DOI: 10.1039/c9cp01622h] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Pump–probe experiments and quantum-chemical simulations of UV-excited isoguanine elucidate its tautomer dependent photochemical properties.
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Affiliation(s)
- Gregory Gate
- Department of Chemistry and Biochemistry
- University of California
- Santa Barbara
- USA
| | - Rafał Szabla
- Institute of Physics
- Polish Academy of Sciences
- 02-668 Warsaw
- Poland
- Institute of Biophysics of the Czech Academy of Sciences
| | - Michael R. Haggmark
- Department of Chemistry and Biochemistry
- University of California
- Santa Barbara
- USA
| | - Jiří Šponer
- Institute of Biophysics of the Czech Academy of Sciences
- 61265 Brno
- Czech Republic
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8
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Abstract
The response of nucleobases to UV radiation depends on structure in subtle ways, as revealed by gas-phase experiments.
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Affiliation(s)
- Samuel Boldissar
- Department of Chemistry and Biochemistry University of California Santa Barbara
- USA
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9
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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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10
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Rovira AR, Fin A, Tor Y. Expanding a fluorescent RNA alphabet: synthesis, photophysics and utility of isothiazole-derived purine nucleoside surrogates. Chem Sci 2017; 8:2983-2993. [PMID: 28451365 PMCID: PMC5380116 DOI: 10.1039/c6sc05354h] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 01/26/2017] [Indexed: 01/09/2023] Open
Abstract
A series of emissive ribonucleoside purine mimics, all comprised of an isothiazolo[4,3-d]pyrimidine core, was prepared using a divergent pathway involving a key Thorpe-Ziegler cyclization. In addition to an adenosine and a guanosine mimic, analogues of the noncanonical xanthosine, isoguanosine, and 2-aminoadenosine were also synthesized and found to be emissive. Isothiazolo 2-aminoadenosine, an adenosine surrogate, was found to be particularly emissive and effectively deaminated by adenosine deaminase. Competitive studies with adenosine deaminase with each analogue in combination with native adenosine showed preference for the native substrate while still deaminating the isothiazolo analogues.
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Affiliation(s)
- Alexander R Rovira
- Department of Chemistry and Biochemistry , University of California , San Diego , La Jolla , California 92093-0358 , USA .
| | - Andrea Fin
- Department of Chemistry and Biochemistry , University of California , San Diego , La Jolla , California 92093-0358 , USA .
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry , University of California , San Diego , La Jolla , California 92093-0358 , USA .
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11
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Zhou Z, Zhou X, Wang X, Jiang B, Li Y, Chen J, Xu J. Ultrafast Excited-State Dynamics of Cytosine Aza-Derivative and Analogues. J Phys Chem A 2017; 121:2780-2789. [DOI: 10.1021/acs.jpca.6b12290] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Zhongneng Zhou
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - Xueyao Zhou
- Department
of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xueli Wang
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - Bin Jiang
- Department
of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yongle Li
- Department
of Physics, International Center of Quantum and Molecular Structures,
Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444, China
| | - Jinquan Chen
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - Jianhua Xu
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
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12
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González J, Usabiaga I, Arnaiz PF, León I, Martínez R, Millán J, Fernández JA. Competition between stacked and hydrogen bonded structures of cytosine aggregates. Phys Chem Chem Phys 2017; 19:8826-8834. [DOI: 10.1039/c6cp08476a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The four bases of DNA constitute what is known as the “alphabet of life”.
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Affiliation(s)
- Jorge González
- Department of Physical Chemistry
- Faculty of Science and Technology
- University of the Basque Country (UPV/EHU)
- Leioa
- Spain
| | - Imanol Usabiaga
- Department of Physical Chemistry
- Faculty of Science and Technology
- University of the Basque Country (UPV/EHU)
- Leioa
- Spain
| | - Pedro F. Arnaiz
- Department of Physical Chemistry
- Faculty of Science and Technology
- University of the Basque Country (UPV/EHU)
- Leioa
- Spain
| | - Iker León
- Department of Physical Chemistry
- Faculty of Science and Technology
- University of the Basque Country (UPV/EHU)
- Leioa
- Spain
| | - Rodrigo Martínez
- Department of Chemistry
- Faculty of Science and Technology
- University of La Rioja
- Logroño
- Spain
| | - Judith Millán
- Department of Chemistry
- Faculty of Science and Technology
- University of La Rioja
- Logroño
- Spain
| | - José A. Fernández
- Department of Physical Chemistry
- Faculty of Science and Technology
- University of the Basque Country (UPV/EHU)
- Leioa
- Spain
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13
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Investigation of the mechanisms of photo-induced formation of cyclobutane dimers of cytosine and 2,4-diaminopyrimidine. J Mol Model 2016; 22:230. [PMID: 27572158 DOI: 10.1007/s00894-016-3087-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 08/05/2016] [Indexed: 10/21/2022]
Abstract
The mechanisms of the formation of cyclobutane dimers (CBD) of cytosine and 2,4-diaminopyrimidine were studied at the CC2 theoretical level and cc-pVDZ basis functions. Four orientations of the two monomers are explored: cys-syn, cis-anti, trans-syn, and trans-anti. The research revealed that in all cases the cyclobutane structures are formed along the (1)ππ* excited-state reaction paths of the stacked aggregates. We localized the S1/S0 conical intersections mediating those transformations. The results obtained agree well with the previously reported investigations on the cis-syn cyclodimer formations of other pyrimidines.
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14
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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: 109] [Impact Index Per Article: 13.6] [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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15
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Kancheva P, Tuna D, Delchev VB. Comparative study of radiationless deactivation mechanisms in cytosine and 2,4-diaminopyrimidine. J Photochem Photobiol A Chem 2016. [DOI: 10.1016/j.jphotochem.2016.02.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Saed B, Omidyan R. Protonation effect on the electronic properties of 2-pyridone monomer, dimer and its water clusters: a theoretical study. J Chem Phys 2014; 140:024315. [PMID: 24437885 DOI: 10.1063/1.4859255] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The CC2 (second order approximate coupled cluster method) has been applied to investigate protonation effect on electronic transition energies of 2-pyridone (2PY), 2-pyridone dimer, and micro-solvated 2-pyridone (0-2 water molecules). The PE profiles of protonated 2-pyridone (2PYH(+)) as well as monohydrated 2PYH(+) at the different electronic states have been investigated. The (1)πσ∗ state in protonated species (2PYH(+)) is a barrier free and dissociative state along the O-H stretching coordinate. In this reaction coordinate, the lowest lying (1)πσ∗ predissociates the bound S1((1)ππ∗) state, connecting the latter to a conical intersection with the S0 state. These conical intersections lead the (1)ππ∗ state to proceed as predissociative state and finally direct the excited system to the ground state. Furthermore, in presence of water molecule, the (1)πσ∗ state still remains dissociative but the conical intersection between (1)πσ∗ and ground state disappears. In addition, according to the CC2 calculation results, it has been predicted that protonation significantly blue shifts the S1-S0 electronic transition of monomer, dimer, and microhydrated 2-pyridone.
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Affiliation(s)
- Behnaz Saed
- Department of Chemistry, University of Isfahan, 81746-73441 Isfahan, Iran
| | - Reza Omidyan
- Department of Chemistry, University of Isfahan, 81746-73441 Isfahan, Iran
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Staniforth M, Stavros VG. Recent advances in experimental techniques to probe fast excited-state dynamics in biological molecules in the gas phase: dynamics in nucleotides, amino acids and beyond. Proc Math Phys Eng Sci 2013; 469:20130458. [PMID: 24204191 PMCID: PMC3780818 DOI: 10.1098/rspa.2013.0458] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 08/07/2013] [Indexed: 11/23/2022] Open
Abstract
In many chemical reactions, an activation barrier must be overcome before a chemical transformation can occur. As such, understanding the behaviour of molecules in energetically excited states is critical to understanding the chemical changes that these molecules undergo. Among the most prominent reactions for mankind to understand are chemical changes that occur in our own biological molecules. A notable example is the focus towards understanding the interaction of DNA with ultraviolet radiation and the subsequent chemical changes. However, the interaction of radiation with large biological structures is highly complex, and thus the photochemistry of these systems as a whole is poorly understood. Studying the gas-phase spectroscopy and ultrafast dynamics of the building blocks of these more complex biomolecules offers the tantalizing prospect of providing a scientifically intuitive bottom-up approach, beginning with the study of the subunits of large polymeric biomolecules and monitoring the evolution in photochemistry as the complexity of the molecules is increased. While highly attractive, one of the main challenges of this approach is in transferring large, and in many cases, thermally labile molecules into vacuum. This review discusses the recent advances in cutting-edge experimental methodologies, emerging as excellent candidates for progressing this bottom-up approach.
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Affiliation(s)
| | - Vasilios G. Stavros
- Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, UK
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Rios AC, Tor Y. On the Origin of the Canonical Nucleobases: An Assessment of Selection Pressures across Chemical and Early Biological Evolution. Isr J Chem 2013; 53:469-483. [PMID: 25284884 PMCID: PMC4181368 DOI: 10.1002/ijch.201300009] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The native bases of RNA and DNA are prominent examples of the narrow selection of organic molecules upon which life is based. How did nature "decide" upon these specific heterocycles? Evidence suggests that many types of heterocycles could have been present on the early Earth. It is therefore likely that the contemporary composition of nucleobases is a result of multiple selection pressures that operated during early chemical and biological evolution. The persistence of the fittest heterocycles in the prebiotic environment towards, for example, hydrolytic and photochemical assaults, may have given some nucleobases a selective advantage for incorporation into the first informational polymers. The prebiotic formation of polymeric nucleic acids employing the native bases remains, however, a challenging problem to reconcile. Hypotheses have proposed that the emerging RNA world may have included many types of nucleobases. This is supported by the extensive utilization of non-canonical nucleobases in extant RNA and the resemblance of many of the modified bases to heterocycles generated in simulated prebiotic chemistry experiments. Selection pressures in the RNA world could have therefore narrowed the composition of the nucleic acid bases. Two such selection pressures may have been related to genetic fidelity and duplex stability. Considering these possible selection criteria, the native bases along with other related heterocycles seem to exhibit a certain level of fitness. We end by discussing the strength of the N-glycosidic bond as a potential fitness parameter in the early DNA world, which may have played a part in the refinement of the alphabetic bases.
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Affiliation(s)
- Andro C. Rios
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0358 (USA), phone: (+1) 8585346401, fax: (+1) 858534 0202
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0358 (USA), phone: (+1) 8585346401, fax: (+1) 858534 0202
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Steber AL, Neill JL, Zaleski DP, Pate BH, Lesarri A, Bird RG, Vaquero-Vara V, Pratt DW. Structural studies of biomolecules in the gas phase by chirped-pulse Fourier transform microwave spectroscopy. Faraday Discuss 2011; 150:227-42; discussion 257-92. [DOI: 10.1039/c1fd00008j] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Abstract
A comprehensive effort in photodynamical ab initio simulations of the ultrafast deactivation pathways for all five nucleobases adenine, guanine, cytosine, thymine, and uracil is reported. These simulations are based on a complete nonadiabatic surface-hopping approach using extended multiconfigurational wave functions. Even though all five nucleobases share the basic internal conversion mechanisms, the calculations show a distinct grouping into purine and pyrimidine bases as concerns the complexity of the photodynamics. The purine bases adenine and guanine represent the most simple photodeactivation mechanism with the dynamics leading along a diabatic ππ* path directly and without barrier to the conical intersection seam with the ground state. In the case of the pyrimidine bases, the dynamics starts off in much flatter regions of the ππ* energy surface due to coupling of several states. This fact prohibits a clear formation of a single reaction path. Thus, the photodynamics of the pyrimidine bases is much richer and includes also nπ* states with varying importance, depending on the actual nucleobase considered. Trapping in local minima may occur and, therefore, the deactivation time to the ground state is also much longer in these cases. Implications of these findings are discussed (i) for identifying structural possibilities where singlet/triplet transitions can occur because of sufficient retention time during the singlet dynamics and (ii) concerning the flexibility of finding other deactivation pathways in substituted pyrimidines serving as candidates for alternative nucleobases.
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Szymczak JJ, Müller T, Lischka H. The effect of hydration on the photo-deactivation pathways of 4-aminopyrimidine. Chem Phys 2010. [DOI: 10.1016/j.chemphys.2010.07.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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The photodynamics of 2,4-diaminopyrimidine in comparison with 4-aminopyrimidine: The effect of amino-substitution. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.07.098] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Nachtigallová D, Lischka H, Szymczak JJ, Barbatti M, Hobza P, Gengeliczki Z, Pino G, Callahan MP, de Vries MS. The effect of C5 substitution on the photochemistry of uracil. Phys Chem Chem Phys 2010; 12:4924-33. [DOI: 10.1039/b925803p] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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