Analyzing Protein NMR pH-Titration Curves

Describing the energy of a protonation state Fitting Protein NMR Titration Curves 

The ability of certain chemical compounds to lose or gain protons has been an active area of research since the formulation the concept of pH in 1909 [1] and the appearance of the Bronsted-Lowry acid-base theory in 1923. According to Bron-sted and Lowry an acid is a compound that can donate a proton, whereas a base is a compound that can accept a proton. The dissociation of a proton from an acid in solution can be modeled by a simple equilibrium constant 

School of Biomolecular and Biomedical Science, Centre for Synthesis and Chemical Biology, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland. E-mail Jens.Nielsen ucd.ie 

The pK of a compound is thus a description of the tendency of a compound to donate its titratable proton. A plot of the fractional proton occupancy of an acid or a base versus pH is called a titration curve and has the familiar sigmoid shape typical of binding reactions. 

While titration curves can easily be measured for simple acids and bases in dilute aqueous solutions with simple titration experiments, the titration curves of indi- 

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