Comparative study of reaction centers from purple photosynthetic bacteria: Isolation and optical spectroscopy

Wang, S.; Lin, Su; Lin, Xiaomei; Woodbury, Neal W.; Allen, James P.

doi:10.1007/bf00018263

Cited by 51 publications

(76 citation statements)

References 50 publications

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“…As described in the text, these values are used for comparative purposes only and may not represent the actual values of D. e This is the lifetime of P* in Rs. rubrum with quinones reduced (Wang et al 1994). The lifetime under the conditions of the present measurement is probably shorter.…”

Section: Resultsmentioning

confidence: 75%

Energy trapping and detrapping by wild type and mutant reaction centers of purple non-sulfur bacteria

et al. 1996

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Time-correlated single photon counting was used to study energy trapping and detrapping kinetics at 295 K in Rhodobacter sphaeroides chromatophore membranes containing mutant reaction centers. The mutant reaction centers were expressed in a background strain of Rb. sphaeroides which contained only B880 antenna complexes and no B800-850 antenna complexes. The excited state decay times in the isolated reaction centers from these strains were previously shown to vary by roughly 15-fold, from 3.4 to 52 ps, due to differences in the charge separation rates in the different mutants (Allen and Williams (1995) J Bioenerg Biomembr 27: 275-283). In this study, measurements were also performed on wild type Rhodospirillum rubrum and Rb. sphaeroides B880 antenna-only mutant chromatophores for comparison. The emission kinetics in membranes containing mutant reaction centers was complex. The experimental data were analyzed in terms of a kinetic model that involved fast excitation migration between antenna complexes followed by reversible energy transfer to the reaction center and charge separation. Three emission time constants were identified by fitting the data to a sum of exponential decay components. They were assigned to trapping/quenching of antenna excitations by the reaction center, recombination of the P(+)H(-) charge-separated state of the reaction center reforming an emitting state, and emission from uncoupled antenna pigment-protein complexes. The first varied from 60 to 160 ps, depending on the reaction center mutation; the second was 200-300 ps, and the third was about 700 ps. The observed weak linear dependence of the trapping time on the primary charge separation time, together with the known sub-picosecond exciton migration time within the antenna, supports the concept that it is energy transfer from the antenna to the reaction center, rather than charge separation, that limits the overall energy trapping time in wild type chromatophores. The component due to charge recombination reforming the excited state is minor in wild type membranes, but increases substantially in mutants due to the decreasing free energy gap between the states P(*) and P(+)H(-).

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Section: Resultsmentioning

confidence: 75%

Energy trapping and detrapping by wild type and mutant reaction centers of purple non-sulfur bacteria

et al. 1996

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“…S4. We note that many experimental parameters can cause shifts in the absorption peaks for the RC cofactors (45,46). In the case of the crystal used in Fig.…”

Section: Resultsmentioning

confidence: 96%

Cofactor-specific photochemical function resolved by ultrafast spectroscopy in photosynthetic reaction center crystals

Huang

Ponomarenko

Wiederrecht

et al. 2012

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

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High-resolution mapping of cofactor-specific photochemistry in photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides was achieved by polarization selective ultrafast spectroscopy in single crystals at cryogenic temperature. By exploiting the fixed orientation of cofactors within crystals, we isolated a single transition within the multicofactor manifold, and elucidated the sitespecific photochemical functions of the cofactors associated with the symmetry-related active A and inactive B branches. Transient spectra associated with the initial excited states were found to involve a set of cofactors that differ depending upon whether the monomeric bacteriochlorophylls, BChl A , BChl B , or the special pair bacteriochlorophyll dimer, P, was chosen for excitation. Proceeding from these initial excited states, characteristic photochemical functions were resolved. Specifically, our measurements provide direct evidence for an alternative charge separation pathway initiated by excitation of BChl A that does not involve P*. Conversely, the initial excited state produced by excitation of BChl B was found to decay by energy transfer to P. A clear sequential kinetic resolution of BChl A and the A-side bacteriopheophytin, BPh A , in the electron transfer proceeding from P* was achieved. These experiments demonstrate the opportunity to resolve photochemical function of individual cofactors within the multicofactor RC complexes using single crystal spectroscopy.photosynthesis | transient absorption | light-harvesting

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“…Here, we present an EPR/ENDOR investigation of the spin density distribution of the primary donor cation radical P + * in RCs and chromatophores of four species of purple bacteria, all containing Bchl a. The obtained orbital asymmetries of the donors from the four species are then related to the electron transfer and recombination rates that have been published elsewhere (Wang et al, 1994).…”

Section: Charge Separation Occurs Only Via the A-branchmentioning

confidence: 99%

Comparative Study of Reaction Centers from Photosynthetic Purple Bacteria: Electron Paramagnetic Resonance and Electron Nuclear Double Resonance Spectroscopy

Rautter¹,

Lendzian²,

Lubitz³

et al. 1994

Biochemistry

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Reaction centers (RCs) from four species of purple bacteria, Rhodobacter sphaeroides, Rhodobacter capsulatus, Rhodospirillum rubrum, and the recently discovered bacterium Rhodospirillum centenum, have been characterized by optical spectroscopy [Wang, S., Lin, X., Woodbury, N. W., & Allen, J. P. (1994) Photosynth. Res. (submitted for publication)] and magnetic resonance spectroscopy. All RCs contain a bacteriochlorophyll (BChl) a dimer as the primary donor. For Rb. sphaeroides and Rs. rubrum the donor QY optical band is at approximately 865 nm, compared to approximately 850 nm for Rb. capsulatus and Rs. centenum. The primary donor in the RCs can be converted between these two forms by the addition or removal of charged detergents. The electronic structure of the cation radical of the primary electron donor P+. was investigated in these species using electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and electron nuclear triple resonance (TRIPLE) spectroscopy. The EPR line widths of P+. vary significantly and the ENDOR and Special TRIPLE spectra reveal drastic differences in the spin density distribution of the dimer for the different species. Reaction centers from Rb. sphaeroides and Rs. rubrum have a slightly asymmetric spin density distribution over the two halves of the dimer. The respective ratios are 2:1 and 1.6:1 in favor of the L-half of the BChl a dimer. In contrast, the spectra of P+. in reaction centers from Rb. capsulatus and Rs. centenum show an almost complete localization of the unpaired electron on the L-half of the dimer (ratio approximately 5:1).(ABSTRACT TRUNCATED AT 250 WORDS)

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Comparative study of reaction centers from purple photosynthetic bacteria: Isolation and optical spectroscopy

Cited by 51 publications

References 50 publications

Energy trapping and detrapping by wild type and mutant reaction centers of purple non-sulfur bacteria

Energy trapping and detrapping by wild type and mutant reaction centers of purple non-sulfur bacteria

Cofactor-specific photochemical function resolved by ultrafast spectroscopy in photosynthetic reaction center crystals

Comparative Study of Reaction Centers from Photosynthetic Purple Bacteria: Electron Paramagnetic Resonance and Electron Nuclear Double Resonance Spectroscopy

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