Average energy terms in various salt-bridge categories.

All: whole dataset of 275 salt-bridges; Stable: 213 salt-bridges with ΔΔGtottot>0 Kcal/mol; Buried: 94 salt-bridges with average ASA of ≤20%; Exposed: 181 salt-bridges with average ASA of >20%; Networked: 125 salt-bridges that participate in salt-bridge networks; Isolated: 150 salt-bridges that do not form part of salt-bridge networks; H-bonded: 226 salt-bridges containing at least one hydrogen bond between side-chain charged groups; and Non H-bonded: 49 salt-bridges that do not contain any hydrogen bond between their side-chain charged groups.