Resonance Raman spectroscopy of 2H-labelled spheroidenes in petroleum ether and in the Rhodobacter sphaeroides reaction centre.
As a step towards the structural analysis of the carotenoid spheroidene in the Rhodobacter sphaeroides reaction centre, we present the resonance Raman spectra of 14-2H, 15-2H, 15'-2H, 14'-2H, 14,15'-2H2 and 15-15'-2H2 spheroidenes in petroleum ether and, except for 14,15'-2H2 spheroidene, in the Rb. sphaeroides R26 reaction center (RC). Analysis of the spectral changes upon isotopic substitution allows a qualitative assignment of most of the vibrational bands to be made. For the all-trans spheroidenes in solution the resonance enhancement of the Raman bands is determined by the participation of carbon carbon stretching modes in the centre of the conjugated chain, the C9 to C15' region. For the RC-bound 15,15'-cis spheroidenes, enhancement is determined by the participation of carbon-carbon stretching modes in the centre of the molecule, the C13 to C13' region. Comparison of the spectra in solution and in the RC reveals evidence for an out-of-plane distortion of the RC-bound spheroidene in the central C14 to C14' region of the carotenoid. The characteristic 1240 cm-1 band in the spectrum of the RC-bound spheroidene has been assigned to a normal mode that contains the coupled C12-C13 and C13'-C12' stretch vibrations.
Kok
P
P
Centre for the Study of Excited States of Molecules, Huygens Laboratory, Leiden University, The Netherlands.
Köhler
J
J
Groenen
E J
EJ
Gebhard
R
R
van der Hoef
I
I
Lugtenburg
J
J
Farhoosh
R
R
Frank
H A
HA
D000473:Alkanes; D002338:Carotenoids / Q000737:chemistry*; D003903:Deuterium; D015394:Molecular Structure; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D012997:Solvents; D013059:Spectrum Analysis, Raman
D000473:Alkanes; D045322:Photosynthetic Reaction Center Complex Proteins; D012997:Solvents; C005637:spheroidene; D002338:Carotenoids; D003903:Deuterium; C004544:naphtha