Antenna Complexes from Green Photosynthetic Bacteria

Effect of Carotenoids and Monogalactosyl Diglyceride on Bacteriochlorophyll c Aggregates in Aqueous Buffer: Implications for the Self-Assembly of Chlorosomes

“…A unique property of chlorosomes is that the main BChl pigments are not present in pigment-protein complexes, rather they form self-assembled aggregates based on their unusual chemical structure (3,4, review by Blankenship and Matsuura (1) and references therein). The main interactions 3 involved in the formation of BChl aggregates are the coordination of the central Mg of a BChl molecule to a hydroxyethyl substituent at C3 1 of a neighboring BChl, which can be also hydrogen-bonded to the keto group at C13 1 of a third BChl molecule (5,6).…”

“…Recently a lamellar model, in which BChl molecules aggregate into semicrystalline lateral arrays, has been proposed (10). Aggregates with very similar optical properties to those in chlorosomes can be prepared in vitro either in non-polar solvents or in aqueous buffers with addition of lipids (4,11, reviews by Blankenship and Matsuura (1) Blankenship et al (12) and Tamiaki (13)).…”

“…2:1 and 20:1 (14−17). In addition, the chlorosomal baseplate, which connects the chlorosome to the cytoplasmic membrane, contains monomeric BChl a in a pigment-protein complex together with the chlorosomal A protein (CsmA) (1,18). Besides pigments, quinones are present in chlorosomes, acting as quenchers of excitation energy (19).…”

Chlorophylls, Symmetry, Chirality, and Photosynthesis

“…In contrast to the protein-organized complexes described previously, chlorosomes contain very little protein and instead are comprised almost entirely of self-assembled chlorophyll aggregates; a small BChl a binding-protein is associated with the chlorosome may serve as an intermediate between the chlorosome and the RC apparatuses (including the FMO protein described above) and is referred to as the "baseplate" [260]. Depending on the particular species, Chlorobiaceae (green sulfur bacteria) contain one of either BChls c, d or e (the Chlorobium chlorophylls) and their corresponding homologues, which differ in the length of the alkyl substituents attached to C8 and C12 as well as the identity of the esterifying alcohol, whereas all Chloroflexaceae (green nonsulfur bacteria) usually contain the BChl c derivatives [260].…”

Light-Harvesting in Photosynthesis

“…Reversible distance control is, in principle, available, even by light [26]. It is presently unclear if this combination also enhances the light-harvesting eciency per unit volume, when the spatial demands are compared to that of plant light harvesting systems, or the compact packing of Chls in chlorosomes [27].…”