Protein Unfolding-Thermodynamic Perspectives and Unfolding Models.

Area of Science:

• Thermodynamics
• Protein dynamics
• Biophysical chemistry

Background:

• Thermal protein unfolding is a complex process involving transient intermediates.
• Differential scanning calorimetry (DSC) measures heat capacity changes (Cp(T)) during unfolding.
• Existing methods often rely on simplified two-state models for thermodynamic analysis.

Approach:

• Direct numerical integration of DSC heat capacity profiles (Cp(T)) to derive enthalpy, entropy, and free energy profiles.
• Evaluating the accuracy of the standard two-state model against experimental data.
• Developing and comparing new thermodynamic models for protein unfolding.

Key Points:

• Direct integration of Cp(T) provides model-independent thermodynamic profiles (ΔH(T), ΔS(T), ΔG(T)).
• The standard two-state model fails to accurately represent experimental enthalpy, entropy, and free energy profiles.
• Statistical-mechanical models, particularly the cooperative multistate model, offer superior thermodynamic consistency and accuracy.

Conclusions:

• New statistical-mechanical models provide a more accurate description of thermal protein unfolding thermodynamics.
• The cooperative statistical-mechanical multistate model accurately predicts unfolding for both small and large proteins.
• This approach enhances the analysis of protein structural transitions and stability.