Electrical measurement of electroneutral fluxes of divalent cations through charged planar phospholipid membranes.

The voltage-sensitive channel-former monazomycin is used as a conductance probe to monitor changes in the trans electrostatic surface potentials of negatively-charged planar phospholipid bilayers. Cis-to-trans electroneutral fluxes of divalent cations mediated by ionophores A23187 and X537A are sensed via the effect of transported divalent cations on the trans surface potentials. Quantitative determinations of neutral Ca2+ and Mg2+ fluxes are made and related to ionophore function.