Low-Temperature Retinal Photoisomerization Dynamics in Bacteriorhodopsin

Logunov, Stephan L.; Masciangioli, Tina; Kamalov, Valey; El‐Sayed, Mostafa A.

doi:10.1021/jp972921a

Cited by 17 publications

(16 citation statements)

References 27 publications

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“…2 B). These results are in general agreement with previous results (Sharkov et al, 1985;Kobayashi et al, 1991;Mathies et al, 1988;Hasson et al, 1996;Logunov et al, 1996Logunov et al, , 1998.…”

Section: Resultssupporting

confidence: 93%

Comparison of the Dynamics of the Primary Events of Bacteriorhodopsin in Its Trimeric and Monomeric States

Wang¹,

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Heyes

et al. 2002

Biophysical Journal

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In this paper, femtosecond pump-probe spectroscopy in the visible region of the spectrum has been used to examine the ultrafast dynamics of the retinal excited state in both the native trimeric state and the monomeric state of bacteriorhodopsin (bR). It is found that the excited state lifetime (probed at 490 nm) increases only slightly upon the monomerization of bR. No significant kinetic difference is observed in the recovery process of the bR ground state probed at 570 nm nor in the fluorescent state observed at 850 nm. However, an increase in the relative amplitude of the slow component of bR excited state decay is observed in the monomer, which is due to the increase in the concentration of the 13-cis retinal isomer in the ground state of the light-adapted bR monomer. Our data indicate that when the protein packing around the retinal is changed upon bR monomerization, there is only a subtle change in the retinal potential surface, which is dependent on the charge distribution and the dipoles within the retinal-binding cavity. In addition, our results show that 40% of the excited state bR molecules return to the ground state on three different time scales: one-half-picosecond component during the relaxation of the excited state and the formation of the J intermediate, a 3-ps component as the J changes to the K intermediate where retinal photoisomerization occurs, and a subnanosecond component during the photocycle.

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Section: Resultssupporting

confidence: 93%

Comparison of the Dynamics of the Primary Events of Bacteriorhodopsin in Its Trimeric and Monomeric States

Wang¹,

Link

Heyes

et al. 2002

Biophysical Journal

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“…In BR the kinetics at 490 nm (excited-state absorption) and 900 nm (stimulated emission) were used to assign the 500-fs transient to the transition to the first ground-state product J (13,31). Because sSRI has similar absorption properties as BR, the 490-nm absorption transient can be taken as an indication that both processes, the 5-ps and the 33-ps process, are related to the S 1 decay.…”

Section: Discussionmentioning

confidence: 99%

Primary reactions of sensory rhodopsins

Lutz¹

2001

Proceedings of the National Academy of Sciences

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The first steps in the photocycles of the archaeal photoreceptor proteins sensory rhodopsin (SR) I and II from Halobacterium salinarum and SRII from Natronobacterium pharaonis have been studied by ultrafast pump͞probe spectroscopy and steady-state fluorescence spectroscopy. The data for both species of the bluelight receptor SRII suggests that their primary reactions are nearly analogous with a fast decay of the excited electronic state in 300 -400 fs and a transition between two red-shifted product states in 4 -5 ps. Thus SRII behaves similarly to bacteriorhodopsin. In contrast for SRI at pH 6.0, which absorbs in the orange part of the spectrum, a strongly increased fluorescence quantum yield and a drastically slower and biexponential decay of the excited electronic state occurring on the picosecond time scale (5 ps and 33 ps) is observed. The results suggest that the primary reactions are controlled by the charge distribution in the vicinity of the Schiff base and demonstrate that there is no direct connection between absorption properties and reaction dynamics for the retinal protein family.S ensory rhodopsin (SR) I and II are members of the family of retinal-containing membrane proteins of archaea, which also includes the well-known ion pumps bacteriorhodopsin (BR) and halorhodopsin (HR). SRI and SRII act as receptors in phototaxis. In this process light absorption triggers movement of the flagellated cells toward favorable or away from unfavorable environments, depending on the wavelength of the absorbed light. Thus, the SRs provide a simple color-sensing mechanism (1) for haloarchaea like Halobacterium salinarum and other species. Attractant and repellent reactions of the cell are triggered by light absorption of specific photochromic states of these photoreceptors. In SRI, the dark-adapted state SRI 587 is converted into a blue-shifted intermediate S 373 by absorbing orange light around 590 nm (2), leading to positive signaling via the closely coupled transducer protein HtrI (3). Absorption of a UV photon in the S 373 state leads to a repellent stimulus, resulting in a photophobic response of the cell. SRII is a blue-light receptor with maximum ground-state absorption around 490 nm. The repellent signaling is initiated by the intermediate SRII 360 (M) in the course of the SRII photocycle (4).SRI and SRII are structurally very similar to BR and HR; sequence homology is especially striking in the chromophore environment (5, 6). Although 13 of 21 residues in a 5-Å shell around the retinal atoms are strictly conserved in BR, HR, and SRI of all species sequenced to date, SRII has three residues less conserved (7). This might be one reason for the blue-shifted absorption maximum of SRII compared with the other archaeal receptor proteins (8). Photoexcitation triggers a series of conformational changes initiated by trans-cis isomerization of the retinal chromophore in all retinal-containing membrane proteins (9). The first events lead to the formation of a red-shifted intermediate observed on the subnanosecond ...

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“…The picosecond fluorescence lifetime of carotenoids, retinoids, diazo dyes, diphenyl, triphenylmethanes, stryryl dyes (Table 3) have been postulated to arise from internal barrierless rotation in the excited state,84 although some reports suggest the involvement of fast internal conversion 85…”

Section: Theory Of Fluorescence Lifetime and Processes Affecting Flmentioning

confidence: 99%