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Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate

The photophysics and photochemistry of water-solvated guanine monophosphate (GMP) are here characterized by means of a multireference quantum-chemical/molecular mechanics theoretical approach (CASPT2//CASSCF/AMBER) in order to elucidate the main photo-processes occurring upon UV-light irradiation. T...

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Autores principales: Altavilla, Salvatore F., Segarra-Martí, Javier, Nenov, Artur, Conti, Irene, Rivalta, Ivan, Garavelli, Marco
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4403598/
https://www.ncbi.nlm.nih.gov/pubmed/25941671
http://dx.doi.org/10.3389/fchem.2015.00029
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author Altavilla, Salvatore F.
Segarra-Martí, Javier
Nenov, Artur
Conti, Irene
Rivalta, Ivan
Garavelli, Marco
author_facet Altavilla, Salvatore F.
Segarra-Martí, Javier
Nenov, Artur
Conti, Irene
Rivalta, Ivan
Garavelli, Marco
author_sort Altavilla, Salvatore F.
collection PubMed
description The photophysics and photochemistry of water-solvated guanine monophosphate (GMP) are here characterized by means of a multireference quantum-chemical/molecular mechanics theoretical approach (CASPT2//CASSCF/AMBER) in order to elucidate the main photo-processes occurring upon UV-light irradiation. The effect of the solvent and of the phosphate group on the energetics and structural features of this system are evaluated for the first time employing high-level ab initio methods and thoroughly compared to those in vacuo previously reported in the literature and to the experimental evidence to assess to which extent they influence the photoinduced mechanisms. Solvated electronic excitation energies of solvated GMP at the Franck-Condon (FC) region show a red shift for the ππ(*) L(a) and L(b) states, whereas the energy of the oxygen lone-pair nπ(*) state is blue-shifted. The main photoinduced decay route is promoted through a ring-puckering motion along the bright lowest-lying L(a) state toward a conical intersection (CI) with the ground state, involving a very shallow stationary point along the minimum energy pathway in contrast to the barrierless profile found in gas-phase, the point being placed at the end of the minimum energy path (MEP) thus endorsing its ultrafast deactivation in accordance with time-resolved transient and photoelectron spectroscopy experiments. The role of the nπ(*) state in the solvated system is severely diminished as the crossings with the initially populated L(a) state and also with the L(b) state are placed too high energetically to partake prominently in the deactivation photo-process. The proposed mechanism present in solvated and in vacuo DNA/RNA chromophores validates the intrinsic photostability mechanism through CI-mediated non-radiative processes accompanying the bright excited-state population toward the ground state and subsequent relaxation back to the FC region.
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spelling pubmed-44035982015-05-04 Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate Altavilla, Salvatore F. Segarra-Martí, Javier Nenov, Artur Conti, Irene Rivalta, Ivan Garavelli, Marco Front Chem Chemistry The photophysics and photochemistry of water-solvated guanine monophosphate (GMP) are here characterized by means of a multireference quantum-chemical/molecular mechanics theoretical approach (CASPT2//CASSCF/AMBER) in order to elucidate the main photo-processes occurring upon UV-light irradiation. The effect of the solvent and of the phosphate group on the energetics and structural features of this system are evaluated for the first time employing high-level ab initio methods and thoroughly compared to those in vacuo previously reported in the literature and to the experimental evidence to assess to which extent they influence the photoinduced mechanisms. Solvated electronic excitation energies of solvated GMP at the Franck-Condon (FC) region show a red shift for the ππ(*) L(a) and L(b) states, whereas the energy of the oxygen lone-pair nπ(*) state is blue-shifted. The main photoinduced decay route is promoted through a ring-puckering motion along the bright lowest-lying L(a) state toward a conical intersection (CI) with the ground state, involving a very shallow stationary point along the minimum energy pathway in contrast to the barrierless profile found in gas-phase, the point being placed at the end of the minimum energy path (MEP) thus endorsing its ultrafast deactivation in accordance with time-resolved transient and photoelectron spectroscopy experiments. The role of the nπ(*) state in the solvated system is severely diminished as the crossings with the initially populated L(a) state and also with the L(b) state are placed too high energetically to partake prominently in the deactivation photo-process. The proposed mechanism present in solvated and in vacuo DNA/RNA chromophores validates the intrinsic photostability mechanism through CI-mediated non-radiative processes accompanying the bright excited-state population toward the ground state and subsequent relaxation back to the FC region. Frontiers Media S.A. 2015-04-20 /pmc/articles/PMC4403598/ /pubmed/25941671 http://dx.doi.org/10.3389/fchem.2015.00029 Text en Copyright © 2015 Altavilla, Segarra-Martí, Nenov, Conti, Rivalta and Garavelli. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Chemistry
Altavilla, Salvatore F.
Segarra-Martí, Javier
Nenov, Artur
Conti, Irene
Rivalta, Ivan
Garavelli, Marco
Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate
title Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate
title_full Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate
title_fullStr Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate
title_full_unstemmed Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate
title_short Deciphering the photochemical mechanisms describing the UV-induced processes occurring in solvated guanine monophosphate
title_sort deciphering the photochemical mechanisms describing the uv-induced processes occurring in solvated guanine monophosphate
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4403598/
https://www.ncbi.nlm.nih.gov/pubmed/25941671
http://dx.doi.org/10.3389/fchem.2015.00029
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