Colloidal Stability & Conformational Changes in β-Lactoglobulin: Unfolding to Self-Assembly

Area of Science:

• Protein chemistry and biophysics
• Food science and technology
• Materials science

Background:

• Understanding protein behavior is crucial for biotherapeutics and food applications.
• Beta-lactoglobulin (BLG) is a key protein in dairy products and a model system for protein studies.
• Controlling protein aggregation and gelation is essential for product stability and functionality.

Purpose of the Study:

• To elucidate the mechanisms of unfolding, aggregation, and rheological changes in beta-lactoglobulin (BLG) across various pH levels.
• To identify key indicators of colloidal stability and protein structural transitions.
• To explore novel methods for deconvoluting protein unfolding and aggregation events.

Main Methods:

• Utilized dynamic light scattering (DLS) for particle size analysis.
• Employed optical microrheology to measure solution viscosity and elasticity.
• Applied Raman spectroscopy to probe protein structure and water hydrogen bonding.
• Used differential scanning calorimetry (DSC) to determine thermal transitions.

Main Results:

• The diffusion interaction parameter (kD) accurately predicted colloidal stability and aggregation trends.
• Significant aggregation and gelation occurred at pH 5.5, with simultaneous secondary and tertiary structure changes.
• Oligomerization without gelation was observed at higher pH (7.0, 8.5), with sequential structural transitions.
• Low-frequency Raman data correlated strongly with rheological changes and protein structuring.

Conclusions:

• Combined low-frequency Raman data and DSC endotherms provide a novel method to distinguish protein unfolding from aggregation/gelation.
• pH-dependent structural changes in BLG dictate its aggregation behavior and rheological properties.
• Findings offer insights for optimizing biotherapeutics stability and food product texture.