Abstract
In green-sulfur bacteria sunlight is absorbed by antenna structures termed chlorosomes, and transferred to the RC via the Fenna-Matthews-Olson (FMO) complex. FMO consists of three monomers arranged in C3 symmetry where each monomer accommodates eight Bacteriochlorophyll a (BChl a) molecules. It was the first pigment-protein complex for which the structure has been determined with high resolution and since then this complex has been the subject of numerous studies both experimentally and theoretically. Here we report about fluorescence-excitation spectroscopy as well as emission spectroscopy from individual FMO complexes at low temperatures. The individual FMO complexes are subjected to very fast spectral fluctuations smearing out any possible different information from the ensemble data that were recorded under the same experimental conditions. In other words, on the time scales that are experimentally accessible by single-molecule techniques, the FMO complex exhibits ergodic behaviour.
Highlights
IntroductionThe generic principle of photosynthesis is that sunlight is absorbed by antenna complexes and this energy is transferred efficiently to the photochemical reaction centre that acts as a transducer
Photosynthesis is one of the most important energy conversion processes on Earth
It features a few diffraction-limited bright spots, each corresponding to an individual FMO complex
Summary
The generic principle of photosynthesis is that sunlight is absorbed by antenna complexes and this energy is transferred efficiently to the photochemical reaction centre that acts as a transducer. Both the antennae and the reaction centre (RC) are pigment-protein complexes accommodating a number of pigments that are properly positioned with respect to each other by the interaction with a protein scaffold. The structure of the FMO complex from the species Chlorobaculum (Cba.) tepidum became available[34], and resembles closely the former one This FMO complex consists of three identical subunits that are arranged in C3 symmetry with respect to each other, such that the C3 axis is perpendicular to the membrane axis, Fig. 1a. We present the fluorescence-excitation and emission spectra from individual FMO complexes from the species Cba. tepidum and find that these complexes behave ergodically on the experimental accessible timescales
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