FIG. 7.

(a) Because H117 is only weakly linked to other residues [see Fig. 3(c), group 11], when H117 switches charge (red short-dashed lines), the eight-vertex polygon representing the possible switches of H122 (purple solid lines), H84 (blue dash-dotted lines), and H14 (green long-dashed lines) undergoes translation with very little distortion (see the text). (b) Because E120 and H122 interact strongly, when E120 changes from charge −1 to 0 the H122 switching segments markedly change slope, distorting the same polygon. (c) Further analysis of the changes in (b), by comparing the full model probabilities with those of a Henderson-Hasselbalch approach. Agreement would correspond to all points being on the solid diagonal line. (c) Illustration that the E120 switch markedly alters some probabilities from Henderson-Hasselbalch values (see the text).