EFFECT OF PROTONATION ON THE ISOMERIZATION PROPERTIES OF n‐BUTYLAMINE SCHIFF BASE OF ISOMERIC RETINAL AS REVEALED BY DIRECT HPLC ANALYSES: SELECTION OF ISOMERIZATION PATHWAYS BY RETINAL PROTEINS

Koyama, Yasushi; Kubo, Keishi; Komori, Mika; Yasuda, H.; Mukai, Yoshihiko

doi:10.1111/j.1751-1097.1991.tb02038.x

Cited by 99 publications

(114 citation statements)

References 16 publications

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“…Without the protein environment, this IVR causes the excitation of dark modes throughout the chromophore and thereby produces isomerization at several different locations, as observed experimentally. 49 However, in the binding pocket of the bR pigment, steric and electrostatic constraints will direct the vibrational excitation to be deposited only into selected torsions and HOOPs of the molecule, thereby causing the very specific isomerization at only the C 13 =C 14 bond. It is interesting to compare the photochemical process of bR with the ultrafast 200-fs-isomerization rhodopsin.…”

Section: -15mentioning

confidence: 99%

Femtosecond Stimulated Raman Study of Excited-State Evolution in Bacteriorhodopsin

2005

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Femtosecond time-resolved stimulated Raman spectroscopy (FSRS) is used to examine the photoisomerization dynamics in the excited state of bacteriorhodopsin. Near-IR stimulated emission is observed in the FSRS probe window that decays with a 400-600-fs time constant. Additionally, dispersive vibrational lines appear at the locations of the ground-state vibrational frequencies and decay with a 260-fs time constant. The dispersive line shapes are caused by a nonlinear effect we term Raman initiated by nonlinear emission (RINE) that generates vibrational coherence on the ground-state surface. Theoretical expressions for the RINE line shapes are developed and used to fit the spectral and temporal evolution of the spectra. The rapid 260-fs decay of the RINE peak intensity, compared to the slower evolution of the stimulated emission, indicates that the excited-state population moves in ∼260 fs to a region on the potential energy surface where the RINE signal is attenuated. This loss of RINE signal is best explained by structural evolution of the excited-state population along multiple low-frequency modes that carry the molecule out of the harmonic photochemically inactive Franck-Condon region and into the photochemically active geometry.

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Section: -15mentioning

confidence: 99%

Femtosecond Stimulated Raman Study of Excited-State Evolution in Bacteriorhodopsin

2005

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“…In contrast, illumination of the all-trans chromophore in solution results in several photoproducts with 11-cis being the most dominant (6)(7)(8). The isomerization quantum yield is greater than 50% in proteins (23), but rarely exceeds 20% in solution (6)(7)(8)(9)(10). Finally, the time scale for isomerization in solution has been measured to be 10 ps (9), while it is faster than 2 ps in protein environments (24,25).…”

mentioning

confidence: 95%

The role of intersection topography in bond selectivity ofcis-transphotoisomerization

Ben‐Nun

Molnár

Schulten

et al. 2002

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

148

146

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Ab initio methods are used to characterize the ground and first excited state of the chromophore in the rhodopsin family of proteins: retinal protonated Schiff base. Retinal protonated Schiff base has five double bonds capable of undergoing isomerization. Upon absorption of light, the chromophore isomerizes and the character of the photoproducts (e.g., 13-cis and 11-cis) depends on the environment, protein vs. solution. Our ab initio calculations show that, in the absence of any specific interactions with the environment (e.g., discrete ordered charges in a protein), energetic considerations cannot explain the observed bond selectivity. We instead attribute the origin of bond selectivity to the shape (topography) of the potential energy surfaces in the vicinity of points of true degeneracy (conical intersections) between the ground and first excited electronic states. This provides a molecular example where a competition between two distinct but nearly isoenergetic photochemical reaction pathways is resolved by a topographical difference between two conical intersections.O ne of the simplest means to convert light into mechanical motion at the atomic scale is cis-trans photoisomerization, and it is widely used in photoactive proteins. Retinal protonated Schiff base (RPSB) is the best known biological chromophore, with five double bonds capable of undergoing photoisomerization. A long-standing question has been the mechanism that selects the isomerizing bond, particularly the role of the protein environment in ''steering'' reactivity. The availability of the structures of rhodopsin (1) and bacteriorhodopsin (2-5), coupled with characterization of RPSB solution-phase photochemistry (6-11), provides a unique opportunity to identify this mechanism. Conical intersections (CIs), geometries where two electronic states are truly degenerate, providing doorways from excited to ground electronic states, are widely believed to be important in photochemistry (12)(13)(14), and their role in photoinduced isomerization has been well documented (14-22). However, their role in bond torsion selectivity has yet to be established. In this paper, we show that the topography, or shape, around CIs determines this selectivity in RPSB. This direct connection between CI topography and photochemical selectivity has significant implications for understanding protein ''steering'' and the rational design of molecular optoelectronic devices.Investigations of the photochemistry of RPSB have established that the protein is not an idle spectator; quantum yield, selectivity, and time scales are all significantly different in solution and protein environments. In the protein environment, isomerization occurs exclusively around a single bond, e.g., 11-cis 3 all-trans in rhodopsin and all-trans 3 13-cis in bacteriorhodopsin. In contrast, illumination of the all-trans chromophore in solution results in several photoproducts with 11-cis being the most dominant (6-8). The isomerization quantum yield is greater than 50% in proteins (23), but rarely excee...

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“…In solution, the photoproduct of all-trans retinal with protonated Schiff base is mainly 11-cis [82% (vol/vol) 11-cis͞6% (vol/vol) 13-cis͞12% (vol/vol) 9-cis in methanol; ref. 18], whereas in BR, the photoproduct is 100% (vol͞vol) 13-cis. The quantum efficiency for isomerization in BR (Ϸ0.…”

Section: B Acteriorhodopsin (Br) Is a Light-driven Proton Pump Inmentioning

confidence: 99%

“…19 and 20) is much higher than for retinal in solution (0.13 in methanol; ref. 18). This efficiency is correlated closely with the rate constant of the isomerization, because it occurs on the femtosecond time scale.…”

Section: B Acteriorhodopsin (Br) Is a Light-driven Proton Pump Inmentioning

confidence: 99%

“…For the present study, we prepared [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] O]threonine-labeled BR and used polarized FTIR spectroscopy to investigate the possible involvement of hydrogen-bonding alterations in the photoisomerization of the retinal chromophore. As a result of the accurate detection that we have developed throughout the mid-IR region (23), we found that three threonines change their hydrogen bonding.…”

Section: B Acteriorhodopsin (Br) Is a Light-driven Proton Pump Inmentioning

confidence: 99%

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Local and distant protein structural changes on photoisomerization of the retinal in bacteriorhodopsin

Kandori

Kinoshita

Yamazaki

et al. 2000

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

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The photoisomerization of the retinal in bacteriorhodopsin is selective and efficient and yields perturbation of the protein structure within femtoseconds. The stored light energy in the primary intermediate is then used for the net translocation of a proton across the membrane in the microsecond to millisecond regime. This study is aimed at identifying how the protein changes on photoisomerization by using the O-H groups of threonines as internal probes. Polarized Fourier-transform IR spectroscopy of [3-18 O]threonine-labeled and unlabeled bacteriorhodopsin indicates that 3 of the threonines (of a total of 18) change their hydrogen bonding. One is exchangeable in D 2O, but two are not. A comprehensive mutation study indicates that the residues involved are Thr-89, Thr-17, and Thr-121 (or Thr-90). The perturbation of only three threonine side chains suggests that the structural alteration at this stage of the photocycle is local and specific. Furthermore, the structural change of Thr-17, which is located >11 Å from the retinal chromophore, implicates a specific perturbation channel in the protein that accompanies the retinal motion. B acteriorhodopsin (BR) is a light-driven proton pump inHalobacterium salinarum that contains all-trans retinal as chromophore (1-4). Its tertiary structure has been determined recently by cryoelectron microscopy (5-7) and x-ray crystallography (8-13). The retinal binds covalently to Lys-216 through a protonated Schiff base linkage. Absorption of light triggers a cyclic reaction that comprises a series of intermediates, designated as the J, K, KL, L, M, N, and O states (1-4). Protein structural changes in these intermediate states cause proton translocation across the protein, and their mechanism is the central question in current studies of BR (14).The all-trans to 13-cis photoisomerization leads to the formation of the primary K intermediate (15)(16)(17). It is well known that photoisomerization in BR is highly selective and efficient. In solution, the photoproduct of all-trans retinal with protonated Schiff base is mainly 11-cis [82% (vol/vol) 11-cis͞6% (vol/vol) 13-cis͞12% (vol/vol) 9-cis in methanol; ref. 18], whereas in BR, the photoproduct is 100% (vol͞vol) 13-cis. The quantum efficiency for isomerization in BR (Ϸ0.6; refs. 19 and 20) is much higher than for retinal in solution (0.13 in methanol; ref. 18). This efficiency is correlated closely with the rate constant of the isomerization, because it occurs on the femtosecond time scale. The protein environment thus certainly facilitates the specificity of the reaction of the retinal chromophore.How does the highly selective and efficient isomerization occur in BR? How does the protein respond to the chromophore motion? To address these questions, structural analysis of the primary intermediates is essential. Cryoelectron microscopy of the K intermediate reported that the structural change at this stage is not resolved with 3.5-Å resolution (21). More recent analysis of the K intermediate by x-ray crystallography identified few...

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EFFECT OF PROTONATION ON THE ISOMERIZATION PROPERTIES OF n‐BUTYLAMINE SCHIFF BASE OF ISOMERIC RETINAL AS REVEALED BY DIRECT HPLC ANALYSES: SELECTION OF ISOMERIZATION PATHWAYS BY RETINAL PROTEINS

Cited by 99 publications

References 16 publications

Femtosecond Stimulated Raman Study of Excited-State Evolution in Bacteriorhodopsin

Femtosecond Stimulated Raman Study of Excited-State Evolution in Bacteriorhodopsin

The role of intersection topography in bond selectivity ofcis-transphotoisomerization

Local and distant protein structural changes on photoisomerization of the retinal in bacteriorhodopsin

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