We review the recent research on kinetic and direct multiparticle modeling of the processes in the
photosynthetic membrane conducted at the Chair of Biophysics of the Biological Faculty, Moscow State University.
The models take into account the modern experimental data on the heterogeneous structure and the
kinetic characteristics of the system. The generalized kinetic model describes the processes in multisubunit
complexes (photosystems I and II, the cytochrome complex), the coupled transmembrane ion fluxes and generation
of the electrical and electrochemical potentials. Identification of the model parameters allows estimation
of the rate constants for reactions that cannot be examined experimentally. Multiparticle models provide a vivid
picture of the interaction between the electron transport chain components in the thylakoid lumen and stroma,
and explicitly represent Brownian diffusion and electrostatic interactions between electron carriers. Combination
of different description methods (differential equations and the Brownian dynamics formalism) makes it
possible to model, in the complicated 3D environment of the plant cell, the processes that in the aggregate
ensure the high efficacy of energy transduction in photosynthesis.
Plastocyanin diffusion in the thylakoid lumen and its binding to cytochrome f (a subunit of the membrane b6f complex) were studied with a direct multiparticle simulation model that could also take account of their electrostatic interaction. Experimental data were used to estimate the model parameters for plastocyanin–cytochrome f complexing in solution. The model was then employed to assess the dependence of the association rate constant on the dimensions of the lumen. Highest rates were obtained at a lumen span of 8–10 nm; narrowing of the lumen below 7 nm resulted in drastic deceleration of complexing. This corresponded to the experimentally observed effect of hyperosmotic stress on the interaction between plastocyanin and cytochrome f in thylakoids.
Рубин Андрей Борисович