Excited Electronic States of DNA

Eisinger, J.; Shulman, R. G.

doi:10.1126/science.161.3848.1311

Cited by 138 publications

(101 citation statements)

References 43 publications

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“…23 The emission of DNA in its polymeric form has been attributed to excimers that give rise to broad, featureless spectra like those we observe. 23,40 We, therefore, speculate that the main contributor to the emission observed for our samples is a 1 G*G excimer. On the basis of this assignment, the sequence, base-stacking, and structural heterogeneity for each quadruplex structure is expected to impact the excited-state and energy transfer properties of the system with effects, ultimately, on the intensity of the steadystate fluorescence spectrum.…”

Section: Discussionmentioning

confidence: 70%

Fluorescence of unmodified oligonucleotides: A tool to probe G‐quadruplex DNA structure

Méndez

Szalai

2009

Biopolymers

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Fluorescence of unmodified oligonucleotides has not been exploited for guanine‐quadruplex (G‐quadruplex) characterization. We observe that G‐rich sequences fluoresce more strongly than duplex or single‐stranded DNA but much more weakly than fluorophores like fluorescein. This increase in the intrinsic fluorescence is not due to an increase in absorption at the excitation wavelength but rather to a change in the quantum yield. We show that unlabeled oligonucleotides that form G‐quadruplexes can be differentiated on the basis of their emission spectra from similar sequences that do not contain consecutive guanines. Intermolecular quadruplexes formed by the oligonucleotides 5′‐T4GnT4‐3′ (n = 4–10) display a nonlinear, but continuous, increase in emission intensity as the G content increases. The sequence 5′‐GGGT‐3′, which has been proposed to form a monomeric quadruplex and an interlocked quadruplex (Krishnan‐Ghosh et al. J Am Chem Soc 2004, 126, 11009), was compared with the similar sequence 5′‐TGGG‐3′, the structure of which has not been characterized. Both the maximum emission intensity and the spectral shape differ for these oligonucleotides as a function of sample preparation, indicating that different types of quadruplexes form for both sequences. Our work is the first to demonstrate that the suprastructure of G‐rich sequences can be probed using fluorescence signatures of unmodified oligonucleotides. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 841–850, 2009.This article was originally published online as an accepted preprint. The ”Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

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Section: Discussionmentioning

confidence: 70%

Fluorescence of unmodified oligonucleotides: A tool to probe G‐quadruplex DNA structure

Méndez

Szalai

2009

Biopolymers

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“…3 Since those features are not observed in the experimental absorption spectra of DNA, which instead closely resemble the sum of the spectra of the constituent bases, the hypothesis of localized excited states prevailed 5 and guided subsequent studies dealing with the photophysics and the photochemistry of DNA.…”

Section: Old Questions Recent Approachesmentioning

confidence: 99%

Excited states and energy transfer among DNA bases in double helices

Markovitsi

Gustavsson

Talbot

2007

Photochem Photobiol Sci

108

174

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Abstract:The study of excited states and energy transfer in DNA double helices has recently gained new interest connected to the development of computational techniques and that of femtosecond spectroscopy. The present article points out contentious questions regarding the nature of the excited states and the occurrence of energy transfer and shows how they are currently approached. Using as example the polymer poly(dA).poly(dT), composed of about 2000 adenine-thymine pairs, a model is proposed on the basis of time-resolved measurements (fluorescence decays, fluorescence anisotropy decays and fluorescence spectra, obtained with femtosecond resolution), associated to steady-state spectra. According to this qualitative model, excitation at 267 nm populates excited states that are delocalized over a few bases (excitons). Ultrafast internal conversion directs the excited state population to the lower part of the exciton band giving rise to fluorescence. Questions needing further investigations, both theoretical and experimental, are underlined with particular emphasis on delicate points related to the complexity and the plasticity of these systems.

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“…[7][8][9] At the same time, they predicted that the formation of exciton states induces large spectral shifts and a visible splitting of the absorption band around 260 nm. 8 Since those features are not observed in the experimental absorption spectra of DNA, which were found to closely resemble the sum of the spectra of the constituent bases, the hypothesis of localized excited states prevailed 10 and guided subsequent studies dealing with the photophysics and the photochemistry of DNA. The possibility of excitation delocalization having been ruled out, any difference in the spectra or the excited state reactivity between double-stranded and monomeric nucleic acids was implicitly attributed to the influence of the local environment.…”

Section: Introductionmentioning

confidence: 99%

Exciton States of Dynamic DNA Double Helices: Alternating dCdG Sequences

et al. 2005

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The present communication deals with the excited states of the alternating DNA oligomer (dCdG) 5 .(dCdG) 5 which correspond to the UV absorption band around 260 nm.Their properties are studied in the frame of the exciton theory, combining molecular dynamics simulations and quantum chemistry data. It is shown that the dipolar coupling undergoes important variations with the site and the helix geometry. In contrast, the energy of the monomer transitions within the double helix is not sensitive to the local environment. It is thus considered to be distributed over Gaussian curves whose maximum and width are derived from the experimental absorption spectra of nucleosides in aqueous solution. The influence of the spectral width on the excited states delocalization and the absorption spectra is much stronger than that of the oligomer plasticity. About half of the excited states are delocalized over at least two bases. Many of them result from mixing of different monomer states and extend on both strands. The trends found in the simulated spectra, when going from noninteracting monomers to the duplex, are in agreement with experimental observations. Conformational changes enhance the diversity of the states which can be populated upon excitation at a given energy. The states with larger spatial extent are located close to the maximum of the absorption spectrum.

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Excited Electronic States of DNA

Cited by 138 publications

References 43 publications

Fluorescence of unmodified oligonucleotides: A tool to probe G‐quadruplex DNA structure

Fluorescence of unmodified oligonucleotides: A tool to probe G‐quadruplex DNA structure

Excited states and energy transfer among DNA bases in double helices

Exciton States of Dynamic DNA Double Helices: Alternating dCdG Sequences

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