Precipitation within unilamellar vesicles. Part 2. Membrane control of ion transport

Abstract

Phosphorus-31 and ¹H n.m.r. spectroscopy have been used to investigate the control of intravesicular pH (pH_in) by lipid membranes. The presence of encapsulated permeable anions is crucial in the intravesicular precipitation of hydroxides and oxides. In the absence of permeable anions no change in pH_in has been observed on increasing extravesicular pH (pH_out) above 12.0. In the presence of permeable NO₃^– ions, pH_in rises only when pH_out is increased above a value of 11.0. These observations are described in terms of the Goldman–Katz–Hodgkin equation for ion fluxes across a membrane permeable to more than one ion.