Real-time tracking of phytochrome's orientational changes during Pr photoisomerization.
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.
Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
Yang
Y
Yang
Martin
M
Linke
Theodore
T
von Haimberger
Janina
J
Hahn
Ricardo
R
Matute
Leticia
L
González
Peter
P
Schmieder
Karsten
K
Heyne
D007536:Isomerism; D008958:Models, Molecular; D055668:Photochemical Processes; D010834:Phytochrome / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D046939:Synechocystis / Q000737:chemistry*
D010834:Phytochrome