FIGURE 1.

Factors influencing the pK values of ionizable groups in proteins. A,apK change due to the Born effect results when an ionizable group is buried in the interior of the protein where the dielectric constant is lower than that of water. The lower dielectric constant favors the neutral form of the ionizable group. B, the pK values of all of the ionizable groups in a protein will be decreased by a positively charged environment and increased by a negatively charged environment.C, the pK values of the ionizable groups will be increased when hydrogen bonding is tighter to the protonated form and decreased when hydrogen bonding is tighter to the deprotonated form.