Frankfurt 2006 – wissenschaftliches Programm
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MO: Molekülphysik
MO 12: Ultrafast Structural Changes
MO 12.5: Vortrag
Montag, 13. März 2006, 15:15–15:30, H12
Structural Evolution in the Primary Stages of Trans/Cis Isomerization of the Chromophore in Photoactive Yellow Protein — •Karsten Heyne1,2, Omar F. Mohammed1, Anwar Usman1, Jens Dreyer1, Erik T.J. Nibbering1, and Michael A. Cusanovich3 — 1Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born Strasse 2A, 12489 Berlin, Germany — 2Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany — 3Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, United States of America
The primary structural evolution upon electronic excitation of photoactive yellow protein (PYP) in solution has been studied with a combined approach of polarization sensitive ultrafast infrared spectroscopy and density functional theory calculations (Heyne et al., J. Am. Chem. Soc., in press). We identify the ν (C8−C9) chromophore marker mode and show that upon generation of the intermediate I0 state with a 3 ps time constant a full trans/cis isomerization occurs. Anisotropy measurements of the ν(C=O) marker mode of Glu46 show that the PYP photoisomerization involves flipping of the enone thioester linkage without significant relocation of the phenolate moiety. Comparison between experiment and theory reveal an important influence of the planarity of the chromophore on the vibrational band patterns. In particular, the chromophore in the dark P state turns out to have a trans geometry with the C=O group slightly tilted out-of-plane, in accordance with an earlier reported structure obtained in an X-ray diffraction study of PYP crystals. In contrast, the I0 state has a planar configuration.