VALENCY RULE AND ALLEGED HOFMEISTER SERIES IN THE COLLOIDAL BEHAVIOR OF PROTEINS : II. THE INFLUENCE OF SALTS

Area of Science:

• Biochemistry
• Physical Chemistry
• Protein Science

Background:

• The Hofmeister series historically describes salt effects on protein properties.
• Previous studies suggested specific ion effects on protein behavior.
• Accurate control of solution pH is crucial for interpreting electrolyte interactions.

Purpose of the Study:

• To re-evaluate the influence of salt ions on protein properties.
• To determine if salt effects are dependent on ion valency or chemical nature.
• To investigate the role of pH in mediating salt-protein interactions.

Main Methods:

• Experiments measuring membrane potentials, osmotic pressure, swelling, and viscosity of protein solutions.
• Controlled variation of salt concentration and type.
• Precise measurement and control of hydrogen ion concentration (pH) in protein solutions and gels.

Main Results:

• Salt effects on membrane potentials, osmotic pressure, swelling, and viscosity are determined by anion valency, not chemical nature, provided pH remains constant.
• Cations showed no effect on these properties when pH was stable.
• The purported Hofmeister series effects were found to be artifacts of uncontrolled pH.

Conclusions:

• The influence of electrolytes on specific protein properties is governed by membrane equilibria, primarily dependent on ion charge.
• The Hofmeister series is a misinterpretation arising from inadequate pH control in prior research.
• Properties not dependent on membrane equilibria, like solubility, can be influenced by ion chemical nature beyond valency.