Nonfreezing Water Structuration in Heteroprotein Coacervates.

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Surface-bound water in protein solutions exhibits a reduced freezing point.
• Nonfreezing water (NFW) is a key factor influencing the properties of macromolecular solutions.

Purpose of the Study:

• To investigate the presence and levels of nonfreezing water (NFW) in various coacervate systems.
• To compare NFW content in coacervates versus control solutions of single macromolecules.

Main Methods:

• Studied protein-polyelectrolyte, micelle-polyelectrolyte, and protein-protein coacervates.
• Analyzed concentrated solutions of individual macromolecules as controls.
• Quantified nonfreezing water (NFW) content using freezing point depression.

Main Results:

• Coacervates exhibited higher NFW levels compared to single macromolecule systems.
• Heteroprotein coacervates, like lactoferrin (LF) and β-lactoglobulin (BLG), showed up to 15% w/w NFW.
• Protein-containing coacervates demonstrated significantly higher NFW/protein ratios than controls.

Conclusions:

• Coacervate formation enhances the binding and retention of nonfreezing water.
• Maximized water-protein contacts and specific structural features in coacervates contribute to increased NFW.
• These findings are structural-assembly dependent and not observed in non-coacervated solutions.