TABLE 2.
31P NMR-derived ΔpH collapse in inhibitor and ionophore-treated M. smegmatis cellsa
| Compound | pH outside | pH inside | ΔpH |
|---|---|---|---|
| No drug | 6.82 | 7.09 | 0.26 |
| Isoniazid | 6.79 | 7.08 | 0.29 |
| Rifampin | 6.81 | 7.08 | 0.27 |
| Streptomycin | 6.77 | 7.05 | 0.28 |
| CCCP (2× MIC) | 6.85 | 6.85 | 0 |
| Nigericin (20 μM) | 6.82 | 6.82 | 0 |
| Valinomycin (33 μM) | 6.83 | 7.07 | 0.24 |
| Ro 48-8071 (2× MIC) | 6.83 | 6.83 | 0 |
| SQ109 (2× MIC) | 6.81 | 6.81 | 0 |
| AU1235 (2× MIC) | 6.82 | 6.82 | 0 |
| BM212 (1× MIC) | 6.85 | 6.85 | 0 |
| 2418 (2× MIC) | 6.81 | 6.81 | 0 |
| THPP-2 (2× MIC)b | 6.82 | 6.82 | 0 |
a
The average pH values were calculated from the equation pH = 6.75 + log (d − 10.85)/(13.25 − d) (49), where d is the 31P NMR chemical shift difference between peaks and that of the α phosphorus on ATP. The error is estimated to be no more than ±0.02 pH units.
b
THPP-2 was tested against M. tuberculosis H37Rv mc26206 cells, since this compound did not show any inhibitory effect against M. smegmatis in culture at the highest concentration tested (22 μg/ml).