Comparison of the fluorescence kinetics of detergent-solubilized and membrane-reconstituted LH2 complexes from Rps. acidophila and Rb. sphaeroides

Pflock, Tobias J.; Dezi, Manuela; Venturoli, Giovanni; Cogdell, Richard J.; Köhler, Jürgen; Oellerich, Silke

doi:10.1007/s11120-007-9245-2

Cited by 38 publications

(51 citation statements)

References 38 publications

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“…The BChl fluorescence lifetime values obtained for the LH2 from Rb. sphaeroides (the LH2 contains Car spheroidene with the S 1 (2 1 A g -) state energy of 13,400 cm -1 ) (Niedzwiedzki et al 2009;Polivka et al 2001) range between 0.9 and 1.0 ns at RT and 1.3-1.8 ns at low temperatures (Bopp et al 1997;Chen et al 2005;Freiberg et al 2003;Monshouwer et al 1997;Pflock et al 2008) and match very well to the values obtained for the LH2 studied in this work. This means, if the quenching effect occurs its rate is very small and is not able to shorten significantly the observed fluorescence lifetime of BChl.…”

Section: Discussionsupporting

confidence: 88%

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

et al. 2011

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The light-harvesting complex 2 from the thermophilic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption and fluorescence, sub-nanosecond-time-resolved fluorescence and femtosecond time-resolved transient absorption spectroscopy. The measurements were performed at room temperature and at 10 K. The combination of both ultrafast and steady-state optical spectroscopy methods at ambient and cryogenic temperatures allowed the detailed study of carotenoid (Car)-to-bacteriochlorophyll (BChl) as well BChl-to-BChl excitation energy transfer in the complex. The studies show that the dominant Cars rhodopin (N=11) and spirilloxanthin (N=13) do not play a significant role as supportive energy donors for BChl a. This is related with their photophysical properties regulated by long π-electron conjugation. On the other hand, such properties favor some of the Cars, particularly spirilloxanthin (N=13) to play the role of the direct quencher of the excited singlet state of BChl.

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Section: Discussionsupporting

confidence: 88%

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

et al. 2011

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“…sphaeroides crtI::crtI Pa grown anaerobically (containing primarily spirilloxanthin) and semi-aerobically (containing a mixture of ketocarotenoids including diketospirilloxanthin), the B850* lifetime at RT is~0.8 ns. This value is modestly shorter than the value of~1 ns or slightly longer than found previously for most LH2 complexes (with generally containing shorter carotenoids) [60][61][62]. However, assessing whether this difference reflects carotenoid quenching of B850* or arises from differences in the time-resolved measurements (e.g., excited-state annihilation) and/or LH2 samples (e.g., different extent of interactions between LH2 rings) must await studies of a unified set of LH2 complexes differing only in carotenoid conjugation length.…”

Section: Discussioncontrasting

confidence: 55%

Functional characteristics of spirilloxanthin and keto-bearing Analogues in light-harvesting LH2 complexes from Rhodobacter sphaeroides with a genetically modified carotenoid synthesis pathway

Niedzwiedzki

Dilbeck

Tang

et al. 2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Light-harvesting 2 (LH2) complexes from a genetically modified strain of the purple photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. Carotenoid synthesis in the Rba. sphaeroides strain was engineered to redirect carotenoid production away from spheroidene into the spirilloxanthin synthesis pathway. The strain assembles LH2 antennas with substantial amounts of spirilloxanthin (total double-bond conjugation length N=13) if grown anaerobically and of keto-bearing long-chain analogs [2-ketoanhydrorhodovibrin (N=13), 2-ketospirilloxanthin (N=14) and 2,2'-diketospirilloxanthin (N=15)] if grown semi-aerobically (with ratios that depend on growth conditions). We present the photophysical, electronic, and vibrational properties of these carotenoids, both isolated in organic media and assembled within LH2 complexes. Measurements of excited-state energy transfer to the array of excitonically coupled bacteriochlorophyll a molecules (B850) show that the mean lifetime of the first singlet excited state (S1) of the long-chain (N≥13) carotenoids does not change appreciably between organic media and the protein environment. In each case, the S1 state appears to lie lower in energy than that of B850. The energy-transfer yield is ~0.4 in LH2 (from the strain grown aerobically or semi-aerobically), which is less than half that achieved for LH2 that contains short-chain (N≤11) analogues. Collectively, the results suggest that the S1 excited state of the long-chain (N≥13) carotenoids participates little if at all in carotenoid-to-BChl a energy transfer, which occurs predominantly via the carotenoid S2 excited state in these antennas.

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“…very fast compared to the decay of the B850 excited singlet state ( 1 B850*) within an isolated LH2, which process has a lifetime of about 1.1 ns. 12,13 Alternatively, the 1 B850* state can decay by intersystem crossing with a time constant on the order of 10 ns to a B850 triplet state ( 3 B850*) that is quenched by tripletÀtriplet energy transfer to an adjacent carotenoid. 14,15 The time constant for this process is also about 10 ns and the lifetime of the excited triplet state of the carotenoid ( 3 Car*) is about 7 μs.…”

Section: ' Introductionmentioning

confidence: 99%

The Electronically Excited States of LH2 Complexes from Rhodopseudomonas acidophila Strain 10050 Studied by Time-Resolved Spectroscopy and Dynamic Monte Carlo Simulations. I. Isolated, Non-Interacting LH2 Complexes

et al. 2011

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We have employed time-resolved spectroscopy on the picosecond time scale in combination with dynamic Monte Carlo simulations to investigate the photophysical properties of light-harvesting 2 (LH2) complexes from the purple photosynthetic bacterium Rhodopseudomonas acidophila. The variations of the fluorescence transients were studied as a function of the excitation fluence, the repetition rate of the excitation and the sample preparation conditions. Here we present the results obtained on detergent solubilized LH2 complexes, i.e., avoiding intercomplex interactions, and show that a simple four-state model is sufficient to grasp the experimental observations quantitatively without the need for any free parameters. This approach allows us to obtain a quantitative measure for the singlet-triplet annihilation rate in isolated, noninteracting LH2 complexes.

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Comparison of the fluorescence kinetics of detergent-solubilized and membrane-reconstituted LH2 complexes from Rps. acidophila and Rb. sphaeroides

Cited by 38 publications

References 38 publications

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

Functional characteristics of spirilloxanthin and keto-bearing Analogues in light-harvesting LH2 complexes from Rhodobacter sphaeroides with a genetically modified carotenoid synthesis pathway

The Electronically Excited States of LH2 Complexes from Rhodopseudomonas acidophila Strain 10050 Studied by Time-Resolved Spectroscopy and Dynamic Monte Carlo Simulations. I. Isolated, Non-Interacting LH2 Complexes

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