Table 1. Kinetic and equilibrium dissociation constants for the interaction of γCD with (α7)2 and α7.
The rate constants values were obtained from at least three different experiments, in each of which at least three γCD concentrations were used in 1M KCl, 25mM Tris.HCl, 50μM EDTA, pH8.0 at 25°C. At each voltage, the dissociation rate constants, koff, were derived at each γCD concentration as the inverse of the mean residence time (τoff) of γCD within the pore. The mean value over all concentrations is given in the Table. The association rate constants, kon, were obtained for each experiment from the slope of a plot of the inverse of the mean inter-event interval (τon) versus γCD concentration. The dissociation constants (Kd) were calculated separately for each experiment from Kd = koff / kon. The mean values of Kd for three or more experiments are reported in the Table.
| Voltage (mV) | kon × 104 (M−1 s−1) | koff (s−1) | Kd (μM) | blockade of Io |
|---|---|---|---|---|
| (α7)2trans | (mean±s.e.m) | (mean±s.e.m) | (mean±s.e.m) | (mean±s.e.m) |
| +40 | 7.1±0.7 | 3.7±0.4 | 49±3 | 55±2 |
| −40 | 8.2±1.1 | 3.2±0.2 | 36±2 | 51±2 |
| +50 | 9.0±1.1 | 3.4±0.4 | 42±3 | 55±2 |
| −50 | 6.1±0.6 | 3.3±0.3 | 54±8 | 48±3 |
| +100 | 8.9±1.0 | 4.2±0.8 | 46±7 | 54±5 |
| −100 | 4.5±0.3 | 2.9±0.5 | 64±11 | 45±6 |
| (α7)2cis | ||||
| +40 | 5.8±0.8 | 6.0±0.4 | 85±12 | 16±2 |
| −40 | 5.6±0.5 | 7.2±1.1 | 110±18 | 17±1 |
| +50 | 6.0±0.5 | 6.9±0.7 | 110±12 | 15±1 |
| −50 | 6.1±1.0 | 6.2±1.0 | 96±9 | 19±1 |
| +100 | 6.3±1.2 | 6.4±2.0 | 110±27 | 13±0.3 |
| −100 | 6.4±1.3 | 10±1.6 | 130±24 | 21±2 |
| α7 trans | ||||
| +40 | 9.5±1.2 | 6.1±0.7 | 76±12 | 65±1 |
| −40 | 5.0±0.1 | 3.1±0.4 | 61±6 | 58±1 |
| +50 | 7.8±0.9 | 6.9±0.9 | 110±37 | 66±1 |
| −50 | 7.2±2.3 | 3.0±0.3 | 47±9 | 58±0.4 |
| +100 | 4.3±1.2 | 12.3±2.0 | 342±63 | 68±0.3 |
| −100 | 6.9±2.8 | 1.7±0.2 | 37±10 | 52±0.1 |