Regensburg 2002 – wissenschaftliches Programm
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SYBM: Physik biologischer Materie
SYBM 202: Spectroscopy of single biomolecules
SYBM 202.3: Vortrag
Dienstag, 12. März 2002, 15:30–15:45, H37
Excitons in a Photosynthetic Light-Harvesting System: A Combined Molecular Dynamics/Quantum Chemistry and Polaron Model Study — •Ulrich Kleinekathöfer1,2, Ana Damjanović3, Ioan Kosztin3, and Klaus Schulten3 — 1Institut für Physik, Technische Universität, D-09107 Chemnitz, Germany — 2International University Bremen, D-28725 Bremen, Germany — 3Beckman Institute and Department of Physics, University of Illinois, Urbana, IL 61801, USA
The dynamics of pigment-pigment and pigment-protein interactions in light-harvesting complexes is studied with a novel approach that combines molecular dynamics simulations with quantum chemistry calculations and a polaron model analysis. The molecular dynamics simulation of light-harvesting complexes was performed on an 87,055 atom system comprised of an LH-II complex of Rhodospirillum molischianum. For each of the 16 B850 BChls we performed 400 ab initio quantum chemistry calculations on geometries that emerged from the molecular dynamical simulations. From the results of these calculations we construct a time-dependent Hamiltonian of the B850 exciton system. A polaron model is introduced to describe both the excitonic and coupled phonon degrees of freedom by quantum mechanics. The polaron model permits the calculation of the absorption and circular dichroism spectra of the B850 excitons from the sole knowledge of the autocorrelation function of the excitation energies of individual BChls, which is readily available from the combined molecular dynamics and quantum chemistry simulations. The obtained results are found to be in good agreement with the experimentally measured absorption and circular dichroism spectra.