Specific Buffer Effects on the Intermolecular Interactions among Protein Molecules at Physiological pH
Andrea Salis, Luca Cappai, Cristina Carucci, Drew F. Parsons, Maura Monduzzi
Abstract
BSA and lysozyme molecular motion at pH 7.15 is buffer-specific. Adsorption of buffer ions on protein surfaces modulates the protein surface charge and thus protein–protein interactions. Interactions were estimated by means of the interaction parameter kD obtained from plots of diffusion coefficients at different protein concentrations (Dapp = D0[1 + kDCprotein]) via dynamic light scattering and nuclear magnetic resonance. The obtained results agree with recent findings confirming doubts regarding the validity of the Henderson–Hasselbalch equation, which has traditionally provided a basis for understanding pH buffers of primary importance in solution chemistry, electrochemistry, and biochemistry.