Berlin 2001 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 17: Poster: Spectroscopy and Single Particle Spectroscopy of Molecular Systems, Photoprocesses, Biological Systems

CPP 17.18: Poster

Dienstag, 3. April 2001, 12:30–15:00, AT1

Transient absorption measurements of a light-harvesting complex 1 (LH1) from Rhodospirillum rubrum containing a carotenoid with reduced conjugation length — •Peter Gärtner¹, Markus Branschädel², Robin Ghosh², and Helmut Port¹ — ¹3. Physikalisches Institut, Universität Stuttgart — ²Biologisches Institut, Abt. Bioenergetik, Universität Stuttgart

A light-harvesting complex 1 from Rhodospirillum rubrum mutant ST4 was isolated in detergent and then dialyzed to yield a ”native“ aggregated form. Previous studies have shown the molecular state of this aggregate to be composed of intact, interacting LH1 rings (16 αβ(BChl)₂-dimers containing one molecule of carotenoid). The LH1 complex from the mutant contains the carotenoid 3,4,3’,4’-tetrahydrospirilloxanthin with 11 conjugated double bonds (compared to 13 conjugated double bonds in the wild-type complex). Transient absorption measurements at room temperature with excitation at 387nm yielded characteristic time constants of 2ps and 20ps for the Q_y band at 882nm (11335 cm⁻¹). These time constants were also observed for a carotenoidless complex employed as a control. In addition, a characteristic time of 100ps appeared which could be assigned to the carotenoid absorption band, presumably due to the 2Ag⁻ state. These results will be discussed in detail.