Absorption and Linear Dichroism of the Fenna-Matthews-Olson Pigment-Protein Complex of Prosthecochloris Aestuarii: An Exciton Model

Authors: Erkut İ. İŞERİ, Demet GÜLEN

Abstract: The long-standing problem of interpretation of the spectroscopy-structure relationship of the Fenna-Matthews-Olson (FMO) protein complex from {\em Prosthecochloris aestuarii} is revisited. The main problems associated with the best current interpretations have been identified and an approach for a better-controlled solution is considered. On the conjecture that a reasonable explanation of the structure-spectroscopy relationship of the FMO should essentially result from the analysis of linear optical data that had not been employed by or available for previous studies, the low temperature (4 K) absorption and linear dichroism spectra have been simulated simultaneously using an exciton model. The model is based on the assumption that the FMO excited states that are responsible for the main function (energy transfer) are the excitonic states resulting from the dipole-dipole interactions of the individual Q_y transitions among the bacteriochlorophylls of the unaggregated C_3 symmetric crystalline form. On the basis of simulations, a preliminary solution to the excited state structure is provided and a strategy for further refinement is suggested. Keywords: Photosynthesis, light-harvesting antenna, exciton, Fenna-Matthews-Olson complex of {\em Prosthecochloris aestuarii}, absorption, linear dichroism.

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