Tracking the origin of photostability in purine nucleobases: the photophysics of 2-oxopurine

Martínez‐Fernández, Lara; Arslancan, Serra; Ivashchenko, Dmytro A.; Crespo‐Hernández, Carlos E.; Corral, Inés

doi:10.1039/c9cp00879a

Cited by 17 publications

(47 citation statements)

References 58 publications

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“…Vast experimental and computational evidence have been presented demonstrating that minor chemical modifications of the pyrimidine and purine core can significantly alter the electronic relaxation pathways by modifying the topology of their excited state potential energy surfaces. [4][5][6][7][8][9][10][11][12][13][14][15] Depending on the specific site of modification on the core, access to specific conical intersections can be made less favorable, often resulting in higher yields of longer-lived excited states and a decrease in photostability. Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

Krul¹,

Hoehn²,

Feierabend³

et al. 2021

Preprint

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Minor structural modifications to the DNA and RNA nucleobases have a significant effect on their excited state dynamics and electronic relaxation pathways. In this study, the excited state dynamics of 7-deazaguanosine and guanosine 5’-monophosphate are investigated in aqueous and in a mixture of methanol and water using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient spectra are collected using photon densities that ensure no parasitic multiphoton-induced signal from solvated electrons. The data can be fit satisfactorily using a two- or three-component kinetic model. By analyzing the results from steady-state, time-resolved, computational calculations, and the methanol-water mixture, the following general relaxation mechanism is proposed for both molecules, Lb ® La ® 1ps*(ICT) ® S0, where the 1ps*(ICT) stands for an intramolecular charge transfer excited singlet state with significant ps* character. In general, longer lifetimes for internal conversion are obtained for 7-deazaguanosine compared to guanosine 5’-monophosphate. Internal conversion of the 1ps*(ICT) state to the ground state occurs on a similar time scale of a few picoseconds in both molecules. Collectively, the results demonstrate that substitution of a single nitrogen for a methine (C-H) group at position seven of the guanine moiety stabilizes the 1pp* Lb and La states and alter the topology of their potential energy surfaces in such a way that the relaxation dynamics in 7-deazaguanosine are slowed down compared to those in guanosine 5’-monophosphate but not for the internal conversion of 1ps*(ICT) state to the ground state.

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Section: Introductionmentioning

confidence: 99%

Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

Krul¹,

Hoehn²,

Feierabend³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

Krul¹,

Hoehn²,

Feierabend³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Minor structural modifications to the DNA and RNA nucleobases have a significant effect on their excited state dynamics and electronic relaxation pathways. In this study, the excited state dynamics of 7-deazaguanosine and guanosine 5’-monophosphate are investigated in aqueous solution using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient absorption spectra are collected under experimental conditions that eliminate the requirement to correct the data for the formation of hydrated electrons, resulting from the two-photon ionization of the solvent. The data is fitted satisfactorily using a two-component sequential kinetic model, yielding lifetimes of 210 ± 50 fs and 1.80 ± 0.02 ps, and 682 ± 40 fs and 1.4 ± 0.03 ps, for 7-deazaguanosine and guanosine 5’-monophosphate, respectively. By analyzing the results from steady-state, time-resolved, and computational calculations, the following relaxation mechanism is proposed for 7-deazaguanosine, S2(Lb) ® S1(La) ® S0, whereas a S2(Lb) ® S1(La) ® S0(hot) ® S0 relaxation mechanism is proposed for guanosine 5’-monophosphate. Interestingly, longer lifetimes for both the Lb ® La and the La ® S0 internal conversion pathways are obtained for 7-deazaguanosine compare to guanosine 5’-monophosphate. Collectively, the results demonstrate that substitution of a single nitrogen for a methine (C-H) group at position seven of the guanine moiety stabilizes the 1pp* Lb and La states and alters the topology of their potential energy surfaces in such a way that the population dynamics of both internal conversion pathways in 7-deazaguanosine are significantly slowed down compared to those in guanosine 5’-monophosphate.

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“…When the photoinduced behavior of a chromophore is theoretically investigated, for example, by computing the potential‐energy curves that connect different stationary points 14–16 or by evolving dynamic trajectories, 17–20 it is usually necessary to compare excitation energies or other electronic properties for different geometries of the chromophore. This is also the case when the absorption spectrum is calculated by considering an ensemble of geometries which are generated by, e.g., molecular dynamic (MD) simulations 21–26 .…”

Section: Introductionmentioning

confidence: 99%

An algorithm to correct for the CASSCF active space in multiscale QM/MM calculations based on geometry ensembles

Cárdenas

Nogueira

2020

Int J of Quantum Chemistry

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When the excitation energies of an ensemble of geometries, computed by the complete active space self‐consistent field (CASSCF) or other CAS‐based methods, are convoluted to obtain the absorption spectrum, it is advisable that all the considered geometries have the same molecular orbitals within the active space. In this work, we present an algorithm that evaluates the molecular orbital overlap matrix between a previously selected reference geometry, with the desired active space, and each of the sampled geometries. Based on the value of the overlap matrix elements, the algorithm determines whether one or more pairs of molecular orbitals of the sampled geometry have to be swapped for a subsequent CASSCF calculation. We have applied the developed algorithm to CASSCF and CASPT2 calculations for sets of geometries of the five canonical nucleobases in vacuum and in aqueous solvent. The algorithm shows a very good efficacy since it recovered the correct active space for 90% of the geometries which presented undesired molecular orbitals in the active space after the first CASSCF wavefunction optimization. In addition, the importance of having the same orbitals within the active space for all the geometries is discussed based on the corrected and uncorrected density of states for the nucleobases.

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Tracking the origin of photostability in purine nucleobases: the photophysics of 2-oxopurine

Abstract: Molding purine PES through functionalization: whilst purine C2-substitution maintains the features of the spectroscopic PES of the heterocycle, C6-functionalization reshapes its topography leading to photostable systems.

Cited by 17 publications

References 58 publications

Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

An algorithm to correct for the CASSCF active space in multiscale QM/MM calculations based on geometry ensembles

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