Figure 2. REFER plots for the wild-type CFTR driven by different ATP analogues as ligands.

A, selective examples of single channel recordings of the wild-type CFTR driven by different ligands (second column). The top level of each trace is a channel closed state. Ligand type is shown above the traces. The values of the equilibrium constant, K, were calculated as a ratio of the areas under the peaks on the all-points histogram (left column) whereas the rate constants were calculated from the dwell-time histograms as k_o= 1/τ_c and k_c= 1/τ_o (two right columns). B, REFER plot for the wild-type CFTR ion channel openings induced by different nucleotides. The specific nucleotides are indicated opposite the experimental points. Each experimental point is a mean value ±s.e.m. of at least 3 in dependent experiments. Slope Φ is shown under the graph. The exact parameters of the best fit are: for the upper line slope is 0.965 ± 0.07 (R= 0.994, P < 0.0063). For the lower line slope is 0.974 ± 0.05 (R= 0.989, P < 0.0001). C, REFER plot for wild-type CFTR channel closing driving by the same set of different nucleotides. Each experimental point is a mean value ±s.e.m. of at least 3 in dependent experiments. Slope Φ is shown under the graph. The exact parameters of the best fit are: for the upper line slope is 0.021 ± 0.048 (R= 0.319, P= 0.681), for the lower line slope is 0.024 ± 0.058 (R= 0.226, P= 0.529).