Studies of the photophysical properties of oligonucleotides and their chromophores can lead to a better understanding of DNA photodegradation which causes cell damage, mutation, and cancer. These systems also serve as model systems to further our knowledge of complex photodynamics. In order to understand the nature of photoinitiated processes in oligonucleotides fully a complete understanding of environmental effects is essential. QM/MM simulations are performed using the algebraic diagrammatic construction through second order level of theory method (ADC(2)) to describe the excited states of an adenine dimer embedded in an oligomer. A system of ~50,000 atoms is utilized to model the influence of the environment on the photophysical behavior of π-stacked adenine in a strand of (dA)20(dT)20 in solution. In this work, we examine the nature of initial absorption in an ensemble of about 200 configurations1 and the subsequent photodecay of the excited states. The results of our studies reveal that, although pure charge-transfer excited states exist at the high energy end of the absorption spectrum, states of mixed excitonic and charge transfer character exist at lower energies in the Franck Condon region. Our calculations show that these mixed states decay to excimers and bonded excimers2 which may prolong the decay lifetime in this system, as has been observed experimentally.3 These results also suggest that similar wavefunction character may contribute to the photochemical behavior of other nucleobases. References: [1] Vincent A. Spata and Spiridoula Matsika, J. Phys. Chem. A. ASAP DOI: 10.1021/jp507520c [2] Vincent A. Spata and Spiridoula Matsika, J. Phys. Chem. A. 2013, 117, 8718-8728. [3] Middleton, C. T.; de La Harpe, K.; Su, C.; Law, Y. K.; Crespo-Hernández, C. E.; Kohler, B. Annu. Rev. Phys. Chem. 2009, 60, 217-239.

QM/MM simulations reveal the involvement of excimers in the photophysics of adenine based oligonucleotides

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.