(
A–D) Logarithmically binned dwell-time histograms (
colored bar charts) of steady-state current segments in 125 μM Ca
2+plus 100 μM ADPR for the recordings shown in
Figure 7A–C, plotted individually for each conductance level (cf.,
dashed lines in
Figure 7A–C), obtained by half-amplitude threshold crossing analysis using an imposed fixed dead time of 0.9 ms. The histogram sets in (
A) (WT, +Mg
2+), (
B) (WT, −Mg
2+), (
C) (E1443I/F1444L), and (
D) (E1446K/E1447K) contain 4560, 7061, 3505, and 1418 events, respectively, in total.
Families of solid black curves illustrate the simultaneous maximum likelihood fits of the sets of dwell-time histograms by the C
slow(1)-O
(3)-C
fast(2) scheme, accounting for the fixed dead time (
Csanády, 2000), with the four rate constants
r13,
r31,
r32,
r23 as free parameters. Fitted rate constants were (
A)
r13 = 9.75 s
−1,
r31=0.880 s
−1,
r32=1.56 s
−1,
r23=633 s
−1, (
B)
r13 = 6.94 s
−1,
r31=1.14 s
−1,
r32=2.28 s
−1,
r23=633 s
−1, (
C)
r13 = 3.96 s
−1,
r31=1.29 s
−1,
r32=1.14 s
−1,
r23=504 s
−1, and (
D)
r13 = 9.99 s
−1,
r31=1.02 s
−1,
r32=0.969 s
−1,
r23=463 s
−1. Calculated bursting parameters (cf.,
Figure 7E–F) were (
A)
τb=1140 ms, τ
ib=103 ms, (
B)
τb=881 ms, τ
ib=144 ms, (
C)
τb=779 ms, τ
ib=253 ms, and (
D)
τb=983 ms, τ
ib=100 ms.