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ELECTRIC DICHROISM OF PURPLE MEMBRANE SUSPENSIONS
Author(s) -
Kimura Yoshiaki,
Ikegami Akira,
Ohno Koki,
Saigo Satoshi,
Takeuchi Yasuaki
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb05443.x
Subject(s) - electric field , membrane , dipole , perpendicular , dichroism , polarizability , linear dichroism , electric dipole moment , circular dichroism , chemistry , molecular physics , materials science , analytical chemistry (journal) , optics , crystallography , physics , chromatography , molecule , biochemistry , geometry , mathematics , organic chemistry , quantum mechanics
— Suspensions of purple membranes were exposed to reversing rectangular pulses of relatively low electric field (less than 100V/cm) at various frequencies. Orientation of the membranes was estimated by measuring linear dichroism at 565nm. In the electric field of frequency lower than about 10Hz the purple membranes tended to align perpendicular to the electric field. This orientation was induced mostly by permanent dipole which was perpendicular to the membrane surface. The value of permanent dipole moment was determined to be 140D per protein at pH 7.0, 25°C, in the presence of 5m M phosphate buffer. In an electric field of frequency more than 100Hz the membrane tended to align parallel to the electric field. Electric polarizability parallel to the membrane surface was estimated to be 1 ± 10 −12 cm 3 under the same conditions. Electric dichroism of light‐adapted and dark‐adapted purple membranes was found to coincide with each other at high frequency. From this result the angle of retinal to the membrane surface was concluded to be the same between light‐adapted and dark‐adapted bacteriorhodopsins.