EXCITED STATE BEHAVIOR OF PHYTOCHROME Pr |
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| Authors: | Klaus Teuchner Michael Schulz Holger Stiel Manfred Maisch Wolfhart Rudiger |
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| Affiliation: | Max-Born-Institute of Nonlinear Optics and Short Pulse Spectroscopy, D-12474 Berlin, Germany;Botany Department, University of Munich, Menzinger Str. 67, D-80638 Munich, Germany |
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| Abstract: | The primary excited state processes of phytochrome, the plant chromoprotein responsible for most photomorphogenetic responses, are investigated by picosecond intensity-dependent transmission measurements. At sufficient high excitation intensity (starting at photon flux densities of about 1′1025 cm?2 s?l) a moderate bleaching of the absorption is observed. For the quantitative analysis of the experimental data a rate equation system approach for the energy levels responsible for the ultrafast transformation Pr→ lumi-R and the photon transport through the sample was utilized. The following was found for the excited state parameters of the phytochrome Pr: (1) an excited state absorption of the same order of magnitude as the ground state absorption (cross section: S?exc= 4′10?16 cm?2 at 650 nm), (2) a fast relaxation of the higher excited singlet state on the femtosecond time scale. |
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