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Exploring the helix-coil transition via all-atom equilibrium ensemble simulations
1Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
Biophysical Journal
|January 25, 2005
Summary
Extensive simulations reveal peptide folding is a complex conformational diffusion, not a simple process. The AMBER-99 phi force field accurately models this behavior, improving agreement with experimental data.
Area of Science:
- Computational chemistry
- Biophysics
- Molecular dynamics
Background:
- Understanding protein folding is crucial for molecular biology.
- Simulating peptide folding requires significant computational resources and accurate force fields.
Purpose of the Study:
- To study the ensemble folding of two 21-residue alpha-helical peptides.
- To quantitatively assess AMBER force field variants for peptide folding simulations.
- To investigate the folding landscape and dynamics using extensive molecular dynamics simulations.
Main Methods:
- All-atom simulations in explicit solvent.
- Utilizing a global distributed computing network for extensive sampling.
- Employing several variants of the AMBER potential, including the new AMBER-99 phi force field.
Main Results:
- Achieved complete convergence to ensemble equilibrium, exceeding experimental folding times.
- The AMBER-99 phi force field demonstrated improved agreement with experimental kinetic and thermodynamic measurements.
- Identified a pseudo-two-state folding landscape characterized by configurational diffusion among diverse conformational microstates.
Conclusions:
- Peptide folding dynamics are better described as conformational diffusion than a simple exponential process.
- Reported equilibrium transition rates spanning several orders of magnitude.
- Helix formation involves nucleation followed by a kinetic alignment phase of helical segments.