Electronic Energy Transfer in Photosynthetic Bacterial Reaction Centers

Jean, John M.; Chan, Chi-Kin; Fleming, Graham R.

doi:10.1002/ijch.198800027

Cited by 49 publications

(84 citation statements)

References 17 publications

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“…[12,25,26]. The overlap between BChl a emission with ground state absorption of P + is a significant factor influencing the rate of BChl a → P y+ EET [44]. Based on time-resolved BChl a fluorescence spectra [43] and calculated absorption properties of P y+ , as depicted in Fig 6a (curve 6) and Table 2 it is deduced that the BChl a → P y+ EET rate can achieve almost maximal values.…”

Section: Discussionmentioning

confidence: 92%

Analysis of absorption spectra of purple bacterial reaction centers in the near infrared region by higher order derivative spectroscopy

Mikhailyuk¹,

Knox²,

Paschenko³

et al. 2006

Biophysical Chemistry

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Section: Discussionmentioning

confidence: 92%

Analysis of absorption spectra of purple bacterial reaction centers in the near infrared region by higher order derivative spectroscopy

Mikhailyuk¹,

Knox²,

Paschenko³

et al. 2006

Biophysical Chemistry

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“…Their pump-probe data identify an absorption feature centered at 825 nm and show rapid spectral changes around 800 nm that are interpreted as a 260 cm -1 red shift of 1 B over 20 fs. The 825 nm band is assigned to P + and, as for Jean et al, 17 the red shift of 1 B is necessary to achieve sufficient spectral overlap with a ground state to P + absorption. The spectral shift they observe contrasts with the time-resolved emission spectrum presented here for WT RCs at 85 K, which shows essentially no Stokes shift on the 100 fs time scale.…”

Section: Discussionmentioning

confidence: 92%

Excited State Energy Transfer Pathways in Photosynthetic Reaction Centers. 3. Ultrafast Emission from the Monomeric Bacteriochlorophylls

et al. 2000

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Ultrafast singlet excited state energy transfer occurs from the monomeric bacteriopheophytin (H) and bacteriochlorophyll (B) chromophores to the primary electron donor or special pair (P) in bacterial photosynthetic reaction centers. Because of rapid quenching of the singlet excited state of B by energy transfer to P, 1 B emission has not previously been observed in functional reaction centers. Using fluorescence upconversion, spontaneous fluorescence associated with the monomeric bacteriochlorophylls is observed for excitation of the monomeric bacteriochlorophylls and bacteriopheophytins at 85 K. The decay kinetics of the fluorescence match the kinetics of the rise of emission from 1 P, the ultimate acceptor of singlet energy. Together with measurements of the time-resolved fluorescence anisotropy, the data suggest that 1 B is populated in the energy transfer pathway from 1 H to P. By exciting H in wild-type and in the reaction center mutant M182HL, where contributions from the chromophores in the B sites on the L and M sides are spectrally resolved, the amplitudes of the kinetic traces at several wavelengths between 790 and 825 nm can be used to construct the time-resolved emission spectrum of 1 B. The Stokes shift of the accessory bacteriochlorophylls in wild-type on the femtosecond time scale is close to zero, while for the monomeric bacteriopheophytin in the B M binding site in the M182HL mutant, the Stokes shift is less than 100 cm -1 . These results have significant implications for the mechanism of ultrafast energy transfer in the reaction center.The bacterial photosynthetic reaction center (RC) is responsible for the initial light-driven charge separation events in photosynthesis. Light energy absorbed by antenna complexes is funneled to the special pair in the RC, and 1 P transfers an electron to an electron acceptor, rapidly trapping the excitation energy in a transient charge-separated species. In isolated RCs, excitation of the special pair can be achieved by rapid singlet excited state energy transfer from the monomeric bacteriopheophytins and bacteriochlorophylls. 1-3 A schematic diagram illustrating the arrangement of the chromophores that are relevant to both the energy and electron-transfer processes is shown in Figure 1 (top panel) based on the X-ray structure, 4 and a putative singlet excitation energy transfer scheme paralleling the structure is shown in Figure 1 (bottom panel). The chromophores labeled B L and B M are monomeric bacteriochlorophylls on the functional and nonfunctional sides, respectively, of the RC; the chromophores labeled H L and H M are monomeric bacteriopheophytins on the functional and nonfunctional sides, respectively. Functional is used here to denote the electrontransfer process 1 P f P + H L -which is found to occur almost exclusively in wild-type RCs at all temperatures, despite the structural symmetry of the RC that suggests that 1 P f P + H M -might be equally likely to occur.It is possible to study the rate of singlet energy transfer from the B and H chromophore...

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“…Excitation transfer from B800 to B850 occurring through the higher lying exciton state would be analogous to what has been proposed for energy transfer from the accessory bacteriochlorophyll to the special pair of the reaction center. 40,42 The distinction between transfer into a vibronic or excitonic level can be experimentally addressed by polarized transient absorption experiments on B850 since transfer into the exciton states may give rise to different polarization behavior than transfer into an excited vibrational level.…”

Section: Nf(e)mentioning

confidence: 99%

Electronic Excitation Transfer in the LH2 Complex ofRhodobacter sphaeroides

et al. 1996

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Ultrafast fluorescence upconversion measurements were carried out on the peripheral (LH2) light harvesting antenna complex of Rhodobacter sphaeroides isolated in the detergents N-octyl--D-glucopyranoside and lauryl dimethylamine oxide. The B800 and B850 bands were excited in separate experiments, and the B850 emission was detected in each case. We make use of the recently determined crystal structure of a purple bacterial LH2 complex to simulate our data and to calculate the exciton level structure of the B850 aggregate. The B800 to B850 excitation transfer occurs with a 650 fs time constant. The depolarization of B850 emission follows a wavelength dependent, biexponential decay with time constants 50-90 and 400-500 fs. We can reproduce the non-exponentiality of the depolarization by assuming incoherent hopping between dimeric sites with a 250 cm -1 full width at half-maximum (fwhm) Gaussian distribution of site energies (inhomogeneity). We calculate the homogeneous hopping time between dimers in B850 to be ∼100 fs. The exciton calculations including pigment energetic disorder demonstrate the validity of a hopping picture of excitation transfer within the B850 band at room temperature.

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Electronic Energy Transfer in Photosynthetic Bacterial Reaction Centers

Cited by 49 publications

References 17 publications

Analysis of absorption spectra of purple bacterial reaction centers in the near infrared region by higher order derivative spectroscopy

Analysis of absorption spectra of purple bacterial reaction centers in the near infrared region by higher order derivative spectroscopy

Excited State Energy Transfer Pathways in Photosynthetic Reaction Centers. 3. Ultrafast Emission from the Monomeric Bacteriochlorophylls

Electronic Excitation Transfer in the LH2 Complex ofRhodobacter sphaeroides

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