title: Variability of aggregation extent of light-harvesting pigments in peripheral antenna of Chloroflexus aurantiacus.
abstract: The stationary ground state and femtosecond time-resolved absorption spectra as well as spectra of circular dichroism were measured at room temperature using freshly prepared samples of chlorosomes isolated from fresh cultures of the green bacterium Chloroflexus aurantiacus. Cultures were grown by using as inoculum the same seed culture but under different light conditions. All measured spectra clearly showed the red shift of BChl c Qybands (up to 5 nm) for low-light chlorosomes as compared to high-light ones, together with concomitant narrowing of these bands and increasing of their amplitudes. The sizes of the unit BChl c aggregates of the high-light-chlorosomes and the low-light ones were estimated. The fit of all experimental spectra was obtained within the framework of our model proposed before (Fetisova et al., Biophys J 71:995-101, 1996). The model assumes that a unit building block of the BChl c antenna has a form of a tubular aggregate of L = 6 linear single or double exciton-coupled pigment chains within a rod element, with the pigment packing density, approximating that in vivo. The simultaneous fit of all experimental spectra gave the number of pigments in each individual linear pigment chain N = 4 and N = 6 for the high-light and the low-light BChl c unit building blocks, respectively. The size of a unit building block in the BChl c antenna was found to vary from L × N = 24 to L × N = 36 exciton-coupled BChl c molecules being governed by the growth-light intensity. All sets of findings for Chloroflexus aurantiacus chlorosomes demonstrated the biologically expedient light-controlled variability, predicted by us, of the extent of BChl c aggregation within a unit building block in this antenna.
authors.affiliation: Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation, 119991. yakov@genebee.msu.ru.
authors.forename: Andrei
authors.identifier: http://orcid.org/0000-0003-0107-619X
authors.initials: A
authors.lastname: Yakovlev
authors.affiliation: Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation, 119991.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Taisova
authors.affiliation: Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation, 119991.
authors.forename: Alexander
authors.initials: A
authors.lastname: Arutyunyan
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, Russian Federation, 142290.|Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation, 119991.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Shuvalov
authors.affiliation: Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation, 119991. zfetisova@genebee.msu.ru.
authors.forename: Zoya
authors.initials: Z
authors.lastname: Fetisova
mesh_terms: D001429:Bacteriochlorophylls / Q000378:metabolism; D041861:Chloroflexus / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000378:metabolism; D002942:Circular Dichroism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism*; D010860:Pigments, Biological / Q000378:metabolism*; D066329:Protein Aggregates; D013057:Spectrum Analysis; D013997:Time Factors
chemical_list: D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D010860:Pigments, Biological; D066329:Protein Aggregates
keywords: Bacterial photosynthesis; Bacteriochlorophyll c antenna; Chloroflexus aurantiacus; Chlorosome; Circular dichroism; Green bacteria; Pump–probe spectroscopy