Figure 8. On/Off current in response to ultrasound in cholesterol membranes.

A.. Current in response to a 10-ms ultrasound application at 1 MHz and 610 mW/cm² in a cholesterol membrane voltage-clamped at −200 mV. The current trace is the average of 50 ultrasound applications. The capacitance of the membrane was 130 pF and the peak negative current is −11 pA. The mean (± SE) peak negative current was −18±3 pA (n = 10, capacitance range 70–130 pF). This small current response was not seen when the aperture on the bilayer partition was occluded with a drop of lipid/decane solution, indicating that it depends on the presence of a nanometer-scale lipid film. B. Off current responses for the cholesterol membrane in A (blue current trace) and in a POPE/POPG bilayer with the same capacitance in response to the same ultrasound stimulus (red current trace), normalized to the peak negative current. The current scale bar is in normalized units.