Efficient Conformational Sampling in Explicit Solvent Using a Hybrid Replica Exchange Molecular Dynamics Method.

Area of Science:

• Computational chemistry
• Biophysics
• Molecular dynamics

Background:

• Replica-exchange molecular dynamics (REMD) is popular for exploring biomolecular energy landscapes.
• Large biomolecular systems require numerous replicas in REMD, increasing computational expense.
• Continuum solvent models reduce system size but can distort free energy landscapes.

Purpose of the Study:

• To develop and evaluate a hybrid implicit/explicit solvent REMD method.
• To decrease the number of replicas needed for REMD simulations of larger systems.
• To maintain the accuracy of explicit solvent simulations using a hybrid approach.

Main Methods:

• Implemented a hybrid REMD method in CHARMM using explicit solvent replicas and GBMV2 implicit solvation for exchanges.
• Ran REMD simulations using implicit solvent, explicit solvent, and the hybrid method.
• Tested the methods on alanine dipeptide, a tetra-peptide, and a β-hairpin peptide.

Main Results:

• Identified discrepancies in free energy landscapes between implicit and explicit solvent models.
• Evaluated the hybrid approach's ability to reduce replica count.
• Compared free energy landscapes using dihedral angles, salt-bridge distance, and folding stability.

Conclusions:

• The hybrid method shows potential for reducing REMD computational cost for larger biomolecular systems.
• The hybrid approach may reproduce the accuracy of explicit solvent simulations.
• Further evaluation is needed to confirm the hybrid method's capabilities.