Modeling DNA electronic circular dichroism by QM/MM methods and Frenkel Hamiltonian

We report the modeling of the electronic circular dichroism spectra of different double helix B-DNA sequences. The circular dichroism spectra have been obtained in the framework of the Frenkel excitation theory, while DNA conformational space has been explored using molecular dynamics. Excited states are obtained using hybrid quantum mechanics/molecular mechanics theory at time-dependent density functional theory level. The validity of the effective Frenkel Hamiltonian approach is assessed by comparison with full quantum mechanics treatment of many interacting chromophores. The convergence of the simulated spectra with the number of interacting chromophores is assessed as well as their behavior with respect to experimental results.