Fig. 2. Effect of varying intravesicular SO₄^2– concentration on the time course of 25 µmol l^{–1 65}Zn²⁺ uptake by LMV. Vesicles were loaded with 200 mmol l^–1 mannitol, 20 mmol l^–1 Hepes/Tris, pH 7.0 and K₂SO₄ concentrations of 25, 50, 100, 250, 500 or 1000 µmol l^–1, and were then incubated in a medium containing 200 mmol l^–1 mannitol, 25 µmol l^{–1 65}Zinc-sulfate, 0.5 mmol l^–1 NTA, 0.2 mmol l^–1 ATP, and 20 mmol l^–1 Hepes/Tris, pH 7.0. Experiments were conducted in triplicate; values are means ± 1 s.e.m. at each time point.