Real-time tracking of phytochrome's orientational changes during Pr photoisomerization |
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Authors: | Yang Yang Linke Martin von Haimberger Theodore Hahn Janina Matute Ricardo González Leticia Schmieder Peter Heyne Karsten |
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Affiliation: | Department of Physics, Freie Universit?t Berlin, Arnimallee 14, 14195 Berlin, Germany. |
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Abstract: | Photoisomerization of a protein bound chromophore is the basis of the light sensing and signaling responses of many photoreceptors. Z-to-E photoisomerization of the Pr Cph1Δ2 phytochrome has been investigated by polarization resolved femtosecond visible pump-infrared probe spectroscopy, which yields structural information on the Pr excited (Pr*), Pr ground, and lumi-R product states. By exhaustive search analysis, two photoreaction time constants of (4.7 ± 1.4) and (30 ± 5) ps were found. Ring D orientational change in the electronic excited state to the transition state (90° twist) has been followed in real-time. Rotation of ring D takes place in the electronically excited state with a time constant of 30 ± 5 ps. The photoisomerization is best explained by a single rotation around C(15)═C(16) methine bridge in the Pr* state and a diffusive interaction with its protein surrounding. |
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