Precipitation within unilamellar vesicles. Part 2. Membrane control of ion transport
Mann S., Kime MJ., Ratcliffe RG., Williams RJP.
Phosphorus-31 and <sup>1</sup>H n.m.r. spectroscopy have been used to investigate the control of intravesicular pH (pH<inf>in</inf>) 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<inf>in</inf> has been observed on increasing extravesicular pH (pH<inf>out</inf>) above 12.0. In the presence of permeable NO<inf>3</inf><sup>-</sup> ions, pH<inf>in</inf> rises only when pH<inf>out</inf> 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.