Titration curves of aspartic acid and histidine amino acid residues as a function of pH obtained by molecular simulations.

(A) Protonation profiles of aspartic acid residues in A.O.2 protein as a function of pH. The curve for ASP 419 is shown in grey. The colored curves correspond to titration curves of all other aspartic acid residues present in the protein. (B) Protonation profiles of histidine residues in A.O.2 protein as a function of pH. The curve for HIS 465 is shown in grey. The colored curves correspond to titration curves of all other histidine residues present in the protein. (C) Protonation profiles of aspartic acid residues in A.O.8 protein as a function of pH. The curve for ASP 401 is shown in grey. (D) Protonation profiles of histidine residues in A.O.8 protein as a function of pH. The curve for HIS 437 is shown in grey. (E) Protonation profiles of aspartic acid residues in A.O.10 protein as a function of pH. The curve for ASP 437 is shown in grey. (F) Protonation profiles of histidine residues in A.O.10 protein as a function of pH. The curve for HIS 483 is shown in grey.