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Vibrational Analysis of Coherent Anti‐Stokes Resonance Raman Spectra from Bacteriorhodopsin Containing Isotopically Substituted Retinal Chromophores
Author(s) -
Popp J.,
Popp A.,
Ujj L.,
Atkinson G. H.,
Sheves M.,
Ottolenghi M.
Publication year - 1996
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199602)27:2<87::aid-jrs928>3.0.co;2-6
Subject(s) - raman spectroscopy , resonance (particle physics) , bacteriorhodopsin , chemistry , picosecond , overtone , chromophore , isotopic shift , raman scattering , molecular vibration , coherent anti stokes raman spectroscopy , analytical chemistry (journal) , retinal , spectral line , nuclear magnetic resonance , photochemistry , laser , optics , atomic physics , organic chemistry , biochemistry , physics , astronomy , membrane
Vibrational spectra recorded by coherent anti‐Stokes resonance Raman scattering (CARS) from bacteriorhodopsin (BR) samples containing isotopically substituted ( 2 H and 13 C) retinal chromophores were measured using high repetition rate, low‐power, picosecond pulsed excitation (λ 1 =580 nm and λ s =640±3 nm). These picosecond resonance CARS (PR/CARS) data were analyzed via third‐order susceptibility relationships [χ ( 3 ) ] to obtain band origins, bandwidths, relative intensities, and electronic phase factors assignable to all significant vibrational Raman features in the 1490–1700 cm −1 wavenumber region (the ethylenic stretching and C = N–H rocking or Schiff base modes). Isotopic substitution selectively places 2 H at C 15 , 13 C singly at the C 10 position and at the C 14 position, and 13 C simultaneously in positions of C 14 and C 15 . Each isotopic BR sample was examined not only in H 2 O, but also in D 2 O, which places a 2 H at the Schiff base nitrogen of the retinal. In addition, PR/CARS data were recorded from each isotopic BR sample following either light adaptation [i.e. the BR sample contained a single retinal isomer (all‐ trans , 15‐ anti or BR‐570)] or dark adaptation [i.e. the BR sample contained a mixture of comparable amounts of retinal isomers (BR‐570 and 13‐ cis , 15‐ syn or BR‐548)]. Excellent agreement was found between the vibrational features observed by PR/CARS and those obtained from spontaneous resonance Raman measurements from the same isotopically substituted BR pigments. Several new vibrational features were also found from the PR/CARS data. Vibrational Raman data from three of the isotopic BR samples in D 2 O are reported for the first time.