Model systems for rhodopsins: The photolysis of protonated retinal Schiff bases, cyanine dye, and artificial cyanine-bacteriorhodopsin

Journal Article · Wed Apr 26 00:00:00 EDT 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00191a015· OSTI ID:5104219

Friedman, N; Sheves, M; Ottolenghi, M ^[1]

---

1. Weizmann Institute of Science, Rehovot (Israel) Hebrew Univ. of Jerusalem (Israel)

Protonated Schiff bases of retinal (RSBH{sup +}), of its (planar) linear polyene analogue 1,1-didemethylretinal (LRSBH{sup +}), and of an analogous cyanine dye (Cy{sup III}) are submitted to pulsed laser photolysis over a range of solvents and temperatures. Transient phenomena observed with the Cy{sup III} dye are attributed to trans {yields} cis isomerization, followed by secondary excitation which induces rotation about an additional bond. In the cases of RSBH{sup +} and LRSBH{sup +} (photostationary mixtures of cis-trans isomers), laser excitation of deaerated solutions leads to the observation of triplet states. The latter are formed via intersystem crossing (ISC) from a short-lived excited state, generated by multiple excitations of the ground state during the (same) intense laser pulse. O{sub 2} saturation of the solutions suppresses the ISC route, giving rise to a short-lived phototransient observed at low temperatures, which is identified as a C-C conformer. The observations are discussed in light of the possibility that C-C conformers may play a role in the photocycles of visual rhodopsins and of bacteriorhodopsin. Experiments were also performed with an artificial bacteriorhodopsin pigment (bR{sub cy}) carrying a cyanine chromophore analogous to Cy{sup III}. A single photointermediate (bR{sub cy}/I), reminiscent of the K phototransient of bR, is observed and is attributed to a cis isomer. The low activation and preexponential parameters which characterize the thermal relaxation of bR{sub cy}/I are discussed in terms of cis {yields} trans isomerization in a rhodopsin binding site.

• OSTI ID: 5104219
• Journal Information: Journal of the American Chemical Society; (USA), Vol. 111:9; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
CYANINE DYES
PHOTOLYSIS
RHODOPSIN
FUNCTIONAL MODELS
SCHIFF BASES
ABSORPTION SPECTROSCOPY
ACTIVATION ENERGY
ARRHENIUS EQUATION
CHEMICAL REACTION KINETICS
EXCITED STATES
EXPERIMENTAL DATA
ISOMERIZATION
LASERS
POTENTIALS
PULSE TECHNIQUES
SOLVENTS
TEMPERATURE DEPENDENCE
TRANSIENTS
VISCOSITY
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DYES
ENERGY
ENERGY LEVELS
EQUATIONS
IMINES
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PIGMENTS
PROTEINS
REACTION KINETICS
SPECTROSCOPY
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)