Supplementary Fig. 14: Detailed analysis of the L_R7 blockades measured using a low-noise setup.

(a) Representative fragment of ionic current recording showing an example of a transition from an open pore current state to a blockade current state. (b) Close-up of both levels from panel a to illustrate the increased noise of the blocked current state in comparison to the open pore current state. (c) Scatterplot (red dots) of the variance of detected current levels versus I/I₀. Note the approximately threefold increase in variance in the blocked state (I/I₀ ≈ 0.385) with respect to the open state (I/I₀ = 1). (d) Histogram of the relative residual current I/I₀ (black trace), scatterplot of blockade duration versus I_b/I₀ (red dots) and a Gaussian fit of the histogram (red trace). Note that the estimated mean values get progressively closer to the population mean with longer dwell times, indicating that current noise and not inter-event-variance is responsible for the width of the Gaussian peak. For panels c & d, histograms and scatter plots are based on the analysis of 7309 events. (e) Power spectral density plots for four blocked levels and four preceding baseline levels (as in panels a and b). (f) Difference of the averages of the four blocked state and four open state spectra, respectively, from panel e. Note the flat curve between 100 Hz and 10 kHz (the cut-off frequency of the 4-pole Bessel filter used). The mean value (respectively uncertainty) of relative residual current of each peptide was obtained as the mean value (respectively standard deviation) of a gaussian fit of the corresponding I_b/I₀ distribution; from single independent experiments. The data were acquired in 4 M KCl, 25 mM HEPES buffer, at 7.5 pH and at room temperature, and under a –50 mV bias applied to the trans compartment, and with a 10 kHz filter and a 1 MHz sampling rate.