Heterogeneous distributions of charge states determine the apparent net charge of intrinsically disordered proteins

Abstract

For proteins with multiple ionizable residues, the canonical assumption is that ionization states of residues are fixed, as dictated by their intrinsic pKa values. Recently, we have applied the formalism of the q-canonical ensemble to analyze and interpret potentiometric measurements of protein net charge as a function of pH. These measurements showed that shifted pKa values and heterogeneous distributions of charge states are required to account for all thermodynamically relevant species in the ensembles that contribute to potentiometric profiles.