Lateral heterogeneity of the proton potential along the thylakoid membranes of chloroplasts.

This work is devoted to critical analysis and reexamination of the problem of lateral heterogeneity of the trans-thylakoid pH difference (ΔpH=pH-pH) in thylakoid membranes of chloroplasts. Correct measurements of ΔpH may be complicated by nonuniform partitioning of the protons pumped into the lumen of granal (stacked) and stroma-exposed thylakoids. We have compared results of ΔpH estimations in isolated bean chloroplasts by two different methods.

Short-term regulation and alternative pathways of photosynthetic electron transport in Hibiscus rosa-sinensis leaves.

In this work, using the EPR and PAM-fluorometry methods, we have studied induction events of photosynthetic electron transport in Hibiscus rosa-sinensis leaves. The methods used are complementary, providing efficient tools for in situ monitoring of P700 redox transients and photochemical activity of photosystem II (PSII). The induction of P700(+) in dark-adapted leaves is characterized by the multiphase kinetics with a lag-phase, which duration elongates with the dark-adaptation time.

Functional and topological aspects of pH-dependent regulation of electron and proton transport in chloroplasts in silico.

In this work, we summarize results of computer simulation of electron and proton transport processes coupled to ATP synthesis in chloroplasts performed within the frames of a mathematical model developed as a system of differential equations for concentrations of electron carriers and hydrogen ion inside and outside the granal and stromal thylakoids. The model takes into account topological peculiarities and lateral heterogeneity of the chloroplast lamellar system. This allowed us to analyze the influence of restricted diffusion of protons inside small compartments of a chloroplast (e.

[pH-dependent regulation of electron transport in chloroplasts. Computer simulation investigation].

A mathematical model for the description of the key stages of photosynthetic electron transport and transmembrane proton transfer in chloroplasts is presented. Numerical modeling of electron and proton transport with due regard for regulatory processes on the donor and acceptor sites of photosystem I (PS I) was performed. The influence of pH-dependent activation of the Calvin cycle enzymes and energy dissipation in PS II (nonphotochemical quenching of chlorophyll fluorescence) on the kinetics of light-reduced redox transients of P700, plastoquinone and NADPH, as well as intrathylakoid pH(in), and ATP was studied.

Effects of diffusion and topological factors on the efficiency of energy coupling in chloroplasts with heterogeneous partitioning of protein complexes in thylakoids of grana and stroma. A mathematical model.

In this work, we studied theoretically the effects of diffusion restrictions and topological factors that could influence the efficiency of energy coupling in the heterogeneous lamellar system of higher plant chloroplasts. Our computations are based on a mathematical model for electron and proton transport in chloroplasts coupled to ATP synthesis in chloroplasts that takes into account the nonuniform distribution of electron transport and ATP synthase complexes in the thylakoids of grana and stroma. Numerical experiments allowed the lateral profiles of pH in the thylakoid lumen and in the narrow gap between grana thylakoids to be simulated under different metabolic conditions (in the state of photosynthetic control and under conditions of photophosphorylation).