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Issue 46, 2015
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Photophysical deactivation pathways in adenine oligonucleotides

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Abstract

In this work we study deactivation processes in adenine oligomers after absorption of UV radiation using Quantum Mechanics combined with Molecular Mechanics (QM/MM). Correlated electronic structure methods appropriate for describing the excited states are used to describe a π-stacked dimer of adenine bases incorporated into (dA)20(dT)20. The results of these calculations reveal three different types of excited state minima which play a role in deactivation processes. Within this set of minima there are minima where the excited state is localized on one adenine (monomer-like) as well as minima where the excited state is delocalized on two adenines, forming different types of excimers and bonded excimers of varying but inter-related character. The proximity of their energies reveals that the minima can decay into one another along a flat potential energy surface dependent on the interbase separation. Additionally, analysis of the emissive energies and other physical properties, including theoretical anisotropy calculations, and comparison with fluorescence experiments, provides evidence that excimers play an important role in long-lived signals in adenine oligonucleotides while the subpicosecond decay is attributed to monomer-like minima. The necessity for a close approach of the nucleobases reveals that the deactivation mechanism is tied to macro-molecular motion.

Graphical abstract: Photophysical deactivation pathways in adenine oligonucleotides

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Supplementary files

Article information


Submitted
21 Jul 2015
Accepted
27 Oct 2015
First published
28 Oct 2015

Phys. Chem. Chem. Phys., 2015,17, 31073-31083
Article type
Paper

Photophysical deactivation pathways in adenine oligonucleotides

V. A. Spata and S. Matsika, Phys. Chem. Chem. Phys., 2015, 17, 31073
DOI: 10.1039/C5CP04254B

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