Berlin 2014 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 11: Biomolecules 1
MO 11.6: Vortrag
Mittwoch, 19. März 2014, 15:15–15:30, BEBEL HS213
Ultrafast pump-probe spectroscopy on the initial photoreaction of bathy-phytochrome Agp2 of Agrobacterium tumefaciens reveals transient protonation processes — •Patrick Singer1, Sybille Wörner2, Tilman Lamparter2, and Rolf Diller1 — 1Dept. of Physics, Univ. Kaiserslautern, 67663 Germany — 2Dept. of General Botany, KIT, 76131 Germany
Plant photomorphogenesis is regulated by the photoreceptor phytochrome, a light controlled protein in plants, bacteria and fungi. Photoinduced interconversion between a thermally stable red absorbing state Pr and the biologically active far red absorbing state Pfr is initiated by light absorption of the open chain tetrapyrrole bilin chromophore, undergoing a rapid isomerization reaction (femtosecond timescale)1. In this study we investigate Agp2 from A. tumefaciens, which fundamentally differs from common phytochromes in its photodynamic properties caused by a thermally (in-)stable (Pr)Pfr ground state (bathy-phytochrome). Previous investigations reveal protonation/deprotonation of the Pr chromophore with an unusually low pKa = 7.85 (pKa > 11 in common phytochromes)2. We performed transient UV/Vis pump-probe spectroscopy on the fs-time scale in different buffer-conditions (H2O/D2O; pH6 - pH9) to investigate spectral and kinetic properties of the primary photoreaction of the Pr state. Transient measurements reveal two fast decaying intermediate species dependent on buffer condition. The results are discussed in context of chromophore protonation processes. 1C. Schumann et al. Biophys.J. 94 3189-3197(2008) 2B. Zienicke et al. JBC 288 31738-31751(2013)