title: Self-assembly of natural light-harvesting bacteriochlorophylls of green sulfur photosynthetic bacteria in silicate capsules as stable models of chlorosomes.
abstract: Naturally occurring bacteriochlorophyll(BChl)s-c, -d, and -e from green sulfur photosynthetic bacteria were self-assembled in an aqueous solution in the presence of octadecyltriethoxysilane and tetraethoxysilane, followed by polycondensation of the alkoxysilanes by incubation for 50 h at 25 degrees C. The resulting BChl self-assemblies in silicate capsules exhibited visible absorption and circular dichroism spectra similar to the corresponding natural light-harvesting systems (chlorosomes) of green sulfur bacteria. Dynamic light scattering measurements indicated that the silicate capsules had an average hydrodynamic diameter of several hundred nanometers. BChl self-aggregates in silicate capsules were significantly stable to a nonionic surfactant Triton X-100, which was apt to decompose the BChl aggregates to their monomeric form, compared with conventional micelle systems. BChls in silicate capsules were more tolerant to demetalation of the central magnesium under acidic conditions than the natural systems.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Saga
authors.forename: Sho
authors.initials: S
authors.lastname: Akai
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Miyatake
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D001429:Bacteriochlorophylls / Q000378:metabolism*; D019414:Chlorobi / Q000378:metabolism*; D002942:Circular Dichroism; D008670:Metals / Q000378:metabolism; D017640:Silicates / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D001429:Bacteriochlorophylls; D008670:Metals; D017640:Silicates