Specific Buffer Effects on the Intermolecular Interactions among Protein Molecules at Physiological pH

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 <i>k</i>_D obtained from plots of diffusion coefficients at different protein concentrations (<i>D</i>_app = <i>D</i>₀[1 + <i>k</i>_D<i>C</i>_protein]) 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.