Excited State Proton Transfer Is Not Involved in the Ultrafast Deactivation of Guanine–Cytosine Pair in Solution

Biemann, Lars; Kovalenko, Sergey A.; Kleinermanns, Karl; Mahrwald, Rainer; Markert, Morris; Improta, Roberto

doi:10.1021/ja2089734

Cited by 56 publications

(49 citation statements)

References 23 publications

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“…In solution with polar solvents, the SDHT mechanism is presumably altered inactivating the internal conversion channel which brings the WC GC base pair back to its ground state equilibrium structure or to new tautomeric configurations. 96 However, the DNA-embedded GC dimer studied by the QM/MM computational approach manifests the same qualitative behavior for the double proton/hydrogen-transfer processes as in vacuo. This supports experimental observations 86,90,91 and previous theoretical predictions 85,93 pointing out to the proton/hydrogen-transfer as a relevant process in the photochemistry of DNA duplexes.…”

Section: Summary and Concluding Remarksmentioning

confidence: 86%

“…89 In this line, a combined experimental and time-dependent density functional theory (TD-DFT) study on the GC base pair in solution with CHCl 3 has also pointed out to a non-efficient process in solution. 96 The authors of this work have also suggested that the photoinduced hydrogen transfer cannot be considered as a relevant deactivation path in DNA. However, the most recent experiments from de La Harpe et al have reported pronounced isotope effects on the long-lived exciplex excited states of a d(GC) 9 ·d(GC) 9 double-strand, 91 in agreement with independent studies by Doorley et al 90 In this scenario, a model based on the fully characterization of the energy-decay channels involving proton/hydrogen transfer in the GC base pair seems timely in order to establish the operative mechanisms for photostability and tautomerism and to shed some light into the relevance of basepairing in the photodynamics of DNA.…”

Section: Introductionmentioning

confidence: 87%

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Proton/Hydrogen Transfer Mechanisms in the Guanine–Cytosine Base Pair: Photostability and Tautomerism

Sauri

Gobbo

Serrano-Pérez

et al. 2012

J. Chem. Theory Comput.

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Proton/hydrogen-transfer processes have been broadly studied in the last fifty years to explain the photostability and the spontaneous tautomerism in the DNA base pairs. In the present study, the CASSCF/CASPT2 methodology is used to map the two-dimensional potential energy surfaces along the stretched NH reaction coordinates of the guanine-cytosine (GC) base pair. Concerted and stepwise pathways are explored initially in vacuo and three mechanisms are studied: the stepwise double proton transfer, the stepwise double hydrogen transfer, and the concerted double proton transfer. The results are consistent with previous findings related to the photostability of the GC base pair and a new contribution to tautomerism is provided. The C-based imino-oxo and imino-enol GC tautomers, which can be generated during the UV irradiation of the Watson-Crick base pair, have analogous radiationless energy-decay channels to those of the canonical base pair. In addition, the C-based imino-enol GC tautomer is thermally less stable. A study of the GC base pair is carried out subsequently taking into account the DNA surroundings in the biological environment. The most important stationary points are computed using the quantum mechanics/molecular mechanics (QM/MM) approach, suggesting a similar scenario for the proton/hydrogen-transfer phenomena in vacuo and DNA. Finally, the static model is complemented by ab initio dynamic simulations, which show that vibrations at the hydrogen bonds can indeed originate hydrogen-transfer processes in the GC base pair. The relevance of the present findings for the rationalization of the preservation of the genetic code and mutagenesis is discussed.

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Section: Summary and Concluding Remarksmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 87%

Proton/Hydrogen Transfer Mechanisms in the Guanine–Cytosine Base Pair: Photostability and Tautomerism

Sauri

Gobbo

Serrano-Pérez

et al. 2012

J. Chem. Theory Comput.

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“…[11][12][13][14][15] In spectroscopic experiments, the effect of hydrogen bonding on the excited-state lifetime of the base pairs has been of great interest. [16][17][18][19][20][21][22][23][24][25][26] In the present work, excited-state potential energy profiles of the Watson-Crick form of the guaninecytosine (GC) base pair are theoretically studied for all of the potentially competing reactions mentioned above: SPT and DPT between guanine (G) and cytosine (C) as well as nonradiative decay in each single base under hydrogen bonding. One purpose of this study is to assess the favorability of the decay process in the G monomer with hydrogen-bonded to C, which was rarely discussed in previous studies.…”

Section: Introductionmentioning

confidence: 99%

Photoreaction channels of the guanine–cytosine base pair explored by long-range corrected TDDFT calculations

Yamazaki

Taketsugu

2012

Phys. Chem. Chem. Phys.

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Electronic supplementary information (ESI) available: vertical excitation energies calculated with basis sets of double-zeta plus polarization quality, and additional figures of potential energy profiles. 2 AbstractPhotoinduced processes in the Watson-Crick guanine-cytosine base pair are comprehensively studied by means of long-range corrected (LC) TDDFT calculations of potential energy profiles using the LC-BLYP and CAM-B3LYP functionals. The ab initio CC2 method and the conventional TDDFT method with the B3LYP functional are also employed to assess the reliability of the LC-TDDFT method. The present approach allows us to compare the potential energy profiles at the same computational level for excited-state reactions of the base pair, including single and double proton transfer between the bases and nonradiative decay via ring puckering in each base. In particular, long-range correction to the TDDFT method is critical for a qualitatively correct description of the proton transfer reactions. The calculated energy profiles exhibit low barriers for out-of-plane deformation of the guanine moiety in the locally-excited state, which is expected to lead to a conical intersection with the ground state, as well as for single proton transfer from guanine to cytosine with the well-known electron-driven proton transfer mechanism. Thus the present results suggest that both processes can compete in hydrogen-bonded base pairs and play a significant role in the mechanism of photostability.3

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“…TD-DFT calculations also indicate that even a weakly polar solvent can dramatically alter the energetics of the relevant excited states, leading to a barrier to PT not seen in the gas-phase calculations [178]. Significantly, long-lived excited states with lifetimes of~20 ps are readily observed in a variety of duplexes formed from GC base pairs [180].…”

Section: Single Base Pairsmentioning

confidence: 98%

“…More recent experiments on single base pairs in chloroform have revealed dynamics resembling those of a monomer and failed to document ultrafast PT [70,178,179]. TD-DFT calculations also indicate that even a weakly polar solvent can dramatically alter the energetics of the relevant excited states, leading to a barrier to PT not seen in the gas-phase calculations [178].…”

Section: Single Base Pairsmentioning

confidence: 99%

Excited States in DNA Strands Investigated by Ultrafast Laser Spectroscopy

Chen

Zhang

Kohler

2014

Photoinduced Phenomena in Nucleic Acids II

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Ultrafast laser experiments on carefully selected DNA model compounds probe the effects of base stacking, base pairing, and structural disorder on excited electronic states formed by UV absorption in single and double DNA strands. Direct π-orbital overlap between two stacked bases in a dinucleotide or in a longer single strand creates new excited states that decay orders of magnitude more slowly than the generally subpicosecond excited states of monomeric bases. Half or more of all excited states in single strands decay in this manner. Ultrafast mid-IR transient absorption experiments reveal that the long-lived excited states in a number of model compounds are charge transfer states formed by interbase electron transfer, which subsequently decay by charge recombination. The lifetimes of the charge transfer states are surprisingly independent of how the stacked bases are oriented, but disruption of π-stacking, either by elevating temperature or by adding a denaturing co-solvent, completely eliminates this decay channel. Time-resolved emission measurements support the conclusion that these states are populated very rapidly from initial excitons. These experiments also reveal the existence of populations of emissive excited states that decay on the nanosecond time scale. The quantum yield of these states is very small for UVB/UVC excitation, but increases at UVA wavelengths. In double strands, hydrogen bonding between bases perturbs, but does not quench, the long-lived excited states. Kinetic isotope effects on the excited-state dynamics suggest that intrastrand electron transfer may couple to interstrand proton transfer. By revealing how structure and non-covalent interactions affect excited-state dynamics, on-going experimental and theoretical studies of excited states in DNA strands can advance understanding of fundamental photophysics in other nanoscale systems.

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Excited State Proton Transfer Is Not Involved in the Ultrafast Deactivation of Guanine–Cytosine Pair in Solution

Cited by 56 publications

References 23 publications

Proton/Hydrogen Transfer Mechanisms in the Guanine–Cytosine Base Pair: Photostability and Tautomerism

Proton/Hydrogen Transfer Mechanisms in the Guanine–Cytosine Base Pair: Photostability and Tautomerism

Photoreaction channels of the guanine–cytosine base pair explored by long-range corrected TDDFT calculations

Excited States in DNA Strands Investigated by Ultrafast Laser Spectroscopy

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