Berlin 2001 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 17: Poster: Spectroscopy and Single Particle Spectroscopy of Molecular Systems, Photoprocesses, Biological Systems
CPP 17.20: Poster
Tuesday, April 3, 2001, 12:30–15:00, AT1
Probing the Symmetry of Photosynthetic Aggregates — •Britta Götze1, Uwe Gerken1, Carsten Tietz1, Fedor Jelezko1, Markus Branschädel2, Robin Ghosh2, and Jörg Wrachtrup1 — 13. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany — 2Biologisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
An intriguing point in structure of photosynthetic proteins is the highly symmetrical arrangement of pigments in bacterial antenna. Both purple bacterial antennas (core antenna LH1 and peripheral LH2) reveal a ring-like symmetry only differing in diameter and pigment content. However, it is under debate to clarify whether the circularly closed shape of the aggregate is an artefact of the crystallization procedure.
In both antennas, the BChl molecules are arranged in close packed rings comprising 32 (LH1) and 18 (LH2) molecules, respectively. Hence, in both cases a strong excitonic coupling of the molecules is expected determining the polarization properties of the absorption and emission states of the aggregates.
Polarization studies show that in the case of LH2 there are only minor distortions of the ring shaped aggregate. At room temperature, elliptical deformations on a millisecond timescale are found. On the other hand, the optical properties of single LH1 complexes differ completely from a ring shaped aggregate. First single molecule experiments on photosynthetic proteins in liposomes are presented. These results are discussed in term of the open-ring structure of LH1 protein in native environment.