Energy Transfer and Trapping in Spectrally Disordered Photosynthetic Membranes

Abstract

The very efficient transformation of solar energy into electrochemical free energy, which is subsequently utilized in dark biochemical reactions, takes place in a complex aggregate of pigment molecules and proteins called a photosynthetic unit (PSU). The main subunits of PSU are a reaction centre (RC), where the conversion of the energy of singlet excited states of RC pigiments into the potential energy of separated charges occurs, and a number of surrounding light-harvesting antenna pigment-protein complexes (LHC) which serve to absorb radiant energy and to transport excitations with possibly minimum losses to the RC. Usually, the major part of PSU is located within the lipid bilayer membrane, which in many cases determines that the energy transport takes place mainly in two dimensions instead of three dimensions. Green photosynthetic bacteria and cya-nobacteria have additional peripheral antenna systems, called respectively chlorosomes and phycobi1isomes, that are localized on the surface of the membrane.