Folding-free-energy contribution, ΔW (kcal/mol), as a function of the distance, d, between side-chain descriptors for the thermoresistant protein subset (red), the mesoresistant subset (blue), and the reference subset (dashed line). The molecular structures drawn correspond to examples of the interactions DE-KR (A), DE-KR (B), KR-FWY (C), F-W (D), DE-Y (E), NQST-NQST (F), DE-NQST (G), and G-AG (H). Plots designed with PyMol and XmGrace (38,39). The side-chain descriptor is the Cμ pseudoatom in A, C, D, F, and G, and the Cν pseudoatom in B, E, and H.