The Excited‐State Lifetimes in a G⋅C DNA Duplex are Nearly Independent of Helix Conformation and Base‐Pairing Motif

Harpe, Kimberly de La; Crespo‐Hernández, Carlos E.; Kohler, Bern

doi:10.1002/cphc.200900004

Cited by 23 publications

(35 citation statements)

References 44 publications

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“…We judge that the reproducibility of successive signals recorded for the same solution is a better criterion than changes in the absorbance of the sample (Fig. SI-2), used in transient absorption measurements of similar systems [8] . nm, before (blue) and after (green) irradiation with 267 nm laser pulses having an intensity 0.5 GW/cm 2 .…”

Section: Experimental Setups and Methodsmentioning

confidence: 99%

“…The detailed nature of these states is still under debate [1][2][3][4][5][6] . However, based on results from transient absorption measurements performed for short helices at selected wavelengths, the following picture has been proposed [6][7][8] . The initially populated * states relax within 100 fs to energetically low-lying excimers or exciplexes decaying with time constants up to ca.…”

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confidence: 99%

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High‐Energy Long‐Lived Excited States in DNA Double Strands

et al. 2010

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Section: Experimental Setups and Methodsmentioning

confidence: 99%

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confidence: 99%

High‐Energy Long‐Lived Excited States in DNA Double Strands

et al. 2010

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“…The Quinn group [350] reported that the nonradiative decay takes longer for the Z-form than for the B-form of poly (dCdG)·poly(dGdC), with experimental monoexponential time constants of 16-20 ps. By contrast, the Kohler group [351] reported that the experimentally observed nonradiative decay lifetime of (dCdG) 9 ·(dGdC) 9 is independent of the helix conformation (also in the region of several picoseconds). These findings call for theoretical studies on Z-DNA to check whether the established theoretical explanations for B-DNA photodynamics carry over to the more loosely stacked Z-DNA strands.…”

Section: Other Helical Conformations and Modified Strandsmentioning

confidence: 91%

Computational Modeling of Photoexcitation in DNA Single and Double Strands

Lü

Lan

Thiel

2014

Topics in Current Chemistry

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The photoexcitation of DNA strands triggers extremely complex photoinduced processes, which cannot be understood solely on the basis of the behavior of the nucleobase building blocks. Decisive factors in DNA oligomers and polymers include collective electronic effects, excitonic coupling, hydrogen-bonding interactions, local steric hindrance, charge transfer, and environmental and solvent effects. This chapter surveys recent theoretical and computational efforts to model real-world excited-state DNA strands using a variety of established and emerging theoretical methods. One central issue is the role of localized vs delocalized excitations and the extent to which they determine the nature and the temporal evolution of the initial photoexcitation in DNA strands.

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“…AT base pairing measurably affects nonradiative decay rates in AT duplexes, but other experiments have shown that excimer lifetimes are insensitive to base-pairing motif and helix conformation [184]. de La Harpe et al studied a d(GC) 9 · d(GC) 9 duplex by fs-TA spectroscopy [184].…”

Section: Long-lived Excited States and Helix Conformationmentioning

confidence: 98%

“…de La Harpe et al studied a d(GC) 9 · d(GC) 9 duplex by fs-TA spectroscopy [184]. This self-complementary DNA duplex adopts different conformations in solution depending on the ionic strength and pH, allowing the effect of different base stacking motifs on excited-state dynamics to be studied in a system of constant base sequence.…”

Section: Long-lived Excited States and Helix Conformationmentioning

confidence: 98%

Excited States in DNA Strands Investigated by Ultrafast Laser Spectroscopy

Chen

Zhang

Kohler

2014

Topics in Current Chemistry

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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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The Excited‐State Lifetimes in a G⋅C DNA Duplex are Nearly Independent of Helix Conformation and Base‐Pairing Motif

Abstract: DNA photophysics: Femtosecond transient absorption experiments reveal that excited states produced by UV light in a duplex DNA oligonucleotide decay at essentially the same rate in B and Z helix conformers (see figure).

Cited by 23 publications

References 44 publications

High‐Energy Long‐Lived Excited States in DNA Double Strands

High‐Energy Long‐Lived Excited States in DNA Double Strands

Computational Modeling of Photoexcitation in DNA Single and Double Strands

Excited States in DNA Strands Investigated by Ultrafast Laser Spectroscopy

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