Table 5. Activation Barriers (in kilocalories per mole) Calculated for Nucleophilic Attack at C(1) and C(2) in t-SO, t-DPPO(1), and t-DPPO(2) for the Protonated His523 Model with B3LYP/6-31G(d)/CHARMM22 (ΔEQM/MM⧧) and from Single-Point [B3LYP/6-31G(d)] Energy Calculations on the QM Atoms of the B3LYP/6-31G(d)/CHARMM22 Structures in the Gas Phase (ΔEgas) and with Continuum Solvation (ΔEgas+solv⧧).
| ΔEQM/MM⧧ | ΔEgas⧧ | ΔEgas+solv⧧ | ||
|---|---|---|---|---|
| t-SO | C(1) | 6.9 | 14.7 | 15.6 |
| C(2) | 14.8 | 17.8 | 20.5 | |
| t-DPPO(1) | C(1) | 6.7 | 14.9 | 13.0 |
| C(2) | 10.5 | 20.2 | 19.2 | |
| t-DPPO(2) | C(1) | 9.2 | 14.3 | 14.0 |
| C(2) | 11.3 | 17.8 | 20.2 |