Fluorescence detected magnetic resonance (FDMR) of green sulfur photosynthetic bacteria Chlorobium sp.

Abstract

Fluorescence Detected Magnetic Resonance (FDMR) spectra have been measured for whole cells and isolated chlorosomal fractions for the green photosyntheic bacteria Chlorobium phaeobacteroides (containing bacteriochlorophyll e, and isorenieratene as major carotenoid) and Chlorobium limicola (containing bacteriochlorophyll c, and chlorobactene as major carotenoid). The observed transition at 237 MHz (identical in both bacteria) and > 1100 MHz can be assigned, by analogy with published data on other carotenoids, to the 2E and D + E transitions, respectively, of Chlorobium carotenoids. Their zero field splitting (ZFS) parameters are estimated to be: |D|=0.0332 cm(-1) and |E|=0.0039 cm(-1) (chlorobactene), and |D|=0.0355 cm(-1) and |E|=0.0039 cm(-1) (isorenieratene). In the intermediate frequency range 300-1000 MHz the observed transitions can be assigned to chlorosomal bacteriochlorophylls c and e, and to bacteriochlorophyll a located in the chlorosome envelope and water-soluble protein. The bacteriochlorophyll e triplet state measured in 750 nm fluorescence (aggregated chlorosomal BChl e) is characterised by the ZFS parameters: |D|=0.0251 cm(-1) and |E|=0.0050 cm(-1).

Investigation on chlorosomal antenna geometries: tube, lamella and spiral-type self-aggregates

“…A typical feature for the chlorosome absorption spectrum is a very large red shift (about 70-110 nm) of the Q y band with respect to the monomer absorption of Bchl c, d, or e at about 650 nm (Brune et al 1987;Martyiski et al 1998;Psencik et al 1997;Saga et al 2006c;Savikhin et al 1998;Steensgaard et al 1999;Wang et al 1995). The shifts and the shapes of the absorption, circular dichroism (CD), and linear dichroism (LD) spectra are very similar to those observed for Chl a--water, Bchl a--water, and for pure in vitro Bchl c, d, and e and metal chlorin aggregates in solution (Brune et al 1987;Huber et al 2005;Linnanto et al 1998Linnanto et al , 2002Nozawa et al 1993;Oksanen et al 1996;Saga et al 2006c;Steensgaard et al 2000;Tamiaki et al 1996bTamiaki et al , 2003.…”

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

“…A number of results indicates that one part of Car is present in the baseplate (20,21) and another part must be in close contact with chlorosomal BChl (22,23). The lamellar model provides plausible explanation for the location of 'chlorosomal' Car in the lipid-like space between the 4 planes (10).…”

“…The lamellar model provides plausible explanation for the location of 'chlorosomal' Car in the lipid-like space between the 4 planes (10). The strong interaction between 'chlorosomal' Car and BChl is also manifested by fast energy transfer from the S 2 state of Car to BChl (<100 fs -1 ) (24) and by triplet-triplet energy transfer from BChl to Car (21,22,25), for which an overlap of electron wave functions is a prerequisite. Moreover, the amount of 'chlorosomal' Car affects optical spectra of BChl aggregates (23).…”

Optically detected magnetic resonance (ODMR) of photoexcited triplet states

“…These states have been studied by ODMR in many systems (for some examples, see: Carbonera et al 1992aCarbonera et al , b, 1996Carbonera et al , 2001Carbonera et al , 2002Santabarbara et al 2003Santabarbara et al , 2007Bordignon et al 2002;Van der Vos et al 1991;Aust et al 1990Aust et al , 1991Psencik et al 1994;Ullrich et al 1989;Lampoura et al 2002;Di Valentin et al 2008).…”

“…An important aspect of the application of ODMR in photosynthesis is that the technique can be used to study energy transfer and trapping processes in intact systems, such as large particles or even thylakoids, chloroplasts, and leaves, due to the high sensitivity and selectivity of the technique Psencik et al 1994;Santabarbara et al 2003Santabarbara et al , 2007.…”