Table II

Parameters of Activation Kinetics

Channelτ0*vshiftk*τmin*ve-fold change§n*
msmVmsmV
IFMQ30.5 ± 0.1n.a.‖2.6 ± 0.30.4 ± 0.1 9.79
1R2Q0.2 ± 0.0176−9.93.1 ± 0.11760.4 ± 0.1 8.15
1R2K0.4 ± 0.2−2.22.4 ± 0.40.4 ± 0.110.25
1K4Q1.1 ± 0.21768.62.3 ± 0.50.5 ± 0.110.86
1K4R0.4 ± 0.1−2.12.8 ± 0.30.4 ± 0.1 9.06
2R2Q0.5 ± 0.11.42.4 ± 0.30.8 ± 0.210.55
2R2K0.9 ± 0.21766.52.5 ± 0.30.5 ± 0.1 9.94
2K4Q1.3 ± 0.4176   10.22.9 ± 0.30.5 ± 0.1 8.64
2K4R0.4 ± 0.3−2.13.0 ± 0.70.4 ± 0.2 8.45
3R2Q0.4 ± 0.1−1.92.7 ± 0.10.4 ± 0.3 9.35
3R2K0.3 ± 0.1−3.93.2 ± 0.41760.4 ± 0.1 7.84
3R4Q0.8 ± 0.41765.52.0 ± 0.31760.5 ± 0.112.63
3R4K0.6 ± 0.12.42.8 ± 0.30.4 ± 0.2 9.08
4R2Q0.5 ± 0.21.23.0 ± 0.31760.4 ± 0.1 8.47
4R2K0.3 ± 0.0−2.72.6 ± 0.10.4 ± 0.1 9.53
4R4Q0.2 ± 0.1176−7.62.2 ± 0.30.3 ± 0.211.26
4R4K0.4 ± 0.1−1.52.1 ± 0.40.3 ± 0.111.67
1K4Q:2K4Q2.4 ± 0.4176   16.21.7 ± 0.41760.3 ± 0.114.89
3R4Q:4R4Q0.4 ± 0.1−0.71.7 ± 0.21760.3 ± 0.114.78
  • * τ0, τmin, and k were determined by least-squares fits of the data (n = number of separate determinations) to a voltage-dependent single exponential as described in materials and methods.  

  • vshift is the shift in voltage for the mutant τm compared with the IFMQ3 τm, calculated using the IFMQ3 value for k.  

  • § ve-fold change is the voltage required for an e-fold change in τm for the condition when τmin << τm.  

  • n.a., not applicable.  

  • 176  Values significantly different from IFMQ3, with a probability <0.05 resulting from random variation (based on Student's unpaired t test).