Origin of non-conservative circular dichroism of the CP29 antenna complex of photosystem II

Abstract

The origin of the non-conservative nature of the circular dichroism spectrum of the CP29 light-harvesting complex in the Q_y spectral region is investigated. A structure-based Hamiltonian of coupled Q_y transitions, determined previously [Müh et al., Phys. Chem. Chem. Phys., 2014, 16, 11848] is extended by including higher excited states of the chlorophylls and the S₀ → S₂ transition of carotenoids. Excitonic couplings are calculated with the Poisson-TrESP method, taking into account dipole strengths from experiments on isolated pigments. The coupling between Q_y and higher excited states is found to be responsible for the major part of the non-conservativity of the CD spectrum. The remaining part is explained by the intrinsic CD of the chlorophylls that has been estimated from experiments on isolated pigments.