Figure 6
Detection of slowly developing DPA-induced quenching in response to longer depolarizing steps. (A) Schematic representation of possible secondary tag movements and hypothetical time course of fluorescence signals (F, red lines) in response to more prolonged depolarizing pulses (V, black lines), following the initial fast translocation of DPA. (B) Typical voltage-dependent DPA-induced response from cells expressing GFPf in response to 500 ms depolarization steps as shown on top of the trace. Averaged responses from 50 trials delivered at 2 s intervals are shown. An expanded section of the fluorescence trace is shown in the inset. (C) Representative fluorometric trace from cells expressing hERG channels tagged with CFP at the amino end submitted to voltage-clamp steps as in panel A. A bi-exponential fit is shown superimposed to the data from which time constants of 8 and 275 ms were obtained as indicated. (D) Representative response from cells expressing hERG channels tagged with CFP at position 162. A bi-exponential fit with time constants of 5 and 305 ms is shown superimposed to the data.
