Hannover 2010 – scientific programme
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MO: Fachverband Molekülphysik
MO 5: Femtosecond Spectroscopy I
MO 5.5: Talk
Tuesday, March 9, 2010, 15:00–15:15, F 102
Ultrafast photochemistry in protochlorophyllide-a by femtosecond infrared spectroscopy — •Miriam Colindres1, Matthias M. N. Wolf1, Sonja Seidel2, Gudrun Hermann2, and Rolf Diller1 — 1Fachbereich Physik, TU Kaiserslautern, Kaiserslautern, Germany — 2Institut für Biochemie und Biophysik, Universität Jena, Jena, Germany
Primary light induced processes of protochlorophyllide-a (PChlide), the precursor in the biosynthesis of chlorophyll, were studied applying transient VIS/mid-IR femtosecond absorption spectroscopy. The light dependent reduction of PChlide is catalyzed by the enzyme NADPH:protochlorophyllide oxidoreductase (POR). We present the first results of ultrafast vibrational dynamics on a sub-ps time scale of the enzyme substrate PChlide in solution. Our results suggest the existence of two reaction pathways after electronic excitation [1]. The shift of the C=O stretch vibration around 1600 cm−1 indicates the intramolecular charge transfer state in the reactive channel. In the range 1640-1375 cm−1 C-C and C=C vibrations of the porphyrin backbone dominate the transient vibrational spectra and monitor both the reactive and non-reactive pathway. Our experiments corroborate the model of the primary reaction dynamics of PChlide in solution as presented in ref.[1] and allow for a better understanding of the elementary steps of photochemistry in the enzyme-substrate complex PChlide-POR.
[1] B. Dietzek, S. Tschierlei, G. Hermann, A. Yartsev, T. Pascher, V. Sundström, M. Schmitt and J. Popp, ChemPhysChem 2009, 10, 144-150