Average values (SDs are in parentheses) of geometrical properties and electrostatic energy terms of all salt bridges calculated over the concatenated equilibrium MD trajectories of the psychrophilic VPR, mesophilic PRK, and thermophilic AQN at the three simulation temperatures.
| Protein | Tempa (K) | P-degreeb (%) | R-SASAc (%) | ΔΔGdslv-sbd (kcal mol−1) | ΔΔGbrd-sbe (kcal mol−1) | ΔΔGprt-sbf (kcal mol−1) | ΔΔGtot-sbg (kcal mol−1) |
|---|---|---|---|---|---|---|---|
| VPR | 283 | 71 (33) | 27.8 (16.6) | 10.3 (5.3) | −5.1 (3.8) | −8.2 (6.3) | −3.0 (3.7) |
| VPR | 300 | 83 (23) | 25.4 (15.1) | 11.4 (5.0) | −6.1 (3.5) | −9.2 (6.6) | −3.8 (3.9) |
| VPR | 343 | 81 (25) | 26.6 (14.2) | 12.4 (5.3) | −6.9 (3.8) | −10.2 (6.8) | −4.7 (4.2) |
| PRK | 283 | 74 (28) | 32.6 (13.6) | 8.6 (4.2) | −4.7 (2.7) | −7.1 (4.9) | −3.2 (2.7) |
| PRK | 300 | 66 (27) | 33.7 (15.9) | 9.1 (5.0) | −4.6 (2.4) | −8.5 (7.9) | −3.9 (4.4) |
| PRK | 343 | 79 (18) | 34.2 (15.2) | 10.6 (4.6) | −6.3 (2.5) | −8.9 (6.7) | −4.6 (3.7) |
| AQN | 283 | 87 (12) | 32.4 (17.9) | 10.6 (5.4) | −6.9 (3.0) | −6.5 (5.6) | −2.8 (3.0) |
| AQN | 300 | 72 (27) | 32.5 (18.6) | 10.9 (5.9) | −6.1 (3.7) | −8.2 (7.0) | −3.4 (3.5) |
| AQN | 343 | 69 (29) | 35.2 (18.3) | 11.4 (6.1) | −6.5 (4.2) | −9.1 (6.8) | −4.2 (3.4) |
a
MD simulation temperature.
b
Persistence degree of the salt bridge.
c
Relative solvent-accessible surface area of the salt bridge.
d
Desolvation free energy penalty paid by the salt bridge.
e
Interaction free energy between the two charged side chains within the salt bridge.
f
Interaction free energy of the salt-bridging side chains with the remainder of the protein.
g
Total electrostatic free energy (or electrostatic strength) of the salt bridge, which is the sum of the above three energy terms.