Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 10: Ultrafast Spectroscopy
CPP 10.3: Vortrag
Donnerstag, 5. April 2001, 16:25–16:45, 110
Ultrafast Dynamics of Phytochrome from Cyanobacterium Synechocystis, reconstituted with Phycocyanobilin (Cph1-PCB) and Phycoerythrobilin (Cph1-PEB) — •Rolf Diller1, Karsten Heyne1, Johannes Herbst1, Dietmar Stehlik1, Berta Esteban2, Tilman Lamparter2, and Jon Hughes3 — 1Inst. f. Exp.-Physik, FU Berlin, 14195 Berlin — 2Inst. f. Pflanzenphys., FU Berlin, 14195 Berlin — 3Inst. f. allg. Botanik u. Pflanzenphys., J.-Liebig Univ. Giessen, 35392 Giessen
Femtosecond time resolved transient absorption spectroscopy was employed to characterize for the first time the primary photoisomerizations of a bacterial phytochrome system. The 84 kDa Phytochrome Cph1, expressed from the gene of Cyanobacterium Synechocystis, was reconstituted with Phycocyanobilin (Cph1-PCB) and Phycoerythrobilin (Cph1-PEB). The Pr-form of Cph1-PCB shows a ca. 150 fs relaxation in the S1-state after photoexcitation (650 nm). The subsequent Z-E-isomerization of the linear tetrapyrrole-chromophore is best described by a distribution of rate constants with the first moment at 1/16 ps. The reverse reaction, starting from the Pfr-form, is characterized by two time constants of 0.5 and 3.2 ps. More information about the chromophore-protein interaction is obtained from Cph1-PEB. Here, double-bond isomerization is inhibited and fast relaxation processes in response to photoexcitation can be isolated.
The experiments allow for the first time the comparison between the primary photoprocesses of the phytochromes of plants and their evolutionary predecessors, bacterial phytochromes.