Relative apparent free energies of channel activation at hyperpolarized and depolarized holding potentials
| Channel | V1/2 (0 mV) | Z (0 mV) | ΔG (0 mV) | V1/2 (−80 mV) | Z (−80 mV) | ΔG (−80 mV) | ΔΔG |
| mV | kcal/mol | mV | kcal/mol | kcal/mol | |||
| WT | −127.8 ± 5.6 | −1.9 ± 0.1 | −5.4 ± 0.2 | −86.9 ± 1.7 | −1.6 ± 0.0 | −3.3 ± 0.1 | 2.10 |
| R1C | −108.8 ± 6.5 | −1.1 ± 0.1 | −2.7 ± 0.1 | −102.3 ± 6.9 | −0.9 ± 0.0 | −2.4 ± 0.1 | 0.38 |
| R2C | −115.7 ± 3.0 | −1.0 ± 0.0 | −2.9 ± 0.1 | −95.2 ± 0.4 | −1.3 ± 0.2 | −3.0 ± 0.2 | 0.02 |
| R3C | −129.6 ± 3.0 | −1.6 ± 0.0 | −4.9 ± 0.2 | −105.3 ± 0.2 | −1.4 ± 0.2 | −3.3 ± 0.4 | 1.62 |
| Channel | V1/2 (0 mV) | Z (0 mV) | ΔG (0 mV) | V1/2 (−80 mV) | Z (−80 mV) | ΔG (−80 mV) | ΔΔG |
| mV | kcal/mol | mV | kcal/mol | kcal/mol | |||
| WT | −127.8 ± 5.6 | −1.9 ± 0.1 | −5.4 ± 0.2 | −86.9 ± 1.7 | −1.6 ± 0.0 | −3.3 ± 0.1 | 2.10 |
| R1C | −108.8 ± 6.5 | −1.1 ± 0.1 | −2.7 ± 0.1 | −102.3 ± 6.9 | −0.9 ± 0.0 | −2.4 ± 0.1 | 0.38 |
| R2C | −115.7 ± 3.0 | −1.0 ± 0.0 | −2.9 ± 0.1 | −95.2 ± 0.4 | −1.3 ± 0.2 | −3.0 ± 0.2 | 0.02 |
| R3C | −129.6 ± 3.0 | −1.6 ± 0.0 | −4.9 ± 0.2 | −105.3 ± 0.2 | −1.4 ± 0.2 | −3.3 ± 0.4 | 1.62 |
Apparent free energy for a two-state model, ΔG, was calculated as a measure for comparing the relative energies of opening WT and mutant channels at holding potentials of 0 or −80 mV as ΔG = −ZFV1/2. Z was the apparent charge, V1/2 the half-activation voltage of charge movement, and F, Faraday’s number (23.061 kcal per volt gram equivalent). The parameters V1/2 and Z were calculated by using the slopes of fits of 1/(1 + exp[RT(V − V1/2)/ZF] to Q-V curves, where R is the universal gas constant, T is temperature in °K, F is the Faraday constant, and Z is the valence. ΔΔG was calculated as ΔΔG = ΔG (−80 mV) − ΔG (0 mV).