VALENCY RULE AND ALLEGED HOFMEISTER SERIES IN THE COLLOIDAL BEHAVIOR OF PROTEINS : I. THE ACTION OF ACIDS.

Area of Science:

• Biochemistry
• Physical Chemistry

Background:

• The Hofmeister anion series is a widely accepted principle in colloid chemistry.
• Previous studies on acid-protein interactions have often overlooked precise pH control and equilibrium conditions.

Purpose of the Study:

• To investigate the influence of acid anions on key gelatin properties.
• To re-evaluate the validity of the Hofmeister series in specific contexts.
• To elucidate the underlying mechanism governing acid-gelatin interactions.

Main Methods:

• Studied the effects of various monobasic, dibasic, and tribasic acids on gelatin's membrane potentials, osmotic pressure, swelling, and viscosity.
• Systematically varied pH and acid concentration to observe property changes.
• Compared experimental results with theoretical predictions based on Donnan equilibrium.

Main Results:

• Gelatin properties were found to be dependent on the anion's valency, not its specific chemical nature.
• Monovalent anions exhibited a more pronounced effect on gelatin properties compared to divalent anions.
• Experimental data strongly supported the valency rule and contradicted the Hofmeister anion series for the studied properties.
• The observed effects align with predictions from the Donnan equilibrium model.

Conclusions:

• The valency of an acid's anion is the primary determinant of its effect on gelatin's membrane potentials, osmotic pressure, swelling, and viscosity.
• The Hofmeister anion series is not applicable to these specific gelatin properties due to the dominant role of Donnan equilibrium.
• Donnan equilibrium dictates that only anion valency influences these protein properties, not other anion characteristics.