Table 1.
Vertical excitation energies of the retinal chromophore incorporated in the protein and in vacuum
| Protein | ΔES1−S0 (Protein) (kcal mol−1) | ΔES1−S0 (Vacuum) (kcal mol−1) | ΔES1−S0 (Protein – Vacuum) (kcal mol−1) |
| KR2 WT | 55.2 | 43.1 | +12.1 |
| P219G | 54.3 (−0.9) | 43.8 (+0.7) | +10.5 (−1.6) |
| P219T | 53.5 (−1.7) | 44.5 (+1.3) | +9.0 (−3.1) |
| S254A | 53.1 (−2.1) | 43.6 (+0.5) | +9.5 (−2.6) |
| P219T/S254A | 51.5 (−3.7) | 45.9 (+2.7) | +5.6 (−6.5) |
The energy differences (ΔES1−S0) between the ground (S0) and first electronically excited state (S1) were calculated by the QM/MM models using the ARM protocol. The values for the retinal chromophore in the protein (Protein), isolated in vacuum (Vacuum), and their difference (Protein − Vacuum) are shown. The values in the parenthesis for the mutants show the difference from KR2 WT