C14-C15 single bond isomerizations of the retinal chromophore involved in the proton-pumping mechanism of bacteriorhodopsin

Journal Article · Sat Feb 01 00:00:00 EST 1986 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.83.4.967· OSTI ID:5630052

Smith, S O; Hornung, I; van der Steen, R; Pardoen, J A; Braiman, M S; Lugtenburg, J; Mathies, R A

Resonance Raman spectroscopy is used to examine the possibility that C14-C15 single bond isomerizations of the retinal prosthetic group are involved in the photochemical reactions of bacteriorhodopsin. Normal mode calculations show that the vibration that contains predominantly C14-C15 stretch character is approximately equal to 70 cm-1 lower in frequency in the 14-s-cis conformer than in the s-trans case. This geometric effect is insensitive to out-of-plane twists and should be observed in the sterically hindered 13-cis, 14-s-cis retinal protonated Schiff base, which has been proposed as the chromophore in the K and L intermediates of bacteriorhodopsin. Resonance Raman spectra were obtained of K625 by using the low temperature (77 K) spinning-cell technique. Isotopic substitutions with 13C and 2H show that significant C14-C15 stretch character is observed in normal modes at approximately equal to 1185-1195 cm-1. The relatively high frequency of the C14-C15 stretch argues that K625 contains a 13-cis, 14-s-trans chromophore. Similarly, isotopic derivatives show that L550 has a localized C14-C15 stretch at 1172 cm-1, consistent with a 14-s-trans chromophore. These results argue that the primary step in bacteriorhodopsin is a C13=C14 trans----cis photoisomerization that does not involve C14-C15 s-cis structures.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 5630052
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 4
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
14 SOLAR ENERGY
RHODOPSIN
PHOTOCHEMICAL REACTIONS
RAMAN SPECTRA
CARBON 13
CAROTENOIDS
DEUTERIUM
ISOMERIZATION
PHOTOSYNTHETIC BACTERIA
PROTONS
RAMAN SPECTROSCOPY
SCHIFF BASES
BARYONS
CARBON ISOTOPES
CHEMICAL REACTIONS
ELEMENTARY PARTICLES
EVEN-ODD NUCLEI
FERMIONS
HADRONS
HYDROCARBONS
HYDROGEN ISOTOPES
IMINES
ISOTOPES
LASER SPECTROSCOPY
LIGHT NUCLEI
NUCLEI
NUCLEONS
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PROTEINS
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
TERPENES
400500* - Photochemistry
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