Preferential solvation changes upon lysozyme heat denaturation in mixed solvents

Area of Science:

• Biophysical Chemistry
• Protein Chemistry
• Thermodynamics

Background:

• Understanding protein behavior in different solvent environments is crucial for biochemistry and drug development.
• Lysozyme is a model protein frequently studied for denaturation and solvation effects.

Purpose of the Study:

• To investigate the preferential solvation of lysozyme during heat denaturation across various solvent systems.
• To determine the factors influencing preferential solvation, such as solvent activity and pH.

Main Methods:

• Analysis of scanning microcalorimetry data from literature and new measurements.
• Calculation of preferential solvation changes for lysozyme in six different solvent mixtures.
• Evaluation of the impact of solvent activity and pH on denaturation-induced solvation changes.

Main Results:

• Preferential solvation changes of lysozyme upon denaturation were quantified in water-cosolvent systems (methanol, ethanol, propanol, acetone, p-dioxane, dimethylsulfoxide).
• Denaturational changes in preferential solvation were found to be independent of the specific cosolvent at low activity ranges (up to 0.3).
• Preferential solvation was independent of pH in dimethylsulfoxide-water solutions, indicating minimal contribution from charged groups.

Conclusions:

• Lysozyme exhibits nonspecific preferential solvation in the studied cosolvents at low activity, interacting similarly with different molecules.
• The exposed charged groups upon denaturation do not significantly influence the preferential interaction with solution components.
• These findings provide insights into protein-solvent interactions and the nature of denaturation.