Estimation of Membrane Potential Δψ in Reconstituted Plasma Membrane Vesicles Using a Numerical Model of Oxonol VI Distribution

A model of membrane potential-dependent distribution of oxonol VI to estimate the electrical potential difference Δψ across Schizosaccharomyces pombe plasma membrane vesicles (PMV) has been developed. Δψ was generated by the H+-ATPase reconstituted in the PMV. The model treatment was necessary since the usual calibration of the dye fluorescence changes by diffusion potentials (K+ + valinomycin) failed. The model allows for fitting of fluorescence changes at different vesicle and dye concentrations, yielding Δψ in ATP-energized PMV of 80 mV. The described model treatment to estimate Δψ may be applicable for other reconstituted membrane systems.