Picosecond Transient Infrared Study of the Ultrafast Deactivation Processes of Electronically Excited B‐DNA and Z‐DNA Forms of [poly(dG‐dC)]<sub>2</sub>

Doorley, Gerard W.; McGovern, David A.; George, Michael W.; Towrie, Michael; Parker, Anthony W.; Kelly, John M.; Quinn, Susan J.

doi:10.1002/anie.200803904

Cited by 54 publications

(36 citation statements)

References 31 publications

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“…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. Especially important shall be certain aspects related to the photochemical channels connecting the WC base pair with other tautomeric configurations.…”

Section: Introductionsupporting

confidence: 83%

“…The long-lived exciplexes, as a consequence of π-stacking, are however sensitive to deuterium substitution at the hydrogen bonds, showing therefore that proton/hydrogen transfers are still present. 90,91 Qualitative predictions for these processes can be established from our calculations. At the time of UV irradiation of the GC base pair, those molecules with a certain momentum in the N' 3 …H 1 N 1 direction (for instance, Sim2 and Sim4) might undergo a double hydrogen-transfer process, resulting in the production of the TAU1 configuration or restoring the WC structure.…”

Section: Concerted Double Proton-transfer (Cdpt) Mechanism Sdpt and mentioning

confidence: 77%

“…Despite the fact that the studies on mimetic models of the GC base pair clearly pointed out to an active participation of the proton/hydrogen transfer in the photochemistry of the systems, the relevance of base pairing in the excited-state dynamics of the DNA molecule is still uncertain. 85,86,87,88,89,90,91,92,93,94,95,96 Shortened fluorescence lifetimes in alternating DNA duplexes poly(dGdC)·poly(dGdC) relative to the G and C mononucleotides have been measured experimentally by using fluorescence upconversion spectroscopy, 86 indicating that proton/hydrogen transfer could be relevant, as suggested by theoretical calculations. 85 On the other hand, transient absorption measurements have showed ground-state recovery in the related d(GC) 9 ·d(GC) 9 DNA double strand an order of magnitude slower than in the monomeric nucleotides, suggesting excited-state decays driven by the formation of π-stacked excited-state species (or exciplexes) and not via interstrand proton/hydrogen transfer.…”

Section: Introductionmentioning

confidence: 93%

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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: Introductionsupporting

confidence: 83%

Section: Concerted Double Proton-transfer (Cdpt) Mechanism Sdpt and mentioning

confidence: 77%

Section: Introductionmentioning

confidence: 93%

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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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“…For example, a 30 ps lifetime detected in the infrared absorption spectrum of the poly(dGdC)·poly(dGdC) duplex was assigned to the n* state localized on cytosine. 33 The steady-state fluorescence spectrum of the same duplex is dominated by emission from "dark" states with nanosecond lifetime. 34 Other dark states, * states, have also been proposed to influence the excited state dynamics in the gas phase.…”

Section: Ultrafast and Effective Non-radiative Decay Routes Exist Formentioning

confidence: 99%

DNA/RNA: Building Blocks of Life Under UV Irradiation

Gustavsson

Improta

Markovitsi

2010

J. Phys. Chem. Lett.

183

201

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International audienceDuring the last 10 years, intense experimental and theoretical work has proven the existence of ultrafast nonradiative decay routes for UV-excited monomeric nucleic acid bases, accounting for their high photostability. This mechanism has been explained by the occurrence of easily accessible conical intersections connecting the first excited ππ* state with the ground state. However, recent studies of substituent and solvent effects indicate that the situation is more complicated than what was initially thought, notably by the presence of dark excited states. Moreover, the actual shape of the excited-state potential energy surface may induce nonexponential dynamics. Further efforts are needed in order to clarify how various environmental factors affect the structural and dynamical aspects of the nucleic acid base excited states

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“…This phenomenon has been recently observed in other polymer systems and may be explained by a delocalization of the excess vibrational energy over neighbouring bases in the polymer form. 8 The longer-lived species is assigned to an excimeric excited state. 3 Next the effect of protonation of the poly(G) has been studied in D 2 O.…”

Section: Poly(g) and Poly(gh + )mentioning

confidence: 99%

A study of the pH dependence of electronically excited guanosine compounds by picosecond time-resolved infrared spectroscopy

McGovern

Doorley

Whelan

et al. 2009

Photochem Photobiol Sci

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The photophysical properties of 5¢-guanosine monophosphate (5¢-GMP) and polyguanylic acid {poly(G)} in D 2 O solutions of varying pH have been studied using picosecond transient infrared absorption spectroscopy. Whereas in neutral or weakly alkaline solution only the vibrationally excited electronic ground state of 5¢-GMP is observed, in acidic solution the relatively long-lived (229 ± 20 ps) electronic excited state of protonated 5¢-GMP, which possesses strong absorptions at 1517 and 1634 cm -1 , could be detected. The picosecond transient behaviour of polyguanylic acid in acidic solution is also very different from that of the polynucleotide in neutral solution due not only to the protonation of guanine moieties yielding the protonated excited state but because of the disruption of the guanine stacks which are present in the species in neutral solution.

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Picosecond Transient Infrared Study of the Ultrafast Deactivation Processes of Electronically Excited B‐DNA and Z‐DNA Forms of [poly(dG‐dC)]₂

Cited by 54 publications

References 31 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

DNA/RNA: Building Blocks of Life Under UV Irradiation

A study of the pH dependence of electronically excited guanosine compounds by picosecond time-resolved infrared spectroscopy

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Picosecond Transient Infrared Study of the Ultrafast Deactivation Processes of Electronically Excited B‐DNA and Z‐DNA Forms of [poly(dG‐dC)]2

Cited by 54 publications

References 31 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

DNA/RNA: Building Blocks of Life Under UV Irradiation

A study of the pH dependence of electronically excited guanosine compounds by picosecond time-resolved infrared spectroscopy

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Product

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Picosecond Transient Infrared Study of the Ultrafast Deactivation Processes of Electronically Excited B‐DNA and Z‐DNA Forms of [poly(dG‐dC)]₂