Figure 4.
Optical responses of the DiO/DPA FRET pair faithfully follow AP voltage waveforms in single sweeps. A, Averaged fluorescence response (black trace; n = 17 sweeps) from a voltage-clamped HEK-293 cell labeled with DiO-C16 and in the presence of 1 μm DPA to an AP waveform used as command voltage (gray trace). The record was filtered offline to 2 kHz and inverted for comparison to AP waveform. B, 100 Hz AP train waveform used as the command voltage for C and D. C, Seven consecutive fluorescence quenching responses to the train of AP waveforms (C), in the presence of 1 μm DPA. Right, The averaged trace (n = 11 sweeps). D, Seven consecutive eGFP-F fluorescence quenching responses to the train of AP waveforms (B), in the presence of 1 μm DPA. Right, The averaged trace (n = 11 sweeps). Single sweeps were filtered offline to 1 kHz. Scale bar in the bottom right of D corresponds to averaged traces in C and D.