Table 1.
Effect of pH and Buffers on the Binding of Actinonin to PDFa
| Buffer | Exothermic Site | Endothermic Site | ||||||
|---|---|---|---|---|---|---|---|---|
| pH 7.0 | n | Ka × 109 (M−1) | ΔH° obs (kcal mol−1) | p | n | Ka × 106 (M−1) | ΔH° obs (kcal mol−1) | p |
| Phosphate | 0.19 ± 0.002 | 0.54 ± 0.1 | −2.2 ± 0.1 | 0.0 | 0.86 ± 0.006 | 2.8 ± 0.3 | 4.0 ± 0.05 | −0.07 |
| Tris | 0.16 ± 0.001 | 0.17 ± 0.03 | −2.2 ± 0.07 | 0.77 ± 0.007 | 0.83 ± 0.06 | 3.3 ± 0.05 | ||
| pH 6.3 | ||||||||
| Phosphate | 0.10 ± 0.01 | 2.6 ± 5.6 | 3.8 ± 0.1 | −0.65 | 0.94 ± 0.01 | 2.3 ± 0.3 | 4.8 ± 0.05 | −0.12 |
| Tris | 0.09 ± 0.001 | 2.5 ± 1.0 | −2.9 ± 0.1 | 0.94 ± 0.006 | 1.7 ± 0.2 | 3.6 ± 0.03 | ||
a
n refers to the stoichiometry of actinonin-PDFEc complex (mol/mol) and p refers to the change in proton inventory.