TABLE 2.
Stability constants K for the inhibition of channel formation by PA by chloroquine and related compounds in lipid bilayer membranes
| Compound* | Side of addition | K / 103 M−1 | K* / 103 M−1(C2II) |
|---|---|---|---|
| 0.15 M KCl | |||
| Chloroquine | Both sides | 676 | 110 |
| Quinacrine | Both sides | 12,300 | 870 |
| Fluphenazine | Both sides | 5353 | 2100 |
| 0.3 M KCl | |||
| Chloroquine | Both sides | 241 | N.D. |
| Quinacrine | Both sides | 3701 | N.D. |
| Fluphenazine | Both sides | 3626 | N.D. |
| 1 M KCl | |||
| Chloroquine | Both sides | 55.2 | 22 |
| cis-side | 56.3 | 16 | |
| trans-side | 1.9 | 4.7 | |
| Quinacrine | Both sides | 740 | 166 |
| Fluphenazine | Both sides | 2100 | 620 |
| cis-side | 909 | 300 | |
| trans-side | 842 | 810 | |
| 3 M KCl | |||
| Chloroquine | Both sides | 31.6 | N.D. |
| Quinacrine | Both sides | 890 | 322 |
| Fluphenazine | Both sides | 2000 | N.D. |
The data represent means of at least three individual titration experiments. The standard deviation was typically <10% of the mean value. The results of similar titration experiments performed with C2II toxin are given for comparison (K*).
*
The membranes were formed from diphytanoyl phosphatidylcholine/n-decane. The aqueous phase contained the indicated KCl and ∼10 ng/ml activated PA63; T = 20°C. K* values from C2II toxin are given for comparison and taken from Bachmeyer et al. (2003).