Table 2.
Root-mean-square errors in the B3LYP/6-311G** substrate chemical shieldings (ppm) in the 5 Å clusters relative to the larger clusters ones with various size-effect estimation strategies.
| Size Effect Correction | ||||||
|---|---|---|---|---|---|---|
| None | MM Point Chargesa | PCM (ε= 2)b | PCM (ε= 4)b | PCM (ε= 8)b | ONIOMc | |
| 2AP system | ||||||
| H | 0.17 | 0.14 | 0.15 | 0.14 | 0.12 | 0.11 |
| C | 1.04 | 0.73 | 0.93 | 0.79 | 0.64 | 0.04 |
| N | 1.33 | 2.45 | 1.12 | 0.94 | 0.80 | 0.21 |
| O | 1.88 | 0.92 | 1.58 | 1.30 | 1.13 | 0.26 |
| P | 0.09 | 0.01 | 0.05 | 0.01 | 0.03 | 0.02 |
| F9 system | ||||||
| H | 0.21 | 0.25 | - | 0.12 | - | 0.19 |
| C | 1.43 | 1.41 | - | 0.66 | - | 0.19 |
| N | 3.59 | 5.05 | - | 1.75 | - | 0.42 |
| O | 1.71 | 1.87 | - | 1.16 | - | 0.59 |
| F | 3.74 | 5.02 | - | 1.83 | - | 0.24 |
| P | 0.05 | 0.02 | - | 0.03 | - | 0.06 |
| S | 0.01 | 1.17 | - | 0.47 | - | 0.17 |
a
B3LYP/6-31G* Mulliken charges.
b
The PCM was applied to both the 5 Å and the larger clusters.
c
The cluster size effect in Eq 1 is approximated using 6-311G** on 2AP and 6-31G on all protein atoms.