Probing the Ultrafast Charge Translocation of Photoexcited Retinal in Bacteriorhodopsin

Schenkl, Selma; Mourik, Frank van; Zwan, Gert van der; Haacke, S.; Chergui, Majed

doi:10.1126/science.1111482

Cited by 140 publications

(189 citation statements)

References 22 publications

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“…4a), similar spectral features appear for both species. As already discussed (19) and shown in Fig. 4 Inset, A 1 ( ) maps the Trp absorption.…”

Section: Resultsmentioning

confidence: 91%

“…19. It rises on a 150-to 200-fs time scale and recovers in a biexponential fashion with time constants of 1 ϭ 420 fs, 2 ϭ 3.5 ps, typical of retinal, and a constant signal ϱ (19). The wavelength-dependent amplitudes of the transients F i (t) are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…F 1 , the only bleach transient, exhibits a rise time longer than the cross correlation, as already discussed in ref. 19. It rises on a 150-to 200-fs time scale and recovers in a biexponential fashion with time constants of 1 ϭ 420 fs, 2 ϭ 3.5 ps, typical of retinal, and a constant signal ϱ (19).…”

Section: Resultsmentioning

confidence: 99%

“…In a recent report (19), we presented results of a fs VIS-pump͞UV-probe transient absorption study of bR, in which we followed the response of the tryptophan (Trp) residues close to retinal, after excitation of the latter. We found that the Trp response evolves on a time scale of 150-200 fs and showed that it results from the longhypothesized (20,21) translocation of charge along excited retinal, which increases the difference dipole moment with respect to the ground state.…”

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confidence: 99%

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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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“…4a), similar spectral features appear for both species. As already discussed (19) and shown in Fig. 4 Inset, A 1 ( ) maps the Trp absorption.…”

Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

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.

Self Cite

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“…Exciton stick spectra for absorption, CD and linear dichroism (LD) were calculated from the orientations of the Trp molecules in the dominant confirmation and the diagonalized Hamiltonian matrix using the formula described by Pearlstein [73]. Experimental spectra were calculated by applying a Gaussian function to each exciton transition using an assumed full-width half maximum value of 3500 cm 21 as commonly observed for Trp [74,75]. These were then compared with experimental absorption, CD and LD spectra adapted from Mozo-Villarias et al [76], Clark et al [77] and Marrington et al [78], respectively.…”

Section: Alignment With Experimental Spectramentioning

confidence: 99%

The feasibility of coherent energy transfer in microtubules

Craddock

Friesen

Mane

et al. 2014

J. R. Soc. Interface.

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It was once purported that biological systems were far too 'warm and wet' to support quantum phenomena mainly owing to thermal effects disrupting quantum coherence. However, recent experimental results and theoretical analyses have shown that thermal energy may assist, rather than disrupt, quantum coherent transport, especially in the 'dry' hydrophobic interiors of biomolecules. Specifically, evidence has been accumulating for the necessary involvement of quantum coherent energy transfer between uniquely arranged chromophores in light harvesting photosynthetic complexes. The 'tubulin' subunit proteins, which comprise microtubules, also possess a distinct architecture of chromophores, namely aromatic amino acids, including tryptophan. The geometry and dipolar properties of these aromatics are similar to those found in photosynthetic units indicating that tubulin may support coherent energy transfer. Tubulin aggregated into microtubule geometric lattices may support such energy transfer, which could be important for biological signalling and communication essential to living processes. Here, we perform a computational investigation of energy transfer between chromophoric amino acids in tubulin via dipole excitations coupled to the surrounding thermal environment. We present the spatial structure and energetic properties of the tryptophan residues in the microtubule constituent protein tubulin. Plausibility arguments for the conditions favouring a quantum mechanism of signal propagation along a microtubule are provided. Overall, we find that coherent energy transfer in tubulin and microtubules is biologically feasible.

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Protein‐Controlled Ultrafast Photoisomerization in Rhodopsin and Bacteriorhodopsin

Kandori

2011

Supramolecular Photochemistry

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Probing the Ultrafast Charge Translocation of Photoexcited Retinal in Bacteriorhodopsin

Cited by 140 publications

References 22 publications

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

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

The feasibility of coherent energy transfer in microtubules

Protein‐Controlled Ultrafast Photoisomerization in Rhodopsin and Bacteriorhodopsin

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