Exploring concerted effects of base pairing and stacking on the excited-state nature of DNA oligonucleotides by DFT and TD-DFT studies

QC 20110520
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 DFTmethods. The spectroscopic states are determined to be of a partial A →A charge transfernature in the A•T oligonucleotides. The T → T charge-transfer transitionsproduce dark states, which are hidden in the energy region of the steady-stateabsorption spectra. This is different from the previous assignment that the T → Tcharge-transfer transition is responsible for a shoulder at the red side of the first strongabsorption band. The A →T charge-transfer states were predicted to have relativelyhigh 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 ofthe A•T oligonucleotides. In addition, the influence of base pairing and stacking on thenature of the 1nΠ* and 1ΠΠ* states are discussed in detail.

In:International Journal of Quantum Chemistry: Wiley111:10, s. 2366-23770020-76081097-461X

By the author/editor: Ai, Yuejie, 1982 ...; Cui, Ganglong, 1 ...; Fang, Qiu; Fang, Weihai; Luo, Yi

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