TOWARD AN INTEGRAL INTERPRETATION OF THE OPTICAL STEADY-STATE SPECTRAOF THE FMO-COMPLEX OF PROSTHECOCHLORIS-AESTUARII - 2 - EXCITON SIMULATIONS

We present a simultaneous simulation of various experimental steady-st ate spectra of the FMO-complex of green sulfur bacteria. The simulatio ns are based on exciton calculations using a significantly lower dipol ar interaction energy as compared to exciton calculations on the FMO-c omplex in the literature. Decrease of the interaction energy was sugge sted by comparing, our results obtained with linear-dichroic absorbanc e-detected magnetic resonance spectroscopy with exciton simulations us ing parameters taken from literature. By considering a single subunit only, we arrive at a minimal set of parameters, consisting of reduced interaction energies between the bacteriochlorophyll molecules, seven different site energies, and a common line width for all transitions o f 80 cm(-1). With such a minimal set of parameters, we have achieved a n unequalled match between the simulations and the experimental spectr a, including the absorption, the linear dichroic, the circular dichroi c, the triplet-minus-singlet, as well as the linear-dichroic triplet-m inus-singlet spectra. We conclude that the structure in the various st eady-state spectra is mainly determined by the variation in site energ y and nearly all interaction energies are substantially less than the inhomogeneous width of the individual transitions within the Qy band o f the FMO-complex.