Superradiance of bacteriochlorophyll c aggregates in chlorosomes of green photosynthetic bacteria

0559500 - BC 2022 RIV GB eng J - Journal Article
Malina, T. - Koehorst, R. - Bína, David - Pšenčík, J. - van Amerongen, H.
Superradiance of bacteriochlorophyll c aggregates in chlorosomes of green photosynthetic bacteria.
Scientific Reports. Roč. 11, č. 1 (2021), č. článku 8354. ISSN 2045-2322. E-ISSN 2045-2322
R&D Projects: GA ČR(CZ) GA20-01159S
Institutional support: RVO:60077344
Keywords : light-harvesting complexes * low-light condition * chromosomes
OECD category: Biophysics
Impact factor: 4.997, year: 2021
Method of publishing: Open access
https://www.nature.com/articles/s41598-021-87664-3

Chlorosomes are the main light-harvesting complexes of green photosynthetic bacteria that are adapted to a phototrophic life in low-light conditions. They contain a large number of bacteriochlorophyll c, d, or e molecules organized in self-assembling aggregates. Tight packing of the pigments results in strong excitonic interactions between the monomers, which leads to a redshift of the absorption spectra and excitation delocalization. Due to the large amount of disorder present in chlorosomes, the extent of delocalization is limited and further decreases in time after excitation. In this work we address the question whether the excitonic interactions between the bacteriochlorophyll c molecules are strong enough to maintain some extent of delocalization even after exciton relaxation. That would manifest itself by collective spontaneous emission, so-called superradiance. We show that despite a very low fluorescence quantum yield and short excited state lifetime, both caused by the aggregation, chlorosomes indeed exhibit superradiance. The emission occurs from states delocalized over at least two molecules. In other words, the dipole strength of the emissive states is larger than for a bacteriochlorophyll c monomer. This represents an important functional mechanism increasing the probability of excitation energy transfer that is vital in low-light conditions. Similar behaviour was observed also in one type of artificial aggregates, and this may be beneficial for their potential use in artificial photosynthesis.
Permanent Link: https://hdl.handle.net/11104/0332779