Primary events in bacteriorhodopsin probed by subpicosecond spectroscopy

Sharkov, A. V.; Pakulev, A. V.; Чекалин, С. В.; Matveetz, Yuri A.

doi:10.1016/0005-2728(85)90031-3

Cited by 148 publications

(111 citation statements)

References 22 publications

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“…1) is not exponential and can be fitted to two lifetime components of Ϸ500 fs (80-95%) and 3 ps (20-5%) (16)(17)(18)(19)(20)(21)(22)(23). With a better signal-to-noise ratio, the early lifetime itself is found to be biexponential with 0.24 and 0.75 ps components in the ratio of 2:1 (24).…”

Section: Discussionmentioning

confidence: 99%

“…The first excitation pulse at 570-580 nm starts the bR photocycle by exciting the retinal molecule into its excited state S 1 . The excited state lifetime is in the 300-to 500-fs range (15)(16)(17)(18)(19)(20)(21)(22). S 1 has an absorption maximum at 490 nm (22).…”

Section: Methodsmentioning

confidence: 99%

“…The specific ultrafast, all-trans, 13-cis photoisomerization of the retinal in bR is the purple membrane photosynthesis key event which has a quantum yield of 55%. The photoisomerization in bR has been studied extensively by using methods of ultrafast optical spectroscopy (15)(16)(17)(18)(19)(20)(21)(22). The results of timeresolved Raman studies show that retinal isomerization takes place on a picosecond timescale (23).…”

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confidence: 99%

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The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies

Logunov

Volkov

Braun

et al. 2001

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

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We present the results of two-pump and probe femtosecond experiments designed to follow the relaxation dynamics of the lowest excited state (S 1) populated by different modes. In the first mode, a direct (S0 3 S1) radiative excitation of the ground state is used. In the second mode, an indirect excitation is used where the S 1 state is populated by the use of two femtosecond laser pulses with different colors and delay times between them. The first pulse excites the S 0 3 S1 transition whereas the second pulse excites the S 1 3 Sn transition. The nonradiative relaxation from the Sn state populates the lowest excited state. Our results suggest that the S 1 state relaxes faster when populated nonradiatively from the Sn state than when pumped directly by the S0 3 S1 excitation. Additionally, the S n 3 S1 nonradiative relaxation time is found to change by varying the delay time between the two pump pulses. The observed dependence of the lowest excited state population as well as its dependence on the delay between the two pump pulses are found to fit a kinetic model in which the S n state populates a different surface (called S 1) than the one being directly excited (S 1). The possible involvement of the Ag type states, the J intermediate, and the conical intersection leading to the S 0 or to the isomerization product (K intermediate) are discussed in the framework of the proposed model. Halobacterium salinarum (Halobium salinarium) is a member of Halobacteria, which is part of the domain Archaea. In an anaerobic condition under light illumination, H. salinarum demonstrates a pH decrease in cell suspension and ATP synthesis (1, 2), the main features of photosynthesis. The photosynthetic activity in H. salinarum was attributed to bacteriorhodopsin (bR), a 26-kDa protein that is hexagonally packed within the purple membrane (1-4). Since the discovery of the purple membrane, its enigmatically efficient photosynthesis is in the center of the most active research. To our surprise, the archaic organism effectively utilizes more than 50% of the absorbed light energy (5, 6).Retinal, a light-absorbing polyene, is the bR chromophore and is linked to its Lys-216 by a protonated Schiff base. The chromophore undergoes light-induced isomerization and masters proton transfer across the membrane (7-11). The photoisomerization of retinal initiates a series of retinal protein structural reconformations of the bacteriorhodopsin that lead to the formation of different intermediates and finally return it to its initial state with all-trans-retinal. Overall, this photocycle consists of at least seven intermediates of bR with different visible absorption spectra and lifetimes bR 568 3 S 1 3 J 3 K 630 3 L 550 3 M 412 3 N 520 3 O 640 3 bR 568 (4).Retinal in solution shows relatively slow and nonselective photoisomerization around several double bonds (12-14) with low yield. The specific ultrafast, all-trans, 13-cis photoisomerization of the retinal in bR is the purple membrane photosynthesis key event which has a quantum yield of 55%. The p...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies

Logunov

Volkov

Braun

et al. 2001

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

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“…rely on the ultrafast isomerization of the retinal chromophore (1). This process has been intensively investigated by fs pump-probe and f luorescence up-conversion spectroscopy in the visible (VIS) and͞or near-IR (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13), revealing the retinal excited-state dynamics before isomerization and the build-up of the isomerized form. Time-resolved VIS-pump͞mid-IR probe experiments on bacteriorhodopsin (bR) established that the isomerization time is Ն400 fs (14).…”

mentioning

confidence: 99%

Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption

Schenkl

Mourik

Friedman

et al. 2006

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

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A visible-pump͞UV-probe transient absorption is used to characterize the ultrafast dynamics of bacteriorhodopsin with 80-fs time resolution. We identify three spectral components in the 265-to 310-nm region, related to the all-trans retinal, tryptophan (Trp)-86 and the isomerized photoproduct, allowing us to map the dynamics from reactants to products, along with the response of Trp amino acids. The signal of the photoproduct appears with a time delay of Ϸ250 fs and is characterized by a steep rise (Ϸ150 fs), followed by additional rise and decay components, with time scales characteristic of the J intermediate. The delayed onset and the steep rise point to an impulsive formation of a transition state on the way to isomerization. We argue that this impulsive formation results from a splitting of a wave packet of torsional modes on the potential surface at the branching between the all-trans and the cis forms. Parallel to these dynamics, the signal caused by Trp response rises in Ϸ200 fs, because of the translocation of charge along the conjugate chain, and possible mechanisms are presented, which trigger isomerization.ultrafast spectroscopy ͉ retinal proteins ͉ translocation of charge ͉ structural dynamics T he different biological functions of retinal proteins (vision, ion pumping, light signaling, etc.) rely on the ultrafast isomerization of the retinal chromophore (1). This process has been intensively investigated by fs pump-probe and f luorescence up-conversion spectroscopy in the visible (VIS) and͞or near-IR (2-13), revealing the retinal excited-state dynamics before isomerization and the build-up of the isomerized form. Time-resolved VIS-pump͞mid-IR probe experiments on bacteriorhodopsin (bR) established that the isomerization time is Ն400 fs (14). Indeed, the excited-state lifetime of 300 -500 fs (12, 15) goes hand-in-hand with the rise times observed for the 13-cis photoproduct (3,4,14), whereas a longer time scale of 3-4 ps has been attributed to vibrational relaxation of the photoproduct (14).The mechanism leading to the isomer is still subject to debate. Using Ͻ5-fs pulses, Kobayashi et al. (11) were able to monitor changes in the high-frequency vibrational spectrum of the excited state, suggesting that retinal is in a twisted, nonplanar configuration during the initial 200 fs. They also showed that the high-frequency modes were modulated with a period of Ϸ200 fs, corresponding to the low-frequency torsional modes observed in transient absorption experiments at 800-nm probe wavelength (16). That the system is all-trans-like during the first 200 fs is in line with Zhong et al. (17), who carried out transient absorption studies on wild-type bR and bR reconstituted with retinal analogs that cannot undergo isomerization and found identical dynamics during the initial 200 fs. In addition, McCamant et al. (18) recently showed by fs-stimulated Raman spectroscopy that the high-frequency modes (1,000-1,500 cm Ϫ1 ) decay on a time scale of Ϸ250 fs. They argued that this observation points to the excited-sta...

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“…lt is thought that the bR photocycle consists of five (perhaps six) intermediates (Xie et al, 1987;Ames & Mathies, 1990;Varo & Lanyi, 1990 (Sharkov et al, 1985;Mathies et al, 1988;Pollard et al, 1990). Femtosecond resonance Raman spectroscopy was usgd to identify J .…”

Section: IIImentioning

confidence: 99%

Trapping the M sub 1 and M sub 2 substrates of bacteriorhodopsin for electron diffraction studies

Perkins¹

1992

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Primary events in bacteriorhodopsin probed by subpicosecond spectroscopy

Cited by 148 publications

References 22 publications

The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies

The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies

Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption

Trapping the M sub 1 and M sub 2 substrates of bacteriorhodopsin for electron diffraction studies

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