ESTIMATION OF MEMBRANE-POTENTIAL DELTA-PSI IN RECONSTITUTED PLASMA-MEMBRANE VESICLES USING A NUMERICAL-MODEL OF OXONOL-VI DISTRIBUTION

A model of membrane potential-dependent distribution of oxonol VI to e stimate the electrical potential difference Delta psi across Schizosac charomyces pombe plasma membrane vesicles (PMV) has been developed. De lta psi was generated by the H+-ATPase reconstituted in the PMV. The m odel treatment was necessary since the usual calibration of the dye fl uorescence changes by diffusion potentials (K+ + valinomycin) failed. The model allows for fitting of fluorescence changes at different vesi cle and dye concentrations, yielding Delta psi in ATP-energized PMV of 80 mV. The described model treatment to estimate Delta psi may be app licable for other reconstituted membrane systems.