(A, B) Violin plots of the distance between the nearest side chain nitrogen atom of lysine/arginine and the side chain oxygen atom of aspartic/glutamic acid in the salt bridge. Each subplot shows the results obtained at 20°C, 0.15 M NaCl (left), 40°C, 0.15 M NaCl (middle), and 20°C, 0.50 M NaCl (right). Each ‘violin’ displays the mean value (the bar in the center of the violin), the range (the stretched line), and the distribution of the distance (kernel density on the side). As we use the numbering of H-NSST, there are position shifts in H-NSBA and H-NSIL: R54 to R53, K57 to K56, and D68 to D67 in H-NSBA; R54 to K53 in H-NSIL. (C) Final snapshots of the R54-E74’ salt bridge in H-NSST and K54-D71’ in H-NSEA. Color scheme of the cartoon: 20°C, 0.15 M NaCl (green), 40°C, 0.15 M NaCl (red), and 20°C, 0.50 M NaCl (cyan). (D) Final snapshots of the K57-D/A68 contact in H-NSST and H-NSIL. Same color scheme as (C). (E) Free energy changes as a result of increased salinity or temperature, according to the potential of mean force (PMF) calculated from umbrella sampling.