FIG. 15.

(a) The pK_1/2 values from simulations of the full model with interactions, on the horizontal axis, are close to the $p{\mathrm{K}}_{\text{eff},{\alpha }_{\ast }}$ values. Red dots result from taking α_* to be the most prominent protonation configuration within 6.6 < pH < 7.3; pK_1/2 values farther from 6.6 < pK_1/2 < 7.3 differ from those $p{\mathrm{K}}_{\text{eff},{\alpha }_{\ast }}$, as expected. Blue open circles result from taking α_* to be the most prominent configuration within 4.4 < pH < 4.6; again pK_1/2 values farther from that of α_* differ more from those of $p{\mathrm{K}}_{\text{eff},{\alpha }_{\ast }}$. (b) Except for H53 and H122 below their respective pK_1/2, histidine titration curves from the full model (solid line) also agree well with Henderson-Hasselbalch curves (dashed line) as parametrized by the $p{\mathrm{K}}_{\text{eff},{\alpha }_{\ast }}$ values of the α_* used in (a).