期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 20, 期 26, 页码 8106-8115出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201400065
关键词
density functional calculations; DNA; excited states; optical spectra; quadruplex
资金
- MIUR
- French Agency for Research [ANR-12-BS08-0001-01]
- Agence Nationale de la Recherche (ANR) [ANR-12-BS08-0001] Funding Source: Agence Nationale de la Recherche (ANR)
Herein, a full quantum mechanical study, in solution, of several models of guanine-quadruplex helices, both parallel and antiparallel, containing up to eight guanine residues, in their electronic excited state is reported. By exploiting TD-DFT calculations and including solvent effects by the polarizable continuum model, we provide the first atomistic description of the processes triggered by the absorption of UV light, reproducing and assigning the experimental optical and electronic circular dichroism spectra. The absorbing excited states are delocalized over multiple bases, whereas emission involves a stacked guanine dimer or a monomer. Several states, with a varying degree of localization and charge-transfer character, rule the photoexcited dynamics, which are deeply affected by the quadruplex topology. The lowest excited-state minimum for parallel quadruplex is an asymmetric excimer involving two stacked guanines, with a small charge transfer character, whereas for the anti-parallel structure, with the same topology of the thrombin binding aptamer, it is a fully symmetric excimer, characterized by a strong decrease of the stacking distance. A monomer-like decay path is the most relevant nonradiative decay pathway. Insights on the effect of the ions (K+ or Na+) on the excited state decay are also provided.
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