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Nucleation theory for helix unfolding in peptide chains
1Instituto de Matemática, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Sur, Avenida Alem 1253, Bahía Blanca 8000, Argentina.
Summary
This study presents a microscopic theory for peptide helix unfolding, estimating the critical bubble size for destruction. This nucleation theory explains helix-coil transitions and predicts denaturation temperature from dynamics, aligning with experimental data.
Area of Science:
- Biophysics
- Theoretical Chemistry
- Computational Biology
Background:
- Helix unfolding in peptide chains is crucial for protein function.
- Existing models lack first-principles justification for critical bubble size.
- Previous dynamic nucleation models estimated kinetic barriers but not critical bubble size.
Purpose of the Study:
- Develop a microscopic nucleation theory for helix unfolding.
- Estimate the critical-size bubble of structural distortion initiating helix destruction.
- Provide a first-principles justification for the critical bubble size.
Main Methods:
- Introduced a microscopic treatment of long-time torsional dynamics.
- Coarse-grained torsional dynamics by discretizing conformational states into torsional isomers.
- Developed a semiempirical formulation linking enthalpy to solvent-exposed surface area changes.
Main Results:
- Derived a functional dependence of unwinding time on bubble size, matching macroscopic models.
- Inferred denaturation temperature from critical bubble formation dynamics, not as a postulate.
- Critical temperature determination aligns with calorimetric and spectroscopic measurements.
Conclusions:
- The microscopic nucleation theory successfully explains helix unfolding dynamics.
- The theory provides a fundamental basis for understanding critical bubble formation.
- This approach offers a novel method for predicting denaturation temperatures from first principles.