Berlin 2005 – wissenschaftliches Programm
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MO: Molekülphysik
MO 12: Biomolecules I
MO 12.2: Vortrag
Freitag, 4. März 2005, 14:30–14:45, HU 2091
Ultrashort Time Resolved VIS-NIR Spectroscopy of the Photosynthetic Unit of Rhodospirillum Rubrum: Importance of RC-H Subunit — •Sergiu Amarie1, Martin O. Lenz1, Domenico Lupo2, Robin Ghosh2 und Josef Wachtveitl1 — 1Institut für Physikalische und Theoretische Chemie, Goethe Universität Frankfurt, Marie-Curie-Str. 11, 60439 Frankfurt am Main — 2Department of Bioenergetics, Institute of Biology, University of Stuttgart, Stuttgart
In the photosynthetic light reaction the primary reactions occur on the subpicosecond and picosecond time scale. The first step is the absorption of a photon by the light harvesting antenna systems (LH), followed by a rapid and efficient transfer of the excitation energy to the reaction center (RC). A series of fast electron transfer (ET) reactions along a chain of chromophores within the RC stabilizes the electrochemical energy via charge separation. The SPUHK1 mutant of R. rubrum was created by deleting the reaction center H subunit during site-directed interposon mutagenesis. The H subunit of the RC is necessary neither for maximal formation of LH1 nor for photosynthetic membrane formation but is essential for functional RC assembly. The spectroscopic properties of the wild-type Rhodospirillum rubrum S1 and the SPUHK1 mutant were studied using femtosecond time-resolved transient absorption spectroscopy from 400 to 1000 nm. Differences in the VIS and NIR region can be identified and attributed to the different temporal behaviour of the energy transfer steps after photoexcitation of the antenna carotenoids around 500 nm. The stabilizing role of the carotenoids for LH1 formation in the absence of the H subunit will be discussed.