Theory of spectroscopy and energy transfer of oligomeric pigments in chlorosome antennas of green photosynthetic bacteria

Alden, R. G.; Lin, Su; Blankenship, R.E.

doi:10.1016/0022-2313(92)90018-5

Cited by 44 publications

(35 citation statements)

References 32 publications

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“…Apparently, at room temperature the thermal energy is sufficient to overcome the binding energies of the higher aggregated forms, i.e. they 'melt' at room temperature, but not at temperatures below about 200 K. A-743 and especially A-755 appear to be weakly fluorescent, in agreement with the short lifetimes observed for higher aggregates of BChl c at room temperature (Brune et al 1987; see also Alden et al 1992 for a discussion of this phenomenon). Interestingly, at 45 K a relatively strong emission at 775 nm was observed, not unlike the emission observed in chlorosomes (van Dorssen et al 1986;Brune et al 1990;Otte et al 1991;Matsuura et al 1993).…”

Section: Discussionsupporting

confidence: 64%

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Aggregation of 8,12-diethyl farnesyl bacteriochlorophyll c at low temperature

Dudkowiak¹,

Francke²,

Amesz³

1995

Photosynth Res

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The effect of temperature on the aggregation of 3(l)R-8,12-diethyl farnesyl bacteriochlorophyll c in a mixture of n-pentane and methylcyclohexane (1/1, v/v) was studied by means of absorption, circular dichroism and fluorescence spectroscopy. At room temperature essentially only two aggregate species, absorbing at 702 nm (A-702) and 719 nm (A-719), were present. Upon cooling to 219 K, A-702 was quantitatively converted to A-719. Further lowering of the temperature led to the stepwise formation of larger aggregates by the conversion of A-719 to aggregate species absorbing at 743 nm (A-743) and 755 nm (A-755). All absorption changes were reversible. A-719 was highly fluorescent (maximum at 192 K: 744 nm), while A-743 and especially A-755 were weakly fluorescent. Below 130 K the mixture solidified, and no major changes in the absorption spectrum were observed upon further cooling. At 45 K, however, a relatively strong emission at 775 nm was observed. Below 200 K, the absorption, fluorescence and circular dichroism spectra resembled that of the chlorosome. These results open up the possibility to study higher aggregates of BChl c as models for the chlorosome by various methods at low temperature, thus avoiding interference by thermal processes.

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Section: Discussionsupporting

confidence: 64%

“…5D). This emission, reminiscent of the emission band from chlorosomes, may be ascribed to higher, fluorescent, aggregates (Alden et al 1992) or to a low energy transition of A-755, which is not visible in either the absorption or the excitation spectrum.…”

Section: Fluorescencementioning

confidence: 99%

Aggregation of 8,12-diethyl farnesyl bacteriochlorophyll c at low temperature

Dudkowiak¹,

Francke²,

Amesz³

1995

Photosynth Res

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“…Such fast excitation transfer along the spiral layer expedites the interrod transfer to BChl a in baseplates, leading to the reaction centers, as shown in Fig. 5C (7,32,39).…”

Section: Excitation Transfer In Chlorosomal Antennas Based On Parallementioning

confidence: 99%

“…The rod elements of Chlorobium limicola, the target of this work, are composed of BChl c. Light energy captured by BChl c in the rod elements is transferred to the reaction centers in the cytoplasmic membrane through BChl a in baseplate proteins (7). The BChl c molecule has two stereoisomers and homologues as shown in 1 -hydroxyl group and the Mg atom and a hydrogen bond between the coordinated 3 1 -hydroxyl and 13 1 -carbonyl groups (9)(10)(11).…”

mentioning

confidence: 99%

Structure of the light-harvesting bacteriochlorophyll c assembly in chlorosomes from Chlorobium limicola determined by solid-state NMR

Egawa

Fujiwara

Mizoguchi

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

101

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We have determined the atomic structure of the bacteriochlorophyll c (BChl c) assembly in a huge light-harvesting organelle, the chlorosome of green photosynthetic bacteria, by solid-state NMR. Previous electron microscopic and spectroscopic studies indicated that chlorosomes have a cylindrical architecture with a diameter of Ϸ10 nm consisting of layered BChl molecules. Assembly structures in huge noncrystalline chlorosomes have been proposed based mainly on structure-dependent chemical shifts and a few distances acquired by solid-state NMR, but those studies did not provide a definite structure. Our approach is based on 13 C dipolar spindiffusion solid-state NMR of uniformly 13 C-labeled chlorosomes under magic-angle spinning. Approximately 90 intermolecular COC distances were obtained by simultaneous assignment of distance correlations and structure optimization preceded by polarization-transfer matrix analysis. It was determined from the Ϸ90 intermolecular distances that BChl c molecules form piggybackdimer-based parallel layers. This finding rules out the well known monomer-based structures. A molecular model of the cylinder in the chlorosome was built by using this structure. It provided insights into the mechanisms of efficient light harvesting and excitation transfer to the reaction centers. This work constitutes an important advance in the structure determination of huge intact systems that cannot be crystallized.spin diffusion ͉ distance analysis ͉ photosynthesis ͉ antenna complex ͉ excitation transfer P hotosynthesis is the primary energy source for all living organisms. Chlorophyll-protein complexes capture light energy in most photosynthetic systems. Their structures are well known (1, 2). However, there are other light-harvesting devices called chlorosomes, which contain bacteriochlorophyll (BChl) assemblies. No protein is present in the BChl assemblies in sharp contrast to the light-harvesting chlorophyll-protein complexes mentioned above. Chlorosomes are found only in green sulfur bacteria and green filamentous bacteria. They catch weak light in an environment (3). A green sulfur bacterium species found in a deep-sea hydrothermal vent (4), for example, uses the dim light of geothermal radiation for photosynthesis. The atomic structure of chlorosomes has not been determined, which has impeded structure-based study of their functions. Because the design of chlorosomes is completely different from that of other light-harvesting devices, elucidation of their structure provides insight into the light-harvesting mechanism involved.Freeze-fracture electron microscopy revealed that chlorosomes were oblong bodies filled with several rod-shaped elements and were attached to the cytoplasmic side of cell membranes (5, 6). The rod elements of Chlorobium limicola, the target of this work, are composed of BChl c. Light energy captured by BChl c in the rod elements is transferred to the reaction centers in the cytoplasmic membrane through BChl a in baseplate proteins (7). The BChl c molecule has two stereoisomers...

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“…All hitherto proposed molecular models of the chlorosome correspond to the two limiting cases of BChl chains packing: (i) noninteracting BChl chains (for review see [10,11]) and (ii) strongly exciton-coupled BChl chains with a high density of packing, postulating self-aggregation of pigments into a tubular macrocycle network [11,12]. For all these models, calculated absorption spectra consist of an intense line corresponding to the lowest exciton level and of weak lines corresponding to higher levels (not shown).…”

Section: Resultsmentioning

confidence: 99%

Antenna size dependent exciton dynamics in the chlorosomal antenna of the green bacterium Chloroflexus aurantiacus

Fetisova¹,

Freiberg²,

Novoderezhkin³

et al. 1996

FEBS Letters

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aldehyde, postfixed with OsO4, embedded in Epon-812, and ultrathinsectioned by standard method [4]. Micrographs of the ultrathin sections were used for morphometric measurements (magnification 50 000 × 10) to obtain histograms of chlorosomes heights and calculate the number of layers of rod elements in the chlorosome, assuming that the diameter of the rod equals 5.5 nm [4,5].Absorption spectra of intact cells were recorded with a Hitachi-557 spectrophotometer (Japan).Spectrally resolved fluorescence measurements for intact cells of C aurantiacus were made with a picosecond spectrochronograph [6]. The pulse source was a mode-locked CW rhodamine 590 dye laser (pulse duration, 3 ps), synchronously pumped at 76 MHz by a NdYag laser (Ontares, 'Coherent'). Emission, viewed at an angle of 90 ° to the exciting beam, was registered with a home-made synchroscan streak camera. The time resolution of the measuring system was 10 ps.

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Theory of spectroscopy and energy transfer of oligomeric pigments in chlorosome antennas of green photosynthetic bacteria

Cited by 44 publications

References 32 publications

Aggregation of 8,12-diethyl farnesyl bacteriochlorophyll c at low temperature

Aggregation of 8,12-diethyl farnesyl bacteriochlorophyll c at low temperature

Structure of the light-harvesting bacteriochlorophyll c assembly in chlorosomes from Chlorobium limicola determined by solid-state NMR

Antenna size dependent exciton dynamics in the chlorosomal antenna of the green bacterium Chloroflexus aurantiacus

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