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Bathoiodopsin, a Primary Intermediate of Iodopsin at Physiological Temperature
Hideki Kandori, Taku Mizukami, Tetsuji Okada, Yasushi Imamoto, Yoshitaka Fukada, Yoshinori Shichida and Toru Yoshizawa
Proceedings of the National Academy of Sciences of the United States of America
Vol. 87, No. 22 (Nov., 1990), pp. 8908-8912
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2355656
Page Count: 5
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Measurement of the primary photochemical reaction of iodopsin, a chicken red-sensitive cone visual pigment, was carried out at room temperature by using picosecond (ps) laser photolysis. Excitation of iodopsin with a ps green pulse (pulse width, 21 ps) caused the instantaneous formation of a bathochromic product, which was stable on a ps time scale. This product may correspond to "bathoiodopsin," which was detected by low-temperature spectrophotometry. Although bathoiodopsin produced at the temperature of liquid nitrogen or helium reverted to the original pigment (iodopsin) on warming (above -170⚬C), the bathoiodopsin produced at physiological temperature decayed to all-trans-retinal and R-photopsin (the protein moiety of iodopsin) presumably through several intermediates. The absorption maximum of bathoiodopsin at room temperature was at 625 nm, a wavelength slightly shorter than that measured at low temperature (λmax, 640 nm). The extinction coefficient of bathoiodopsin at room temperature was lower than that at low temperature and close to that of the original iodopsin at room temperature.
Proceedings of the National Academy of Sciences of the United States of America © 1990 National Academy of Sciences