Sunlight, Purple Bacteria, and Quantum Mechanics

Wednesday, 12. March, 9:45 h, 1A/B/C

The primary reactions of purple bacterial photosynthesis, i.e. lightharvesting and electron transfer, take place within two well defined ring-shaped pigment-protein complexes the peripheral light-harvesting 2 complex, LH2, and the core reaction centre / light-harvesting 1 complex, RC-LH1. By now it has been established that the spatial arrangement of the pigments determine to a large extent the spectroscopic features of these complexes and that collective excitations (Frenkel excitons) play an important role.

Commonly, the great difficulty to determine the various parameters that play a role in the description of the electronic structure of lightharvesting complexes and the process of energy transfer is the fact that the optical absorption lines are inhomogeneously broadened as a result of heterogeneity in the ensemble of absorbing pigments. We circumvent this problem by employing single-molecule spectroscopic techniques which allows to uncover spectral signatures predicted by quantum mechanics that would be completely masked by ensemble averaging in conventional optical experiments. The talk provides an overview over our work on this topic during the last years.

M. Richter et al. Proc. Natl. Acad. Sci. 104, 16 (2007), 6661-6665
R. J. Cogdell, A. Gall, J. Köhler, Q. Rev. Biophysics 39, (2006), 227- 324

Jürgen Köhler
Experimental Physics IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, D-95440 Bayreuth, Germany