Energy migration in purple bacteria. The criterion for discrimination between migration- and trapping-limited photosynthetic units

Borisov, A. Yu.

doi:10.1007/bf00034858

Cited by 12 publications

(20 citation statements)

References 25 publications

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“…The trap-limited model (Pearlstein, 1982;Borisov, 1990) assumes that charge separation is the rate-limiting step in excitation trapping. This implies that the excitation visits the reaction center forming P* many times before charge separation occurs.…”

mentioning

confidence: 99%

Femtosecond Pump-Probe Analysis of Energy and Electron Transfer in Photosynthetic Membranes of Rhodobacter capsulatus

Xiao¹,

Lin²,

Taguchi³

et al. 1994

Biochemistry

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Low-intensity, 295 K, femtosecond pump-probe transient absorption measurements are described that have been performed to investigate energy and electron transfer in photosynthetic membranes from a Rhodobacter capsulatus strain lacking functional light harvesting antenna complex II. Spectral and kinetic similarities between the absorption changes of isolated reaction centers and those of reaction centers in membranes upon 800-nm excitation suggest that the charge separation process in both cases is very similar. An ultrafast energy relaxation process observed near 872 nm when 800-nm excitation is used is interpreted as interexcitonic relaxation within the antenna, though other interpretations, such as vibrational relaxation, are possible. On the basis of global exponential fitting analysis of the time-dependent spectral changes using 800- and 880-nm excitation wavelengths to selectively excite the reaction center and the LHI antenna, respectively, it is found that excitation energy transfer and trapping in Rb. capsulatus is limited by the overall rate of energy transfer between the antenna and the reaction center. This conclusion is supported by the observation that excitation at 800 nm, but not 880 nm, results in absorbance changes indicative of charge separation with a lifetime (3.1 ps) very close to that reported for charge separation in isolated reaction centers (3.5 ps). Thus, most reaction centers that are directly excited undergo charge separation and not backward energy transfer to the LHI antenna complexes. Both a kinetic model analysis and a direct comparison between time-resolved spectra obtained using different excitation wavelengths resulted in an energy-detrapping efficiency of about 15 +/- 10%.

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mentioning

confidence: 99%

Femtosecond Pump-Probe Analysis of Energy and Electron Transfer in Photosynthetic Membranes of Rhodobacter capsulatus

Xiao¹,

Lin²,

Taguchi³

et al. 1994

Biochemistry

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“…This leads to a compact equation for deriving f from the measured fluorescence decay time in open PSUs. Combining (14) and (16) we obtain…”

Section: Random Walk Theorymentioning

confidence: 97%

“…Equation (27) can be recast and somewhat simplified to give a relation for the characteristic fluorescence decay time whose form is similar to (14). Assuming that I is the same for all antenna pigments, it is immaterial for closed traps where the excitation is located in the antenna system at a particular time, and the loss factor l simply follows from the relation 1 '~ = e -l, which with %1 = h ncl gives h In 1--…”

Section: The Characteristic Fluorescence Decay Timementioning

confidence: 99%

“…Changing the various rates into the characteristic times we obtain from (9) for the characteristic fluorescence decay time in open reaction centres rtrdC (14) "re = rtC + rcl with C given by…”

Section: Random Walk Theorymentioning

confidence: 99%

“…Energy transfer in the light-harvesting complexes of the plant and bacterial photosystems as studied optically by fluorescence, photobleaching, fluorescence depolarization and singlet-singlet annihilation experiments (for a review, see [1]), has been described theoretically by random walk theory [2][3][4][5], reviewed in [6][7][8], by numerically or analytically solving the Pauli master equation for antenna arrays [9][10][11][12][13][14][15], and by the transition probability matrix method [16][17][18][19]. The Pauli master equation approach for an array of N pigments allows us to introduce a maximum of N (N-1) different rate constants for energy transfer.…”

Section: Introductionmentioning

confidence: 99%

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Excitation migration and trapping in homogeneous and heterogeneous lattices

Hoff

Fischer

1993

Molecular Physics

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Energy transfer in arrays of photosynthetic antenna pigments containing a photochemical trap is studied combining the transition probability matrix method with random walk theory and experimental data on fluorescence lifetimes and overall trapping efficiencies in systems with open and closed photochemical trap. New exact expressions for the fluorescence decay time and the trapping at infinite time are derived that contain the probability to escape from the trap as a single parameter. Two approximate relations for the fluorescence decay time, ~'e, and T, the probability that trapping has occurred at infinite time, are derived that can be applied to homogeneous and heterogeneous antenna arrays: "I-e = TtTcl/("rt -~ TclPf ) T = Tcl/(Tcl -~-Tt[(l/p -1)/f+ 1]),where ~'t is the characteristic time of photochemical trapping, Tcl the fluorescence decay time for closed traps, f the probability to escape from the trap, and p the equilibrium probability to find the excitation on the trap. p is independent of the initial conditions (selective or random excitation); p = 1/N for homogeneous lattices, while for heterogeneous symmetric lattices p can be easily calculated with the transition probability matrix method. For homogeneous lattices the above relations are accurate to within a few percent over the entire range 0 < f< 1; for the intermediate values off they are a considerable improvement over published expressions for the fast and slow hopping limits 0 c = 1 and f = 0, respectively). The relations derived here are used for determining the escape probabilityf and the mean residence or hopping time h for the core antenna system of the photosynthetic bacterium Rhodobacter sphaeroides.

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Energy transfer from carotenoid and FMO-protein in subcellular preparations from green sulfur bacteria. Spectroscopic characterization of an FMO-reaction center core complex at low temperature

Francke

Otte

Miller³

et al. 1996

Photosynth Res

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The Fenna-Matthews-Olson (FMO)-protein and the FMO-reaction center (RC) core complex from the green sulfur bacterium Chlorobium tepidum were examined at 6 K by absorption and fluorescence spectroscopy. The absorption spectrum of the RC core complex was obtained by a subtraction method and found to have fiye peaks in the QY region, at 797, 808, 818, 834 and 837 nm. The efficiency of energy transfer from carotenoid to bacteriochlorophyll a in the RC core complex was 23% at 6 K, and from the FMO-protein to the core it was 35%. Energy transfer from the FMO-protein to the core complex was also measured in isolated membranes of Prosthecochloris aestuarii from the action spectra of charge separation. Again, a low efficiency of energy transfer was obtained, both at 6 K and at room temperature.

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Energy migration in purple bacteria. The criterion for discrimination between migration- and trapping-limited photosynthetic units

Cited by 12 publications

References 25 publications

Femtosecond Pump-Probe Analysis of Energy and Electron Transfer in Photosynthetic Membranes of Rhodobacter capsulatus

Femtosecond Pump-Probe Analysis of Energy and Electron Transfer in Photosynthetic Membranes of Rhodobacter capsulatus

Excitation migration and trapping in homogeneous and heterogeneous lattices

Energy transfer from carotenoid and FMO-protein in subcellular preparations from green sulfur bacteria. Spectroscopic characterization of an FMO-reaction center core complex at low temperature

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