14-Fluorobacteriorhodopsin and other fluorinated and 14-substituted analogs. An extra, unusually red-shifted pigment formed during dark adaptation

Abstract

Five vinyl-substituted fluororetinal analogues (8-F, 10-F, 12-F, 14-F, and 13,14-F2) were found to give bacteriorhodopsin analogues with properties similar to those of the parent system. Of these, only 14-fluororetinal was found to give an extra red-shifted BR analogue (lambda max less than or equal to 680 nm) in equilibrium with the normal 587-nm pigment. The 680-nm pigment was enriched upon irradiation. It rearranged to the 587-nm pigment at room temperature (delta E [symbol: see text] = 20.8 kcal/mol). Chromophore extraction experiments revealed the all-trans geometry for the 680-nm pigment. 14-Chlororetinal gave a similarly red-shifted pigment while 14-methylretinal did not. A scheme for dark adaptation of the 14-halogenated bacteriorhodopsins has been proposed in which the new red-shifted pigment was assigned the all-trans, 15-syn geometry.

Photochromic polymer films based on a 14-F bacteriorhodopsin derivative

“…Processes of reconstitution with different isomers of 14-F run with different rates, as it has been observed [21], but most likely an equilibrium is established between isomers in reconstituted pigments after 1 h of reconstitution, similar to the observation in Ref. [24], so it is more appropriate that resulted pigment would not be further specified as all-trans and 13-cis.…”

14‐Fluoro‐Bacteriorhodopsin Gelation Films for Dynamic Holography Recording¶

“…Although an O‐intermediate is not formed in the polymer film based on BR (22) and red light does not provide a pathway for P‐ and Q‐like intermediate generation from the O‐intermediate (Scheme 1), the formation of a small amount of the P‐intermediate by excitation of the laser‐induced blue membrane cannot be excluded (23). Alternatively, this blue‐shifted photoproduct might be related to the minor absorption band in the 440‐nm range of 14‐F BR, which would not be involved in the photocycle (8,9). Even the phototransformations of a very small quantity of this photoproduct could contribute to the holographic recording kinetics (12).…”

“…Red‐shifted artificial pigments resulting from the incorporation of strong electron‐withdrawing fluorine substituents in the C‐13 or C‐14 positions of the chromophore polyene chain (such as 13‐trifluorobacteriorhodopsin [13‐CF 3 BR] and 14‐fluorobacteriorhodopsin [14‐F BR]) have already been described (7,8). Upon reconstitution with the white membrane of JW2N strain, 14‐ fluororetinal showed the presence of an extra red‐shifted minor BR‐analog ( λ max = 680 nm) in equilibrium with the major 587 nm pigment (8). This 680 nm pigment displaying an additional absorption band at 440 nm was enriched when irradiated and rearranged to the 587 nm pigment at room temperature.…”

Bacteriorhodopsin Analogs from Diphenylpolyene Chromophores¶

“…Over the years much effort has been directed toward understanding the spectral and photochemical properties of bR. A large number of synthetic chromophore analogs have been incorporated into the binding site of bR, and the observations of the resulting opsin shifts (OS) and photochemical properties have been analyzed in terms of chromophore–protein electrostatic and conformationally restrictive interactions (5–25). It has been found that the binding site of bR is quite flexible because retinal analogs with substantially bulky groups in the ring portion of the retinal can be accommodated in the bR binding site (23,24).…”