Alcohol induced structural and dynamic changes in β-lactoglobulin in aqueous solution: a neutron scattering study

Area of Science:

• Biophysics
• Protein structural dynamics
• Solution scattering and spectroscopy

Background:

• Understanding protein structural transitions in response to solvent composition is crucial for protein folding and stability studies.
• Beta-lactoglobulin (β-LG) is a model protein extensively studied for its conformational changes.

Purpose of the Study:

• To investigate the structural and dynamic alterations of β-LG in aqueous solutions containing varying concentrations of ethanol and trifluoroethanol (TFE).
• To elucidate the role of alcohol-induced changes on protein aggregation and internal molecular motions.

Main Methods:

• Circular Dichroism (CD) spectroscopy to assess secondary structure.
• Small-Angle Neutron Scattering (SANS) to determine protein size, shape, and aggregation state.
• Quasi-Elastic Neutron Scattering (QENS) to probe internal protein dynamics and molecular motions.

Main Results:

• Increasing TFE concentration promoted β-sheet formation in β-LG.
• SANS data indicated native and native-like states at low TFE, transitioning to diffusion-limited colloidal aggregation (DLCA) at higher concentrations.
• QENS revealed increased vibrational amplitudes () with TFE, with aggregation at 20% TFE and nanoscale structural changes at 30% TFE, without further significant changes in .

Conclusions:

• TFE-water mixtures induce significant structural and dynamic changes in β-LG, including secondary structure stabilization, aggregation, and altered internal motions.
• Dynamic measurements are essential for a comprehensive understanding of alcohol-induced protein conformational changes and aggregation processes.
• The study highlights the complex interplay between solvent environment, protein structure, and molecular dynamics.