MODELS FOR THE CHROMOPHORE STRUCTURE OF THE PHOTOTRANSFORMATION INTERMEDIATES OF PEA PHYTOCHROME IN VITRO |
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| Authors: | Tohru Sugimoto Yasunori Inoue Hideo Suzuki Masaki Furuya |
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| Affiliation: | *PL Gakuen Women's Junior College, Tondabayashi-shi, Osaka 584, Japan;†Biology Department, Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan;‡Department of Physics, School of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 160, Japan and Division of Biological Regulation, National Institute for Basic Biology, Okazaki 444, Japan |
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| Abstract: | Abstract— The changes in the chromophore structure of pea phytochrome during phototransformation in vitro from the red-light-absorbing form (Pr) to the far-red-light-absorbing form (Pfr), and from Pfr to Pr, were analysed in terms of wavelength and oscillator strength of absorption, using the zero-differential overlap approximation of the molecular orbital theory for electrons. The effect of a point-charge and a point-dipole on the optical absorption of phytochromobilin intermediates were examined using the stationary perturbation theory for degenerate states. The results indicate that the cis-trans photoisomerization of the pyrrole ring D, if any, occurred within 10 μs after a laser-flash excitation of the phytochrome, and that the conformations of phytochromobilin and the protein moiety of phytochrome were not significantly changed during the period of examination of phototransformation in either direction. |
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