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Between the ground‐ and M‐state of bacteriorhodopsin the retinal transition dipole moment tilts out of the plane of the membrane by only 3°
Author(s) -
Otto Harald,
Heyn Maarten P.
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)81163-3
Subject(s) - bacteriorhodopsin , transition dipole moment , dipole , ground state , chemistry , chromophore , anisotropy , membrane , absorption (acoustics) , halobacterium , molecular physics , crystallography , photochemistry , atomic physics , optics , physics , organic chemistry , biochemistry
The orientation of the transition dipole moments in the ground state and the M‐intermediate of bacteriorhodopsin were determined by time‐resolved and steady‐state polarized absorption spectroscopy on samples of oriented immobilized purple membranes. The angle between the transition dipole moment and the membrane normal decreases from 66.8±0.5° in the all‐ trans ground state to 64.1±0.8° in the 13‐ cis M‐state. The light‐induced isomerization of the chromophore is thus accompanied by an orientational change of only about 3° out of the plane of the membrane. The absorption anisotropy at 410 nm remains constant over more than 4 decades of time covering both the rise and decay of M. Conformational changes accompanying a sequential M 1 →M 2 transition thus do not affect the chromophore orientation.