TABLE 3.
Summary of pKa values for lead oxime RS194B and other selected oximes determined by four different techniques from pH-dependent changes in oxime UV spectra (cf. Fig. 2), oxime 1H NMR spectra in D2O (cf. Fig. 3), oxime-induced ATCh oximolysis (cf. supplemental Fig. S3), and oxime-induced VX Flu-MP oximolysis (cf. supplemental Fig. S4)
Constants were calculated by nonlinear regression using Equation 1. ND, not determined.
| Oxime | Oxime pKa |
Average pKaa | |||
|---|---|---|---|---|---|
| UV spectra | 1H NMR spectraa | Oximolysis |
|||
| ATCh | VX Flu-MP | ||||
| RS194B | 8.8 ± 0.2 | 9.1 ± 0.1 (-OH) | 9.0 ± 0.1 | 8.9 ± 0.1 | 8.8 (-OH) |
| 9.3 ± 0.1 (NH+)b | 8.8 (NH+) | ||||
| 9.2 ± 0.1 (NH+)c | |||||
| RS41A | 8.8 ± 0.1 | ND | 9.0 ± 0.1 | 8.7 ± 0.1 | 8.8 |
| RS186B | 8.3 ± 0.1 | ND | 8.5 ± 0.1 | ND | 8.4 |
| RS150D | ND | ND | 10.1 ± 0.1 | ND | 10.1 |
| RS174C | ND | ND | 6.5 ± 0.1 | ND | 6.5 |
| MINA | 8.3 ± 0.1 | ND | 8.7 ± 0.1 | ND | 8.5 |
| 2PAM | ND | 8.6 ± 0.1 (-OH) | 8.0 ± 0.1 | 8.1 ± 0.2 | 8.1 |
a pKa values determined in D2O, as shown, are typically higher than those determined in H2O by ∼0.5 (27) and were corrected before calculating the average pKa.
b Based on pH induced shift of 3.37 ppm triplet in D2O (Figs. 3B and supplemental Fig. S1).
c Based on pH induced shift of 3.73 ppm triplet in D2O (Figs. 3C and supplemental Fig. S1).