Coupling Coarse-Grained to Fine-Grained Models via Hamiltonian Replica Exchange

Area of Science:

• Computational Chemistry
• Biophysics
• Molecular Dynamics Simulations

Background:

• Biomolecular systems possess complex energy landscapes with numerous local minima separated by high energy barriers.
• Efficiently sampling these landscapes in molecular dynamics (MD) simulations is crucial for understanding molecular behavior but remains challenging.
• Enhanced sampling techniques are often necessary to overcome these limitations in traditional MD.

Purpose of the Study:

• To enhance the sampling efficiency of molecular dynamics simulations.
• To overcome high energy barriers in biomolecular systems using a hybrid force field approach.
• To enable the observation of rare conformational transitions, such as cis-trans isomerization.

Main Methods:

• Coupling of the fine-grained (FG) GROMOS force field with the coarse-grained (CG) Martini force field.
• Implementation of the Hamiltonian replica exchange method (HREM) to facilitate transitions between different sampling resolutions.
• Testing the method's efficiency using a lutein/octane system, known for high energy barriers hindering cis-trans transitions.

Main Results:

• The proposed HREM scheme significantly increased sampling efficiency compared to traditional simulations.
• Numerous cis-trans transitions of lutein, previously unobserved, were successfully sampled.
• The hybrid FG-CG approach effectively navigated the energy landscape, overcoming significant energy barriers.

Conclusions:

• The combination of FG and CG force fields with HREM provides a powerful strategy for enhanced sampling of biomolecular conformations.
• This method allows for the exploration of rare events without sacrificing the accuracy of fine-grained models.
• The approach offers new possibilities for studying complex biomolecular systems and conformational dynamics.