Rapid charge separation and bathochromic absorption shift of flash-excited bacteriorhodopsins containing 13-Cis or all-trans forms of substituted retinals
Bacteriorhodopsins (BRs) containing retinal, 13-ethylretinal, 13-methoxyretinal, and 13-demethylretinal were investigated flash spectroscopically and photoelectrically. In all preparations, bathochromic absorption bands occurred within less than 5 ns although the analogue BRs, due to the chemical structure of the retinal compounds, were in an invariant 13-cis or all-trans form. The lifetimes of these K states varied over 6 orders of magnitude. Photoelectric measurements demonstrated that a rapid charge separation process occurred within less than 100 ps for all preparations. The magnitude and the direction of the charge separation process were nearly the same for all BRs, except of that of 13-demethylretinal-containing BR, which under identical conditions exhibited at 3 times larger amplitude. Thus, an early charge separation connected with a red shift of the absorption maximum is the common consequence of light absorption. This process takes place, regardless of whether the chromophore is originally bound to the protein in the all-trans configuration with the anti-geometry for the Schiff base group or in the 13-cis configuration with the syn geometry for the Schiff base group. The K intermediates form as the result of the disruption of salt bridges between the protonated Schiff bases and their unprotonated counterions for the cis or trans states, respectively, and the subsequent association of the Schiff base groups to another protonated group. On the basis of the generally accepted mechanism, a possible explanation for the exclusively trans-coupled proton translocation and the malfunction of the cis cycle is discussed.
- Research Organization:
- Univ. of Osnabrueck, West Germany
- OSTI ID:
- 6563020
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:3; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ABSORPTION SPECTROSCOPY
CHROMATOGRAPHY
IMINES
LASER SPECTROSCOPY
LASERS
LIQUID COLUMN CHROMATOGRAPHY
NEODYMIUM LASERS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOSYNTHETIC BACTERIA
PIGMENTS
PROTEINS
RHODOPSIN
SCHIFF BASES
SEPARATION PROCESSES
SOLID STATE LASERS
SPECTROSCOPY
STEREOCHEMISTRY
VITAMIN A
VITAMINS