Primary donor state mode structure and energy transfer in bacterial reaction centers

Johnson, Sylvia M.; Tang, D.; Jankowiak, Ryszard; Hayes, John M.; Small, Gerald J.; Tiede, D. M.

doi:10.1021/j100378a045

Cited by 92 publications

(78 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The vibrations reflected in our experiments may correspond to intradimer modes; however, such modes are presumably driven by modes of the protein matrix. It should be noted that the frequency (=120 cm-1) of a special-pair mode characterized by photochemical hole-burning (24) is significantly above the frequency range of the present oscillations. The oscillations are clearly associated with the formation of the excited state P*.…”

Section: Discussionmentioning

confidence: 46%

Direct observation of vibrational coherence in bacterial reaction centers using femtosecond absorption spectroscopy.

Vos

Lambry

Robles

et al. 1991

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

290

190

View full text Add to dashboard Cite

It is shown that vibrational coherence modulates the femtosecond kinetics of stimulated emission and absorption of reaction centers of purple bacteria. In the DLL mutant of Rhodobacter capsUlatus, which lacks the bacteriopheophytin electron acceptor, oscillations with periods of -500 fs and possibly also of :2 ps were observed, which are associated with formation of the excited state. The kinetics, which reflect primary processes in Rhodobacter sphaeroides R-26, were modulated by oscillations with a period of 700 fs at 796 nm and =z2 ps at 930 nm. In the latter case, at 930 nm, where the stimulated emission of the excited state, P*, is probed, oscillations could only be resolved when a sufficiently narrow (10 nm) and concomitantly long pump pulse was used. This may indicate that the potential energy surface of the excited state is anharmonic or that low-frequency oscillations are masked when higher frequency modes are also coherently excited, or both. The possibility is discussed that the primary charge separation may be a coherent and adiabatic process coupled to low-frequency vibrational modes.The quantum efficiency of the initial charge-separation process in the reaction center of photosynthetic bacteria is near unity because of the combination of the extreme rapidity of forward electron transfer and the low probability of back reaction. In conventional electron-transfer theory (1, 2), it is assumed that vibrational relaxation takes place on a time scale faster than electron transfer and that electron transfer is essentially nonadiabatic. It may be questioned whether these assumptions are justified for the ultrafast initial reactions taking place in the bacterial reaction center. In particular, electron transfer from an excited state that is not completely vibrationally relaxed (3) may be at the origin of the high quantum yield of charge separation. In this case, vibrational coherence of modes coupled to electron transfer is not necessarily lost on the time scale of the reaction. Recently, theoretical studies have appeared in which it has indeed been suggested that vibrational coherence or coherence in the electronic coupling, or both, play a role in primary electron transfer (4-7).If the vibrational relaxation takes place on a time scale that is not significantly faster than electron transfer, lowfrequency (<100 cm-') vibrations may interfere with the charge-separation reaction. When such vibrations are coherent, oscillations may in principle be observed in the optical transients of the involved electronic state(s). Here we report the observation of coherent processes associated with the excited state in the photosynthetic reaction center.The reaction center of purple bacteria, which are used in this study, normally contains four bacteriochlorophylls [two of which display strong dimeric interaction and are designated P (for "special pair") and two of which, BL and BM, are more monomer-like], two bacteriopheophytins (HL and HM), and two quinones (QA and QB) bound to the protein subunits L and M (8, 9)...

show abstract

Section: Discussionmentioning

confidence: 46%

Direct observation of vibrational coherence in bacterial reaction centers using femtosecond absorption spectroscopy.

Vos

Lambry

Robles

et al. 1991

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

290

190

View full text Add to dashboard Cite

show abstract

“…We suggest that the approach with a lognormal spectral density describes the phonon lineshape more accurately, 25 although to reveal the difference between our approach and that of Hayes et al, 19 i.e., to compare our parameters with the previously published data, 8,9,28 we also show fits and parameters obtained with the G-L J(ω). On the basis of previous work, 8,9,28 only two profiles corresponding to peak frequencies ω ph and ω sp are required to simultaneously fit the P870 and P960 absorption bands and ω B -dependent photochemical (transient) HB spectra. Consistent with earlier assignment, we refer to ω ph as the mean (or rather peak) phonon frequency and ω sp as the special pair marker mode.…”

Section: A Calculation Of Hb Spectramentioning

confidence: 73%

“…We compare el-ph coupling parameters obtained previously for Rb. sphaeroides 8,28 and Rps. viridis, 9,28 using the approach of Hayes et al, 19 with the parameters obtained in this work (using both G-L and lognormal spectral densities).…”

Section: A Calculation Of Hb Spectramentioning

confidence: 99%

“…This approach is compared below with the mean-phonon approximation used in earlier calculations, 8,9,28 where the spectral density was split into multiple effective phonon densities and the continuous weighting factor n(ω; T) was replaced by an effective factor n(ω k ; T) evaluated at a "mean" phonon frequency ω k near the peak of the kth phonon density; and where in place of numerical convolutions, multi-phonon transitions were described simply as increasingly broadened G-L profiles. We suggest that the approach with a lognormal spectral density describes the phonon lineshape more accurately, 25 although to reveal the difference between our approach and that of Hayes et al, 19 i.e., to compare our parameters with the previously published data, 8,9,28 we also show fits and parameters obtained with the G-L J(ω). On the basis of previous work, 8,9,28 only two profiles corresponding to peak frequencies ω ph and ω sp are required to simultaneously fit the P870 and P960 absorption bands and ω B -dependent photochemical (transient) HB spectra.…”

Section: A Calculation Of Hb Spectramentioning

confidence: 99%

See 1 more Smart Citation

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

Reppert

Kell

Pruitt

et al. 2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths. A corrected lineshape function L(ω) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, ωsp, for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers.

show abstract

“…The absorption and hole burning measurements at 2-60K on bacterial RCs have revealed the progression of the enhanced (S --1.2-2) around 150 cm -~ (73, 110 and 148 cm -I) frequency modes which are accompanied by a -30 cm-~ protein mode seen clearly for hole burning in RCs with prereduced HL [3] and found later for neutral acceptor state (with much less spectral resolution) [4,5]. The frequencies found in hole burning experiments in the range of 30-150 cm -~ were established in Raman spectra as well [6].…”

Section: Introductionmentioning

confidence: 98%

Dynamic hole burning within special pair absorption band of Rhodobacter sphaeroides (R‐26) reaction center at room temperature

et al. 1995

View full text Add to dashboard Cite

The absorbance spectrum of reaction centers of Rhodobacter sphaeroides at room temperature consists of relatively narrow spectral components which are moving in the femtosecond time scale and can be bleached by femtosecond laser pulses in the short wavelength region with a subsequent broadening and red shift of the bleaching (time constant ~ 250 fs). These data are discussed in terms of the population of the vibronic wave packets in the ground state by the interaction with phonons at 293K. The motion of these packets is probably responsible for the absorbance spectrum of the primary electron donor P at 293K with enhanced short wavelength components and with suppressed Stokes components.

show abstract

Primary donor state mode structure and energy transfer in bacterial reaction centers

Cited by 92 publications

References 0 publications

Direct observation of vibrational coherence in bacterial reaction centers using femtosecond absorption spectroscopy.

Direct observation of vibrational coherence in bacterial reaction centers using femtosecond absorption spectroscopy.

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

Dynamic hole burning within special pair absorption band of Rhodobacter sphaeroides (R‐26) reaction center at room temperature

Contact Info

Product

Resources

About