Fig. 2. (a) Voltage-dependent membrane capacitance of TSA-201 cells transiently transfected with wild type (positive control), Del719, Del709, Y520A/Y526A, as well as untransfected cells (negative control). All capacitance plots are normalized to the maximum of the corresponding (same transfection, same experiment) wild-type NLC function. (b). Membrane capacitance for constructs Del709, Y520A/Y526A, and a negative control plotted relative to their minimum capacitance value. The capacitance waveforms for these constructs are relatively flat and similar to the negative control. The voltage at the peak of the capacitance function represents most efficient charge transfer, while the peak itself relates to the amount of charge translocated. The double point mutation Y520A/Y526A and Del709 mutants exhibited no measurable NLC, whereas the Del719 mutation has normal capacitance relative to wild-type control cells from the same transfection batch. NLC measurements are analyzed by extracting parameters that describe the cell's Q_max, , V and C_lin. The parameters are obtained from measurements where the voltage range was between –150 mV and +120 mV. The individual plots shown are representative of the average parameters (n>10).