Table 5. Summary of the Components of the Total Electrostatic Energy Computed by the DFT/COSMO and DFT/SCRF89 Methods for Different Protonation States of the Oxidized IspH Active Sitej.
| A. | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| DFT/COSMO |
DFT/SCRF |
|||||||||
| state (charge) | E0a | ESolv,COSMOb | ETot,COSMOc | E0 | EStraind | EPe | ERFf | Eenv,SCRFg | ETot,RFh | ETot,SCRFi |
| RO–P–EH (−3) | –26445.7 | –286.7 | –26732.4 | –26445.7 | 53.9 | –129.9 | –304.3 | –380.3 | –26750.0 | –26826.0 |
| RO–PHEH (−2) | –26541.2 | –195.0 | –26736.2 | –26542.8 | 52.1 | –110.9 | –218.1 | –276.9 | –26760.9 | –26819.7 |
| ROHP–E– (−3) | –26440.5 | –293.1 | –26733.6 | –26440.5 | 54.8 | –133.3 | –308.7 | –387.2 | –26749.2 | –26827.7 |
| ROHPHE– (−2) | –26528.4 | –204.2 | –26732.7 | –26529.1 | 52.9 | –115.3 | –226.2 | –288.5 | –26755.3 | –26817.6 |
| ROHP–EH (−2) | –26537.7 | –197.3 | –26735.0 | –26537.7 | 53.2 | –114.2 | –219.4 | –280.4 | –26757.1 | –26818.1 |
| ROHPHEH (−1) | –26592.2 | –141.6 | –26733.8 | –26592.2 | 49.8 | –96.5 | –167.3 | –214.0 | –26759.5 | –26806.2 |
| B. | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| DFT/COSMO |
DFT/SCRF |
|||||||||
| state (charge) | ΔE0 | ΔESolv,COSMO | ΔETot,COSMO | ΔE0 | ΔEStrain | ΔEP | ΔERF | ΔEenv,SCRF | ΔETot,RF | ΔETot,SCRF |
| RO–P–EH (−3) | –5.2 | 6.4 | 1.3 | –5.2 | –0.9 | 3.4 | 4.4 | 6.9 | –0.8 | 1.7 |
| RO–PHEH (−2) | –100.7 | 98.1 | –2.6 | –102.3 | –2.7 | 22.4 | 90.6 | 110.3 | –11.7 | 8.0 |
| ROHP–E– (−3) | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| ROHPHE– (−2) | –87.9 | 88.9 | 1.0 | –88.6 | –1.9 | 18.0 | 82.5 | 98.7 | –6.1 | 10.1 |
| ROHP–EH (−2) | –97.2 | 95.9 | –1.3 | –97.2 | –1.6 | 19.1 | 89.3 | 106.8 | –7.9 | 9.6 |
| ROHPHEH (−1) | –151.7 | 151.5 | –0.2 | –151.7 | –5.0 | 36.8 | 141.4 | 173.2 | –10.3 | 21.5 |
The total gas-phase electronic energy of the active site quantum cluster obtained following geometry optimization with the DFT/COSMO method.
The stabilization of the quantum cluster from COSMO solvation with ε = 20 (obtained from eq 7). Esolv,COSMO contains both quantum cluster polarization, solvent interaction and electronic strain terms, analogous to those in Eenv,SCRF.
The total energy computed using the DFT/COSMO method (i.e., the sum of E0 and ESolv,COSMO) performed on the COSMO optimized geometry and used to compute relative energies in Table 4A.
The energetic cost of polarizing the active site quantum cluster in response to the protein and reaction potentials in the DFT/SCRF scheme.
The total protein field energy, including electronic polarization of the quantum cluster, resulting from interactions between active site and protein charges that are screened by the three dielectric media (ε = 1, 4, and 80 for the quantum cluster, protein region, and solvent, respectively).
The total reaction field energy, including electronic polarization of the quantum cluster, arising from the dielectric response of the protein (ε = 4) and solvent (ε = 80) environments from the cluster charges.
The total environmental (env) energy from the DFT/SCRF method (i.e., the sum of EStrain, EP, and ERF).
The total free energy associated with the total gas-phase electronic energy of the quantum cluster and the reaction field component of the DFT/SCRF method (i.e., the sum of E0 and ERF), also used to generate the relative energies given in Table 4B.
The electrostatic free energy of a given state computed by the full DFT/SCRF method (i.e., the sum of E0, EStrain, EP, and ERF) and used to obtain the relative energies in Table 4C.
(A) Energies (in kcal mol–1) are presented as total energies, and (B) relative energies (in kcal mol–1) are given with respect to the energy of the ROHP–E– state.