A resonance Raman study of the C=C stretch modes in bovine and octopus visual pigments with isotopically labeled retinal chromophores.
Previous resonance Raman spectroscopic studies of bovine and octopus rhodopsin and bathorhodopsin in the C-C stretch fingerprint region have shown drastically different spectral patterns, which suggest different chromophore-protein interactions. We have extended our resonance Raman studies of bovine and octopus pigments to the C=C stretch region in order to reveal a more detailed picture about the difference in retinal-protein interactions between these two pigments. The C=C stretch motions of the protonated retinal Schiff base are strongly coupled to form highly delocalized ethylenic modes located in the 1500 to 1650 cm-1 spectral region. In order to decouple these vibrations, a series of 11,12-D2-labeled retinals, with additional 13C labeling at C8, C10, C11 and C14, respectively, are used to determine the difference of specific C=C stretch modes between bovine and octopus pigments. Our results show that the C9=C10 and C13=C14 stretch mode are about 20 cm-1 lower in the Raman spectrum of octopus bathorhodopsin than in bovine bathorhodopsin, while the other C=C stretch modes in these two bathorhodopsins are similar. In contrast, only the C9=C10 stretch mode in octopus rhodopsin is about 10 cm-1 lower than in bovine rhodopsin, while other C=C stretches are similar.
Huang
L
L
Department of Physics, City College of City University of New York, NY 10031, USA.
Deng
H
H
Koutalos
Y
Y
Ebrey
T
T
Groesbeek
M
M
Lugtenburg
J
J
Tsuda
M
M
Callender
R H
RH
D000818:Animals; D002244:Carbon / Q000737:chemistry; D002417:Cattle; D007553:Isotope Labeling; D049831:Octopodiformes; D012160:Retina / Q000737:chemistry*; D012243:Rhodopsin / Q000031:analogs & derivatives* / Q000737:chemistry; D013059:Spectrum Analysis, Raman
C015017:bathorhodopsin; D002244:Carbon; D012243:Rhodopsin