Parts | Days | Selection | Search | Downloads | Help
MO: Fachverband Molekülphysik
MO 11: Biomolecules
MO 11.3: Talk
Monday, March 19, 2007, 14:30–14:45, 6B
Excitation Energy Transfer via Optically "Dark" States of Carotenoids in Photosynthetic Antenna Complexes investigated by Femtosecond Two-Photon Fluorescence Exciatation Spectroscopy — •Alexander Betke1, Bernd Voigt1, Heiko Lokstein2, and Ralf Menzel1 — 1Institut für Physik, Lehrstuhl für Photonik, Universität Potsdam — 2Institut für Biochemie und
Biologie, Universität Potsdam
Carotenoids play several important roles in photosynthetic organisms: as integral structural components of pigment-protein-complexes, as light-harvesting pigments, and in photoprotection.
To study the last two mentioned functions and the underlying mechanism(s) it is vital to know the energetic positions of the lowest-lying excited singlet state, S1 (21Ag−) of relevant carotenoids. The latter states are assumed to be close to the (bacterio-)chlorophyll S1 state. Due to their "optically forbidden" character, the carotenoid S1 state is difficult to investigate by conventional one-photon spectroscopy. However, the 11Ag− to 21Ag− transition is strongly two-photon allowed. Thus, simultaneous two-photon absorption of tuneable femtosecond near infrared pulses monitored by (bacterio-) chlorophyll fluorescence is a powerful approach to study the role of these "dark" states in excitation energy transfer and dissipation in light-harvesting complexes. We will present recent results obtained with different light-harvesting complexes and highlight advantages as well as possible pitfalls of this approach.
This research is supported by the DFG (SFB 429, TP A2).