Interactions between adsorbed layers of alphaS1-casein with covalently bound side chains: a self-consistent field...

Area of Science:

• Colloid and Surface Science
• Biophysical Chemistry
• Materials Science

Background:

• Alpha S1-casein is a key protein in milk, influencing food texture and stability.
• Understanding protein adsorption and interactions is crucial for food processing and biomaterial design.
• Modification of proteins can alter their interfacial and colloidal properties.

Purpose of the Study:

• To investigate how covalently attaching uncharged polysaccharide side chains to alpha S1-casein affects its adsorbed layer properties.
• To study the interactions between surfaces coated with modified alpha S1-casein under varying pH and ionic strength.
• To determine the impact of polysaccharide side chain length and attachment position on colloidal stability.

Main Methods:

• Utilized lattice-based self-consistent field (SCF) theory to model the system.
• Represented modified alpha S1-casein as a flexible polyampholyte with hydrophobic, polar, and charged units.
• Analyzed surface-surface interaction potential, protein bridging, and segment distribution.

Main Results:

• Unmodified alpha S1-casein layers show attractive interactions at high ionic strength.
• Polysaccharide-modified alpha S1-casein can exhibit net repulsive interactions across a broad salt concentration range.
• The position of polysaccharide attachment significantly influences colloidal stabilizing properties, with potential for both enhancement and worsening.

Conclusions:

• Covalent attachment of polysaccharide side chains offers a strategy to control interfacial and colloidal behavior of alpha S1-casein.
• The precise location of side chain attachment is critical for achieving desired stabilizing effects.
• SCF theory provides valuable insights into the complex interplay of protein structure, modification, and environmental conditions on colloidal systems.