Table 1.
Binding free energy contributions at 298 K, kcal/mol
| Contribution | Sc24 (Cl-Br) | NMA | Ab-DXN | BTN-STP |
|---|---|---|---|---|
| Polar solvation | 4.8 ± 0.5 | 7.9 ± 0.4 | 16.3 ± 0.5 | 84.4 ± 1 |
| Nonpolar solvation | 0 | −0.6 ± 0.1 | −4.1 ± 0.1 | −3.3 ± 0.1 |
| Total solvation | 4.8 ± 0.5 | 7.3 ± 0.4 | 12.2 ± 0.5 | 81.1 ± 1 |
| van der Waals + internal | −4.0 | −2.0 | −2.3 | −44.8 |
| Electrostatic | −6.5 | −7.0 | −31.5 | −62.1 |
| Translation (at 1 M) | −0.7 ± 0.1 | 2.4 ± 0.1 | 4.3 ± 0.1 | 4.3 ± 0.1 |
| Rotation | 0 | 0.8 ± 0.1 | 5.0 ± 0.1 | 4.2 ± 0.1 |
| Internal vibration | 1.6 ± 0.5 | 1.0 ± 2 | 0.0 ± 3 | 3.5 ± 4 |
| Total nonsolvation | −9.6 ± 0.6 | −4.8 ± 2 | −24.5 ± 3 | −94.9 ± 4 |
| Total ΔG at 1 M | −4.8 ± 0.8 | 2.5 ± 2.5 | −12.3 ± 3 | −13.8 ± 5 |
| Measured ΔG at 1 M | −4.2 | 3.1 | −13.9 | −18.3 |
Ab-DXN, antibody FAB fragment–digoxigenin; BTN-STP, biotin–streptavidin.
*
Binding of Cl relative to Br.
†
−5.7 kcal/mol of which comes from the difference in ion hydration free energies.
‡
Includes −2.8 kcal/mol from polarization of Sc24 by the anion.
§
Includes a factor of ln(2) for the exchange symmetry of the dimer.