On the energy transfer between quasi-degenerate states with uncorrelated site distribution functions: An application to the CP43 complex of Photosystem II

The possible influence of excitation energy transfer on various spectra observable in hole burning (HB) experiments has been analyzed for pigments with quasi-degenerate absorption bands with uncorrelated site distribution functions. It was shown that ignoring this influence can lead to incorrect interpretation of experimental results. Application of the model is demonstrated for the CP43 core antenna complex of plant Photosystem II, which possesses two quasi-degenerate lowest-energy states [Jankowiak et al., J. Phys. Chem. B 104 (2000) 11805]. According to the model, bands A and B observed in HB experiments do not truly represent the whole absorption bands of the two lowest-energy states in CP43. Assuming that the sample can be represented as a sum of the sub-ensembles of the CP43 complexes where one or another state is the lowest-energy one (and therefore is incapable of downhill energy transfer), bands A and B are the lowest-energy bands of these sub-ensembles. With this restriction, the model allows for fast energy transfer between the two lowest-energy chromophores (states) in CP43. It is shown that the transient and persistent HB spectra of the isolated CP43 complexes are in good agreement with the model.