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Picosecond Resonance Coherent Anti‐Stokes Raman Spectroscopy of Light‐ and Dark‐Adapted Bacteriorhodopsin
Author(s) -
Ujj L.,
Atkinson G.H.
Publication year - 1993
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.199300026
Subject(s) - chemistry , bacteriorhodopsin , picosecond , resonance raman spectroscopy , raman spectroscopy , resonance (particle physics) , spectroscopy , coherent anti stokes raman spectroscopy , coherent spectroscopy , nuclear magnetic resonance , photochemistry , molecular physics , atomic physics , optics , raman scattering , laser , physics , astronomy , biochemistry , membrane
Coherent anti‐Stokes Raman scattering (CARS) from the C=C stretching band region of retinal, recorded with low‐power, 7‐ps (fwhm) laser excitation selected to be in electronic resonance with the retinal chromophore, is presented for light‐ and dark‐adapted bacteriorhodopsin (BR) samples. By minimizing photochemistry with low‐power excitation, the picosecond resonance CARS (PR/CARS) spectrum of BR‐570 (13‐ trans , 15‐ anti ‐retinal) is obtained directly from the light‐adapted BR sample. The PR/CARS spectrum of BR‐548 (13‐ cis , 15‐ syn retinal) is derived from a quantitative analysis of PR/CARS data from dark‐adapted BR which contains comparable amounts of BR‐570 and BR‐548. Band origin positions, lineshapes, relative intensities, and phase factors describing the electronic resonances are obtained from a quantitative fit of the PR/CARS spectra to third‐order susceptibility (χ (3) ) relationships. These PR/CARS data, the first reported for a molecular system as large as BR, demonstrate the experimental viability of CARS for recording the vibrational spectrum of a chromophore within a trans‐membrane protein. In addition, the χ (3) analysis shows that a CARS spectrum of a mixture of isomeric chromophores can be quantitatively separated into CARS data assignable to its individual components. The significance of these results with respect to analyzing picosecond time‐resolved CARS data from intermediates in the BR photocycle is discussed.