Structure of bacteriochlorophyll aggregates in chlorosomes of green bacteria: a spectral hole burning study.

Exciton level structure, homogenous absorption and hole-burning spectra were calculated for different models of bacteriochlorophyll aggregation in chlorosomal antennae of green bacteria. It was demonstrated that none of the earlier proposed models of noninteracting linear bacteriochlorophyll aggregates and linear bacteriochlorophyll chains assembling in tubular aggregates with high density of packing, exhibits the in vivo exciton level structure revealed by hole-burning experiments on intact cells of green bacteria. The models of linear exciton-coupled bacteriochlorophyll chains with a low packing density, approximating that in vivo, were proposed as alternative, to obtain the main spectral features found in natural antennae.