GENERATION OF DELTA-PH IN CHLOROPLASTS SU SPENDED IN THE MEDIA WITH DIFFERENT ION COMPOSITION AND OSMOLARITY

A transmembrane pH difference (Delta pH) was measured in class B chlor oplaste . isolated from bean leaves. The values of Delta pH were deter mined by the EPR spectroscopy method based on the effect of concentrat ional broadening of the EPR signal from TEMPOamine molecules accumulat ing inside the thylakoids. It has been demonstrated that the steady st ate Delta pH values in chloroplasts functioning in both metabolic stat es (either under phosphorylating conditions, state 3, or basal electro n transport conditions, state 4) Increase from 1,6 up to 2,9 with the rise the concentration of sucrose in the suspension medium from 10 to 40 mM. Addition of KCl stimulates the light-incluced uptake of TA by c hloroplasts. Chloroplasts suspended in low-osmotic medium (10 mM sucro se) in the presence of 100 mM KCl reveal the difference between mu pH values measured in states 4 and 3, Delta (Delta pH) congruent to 0,3, which disapprears at higher concentrations (100-400 mM) of sucrose. Al l the data obtained indicate on the nonuniform distribution of Delta p H over the stroma- and grana-exposed thylakoids functioning under phos phorylating conditions, which is determined by the lateral heterogenei ty of thylakoid membranes.