Selective separation of proteins from mixtures using polysaccharides

Area of Science:

• Biochemistry
• Physical Chemistry
• Polymer Science

Background:

• Understanding protein-solvent interactions is crucial for biomolecular applications.
• Phase separation in multi-component systems is complex and influenced by various factors.
• Dextran's role in modulating protein behavior in solution requires further investigation.

Purpose of the Study:

• To investigate the phase behavior of ternary (protein + dextran + solvent) and quaternary (protein 1 + protein 2 + dextran + solvent) aqueous solutions.
• To elucidate the mechanisms of protein self-association and phase separation under varying conditions.
• To explore the potential for selective protein partitioning in multi-component systems.

Main Methods:

• Turbidity measurements were used to monitor phase separation.
• Systematic variation of ionic strength and pH to probe solution conditions.
• Analysis of protein self-association mechanisms (electrostatic, van der Waals, hydrophobic).

Main Results:

• Phase separation in ternary systems was favored by conditions promoting protein self-association.
• Bovine serum albumin (BSA) and gamma-globulin self-associated at isoelectric points via electrostatic interactions.
• Lysozyme self-association and phase separation were promoted by electrolytes, likely due to van der Waals/hydrophobic forces.
• Dextran influenced phase separation via polymer depletion effects, creating an attractive force.
• Quaternary systems allowed selective partitioning of proteins into distinct liquid layers (segregative or associative mechanisms).

Conclusions:

• Protein self-association and phase separation are tunable by solvent conditions, ionic strength, and pH.
• Dextran acts as a phase separator through polymer depletion, influencing protein interactions.
• The study demonstrates controlled separation of different proteins within complex aqueous solutions.