INTERPRETATION OF THE 'DICHROIC ORIENTATION' OF PHYTOCHROME |
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Authors: | Tohru Sugimoto Etsuro Ito Hideo Suzuki |
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Institution: | Biophysics Laboratory, College of Engineering, Kanto Gakuin University, Mutsuura, Kanazawa-ku, Yokohama 236, Japan;Department of Physics, School of Science and Engineering, Waseda University, Okubo, Shinjuku-ku, Tokyo 160, Japan |
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Abstract: | The dichroic orientation of phytochrome observed both in the phytochrome-mediated phototropism in Adiantum protonemata and in the phytochrome-mediated chloroplast movement in Mougeotia were analyzed in terms of the orientation of the transition moment associated with the long-wavelength absorption band, assuming that phytochrome, associated with the plasma membrane, rotates around the normal to the membrane. The orientation of the long-wavelength transition moment of the phytochrome chromophore was calculated using the zero-differential overlap approximation of the molecular orbital theory for ir-electrons. The results indicate that the orientation of the long-wavelength transition moment mainly changes later than 2 ms after red light excitation of Pr, and that the different dichroic orientations of Pr and Pfr can be attributed to the change in the angle of the long-wavelength transition moment of phytochrome with the plasma membrane from 18o to 72o during phototransformation. |
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