Optical properties, excitation energy and primary charge transfer in photosystem II: Theory meets experiment

In this review we discuss structure–function relationships of the core complex of photosystem II, as uncovered from analysis of optical spectra of the complex and its subunits. Based on descriptions of optical difference spectra including site directed mutagenesis we propose a revision of the multimer model of the symmetrically arranged reaction center pigments, described by an asymmetric exciton Hamiltonian. Evidence is provided for the location of the triplet state, the identity of the primary electron donor, the localization of the cation and the secondary electron transfer pathway in the reaction center. We also discuss the stationary and time-dependent optical properties of the CP43 and CP47 subunits and the excitation energy transfer and trapping-by-charge-transfer kinetics in the core complex.

► Structure-function relationships of photosystem II are uncovered.
► An asymmetric exciton model is proposed.
► Evidence is provided for the identity of functional states.
► The light-harvesting is shown to be transfer-to-the-trap limited.