Analyzing Protein NMR pH-Titration Curves

The pH-dependence of the NMR chemical shift for protein residues provides a wealth of information on biophysical characteristics important for the function of proteins. It is well known that pKa values can be extracted from protein NMR pH-titration curves, but recent work has illustrated that NMR titration curves also can give information on pair wise electrostatic interaction energies, the propagation of the electric field and conformational changes in proteins. This review gives a brief introduction to protein titration in general and highlights a number of studies that have improved our understanding of protein NMR pH-titration curves and our ability to analyze them.