Exploring concerted effects of base pairing and stacking on the excited‐state nature of DNA oligonucleotides by DFT and TD‐DFT studies |
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Authors: | Yue‐Jie Ai Gang‐Long Cui Qiu Fang Wei‐Hai Fang Yi Luo |
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Institution: | 1. College of Chemistry, Beijing Normal University, Beijing 100875, China;2. Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, S‐106 91 Stockholm, Sweden |
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Abstract: | We have taken (dA)5, (dT)5, and (dA)5·(dT)5 as model systems to study concerted effects of base pairing and stacking on excited‐state nature of DNA oligonucleotides using density functional theory (DFT) and time dependent DFT methods. The spectroscopic states are determined to be of a partial A → A charge‐transfer nature in the A·T oligonucleotides. The T → T charge‐transfer transitions produce dark states, which are hidden in the energy region of the steady‐state absorption spectra. This is different from the previous assignment that the T → T charge‐transfer transition is responsible for a shoulder at the red side of the first strong absorption band. The A → T charge‐transfer states were predicted to have relatively high energies in the A·T oligonucleotides. The present calculations predict that the T → A charge‐transfer states are not involved in the spectra and excited‐state dynamics of the A·T oligonucleotides. In addition, the influence of base pairing and stacking on the nature of the 1nπ* and 1ππ* states are discussed in detail. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 |
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Keywords: | DNA oligonucleotides DFT excited states |
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