The Mechanism of Energy Storage in the Reaction Center in Photosynthetic Bacteria and Attempts to Simulate Processes using Monolayer Assembly Technique

Abstract

Organized assemblies of monolayers are useful tools in stu¬dying energy and electron transfer in planned molecular arrangements of well-defined geometry. Systems of dye aggregates and energy or elec¬tron acceptors designed for studying exciton motion and trapping are investigated and the results are found to be in good agreement with a simple model based on a classical description of interactions. Monolayer assemblies of particular architecture are used to find the role of energy transfer and electron injection in the spectral sensitization of the photographic process. Arrangements are investigated where a π-electron system is positioned between a dye molecule and an electron acceptor. Such arrangements allow photoinduced charge separation at high energetic level. They illustrate design principles for energy storing systems. The structure of the photosynthetic reaction center recently resolved by Deisenhofer et al. is considered in connection with these design principles. Each chromophore component in the reaction center appears to be positioned optimally for the purpose of energy storage. This can be shown by calculating the rate of each electron transfer step for the arrangement given by Deisenhofer et al. and for other similar arrangements. The rates are deduced by taking the electronic structure of the chromophores and their geometrical arrangement explicitely into account, while the protein portion is considered as a dielectric continuum. The values thus obtained are in good agreement with the experimental data.