title: Temperature and ionic strength effects on the chlorosome light-harvesting antenna complex.
abstract: Chlorosomes, the peripheral light-harvesting antenna complex from green photosynthetic bacteria, are the largest and one of the most efficient light-harvesting antenna complexes found in nature. In contrast to other light-harvesting antennas, chlorosomes are constructed from more than 150,000 self-assembled bacteriochlorophylls (BChls) and contain relatively few proteins that play secondary roles. These unique properties have led to chlorosomes as an attractive candidate for developing biohybrid solar cell devices. In this article, we investigate the temperature and ionic strength effects on the viability of chlorosomes from the photosynthetic green bacterium Chloroflexus aurantiacus using small-angle neutron scattering and dynamic light scattering. Our studies indicate that chlorosomes remain intact up to 75 °C and that salt induces the formation of large aggregates of chlorosomes. No internal structural changes are observed for the aggregates. The salt-induced aggregation, which is a reversible process, is more efficient with divalent metal ions than with monovalent metal ions. Moreover, with treatment at 98 °C for 2 min, the bulk of the chlorosome pigments are undamaged, while the baseplate is destroyed. Chlorosomes without the baseplate remain rodlike in shape and are 30-40% smaller than with the baseplate attached. Further, chlorosomes are stable from pH 5.5 to 11.0. Together, this is the first time such a range of characterization tools have been used for chlorosomes, and this has enabled elucidation of properties that are not only important to understanding their functionality but also may be useful in biohybrid devices for effective light harvesting.
authors.affiliation: Department of Biology, Campus Box 1137, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
authors.forename: Kuo-Hsiang
authors.initials: KH
authors.lastname: Tang
authors.forename: Liying
authors.initials: L
authors.lastname: Zhu
authors.forename: Volker S
authors.initials: VS
authors.lastname: Urban
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Collins
authors.forename: Pratim
authors.initials: P
authors.lastname: Biswas
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D041861:Chloroflexus / Q000737:chemistry; D004736:Energy-Generating Resources; D045342:Light-Harvesting Protein Complexes; D009994:Osmolar Concentration; D055503:Protein Multimerization; D013696:Temperature
chemical_list: D045342:Light-Harvesting Protein Complexes