CHAPTER 5. Tracking Excited Electronic States in DNA From Formation to Deactivation

Hanes, A.; Zhang, Yuyuan; Kohler, Bern

doi:10.1039/9781839165580-00077

“…A series of articles published since the beginning of this century [ 1 , 2 , 3 , 4 , 5 ] showed that time-resolved fluorescence spectroscopy (TRFS) is a very sensitive tool for studying excited state relaxation in DNA duplexes, despite their extremely low fluorescence quantum yields ϕ, which is of the order of 10 −4 . Compared to transient absorption spectroscopy, probing strongly populated excited states [ 4 , 6 , 7 , 8 , 9 ], fluorescence spectroscopy is capable of detecting emission related to minor populations, that evolve along different deactivation routes. Thus, for all the studied DNA duplexes, TRFS has revealed the existence of long-lived excited states decaying on the nanosecond timescale, while those monitored by transient absorption decay on the sub-ns timescale.…”

Section: Introductionmentioning

confidence: 99%

High-Energy Long-Lived Emitting Mixed Excitons in Homopolymeric Adenine-Thymine DNA Duplexes

Vayá

¹

,

Gustavsson

²

,

Markovitsi

³

2022

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The publication deals with polymeric pA●pT and oligomeric A20●T20 DNA duplexes whose fluorescence is studied by time-correlated single photon counting. It is shown that their emission on the nanosecond timescale is largely dominated by high-energy components peaking at a wavelength shorter than 305 nm. Because of their anisotropy (0.02) and their sensitivity to base stacking, modulated by the duplex size and the ionic strength of the solution, these components are attributed to mixed ππ*/charge transfer excitons. As high-energy long-lived excited states may be responsible for photochemical reactions, their identification via theoretical studies is an important challenge.

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Circularly Polarized Light Probes Excited‐State Delocalization in Rectangular Ladder‐type Pentaphenyl Helices

Ammenhaeuser

¹

,

Klein

²

,

Schmid

³

et al. 2022

Angewandte Chemie

2

0

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Ladder-type pentaphenyl chromophores have a rigid, planar π-system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro-linked ladder-type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born-Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

show abstract

Circularly Polarized Light Probes Excited‐State Delocalization in Rectangular Ladder‐type Pentaphenyl Helices

Ammenhaeuser

¹

,

Klein

²

,

Schmid

³

et al. 2022

View full text Add to dashboard Cite

Ladder-type pentaphenyl chromophores have a rigid, planar π-system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro-linked ladder-type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born-Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

show abstract

CHAPTER 5. Tracking Excited Electronic States in DNA From Formation to Deactivation

Cited by 3 publications

References 0 publications

High-Energy Long-Lived Emitting Mixed Excitons in Homopolymeric Adenine-Thymine DNA Duplexes

High-Energy Long-Lived Emitting Mixed Excitons in Homopolymeric Adenine-Thymine DNA Duplexes

Circularly Polarized Light Probes Excited‐State Delocalization in Rectangular Ladder‐type Pentaphenyl Helices

Circularly Polarized Light Probes Excited‐State Delocalization in Rectangular Ladder‐type Pentaphenyl Helices

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