Figure 6. Direct transitions between consecutive open-channel current levels.

Plots show the number of direct transitions between consecutive open-channel current levels (shut level not included) in outside-out patches containing only high conductance unitary currents (A and B) or high and low conductance unitary currents (C and D). An amplitude-based separation of unitary currents was obtained by calculating critical amplitude values (A_crit) producing an equal percentage of misclassified events between the Gaussian components fitted to the amplitude distribution such as illustrated in Fig. 2C and D. A _crit values indicated by the dashed lines in A and C were 2.87 pA in A and 1.71, 2.35 and 3.05 pA in C. In A and C, each dot represents a direct transition, considered as a change in open-channel current level from one amplitude level to another (each amplitude level having a duration longer than 2.5 filter rise times: 415 μs) without intervening closures longer than the shut time resolution (50 μs in these examples). B and D are three-dimensional representations of the data shown in A and C, respectively. The volume of each peak indicates the relative frequency of each type of transition. In the patch illustrated in A and B, 49.2 % of direct transitions between open levels were from 51-42 pS while 50.8 % were from 42-51 pS level. In C and D, 47.5 % of direct transitions between 49 and 42 pS levels were from 49-42 pS while 52.5 % were from 42-49 pS. In contrast, 65.2 % of transitions between 17 and 49 pS levels were from 49-17 pS while only 34.8 % were from 17-49 pS.