Protein adsorption at solid-liquid interfaces: Part III--Adsorption from ternary protein mixture.

Area of Science:

• Colloid and Surface Science
• Biophysical Chemistry
• Materials Science

Background:

• Understanding protein adsorption at interfaces is crucial for various applications, including biomaterials and food processing.
• The behavior of mixed protein systems differs significantly from single-component adsorption.
• Alumina-water interfaces are relevant in areas like water treatment and biomedical devices.

Purpose of the Study:

• To investigate the simultaneous adsorption of bovine serum albumin (BSA), beta-lactoglobulin, and gelatin from ternary mixtures onto an alumina-water interface.
• To determine how factors like protein concentration, pH, ionic strength, temperature, and protein ratios affect adsorption.
• To quantify protein affinities and competitive adsorption behaviors.

Main Methods:

• Studied simultaneous adsorption of three proteins from aqueous ternary mixtures onto alumina.
• Varied protein concentrations, pH, ionic strength, temperature, and weight fraction ratios.
• Analyzed adsorption extents (gamma w) for each protein (BSA, beta-lactoglobulin, gelatin).
• Expressed protein affinities using scales of total adsorption and standard free energies.

Main Results:

• Preferential adsorption of beta-lactoglobulin was observed, significantly influenced by BSA and gelatin presence.
• High beta-lactoglobulin adsorption led to BSA displacement (negative gamma w(ser)), indicating beta-lactoglobulin and water preferentially adsorb.
• Gelatin adsorption (gamma w(gel)) generally increased with beta-lactoglobulin adsorption (gamma w(lac)), but varied with solution parameters.
• Increased ionic strength and temperature at pH 5.2 enhanced adsorption of all proteins.
• Adsorption of all proteins increased as pH shifted from 5.2 to 6.4.

Conclusions:

• Beta-lactoglobulin can competitively displace BSA from the alumina-water interface.
• The adsorption of gelatin is mutually influenced by beta-lactoglobulin adsorption.
• Solution parameters (pH, ionic strength, temperature) critically control the competitive adsorption and affinities of proteins in mixtures.
• The study provides insights into protein-surface interactions in complex biological and industrial systems.