Relation between the convergence temperatures Th* and Ts* in protein unfolding

Area of Science:

• Thermodynamics
• Protein Folding
• Biophysical Chemistry

Background:

• Privalov's 1979 puzzle questions the convergence of specific enthalpy and entropy in protein unfolding at similar temperatures (Th* ≈ Ts*).
• Previous models explained entropy convergence (Ts*) using the hydrophobic effect but not enthalpy convergence (Th*) or the Th* ≈ Ts* equality.

Purpose of the Study:

• To provide a unified explanation for Privalov's puzzle using the liquid hydrocarbon model.
• To demonstrate that Th* ≈ Ts* can be derived without assumptions on polar interactions or splitting the hydrophobic effect.

Main Methods:

• Utilized the liquid hydrocarbon model to analyze thermodynamic properties of protein unfolding.
• Derived the relationship Th* ≈ Ts* without invoking specific models for polar interactions or complex hydrophobic effect partitioning.

Main Results:

• The liquid hydrocarbon model successfully explains both the convergence of specific enthalpies at Th* and the equality Th* ≈ Ts*.
• Demonstrated that size corrections in hydrophobic interaction calculations do not alter the model's explanation for entropy convergence at Ts*.

Conclusions:

• The liquid hydrocarbon model provides a comprehensive explanation for Privalov's thermodynamic puzzle in protein unfolding.
• The model's validity is supported by independent findings and its ability to account for hydrophobic effects without complex assumptions.