A tool to calculate protonation states for intrinsically disordered peptides and proteins
When the calculations are done, you will find the resulting pKa constants and Hill parameters for each titration site in the box below. You will also find graphical output: (1) deviation of pKa value for each site (2) total peptide charge as function of pH, (3) titration curves for each site. You can download each graph by clicking on it. In each graph the blue line represents the calculated charge at that site as a function of pH, the green curve is a fit to the Henderson-Hasselbalch equation, which includes a fitted pKa value and Hill parameter (nH: a measure of cooperativity) and in red the derivative of the blue curve, the "proton binding capacitance", which more clearly shows electrostatic coupling in the system. For further explanations, please see Lindman et al. Biochemistry 45, 13993-14002 (2006).