On the role of spectral and spatial antenna inhomogeneity in the process of excitation energy trapping in photosynthesis

Abstract

This paper addresses the temperature dependence of the rate and quantum yield of energy trapping by reaction centres (RCs) in the purple bacterium Rhodospirillum rubrum. A simple kinetic model is presented which takes into account the spectral inhomogeneity of the light-harvesting antenna. The description of the excitation decay kinetics at room temperature, using the excitation migration rate extracted from the singlet-singlet annihilation, indicates that the distance between the RC and the antenna is approximately 1.8 times the lattice spacing of the antenna (assuming a square lattice model). The spectral inhomogeneity of the light-harvesting antenna, as shown by the experimental data, becomes important only at low temperature (less than 100 K). The present model enables us to explain the kinetic measurements at various temperatures (300—4 K) and various initial states of the RCs and is consistent with the results from singlet-singlet annihilation measurements.