Figure 4.

Higher ionic strength stabilizes the SSCs. (A–D) Representative current traces of OmpU recorded at various symmetric KCl concentrations (pH 7.2), as indicated. The open trimer conductance is increased by higher ionic strength as indicated by the change in scale bar from A to D. The pipette voltage was +50 mV. Note that the SSCs become larger, longer in duration and more frequent as the buffer ionic strength is increased. (A,C,D) Recorded in planar lipid bilayer. (B) Recorded in patch-clamp. (E) Plot of the average ratio of SSC conductance (g(SSC)) over the open trimer conductance (g(trimer)) versus KCl concentration in the buffer. Error bars are SE (n ≥ 3). (F) Plot of the average dwell time of the SSC (average t_c; black histogram bars) and of the dwell time of the fully open trimer (average t_o; white histogram bars) versus KCl concentration in the buffer (at pipette voltage of +50 mV). Error bars are SE (n ≥ 3). Note the logarithmic scale for the left y axis.