Figure 1.

The folding free energy contribution $\mathrm{\Delta }W(\mathrm{Asp},\mathrm{Lys},d)$ of the salt bridge interaction Asp-Lys differs according to whether the potentials are derived from soluble or weakly soluble proteins. The energies are in kcal/mol, the distance d (in Å) is computed between residue side chain centroids, and the residues are separated by at least 8 residues along the chain. Distance bins containing ten occurrences or less are not drawn (see Eq. (6)).