Dynamics of Cytochrome bf Complex of Photosynthesis Apparatus

Compared to the man-made devices, the photosynthesis apparatus is much more efficient. This high efficiency comes from its elaborate structure, very fast transition rates and a complex electron and proton transfer chain among the subunits of the apparatus. Its main subunits (Photosystem I (PSI), bf complex and photosystem II (PSII)) are connected through different mobile carriers. Among these, the cytochrome bf complex, connecting PSI and PSII, plays an essential role in the photosynthetic process. During recent years, the function and structure of this complex has been studied using different experimental methods. On the other hand, to explain its dynamic, the complex has been mathematically modeled. In this paper, based on a kinetic model, proposed earlier by one of the authors, an improved model has been introduced and the new experimental data has been analyzed. The model is a comprehensive one that considers the different components of the complex and also its relation with mobile charge carriers (plastocyanin and plastoquinones). Via comparison with experimental data, the rate of redox reactions has been determined by using the mathematical methods of parameter identification. Despite the large number of parameters, nonlinearity and coupling of governing equations, and indeterminacy of the initial values, the results of modeling conforms well to the experimental data. This may help to a better understanding of the bf complex structure and behavior, in particular, and of the photosynthesis apparatus as a whole.