Purification of Plant Plasma Membranes by Two-Phase Partitioning and Measurement of H+ Pumping

Purification of plasma membranes by two-phase partitioning is based on the separation of microsomal membranes, dependent on their surface hydrophobicity. Here we explain the purification of plasma membranes from a relatively small amount of material (7–30 g). The fluorescent probe ACMA (9-amino-6-chloro-2-metoxyacridine) accumulates inside the vesicles upon protonation. Quenching of ACMA in the solution corresponds to the H+ transport across the plasma membrane. Before running the assay, the plasma membranes are incubated with the detergent Brij-58 in order to create inside-out vesicles.