Fluctuating antenna model: Applications and prospects

Abstract

Recently, we proposed a simple conceptual fluctuating antenna model (FAM), describing excitation diffusion and trapping in a continuous medium, where variations of the excitation transfer pathways are taken into account by the introduced fractional space dimension. Since then, this model has been successfully applied to simulate multi-exponential excitation quenching kinetics in a series of plant photosynthetic systems, purified from the thylakoid membranes, without invoking a radical pair state in the reaction centre. Here, we overview this model and its parameters obtained for various systems, and extend the area of its applications to several pigment–protein supercomplexes containing the photosystem I (PSI). We show that while the diffusion in the PSI core is virtually three-dimensional, the PSI core aggregates interconnected with other light-harvesting complexes (LHCI and/or LHCII) are characterized by a substantially reduced dimension, which indicates a smaller number of energy transfer links from LHCI to the PSI core. We also suggest that in vivo both PSI and PSII antennae are substantially larger than those observed in the isolated systems: PSII antenna contains in total about 6 LHCII trimers while PSI is aggregated with at least one LHCII trimer. The obtained results show that FAM can be a very useful tool to follow photosynthetic apparatus transformations during short- and long-term adaptation to varying light, monitored by kinetic fluorescence spectroscopy.