Dresden 2003 – wissenschaftliches Programm

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SYCN: Computational nanoscience - from materials to biology

SYCN 102: Computational Nanoscience: From Materials to Biology (Poster, gemeinsam mit SYSE)

SYCN 102.13: Poster

Dienstag, 25. März 2003, 19:00–21:00, ZEU/160

Effect of Dynamic Disorder on the Excitonic States of LH2 Antenna Complexes — •Ulrich Kleinekathöfer¹, Ana Damjanović², Ioan Kosztin³, and Klaus Schulten⁴ — ¹International University Bremen, 28725 Bremen, Germany — ²Dept. of Chemistry, University of California at Berkeley, USA — ³Dept. of Physics, University of Missouri at Columbia, USA — ⁴Beckman Institute and Department of Physics, University of Illinois, Urbana, USA

A novel approach, that combines molecular dynamics (MD) simulations with quantum chemistry (QC) calculations, is used to investigate the effect of dynamic disorder on the excitonic states of the LH2 light-harvesting antenna complex of Rhodospirillum molischianum. The MD simulations, performed on a solvated LH2 complex embedded in a lipid bilayer, provided information about the extent and timescales of geometrical deformations of the bacteriochlorophyll (BChl) and protein residues at room temperature and normal pressure. The fluctuations of the excitation energies of the BChls have been determined by ab initio QC calculations on geometries that emerged from the MD simulations. Finally, a polaron model is introduced to describe both the excitonic and coupled phonon degrees of freedom by quantum mechanics. The exciton-phonon coupling that enters into the polaron model, and the corresponding phonon spectral function are derived from the MD/QC simulations. The polaron model permits the calculation of the absorption and circular dichroism spectra of the excitons from the sole knowledge of the autocorrelation function of the excitation energies of individual BChls. The obtained results are found to be in good agreement with the experiment.